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  • 1995-1999  (1,136)
  • 1995  (1,136)
  • Engineering General  (737)
  • Physical Chemistry  (241)
  • crystal structure  (158)
  • Nuclear reactions
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  • 1995-1999  (1,136)
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Linear and Nonlinear Optical Properties Of Racemic (±)2-(α-Methylbenzylamino)-5-Nitropyridine Single Crystals (1995)
    Springer
    Optical review 2 (1995), S. 128-131 
    Details
    ISSN: 1349-9432
    Keywords: organic crystal ; racemic form ; second-harmonic generation ; refractive index ; nonlinear optical coefficient ; crystal structure ; oriented-gas model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Linear and nonlinear optical properties of racemic (±)2-(α-methylbenzylamino)-5-nitropyridine ((±)MBANP) single crystals have been comprehensively investigated and compared with those of the enantiomorph (–)2-(α-methylbenzylamino)-5-nitropyridine ((–)MBANP) crystals. (±)MBANP crystal exhibits very high chemical and physical stability, but relatively small nonlinear optical coefficients (d31 = 6.8 pm/V, d32 = 4.7 pm/V, d33 = 0.84 pm/V). A comparison between the nonlinear optical coefficients of (±)MBANP and (–)MBANP demonstrates the validity of the oriented-gas model in molecular crystals that neglects all the contributions from intermolecular interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10043-995-0128-5
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  • 2
    Electronic Resource
    Electronic Resource
    Nucleophilic additions of primary and secondary amines to pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 633-640 
    Details
    ISSN: 1572-8854
    Keywords: Amines ; crystal structure ; pentacycloundecane-8,11-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of three compounds formedvia nucleophilic attack of a heterocyclic secondary amine on PCU-8,11-dione, with the concomitant intramolecular attack of one keto oxygen on the carbon of the other ketone, are presented. In all three compounds, the bridging oxygen contains substantial p-character, and the bonds to the “attacking” nitrogen are significantly shorter than would be expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665969
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  • 3
    Electronic Resource
    Electronic Resource
    Dialkylimidazolium-sodium chloroaluminate ternary salt system: phase diagram and crystal structure (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 57-62 
    Details
    ISSN: 1572-8854
    Keywords: phase diagram ; buffered chloroaluminate ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The phase diagram of the buffered neutral aluminum chloride + 1-ethyl-3-methyl-1H-imidazolium chloride + sodium chloride (AlCl3-EMIC-NaCl) ternary melt system can be represented by a binary phase diagram composed of (EMI)AlCl4 and NaAlCl4. In the binary phase diagram, the salts are liquid at, or near, room temperature for a wide range of compositions. At the 1∶1 composition, the congruently melting compound (EMI)(Na)(AlCl4)2 with m.p.=36.7°C is formed. Crystals of this mixed organic-inorganic salt were grown for single crystal x-ray diffraction analysis. The compound crystalizes in the space group $$P\bar 1$$ with lattice parametersa=10.321(1) Å,b=10.895(3) Å,c=9.284(4) Å, α=98.31(2)°, β=100.83(4)°, γ=101.95(3)°. Data collected at −120°C gave final residuals ofR=0.037 andR w=0.045 using 2713 observed reflections. The packing diagram reveals Na+ ion zig-zag chains running along thea-axis with each Na+ surrounded by four AlCl 4 − units, reminiscent of NaAlCl4. The AlCl 4 − ions form a distorted square planar coordination sphere around Na+ at an average Na−Al distance of 3.76(4) Å. Using a sodium ionic radius of 1.16 Å, a new AlCl 4 − ionic radius of 2.60 Å is calculated. This radius is 0.21 Å shorter than the reported thermodynamic radius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01667037
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of a chiral calixarene: 5,11,17,23-tetra (tert-butyl)-25,27-bis[((+)-camphor-10-sulfonyl)-oxy]-calix[4]arene-26,28-diol: crystal and molecular structure of its (1∶2) complex with toluene (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 401-406 
    Details
    ISSN: 1572-8854
    Keywords: Calixarene ; complex ; crystal structure ; chirality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound was obtained by treatment ofp-tert-butylcalix[4]arene with (+) camphorsulfonyl chloride in triethylamine and toluene. A (1∶2) complex with toluene has been found. Its structure has been determined by X-ray crystallography. Crystals are triclinic with space group P1,a=16.426(3),b=18.553(3),c=13.661(2) Å, α=94.78(2), β=110.76(2), γ=72.83(2)°,V=3720(2) Å3,d c =1.127 g/cm3 Z=2. Refinement based on 10495 observed reflections led to a finalR value of 0.100. The two independent molecules of calixarene in the asymmetric unit are in the cone conformation and the calixarene cavities are empty. The guest molecule occupies the interhost space. The norborane skelton of (+) camphorsulfonyl group is the same as ones found in literature. Only van der Waals interactions exist between the host and the guest molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665277
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  • 5
    Electronic Resource
    Electronic Resource
    Mercury(II) complex with terpyridine: structure of the 2∶1 solvate of [Hg(terpy)2](CF3SO3)2 with acetone (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 453-458 
    Details
    ISSN: 1572-8854
    Keywords: Mercury(II) terpyridine complex ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract [Hg(terpy)2](CF3SO3)2·0.5(CH3)2CO crystallizes in the triclinic $$P\bar 1$$ space group witha=14.631(6),b=15.258(4),c=18.785(7) Å, α=69.66(2), β=70.72(1), γ=88.55(1)°. The crystal structure consists of two independent [Hg(terpy)2]2+ cations, four trifluoromethanesulfonate anions and an acetone molecule in the asymmetric unit. Each mercury atom is coordinated by two tridentate terpyridine ligands forming an irregular six-coordination polyhedron. The Hg−N bond lengths range from 2.27(2) to 2.53(2) Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665700
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  • 6
    Electronic Resource
    Electronic Resource
    Synthesis and structural characterization of [Au2Pd14(μ3-CO)7(μ2-CO)2(PMe3)11](PF6)2—An icosahedrally-based high nuclearity mixed metal cluster (1995)
    Springer
    Journal of cluster science 6 (1995), S. 71-91 
    Details
    ISSN: 1572-8862
    Keywords: Palladium ; gold ; cluster ; phosphine ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract [Au2Pd14(μ3-CO)7(μ2-CO)2(PMe3)11](PF6)2 has been synthesized from [Pd8(CO)8(PMe3)7] and AuCl(PCy3) in the presence of TIPF6. It has been characterised on the basis of mass spectrometry, infrared and NMR spectroscopy, and a single crystal X-ray diffraction study. The structure is based on a palladium-centered Au2Pd11 icosahedron which shares an edge with a Pd5 trigonal bipyramid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01175837
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis, chemical, and electrochemical characterization of the [Ag13{μ3-Fe(CO)4}] n− (n = 3, 4, 5) cluster anions: X-Ray structural determination of [N(PPh3)2]3 [Ag12(μ12-Ag){μ3Fe(CO)4}8]1 (1995)
    Springer
    Journal of cluster science 6 (1995), S. 107-123 
    Details
    ISSN: 1572-8862
    Keywords: Silver ; iron ; carbonyl ; cluster ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The oxidation of the [Fe(CO)4]2− dianion with Ag+ salts occurs through a particularinner-sphere mechanism, which involves an intermediate cascade of silver clusters stabilized by Fe(CO)4 ligands. The last detectable Ag-Fe cluster of the sequence is the [Ag13{μ-Fe(CO)4}8]3− trianion, which has been selectively obtained by using ca. 1.7 equivalents of Ag+ per mole of [Fe(CO)4]2−. The [Ag13{μ-Fe(CO)4}8]3−- trianion has been isolated in a crystalline state with several quaternary cations, and has been characterized by X-ray diffraction studies of its bis(triphenylphosphine)iminium salt. [N(PPh3)2]3 [Ag13{μ 3-Fe(CO)4}8]·2(CH3)2CO, monoclinic, space group P21 (No.4),a = 16.284(2) Å,b =18.767(5) Å,c = 25.905(4) Å,β = 90.46(1)°,V = 7916(3) Å3,Z = 2,R = 0.0324. The molecular structure of the anion consists of a centered cuboctahedron of silver atoms with the triangular faces capped by Fe(CO)4 units. Chemical reduction of ( Ag13{μ 3-Fe(CO)4}8]3− affords the corresponding [Ag13{μ 3-Fe(CO)4)8]4−, which in turn gives [Ag13{μ 3-Fe(CO)4)8]5− and [Ag6{μ 3-Fe(CO)4}4]– upon further reduction. Electrochemical investigations confirm the reversibility of the [Ag13{μ 3-Fe(CO)4}8]3−/4− redox change. Furthermore, in spite of some electrode poisoning effects, evidence of the existence of the [Ag13{μ 3-Fe(CO)4}8]5− pentaanion was obtained. The yet structurally uncharacterized [Ag6{μ 3-Fe(CO)4)4]2− dianion is quantitatively obtained by reaction of [Fe(CO)4]2− with ca. 1.5 equivalents of Ag+ or by addition of one equivalent of Ag+ to solutions of the [Ag5{Fe(CO)4}4]3− trianion. All attempts to isolate its quaternary salts as crystalline materials failed owing to formation of amorphous insoluble precipitates. The above series ofμ 3-Fe(CO)4 octa-capped cuboctahedral Ag13 clusters can be envisioned as the Ag+ . Ag and Ag− cryptates of the [Ag12{μ}3-Fe(CO)4}8]4− cryptand. respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01175839
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  • 8
    Electronic Resource
    Electronic Resource
    The synthesis and structural characterization of Os3(CO)8[Si(OMe)3][μ-PMe2(C6H4](μ-H)2: An unusual unsaturated triosmium cluster complex (1995)
    Springer
    Journal of cluster science 6 (1995), S. 437-447 
    Details
    ISSN: 1572-8862
    Keywords: Osmium ; unsaturated cluster ; ortho-metallation ; siloxyl ligand ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The reaction of Os3(CO)10(NCMe)[Si(OMe)3](μ-H),1, with PMe2Ph yielded the new complex Os3(CO)10(PMe2Ph)[Si(OMe)3](μ-H),2 by substitution of the MeCn ligand with the phosphine ligand. When heated to 125°C compound2 was decarbonylated and transformed into the new unsaturated cluster complex Os3(CO)8[μ-PMe2(C6H4)][Si(OMe)3](μ-H)2,3 in 54% yield. Compound3 was characterized by a single crystal X-ray diffraction analysis, osmium bonds. The phenyl ring of the phosphine ligand has undergoneortho-metallation by a neighboring metal atom. A terminally coordinated Si(OMe)3 ligand is coordinated to the third osmium atom. The cluster is unsaturated by the amount of 2 electrons, and there is an open coordination site on the siloxyl substituted osmium atom that is partially filled by a weak interaction with one of the π-bonds of theortho-metalled phenyl ring. Complex3 reacts with CO at 1 atm to reform compound2 in 85% yield in 5 h at 40°C. Crystal Data: for3: space group = P21/n,a = 9.911(2) Å,b = 18.451(6) Å,c = 14.872(2) Å,β = 95.64(2)°,Z = 4, 1994 reflections,R = 0.028.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01165472
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  • 9
    Electronic Resource
    Electronic Resource
    Doubly-bridged binuclear complexes of oxomolybdenum(V) and oxotungsten(V) containing sexadentate ligands (1995)
    Springer
    Journal of cluster science 6 (1995), S. 549-566 
    Details
    ISSN: 1572-8862
    Keywords: Molybdenum ; tungsten ; di-μ-oxo bridge ; sexadentate ligands ; asymmetric distortion ; stereoselectivity ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Binuclear oxomolybdenum(V) and oxotungsten(V) complexes of the type, [M 2(O)2(μ-X)(μ-X 1)]”, where M=Mo, W;X.X 1=O, S; L=edta, pdta (n=2-), tpen, tppn (n=2+) (edta4– =ethylenediaminetetraacetate(4–), pdta=R- orR,S-propylenediaminetetraacetate(4–), tpen=N,N,N 1,N1-tetrakis(2-pyridyhnethyl)-ethylenediamine, and tppn=R- orR,S-N,N,N 1,N1-tetrakis(2-pyridylmethyl)-propylenediami ne) are reviewed with respect to their preparation, structure, spectroscopic properties, reactivities, and in particular asymmetric distortion around the bicyclo [4.1.1 ] type core and stereoselectivity related to this distortion,
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01165773
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  • 10
    Electronic Resource
    Electronic Resource
    Comparison of the crystal structure and molecular models of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide (CMPO) (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 43-49 
    Details
    ISSN: 1572-8854
    Keywords: Molecular mechanics ; molecular dynamics ; MNDO ; CMPO ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide, or CMPO was recently determined. The compound crystallizes in the space group P21/c witha=13.446(6),b=22.280(7),c=17.217(7) Å, β=92.07(4)°, andD calc=1.05 g/cm3 forZ=8 @20°C). Molecular mechanics, molecular dynamics, and MNDO calculations were also performed on CMPO utilizing the SYBYL1 suite of programs. The results from these calculations are compared to the crystal structure and to similar calculations performed on CMPO using ALCHEMY2,3. In general, the results from the calculations agree fairly well with the parameters from the crystal structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666193
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  • 11
    Electronic Resource
    Electronic Resource
    Antifungal copyrine alkaloids: crystal structure of 3-methylsampangine (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 223-226 
    Details
    ISSN: 1572-8854
    Keywords: Antifungal alkaloids ; 3-methylsampangine ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 3-Methylsampangine, C16H10N2O, crystallizes in the monoclinic space group P21/c witha=7.260(3),b=10.697(5),c=15.342(6) Å, and β=102.69(4). All nonhydrogen atoms of this potent antifungal agent are planar to within 0.082 Å. The title compound exhibits potentin vitro antifungal activity againstC. neoformans, C. albicans andA. fumigatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665173
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  • 12
    Electronic Resource
    Electronic Resource
    Unusual occurrence of photooxidation of a cage diol (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 295-298 
    Details
    ISSN: 1572-8854
    Keywords: Cage-diol ; crystal structure ; photooxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract An unusual photooxidation was noted upon photolytic cage closure of a substituted tricyclo[6.2.1.02.7]undecane-exo, exo-diol. The resultant compound, which may be regarded as a mono-reduced pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione, was characterizedvia X-ray crystallography. This species could be reduced to the tricyclo[6.2.1.02,7]undecane-endo, exo-diol under conditions previously shown to be inert for the parent dione.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01796053
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  • 13
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of 6,7-benzo-3,4 (1,4-dimethoxy-2,3-naphtho)-1,5-dioxosuberane (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 379-382 
    Details
    ISSN: 1572-8854
    Keywords: Benzonaphthodioxosuberane ; crystal structure ; radermachol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the title compound (2) C21H16O4 has been determined by an X-ray analysis, by direct methods from diffractometer data and refined by full-matrix least squares. The compound (2) crystallizes in the space group P21/a, with cell parameters:a=36.432(5),b=5.512(3),c=8.269(5) Å, β=108.0(3)°,z=4,D c =1.397 g/cm−3,R=7.8 for 1136 observed reflections. The conformation of the tetracyclic ring system shows a folding of two planar parts of the carbon skeleton about an axis passing thorough C8 and C16 of the seven membered ring C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665273
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  • 14
    Electronic Resource
    Electronic Resource
    Molecular Structure of 5-Methylchrysene-7,8-dihydro-7,8-trans-(e, e)-diol (1995)
    Springer
    Structural chemistry 6 (1995), S. 57-63 
    Details
    ISSN: 1572-9001
    Keywords: Hydrogen bonding ; carcinogen ; polycyclic aromatic hydrocarbon derivative ; dihydrodiol ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal structure of the weak carcinogen 5-methylchrysene-7,8-dihydro-7,8-trans-(e,e)-diol is reported. This molecule contains a distorted bay region as a result of the presence of the 5-methyl group as found in 5-methylchrysene and 5,6- and 5, 12-dimethylchrysene. One torsion angle in this bay region is 20
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263528
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  • 15
    Electronic Resource
    Electronic Resource
    The synthesis and X-Ray crystallographic analysis of a stable norbornadienone: 17-Oxo-7,16-methano-7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene (1995)
    Springer
    Structural chemistry 6 (1995), S. 167-173 
    Details
    ISSN: 1572-9001
    Keywords: MM3 ; PM3 ; MMX ; crystal structure ; norbonadienone ; distorted compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction of 4,5-didehydroacenaphthene with phencyclone yields the title compound, a stable dibenzo-fused norbornadienone (8). The X-ray structure of8 is presented and compared with the structure predicted from a MM3, PM3, and a MMX calculation. Thermal decomposition of 8 produces, 7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene (9), a hydrocarbon that is computed to have a significantly twisted polycyclic aromatic skeleton with 19 kcal/mole of strain energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02286444
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  • 16
    Electronic Resource
    Electronic Resource
    Lattice dynamics of (Ba/K)BiO3 (1995)
    Springer
    Journal of superconductivity 8 (1995), S. 595-598 
    Details
    ISSN: 1572-9605
    Keywords: (Ba/K)BiO3 ; lattice dynamics ; electron phonon coupling ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The Lattice dynamics of Ba.6K.4BiO3 was investigated by inelastic neutron scattering on a superconducting single crystal (T c =26 K (midpoint)). At low frequencies the dispersion curves are very similar to those observed in BaPb.75Bi.25O3. Differences were found in the bond bending vibrations of the BiO6 octahedra which indicate that the binding in the K-doped compound is more ionic. Rather anomalous features were observed in the high frequency Bi-O bond stretching vibrations which resemble those observed in the high T c cuprates La1.85Sr.15CuO4 and YBa2Cu3O7. The observed frequency shifts are interpreted as the consequence from a strong electron phonon coupling. The data are compared to the results obtained on non superconducting Ba.98K.02BiO3.
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    URL: http://dx.doi.org/10.1007/BF00727434
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  • 17
    Electronic Resource
    Electronic Resource
    Effect of Humidity-Dependent Changes in Crystal Structure on the Solid-State Fluorescence Properties of a New HMG-CoA Reductase Inhibitor (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 556-559 
    Details
    ISSN: 1573-904X
    Keywords: HMG-CoA reductase inhibitor ; SQ-33600 ; crystal structure ; hydrates ; solid-state fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It has been shown previously that the disodium salt of a new HMG-CoA reductase inhibitor (SQ-33600) is capable of existing as a number of hydrate species [1]. Three crystalline solid hydrates and one liquid crystalline phase have been identified, each having a definite stability over a defined range of humidity. These forms have been found to exhibit varying fluorescence properties in their respective solid states, with differences in bandshapes and intensities being noted for each. These spectral variations have been correlated with the known pseudopolymorphism of the compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016206130213
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  • 18
    Electronic Resource
    Electronic Resource
    Crystal Structure of 2-Debenzoyl, 2-Acetoxy Paclitaxel (Taxol®): Conformation of the Paclitaxel Side-Chain (1995)
    Springer
    Pharmaceutical research 12 (1995), S. 337-341 
    Details
    ISSN: 1573-904X
    Keywords: 2-debenzoyl, 2-acetoxy paclitaxel ; docetaxel ; paclitaxel side-chain ; crystal structure ; solid state conformation ; intramolecular hydrogen bonding ; intermolecular hydrogen bonding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Crystals of the C2-acetate analog of paclitaxel, grown from a mixture of isopropyl alcohol and methanol, belong to the space group P2l with a = 9.058(3), b = 18.306(5), c = 15.043(1) Å, β = 97.09(1)°, Z = 2, V = 2475.1(9)Å3, D calc = 1.269 gcm−3 and µ = 0.75 cm−1. The structure was determined by direct methods and refined to R(F) = 0.054 and wR(F) = 0.057 for 605 variables and 3496 observed reflections. The paclitaxel side chain possesses a conformation similar to that observed in the crystal structure of docetaxel (Taxotere®). A three dimensional network of hydrogen bonds is formed through solvent molecules and stabilizes the crystal lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016236014766
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  • 19
    Electronic Resource
    Electronic Resource
    X-ray structure of sesterterpene, 16β-acetoxy-24-methyl-12,24-dioxoscalaran-25-al (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 765-768 
    Details
    ISSN: 1572-8854
    Keywords: Sesterterpene ; scalaran ; crystal structure ; marine compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The molecular geometry of a tetracyclic sesterterpene has been determined by X-ray diffraction. The conformation of the aldehyde group as observed in the crystal structure supports the rationalization for the absence of aldehyde proton coupling in the nmr spectra of the compound. Crystal data: C28H42O5, M.W.=458.6; orthorhombic, P212121;a=10.797(2),b=29.270(9),c=8.033(1)Å,V=2538.7Å3,Dx=1.199 g cm−3;R=0.045 for 2287 observed reflections.
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    URL: http://dx.doi.org/10.1007/BF01670333
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  • 20
    Electronic Resource
    Electronic Resource
    α-Iminohydroxylamine-α-aminonitrone tautomerism: a 1∶1 mixture of two tautomeric forms in crystals of N-(4,5-dihydro-1H-imidazol-2-yl)-N-phenyl-hydroxylamine (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 813-821 
    Details
    ISSN: 1572-8854
    Keywords: Tautomerism ; hydrogen bonding ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystals consisting of two distinct chemical entities, tautomers of each other, in exact 1∶1 ratio, have been obtained and their structure determined by X-ray analysis. The crystals of C9H11N3·C9H11N3 are monoclinic,P21/c,a=15.674(3),b=17.085(3),c=13.758(3)Å, β=90.78(2)°,Z=8. There are two hydroxylamine and two aminonitrone molecules in the asymmetric unit. Hydrogen bonds connect those molecules into chiral layers. Layers of opposite chirality alternate andthe crystal is centrosymmetric as a whole. Within those layers chains of tautomers joined by very strong O−H... O and strong N−H... N bonds can be recognized. Proton transfer along those chains with simultaneous rearrangement of π-bonds within the molecules would result in interconversion of tautomers and would affect chirality of the layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01671076
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  • 21
    Electronic Resource
    Electronic Resource
    Crystal structure of decacalcium tetrapotassium hexakis (pyrophosphate) nonahydrate (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 219-222 
    Details
    ISSN: 1572-8854
    Keywords: Calcium phosphate ; calcium pyrophosphate ; calcium potassium pyrophosphate ; crystal structure ; layer-type structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structure of Ca10K4(P2O7)6·9H2O has been determined by single crystal X-ray diffraction. Crystals are hexagonal, space group P63cm witha=11.761(1),c=9.770(1) Å, andZ=1. The structure was refined toR=0.028 andR w=0.037 for 468 reflections withI≥3σ(I). The structure consists of a compact assembly of Ca and P2O7 ions arranged in layers perpendicular to thec-axis in a hexagonal array with relatively large open channels along thec-axis. The K ions and the water molecules are located in these open channels and are disordered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665172
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  • 22
    Electronic Resource
    Electronic Resource
    Crystal structures of twoN-substituted 2-thioxo-1,3-dithiole-4-carboxamides (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 463-467 
    Details
    ISSN: 1572-8854
    Keywords: 1,3-dithiole-4-carboxamides ; resonance effect ; short intramolecular S...O contact ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The two closely related compoundsN,N-dimethyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide1 andN-(p-methoxy-phenyl)-N-methyl 5-(methylthio)-2-thioxo-1,3-dithiole-4-carboxamide2 have been characterized by X-ray crystal structure determination. Crystal data for1: triclinic, $$P\bar 1$$ ,a=6.767(1),b=12.594(2),c=6.648(1) Å, α=101.38(1), β=93.37(2), γ=79.62(1)°,V=546.2 Å3,Z=2. Crystal data for2: monoclinic, Cc,a=19.836(4),b=6.057(1),c=15.860(3) Å, β=127.61(3)°,V=1509.5Å3,Z=4. The molecular structures of1 and2 show remarkable differences concerning the conformational behavior. These differences are related to the nature of the substituents at the nitrogen atom. The presence of an aromatic system in2 leads to an almost planar arrangement of the α-oxoketene dithioacetal moiety. This effect is accompanied by a short intramolecular S...O contact of 2.648(2) Å. In the absence of an aromatic system, as is the case for compound1, neither a resonance effect along the α-oxoketene dithioacetal fragment nor a short S...O distance is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01665702
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  • 23
    Electronic Resource
    Electronic Resource
    The crystal structure of a heterobimetallic crown ether complex: [Na(dibenzo-18-crown-6)][FeCl4] (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 579-582 
    Details
    ISSN: 1572-8854
    Keywords: Dibenzo-18-crown-6 ; hetero bimetallic ; crown ether ; crystal structure ; ferric chloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Slow evaporation of a solution of ferric chloride and dibenzo-18-crown-6 in 3∶1 CH3CN∶CH3OH produced single crystals of the title complex. This heterobimetallic crown ether complex, [Na(dibenzo-18-crown-6)][FeCl4], crystallizes in the monoclinic space group P2t/n with cell parameters (at 22°C)a=14.608(6),b=10.466(9),c=17.276(9)Å, β=91.47(6)°, andD calc=1.46 g cm−3 for Z=4. The structure consists of discrete ions with the shortest Na ... Cl distance a lengthy contact of 3.56(1)Å. The average Na...O separation is 2.69(3)Å. The [FeCl4]− anion exhibits a distorted tetrahedral geometry with an average Fe−Cl bond length of 2.16(2)Å.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01667027
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  • 24
    Electronic Resource
    Electronic Resource
    The synthesis and reactivity of the heptanuclear dianion [Os7(CO)20]2− including the synthesis and structural characterizations of the compounds [Os7(CO)20(AuPEt)3 2] and [Os8(CO)20(η6-C6H6] (1995)
    Springer
    Journal of cluster science 6 (1995), S. 163-173 
    Details
    ISSN: 1572-8862
    Keywords: Cluster carbonyl ; osmium ; gold ; arene ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Reduction of the heptaosmium cluster [Os7(CO)21] With [Et4N][NH4) gives the cluster dianion [Os7(CO)20]2−,1, in high yield. The reaction of the dianion with [AuPR 3Cl] (R=Et or Ph) in the presence of TlPF6 forms [Os7((CO)20(AuPR 3)2] [R=Et (2a);R = Ph(2b)] in 80% yield, while the corresponding reaction with (Os(C6H6)(CH3CN)3]2+ gives [Os8(CO)20 (η 6-C6H6)] (3) in reasonable yield (ca. 30%). The dianion,1, and the clusters2 and3 have been fully characterized by bout spectroscopic and crystallographic methods. The crystal structure of the [Ph4P]+ salt of1 shows that the metals in the anion adopt a capped octahedral geometry, with all twenty carbonyl ligands in terminal sites. The metal core geometry in2a is best described as a tricapped octahedron, and is based on the structure of the dianion1 with two adjacent octahedral faces capped by the Au atoms of the two AuPEt3 groups. In a similar fashion, the geometry of3 is related to that of1 with the addition of an Os(C6H6) unit capped to a triangular face, to give a bicapped octahedral framework.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01175843
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  • 25
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of the undecaosmium carbido carbonyl cluster: Crystal and molecular structures of [N(PPh3)2][Os11C(CO)27(μ-Cl)] (1995)
    Springer
    Journal of cluster science 6 (1995), S. 343-346 
    Details
    ISSN: 1572-8862
    Keywords: Undecaosmium carbido cluster ; µ-bridged chlorol preparation ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A chloro-derivative of undecaosmium carbido cluster [Os11C(CO)27(µ-Cl)]-1 anion has been prepared and fully characterized by spectroscopic and crystallographic methods. The structure1 is an important intermediate for the conversion of [Os11C(CO)27]2 2 dianion to [OS10C(CO)24]2-3 dianion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01169700
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  • 26
    Electronic Resource
    Electronic Resource
    Synthesis and structure of a seven electron triangular cluster complex [Mo3S4Cl3(dppe)2(PEt3] (1995)
    Springer
    Journal of cluster science 6 (1995), S. 523-532 
    Details
    ISSN: 1572-8862
    Keywords: Molybdenum ; reduction ; seven-electron triangular cluster ; bridging sulfide ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The triangular six-electron cluster complex [Mo3S4Cl4(PEt3) x (thf)5] produced by the excision reaction of Mo3S7Cl4 with triethypholsphine is reduced by magnesium at − 20°C. Subsequent addition of dppe (=1,2-his(diphenylphosphino)ethane) to the reduced species affords a seven-electron triangular cluster complex [Mo3S4Cl3(dppe)2(PEt3)]. The complex crystallizes in the space groupCm witha=17.170(6),b-19.878(6),c = 13.289(5)β = 121.73(2)°,V = 3858(2) A3, andZ = 2. The structure shows an almost equilateral triangle of three molybdenum atoms capped by a Sulfur atom and bridged by three sulfur atoms. The Mo Mo distances, ranging from 2.804(1) to 2.809(1) A are elongated ca. 0.04 A as compared with lose of a six-electron cluster complex with drape ligands. Two molybdenum atoms have a chlorine and a dppe ligands, and the other molybdenum atom bas a chlorine and a triethylphosphine ligands. The UV-Vis spectrum has a characteristic broad hand centered at 1410 n m, which is not observed for six-electron clusters. The ESR spectrum indicates the presence of an unpaired electron consistent with the formulation of the compound as a seven-electron cluster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01165771
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  • 27
    Electronic Resource
    Electronic Resource
    The 7.25-hydrate oftert-butylamine. A semi-clathrate and complex variant of the cubic 12 Å structure type (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 145-154 
    Details
    ISSN: 1573-1111
    Keywords: tert-Butylamine 7.25 H2O ; amine hydrate ; semi-clathrate ; clathrate hydrate ; hydrate ; hydrogen bonding ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Of the various hydrates oftert-butylamine, the title compound has been identified as the second-highest, melting incongruently at −19°C. Its crystal structure (orthorhombic, space groupPca21,Z=32 formula units per unit cell,a=24.80,b=16.440,c=25.29 Å) and the exact composition have been determined from X-ray diffraction at −150°C. The hydrate is a rather complex semi-clathrate, with the amine molecules not merely encaged, but also hydrogen-bonded, in a three-dimensional water host structure, which in turn is not fully four-connected. Nevertheless, it bears a clear relationship to the basic and genuine clathrate-hydrate cubic 12 Å type.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707689
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  • 28
    Electronic Resource
    Electronic Resource
    TheO, O′-dibenzoyl derivative of (R, R)-tartaric acid as a host compound for simple organic ethers (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 211-219 
    Details
    ISSN: 1573-1111
    Keywords: (R, R)-Tartaric acid derivatives ; host-guest compounds ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract TheO, O′-dibenzoyl derivative of (R, R)-tartaric acid shows a good inclusion ability for diethyl and di-n-propol ethers. The two crystalline inclusion compounds have 1:1 stoichiometry and reveal isomorphous structures. Hydrogen bonded host molecules form chains running along thez axis of the unit cell and guest molecules join to these chains by short O−H...O hydrogen bonds. Hydrogen bonding in the crystals is characterized by a C(7)D first-order network. The ether molecules are in a fully extended conformation. They are accommodated in channel-like voids running along thex axis. Atomic displacement parameters are significantly larger for diethyl ether than for the di-n-propyl ether molecule reflecting less dense packing for this inclusion compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707084
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  • 29
    Electronic Resource
    Electronic Resource
    Crystal and molecular structures of binuclear caesium complexes with 1,3-calix[4]-bis-crown-6 and 1,3-calix[4]-bis-benzo-crown-6 (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 23 (1995), S. 305-312 
    Details
    ISSN: 1573-1111
    Keywords: Bridged calix[4]arene ; caesium complex ; ditopic receptor ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal structures of two binuclear complexes between caesium and 1,3-calix[4]-bis-crowns have been determined. Cs2 Bis-benzoC6(NO3)2. 3CHCl3 (1) in whichBis-benzoC6 is 1,3-calix[4]-bis-benzo-crown-6, crystallizes in the orthorhombic system: space groupPca2 1 a=19.513(10),b=15.382(5),c=23.708(9) Å,V=7116(5) Å3,Z=4. Refinement led to a final conventionalR value of 0.065 for 2321 reflections. The structure of (1) is analogous to those already reported withBis-C6, (in whichBis-C6 is, 1,3-calix[4]-bis-crown-6) and NO 3 − as a counter-ion. Cs2 Bis-C6(NCS)2 (2) crystallizes in the monoclinic system: space, groupC2 a=36.57(2),b=11.47(1),c=13.65(1) Å, β=109.03(5)°.,V=5415(6) Å3,Z=4. Refinement led to a final conventionalR value of 0.063 for 2227 reflections. Compound (2) is made of dimers bridged by a disordered NCS− ion. The crown ether chain conformations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707934
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  • 30
    Electronic Resource
    Electronic Resource
    Structure ofp-tetrakis-(4-nitrophenylazo)calix[4]-arene-4-picoline (1∶4) complex (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 33-40 
    Details
    ISSN: 1573-1111
    Keywords: Calixarene-dye ; crystal structure ; inclusion compound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structure of thep-tetrakis-(4-nitrophenylazo)calix[4]arene-4-picoline (1∶4) complex has been determined by X-ray crystallography. Crystals are monoclinic, space groupC2/c,a=24.9097) Å,b=8.425(6) Å,c=33.81(1) Å, β=101.13(2)°,D c =1.330 g/cm3,Z=4, finalR value =0.067. The cone conformation adopted by this azocalixarene is disturbed by the positions of the picoline molecules. Two of them are inside the macorocycle cavity and the two others are outside.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00706496
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  • 31
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    Electronic Resource
    Crystal structure of supramolecular complexes formed by 18-crown-6 andcis-anti-cis-dicyclohexano-18-crown-6 (host) with 3,4-diaminofurazane (guest) (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 23 (1995), S. 181-193 
    Details
    ISSN: 1573-1111
    Keywords: 18-crown-6 ; diaminofurazane ; crystal structure ; host-guest complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An X-ray—diffraction study is reported for two molecular complexes containing 3,4-diamino-1,2,5-oxadiazole as guest (G) with 18-crown-6 (18-C-6) andcis-anti-cis-dicyclohexano-18-crown-6 (DCH-6B) as host. Both complexes are of the polymeric-chain structure with the guest molecule bridging two crown neighbours. ComplexI: [18-C-6*G*H2O], 1∶1∶1, monoclinic,P21/n,a=8.171(1),b=15.042(2),c=16.209(6) Å, β=101.15(2)°, finalR-factor 0.068. ComplexII: [DCH-6B*G], 1∶1, monoclinicC2/c,a=21.212(4),b=9.380(2),c=13.049(3) Å, β=108.61(3)°, finalR 0.047.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00709576
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  • 32
    Electronic Resource
    Electronic Resource
    New synthesis and complexing properties ofp-tert-butyldihomooxacalix[4]arene. Structure of its 1∶2 complex with tetrahydrofuran (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 119-130 
    Details
    ISSN: 1573-1111
    Keywords: Calixarene ; complexation ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new method is described for the synthesis of isolatedp-tert-butyldihomooxacalix[4]arene (CALO) with a 24% yield. The ability of CALO to form complexes in the solid state with small neutral molecules has been studied; the potential guests were common solvents bearing various chemical functions. The powder obtained after evaporation of the solvent has been characterized by the X-ray powder diffraction technique. Analysis of the patterns shows the non-complexation of linear alkanes and alcohols, but formation of complexes when the guest is cyclic or when it bears an amine or a ketone function. As illustration of the possible arrangement of molecules in complexes, the structure of the 1:2 complex with tetrahydrofuran (THF) is presented: the crystals are monoclinic, space groupP21/c,a=9.459(2) Å,b=17.286(2) Å,c=30.469(6) Å, β=92.52(2)o,V=4977(2) Å3,Z=4,D c=1.099 Mg m−3, λ=1.54178 Å, μ=5.6 cm−1,R=0.086 for 3590 reflections withF〉4σ (F); one of the THF molecules is inside the cavity of the macrocycle, while the other, in the interhost space, exhibits disorder. In the CALO molecule, three out of the fourtert-butyl groups are disordered which may induce the disorder of the THF molecule.
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    URL: http://dx.doi.org/10.1007/BF00707687
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  • 33
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    Inclusion compounds of (±) gossypol. Structure of the gossypol-n-valeric acid (1/2) coordinato-clathrate (1995)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 22 (1995), S. 187-201 
    Details
    ISSN: 1573-1111
    Keywords: Inclusion compounds ; gossypol ; crystal structure ; hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal structure of the inclusion compound of gossypol withn-valeric acid as a guest molecule has been determined by X-ray structure analysis. The crystals of C30H30O8·(C5H10O2)2, are triclinic, space group $$P\bar 1$$ ,a=6.912(2),b=14.506(3),c=19.387(4) Å, α=78.85(2)°, β=83.92(3)°, γ=86.78(3)°V=1895(1) Å3,Z=2,D x=1.267 g cm−3, μ (CuK α)=0.768 mm−1,T=292 K. The structure has been solved by direct methods on intensity data collected for a twinned crystal and refined to the finalR value of 0.062 for 1606 observed reflections and 470 refined parameters. Gossypol-n-valeric acid (1/2) coordinato-clathrate is not isostructural with any of the previously investigated gossypol inclusion compounds but shows some structural similarities to gossypol-acetic acid (1/1). The host and one of the carboxylic acid molecules are connected via hydrogen bonds into molecular assemblies of a column type which are further bonded to centrosymmetric dimers of the secondn-valeric acid molecule. In effect, host and guest molecules are assembled into layer-type H-bonded aggregates. Structural features common to gossypol-n-valeric acid (1/2) and other earlier reported gossypol inclusion compounds are discussed.
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    URL: http://dx.doi.org/10.1007/BF00707082
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  • 34
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    Electronic Resource
    Binding geometry of α-helices that recognize DNA (1995)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 23 (1995), S. 525-535 
    Details
    ISSN: 0887-3585
    Keywords: DNA-protein interaction ; crystal structure ; transcription factor ; gene regulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Many transcription factors have an α-helix that binds to DNA bases in a specific fashion. The DNA-binding geometry of these recognition helices varies substantially. We define a set of parameters to describe the binding geometry of recognition helices and analyze specific stereochemical elements that determine particular geometries. Because the convex surface of the helix must fit into the concave surface of the DNA major groove, the number of degrees of freedom of the recognition helix is reduced from a possible six to a single angle, which we call α. The chemically interacting DNA bases and amino acid residues must lie along a common line and have the same spacing along it. This pairing of base positions with residue positions seems to restrict the binding geometry further to a set of discrete values for α. © 1995 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/prot.340230407
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  • 35
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    Absolute configurations and conformations of the opioid agonist and antagonist enantiomers of picenadol (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 518-525 
    Details
    ISSN: 0899-0042
    Keywords: crystal structure ; molecular mechanics ; MM2-87 ; opioid ligand model ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The absolute configurations of the enantiomers of the opiod picenadol [cis-1,3-dimethyl-4-propyl-4-propyl-4-(3-hydroxyphenyl)piperidine; cis-3-methyl, 4-propyl] have been determined by an X-ray crystallographic study of the chloride salt of the (+)-enantiomer. The agonist (+)-enantiomer and the antagonist (-)-enantiomer were found to have the 3R, 4R and 3S, 4S absolute configurations, respectively. The conformational properties of the enantiomers were also examined with MM2-87 calculations. There was good agreement between the computed global minimum and the crystallographic structure with the phenyl ring approximately bisecting the piperidine ring by both methods. This orientation of the phenyl ring differs from that of related opioids such as the phenylmorphans, prodines, meperidine, and ketobemidone in which the phenyl ring tends to eclipse one edge of the piperidine ring. Because the phenyl ring bisects the piperidine ring in picenadol, there is little difference in the three-dimensional orientations of the phenyl rings of the two enantiomers when one superimposes the piperidine rings. The agonist (+)-enantiomer is ambiguous with respect to an opioid ligand model, which suggests that agonist activity requires a specific range of dihedral angles for the phenyl ring. While the global minimum of the agonist is not consistent with the model, a second conformer that is only 1.2 kcal/mol above the global minimum is consistent. An alternative explanation is that agonist or antagonist activity is solely due to the presence of the 3-methyl group on the different edges of the piperidine ring. MM2-87 calculations were also performed on the opioid agonist des-3-methyl analog of picenadol and the closely related trans-1,3,4-trimethyl-4-(3-hydroxyphenyl)piperidines (trans-3-methyl, 4-methyl) in which both enantiomers are opioid antagonists. The conformational properties of these compounds are consistent with the ligand model. © 1995 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070705
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  • 36
    Electronic Resource
    Electronic Resource
    Masthead (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080101
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  • 37
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    Announcement (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. i 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080102
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  • 38
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    Relative thermodynamic stabilities of 2-(methoxymethylene)tetrahydrofuran and 5-methoxymethyl-2,3-dihydrofuran (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 1-4 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relative thermodynamic stabilities of the title compounds were determined by iodine catalyzed chemical equilibration in cyclohexane solution. The main point of interest was a determination of the thermodynamic stability of the —O—C=C—O— moiety found in the exocyclic isomers, i.e. the stabilizing effect of a MeO group on the olefinic linkage of 2-methylenetetrahydrofuran. All three isomeric compounds have essentially similar enthalpy values, which, in comparison with some previous thermodynamic data, shows that the double bond stabilization energy of the MeO group in the exo isomers is only ca 3 kJ mol-1. The entropy difference between the geometrical isomers is negligible, whereas the endo isomer is favoured by an entropy contribution of ca 9 J K-1 mol-1.
    Additional Material: 1 Tab.
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    Hyperbolic Model for the meta-para interrelationship in benzene derivatives (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 5-14 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new approach to the long-standing problem of interrelating meta and para substituent constants is presented. An analysis of the unified σ0-scale shows that the interrelation between σ40 and σ40/σ30 can be modelled by a pair of conjugate rectangular hyperbolae, one for normal (n) and the other for special (s) substituents. The latter are characterized by a lone electron pair in the first atom. The equations σ4n0 (σ4n0 - γ0)/(σ4n0 - 2γ0) = λ0 σ3n0 and σ4s0 = γ0 + λ0 σ3s0 are derived and discussed in terms of Taft's separation of mesomeric and non-mesomeric effects. Asymptotic values λ = 0.960 γ = -0.225 were obtained by non-linear least rectangles fitting. A nonnegligible mesomeric contribution to σ0 constants for normal substituents is predicted by the hyperbolic model. The present results are at variance with Exner's analysis of the meta-para interrelationship in benzene compounds with normal substituents. This divergence is ascribed to opposite views concerning the role of the π-inductive effect.
    Additional Material: 4 Ill.
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    Photoisomerization of 3-benzoylacrylates on a silica gel surface: Effect of reaction environment on selectivity (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 31-34 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: On irradiation on a dry silica gel surface, 2-(N, N-dialkylamino)ethyl 3-benzoylacrylates undergo selective E-Z isomerization. Competing processes, such as remote-hydrogen abstraction via a charge-transfer state, with the photoisomerization in solution are completely suppressed on the surface. The yield of the Z - from the E- isomer increases with increase in the coverage of the E-isomer on the surface, reaching a limiting value. Thermal isomerization of the Z- to the E- isomer occurs easily on the silica gels surface when the alkyl group on the nitrogen atom is small. Benzoylacrylates without any amino group also undergo selective photoisomerization.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080107
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    Solvation effects on the relative basicity of propylamines (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 26-30 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Slight structural moiecular variations are known to affect different properties of compounds. In solution, different solute-solvent interactions are known also to alter the properties of numerous compounds. Quantitative structure-activity relationships (QSAR) are used regularly to analyze and predict the variations of different properties of compounds that are caused by structural variations and significant solute-solvent interactions. The relative basicities of n-propylamine, dipro;ylamine and tripropylamine were determined in nine different solvents from potentiometric titrations. QSAR that were developed from these experimental basicity values were used to evaluate the type and significance of the solute-solvent interactions. The important interactions that influence basicity variations for the propylamines studied are dipolarity-polarizability interaction between the solute and the solvent and hydrogen bonds from the propylammonium ions to basic solvents. The role of hydrogen bonds from the propylamines to acidic solvents is minor.
    Additional Material: 2 Tab.
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    Interrelations Of the energetics of amides and alkenes: Enthalpies of formation of N,N-dimethyl derivatives of pivalamide, 1-adamantylcarboxamide and benzamide, and of styrene and its α-, trans-β- and β,β-methylated derivatives (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 15-25 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enthalpies of formation of the condensed phase and gaseous N,N-dimethyl derivatives of pivalamide, 1-adamantylcarboxamide and benzamide were determined by combustion calorimetry and the associated enthalpies of vaporization and sublimation. The enthalpies of formation of styrene and its α-, trans-β- and β,β-methylated derivatives were determined from measurements of their enthalpies of hydrogenation in dilute hydrocarbon solution. Strain and resonance effects of amides and alkenes are discussed in terms of the exo-/endothermicity of the following reactions: and in terms of the difference of enthalpies of formation of the isomeric (Z)- and E-RCH=CHCH3.
    Additional Material: 6 Tab.
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    Substituent effects for the BF3-mediated reactions of allyltributyltin and allyltriethyllead with benzaldehyde (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 35-40 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Substituent effects were measured for the reactions of substituted benzaldehydes with allytributylin (1) and allyltriethyllead (2) reagents in the presence of BF3.OEt2 in CH2Cl2. The Hammett p values were small and positive at 25 °C and negative at -78 °C for both 1 and 2. These could be interpreted in terms of the contribution of electrophilic complexation between the aldehyde function and BF3 as a rate-limiting step. A large negative p value was observed for the complex-formation equilibria between substituted benzaldehydes and BF3.
    Additional Material: 3 Ill.
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    Control of the thermal cis to trans isomerizations of azobenzene and thioindigo derivatives by the formation of supramolecular H-bonded assemblies (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 54-62 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 2,3-Bis(aminocyclohexyl)-6-methoxy-1,3,5-triazine (1a) forms intermolecular H-bonded complexes with 3,3′-diacetyl-cis-azoenzene (4) and 6,6′-diethoxy-cis-thioindigo (5b), (association constants K = 4.9 × 104 and 3.5 × 105 1 mol-1, respectively). The thermal cis→trans isomerization of 4b and 5b to 3,3′-diacetyl-trans-azobenzene (4a), and 6,6′-diethoxy-trans-thioindigo (5a), is inhibited in the intermolecular complex 1a-4b and 1a-5b. Molecular mechanics calculations support the formation of the intermolecular H-bonded complexes between 1a and 4b or 5b.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080111
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    Reaction of phenoxy radical with nitric oxide (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 47-53 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The associationof C6H5O with NO was studied with the cavity-ring-down method by directly monitoring the decay of C6H5O in the presence of varying, excess amounts of NO. The biomolecular rate constant determined in the temperature range 297-373 K can be effectively rate constant determined in the temperature range 297-373 K can be effectively represented by k1 = 10- 12 · 12 ± 0.24e (194±185)/r cm3 molecule-1 with a negative activation energy of 0.8 kcal mol-1 (1 kcal = 4.184 kJ). In order to understand better the mechanism of the reaction, ab initio molecular orbital calculations were also carried out at the MP4(SDQ)/6-31G* level of theory using the HF optimized geometries. The molecular structues and energetics of five C6H5N1O2 isomers were calculated. Among them, the most likely and stable association product, phenyl nitrite (C4H5ONO), was found to be 17 kal mol-1 below the reactants, C6H5O + NO. Combining the measured rate constant and the calculated equilibrium constant for the association reaction, C6H5O + NO = C6H5ONO the rate constant for the unimolecular decomposition of C6H5ONO was obtained as k-1 = 4.6 × 1015E-8580/T s-1. The relatively large frequency factor suggests that a loose transition state was involved in the reaction, akin to those of its alkyl analogs (RONO, R = CH3, C2H5, etc.).
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080110
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    Structural study on quasi-phosphonium salts containing phosphorus-oxygen, phosphorus-oxygen, phosphorus-nitrogen and phosphorus-sulphur bonds (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 41-46 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal and molecular structues of six quasi-phosphonium salts containing phosphorus-heteroatom heteroatom=oxygen, sulphur or nitrogen0 bonds were determined. Comparison of the molecular parameters obtained with those available for reference structures demonstrated that the ‘double bond’ character for the P+ — Y bond decreases in the order Y = N ≫ O 〉 S.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080109
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    Masthead (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080201
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    Pressure and solvent effects on the kinetics of a Menshutkin reaction in aliphatic alcohols (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 63-70 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the Menshutkin reaction between triethylamine and iodoethane was studied at 313 K in seven primary and secondary alkanols. An accurate conductimetric method was employed to obtain second-order rate constants at pressures of 0·1-200 MPa. Volumes and isothermal compressions of activation were calculated by different model-based equations which are compared. Activation volumes at 0·1 MPa are in the range -26 to -33 cm3 mol-1. Procedures for dissecting intra- and intermolecular contributions to the volume of activation are discussed. A clear dependence of model parameters on the solvent volumetric properties was found.
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    URL: http://dx.doi.org/10.1002/poc.610080202
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    Oil-in-water microemulsions based on chemodegradable surfactants as reaction media (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 71-76 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of 2-(p-nitrophenyl)ethyl bromide with hydroxide ion was studied in oil-in-water (o/w) microemulsions at 50°C. The octane-in-water microemulsion systems were stabilized by chemodegradable cyclic acetal-type cationic surfactants as [(2-alky-1,3-dioxolan-4-yl)methyl]trimethylammonium bromides Ia-c (alkyl: a = n-C9H19; b = C11H23; c = C13H27) and butan-1-ol as co-surfactant. The rate constants were also determined in the corresponding aqueous micelles and in water. The hydrolytic lability of Ia-c in the microemulsion systems was achieved at 50°C by acid hydrolysis of the 1,3-dioxolane ring. Systematic synthetic studies of the dehydrobromination were performed in order to develop a preparative approach for the product separation without unfavourable process such as foaming and emulsification.
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    URL: http://dx.doi.org/10.1002/poc.610080203
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    Infrared study of the proton acceptor ability of metyrapone (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 77-83 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The hydrogen bond complexes between metyrapone [methyl-1,2-di(3-pyridyl)propan-1-one] and hydroxylic proton donors (phenols, water) were investigated by infrared spectroscopy. The thermodynamic and spectroscopic data determined in carbon tetrachloride suggest that the nitrogen atom of the pyridine ring A [bonded to the C(CH3)2 group] is the main hydrogen bond interaction site. The data are compared with di-2-pyridylglyoxal complexes where the hydrogen bonds are formed on the oxygen atom of the carbonyl function. In the solid adduct of metyrapone with HCl, protonation takes place on the two nitrogen atoms of the pyridine rings. The data from this work are compared with those from chemical oxidation, which leads predominantly to the formation of mono-N-oxide A and di-N-oxide.
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    URL: http://dx.doi.org/10.1002/poc.610080204
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    Isotherm of water sorption by human serum albumin in dioxane: Comparison with calorimetric data (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 84-88 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependence of the amount of water bound to human serum albumin (HSA) suspended in water-dioxane mixtures vs the equilibrium water concentration in the liquid phase was determined by the Fisher method at 298 K. The Langmuir model was used in order to describe the isotherm of the sorption of water by HSA at low water concentrations in the solvent. The calculated equilibrium constant of water adsorption (3.8 ± 0.6 l mol-1) is in good agreement with the adsorption constant obtained earlier from calorimetric data. The comparison of the determined isotherm of water sorption by HSA with the reported enthalpies of suspension formation showed that at low water concentrations in the solvent, water sorption is the only process contributing to the heat effects of the formation of the ‘protein + liquid’ heterogeneous system. From this comparison, the enthalpy of water adsorption by HSA was evaluated as -11.9 ± 1.7 kJ mol-1. At higher water concentrations in the solvent the amount of water adsorbed by HSA increased considerably. This increase in the amount of water on HSA at water activities above 0.5 is assumed to be due to the enlargement of the protein surface area.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080205
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    The solvent effect on the conformational equilibria of 4-substituted cyclohexenes (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 89-93 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Conformational preferences have been measured for 4-X-cyclohexenes (X = Br, Cl, CHO, COOH) in a series of solvents with increasing polarity. The conformational equilibrium exhibits a very weak solvent dependence. ΔG varies at most by 0·25 kcal mol-1 (1 kcal = 4·184 kJ) shifting from a non-polar mixture (CS2-CDCI3) to highly polar (CD3)2SO. The reaction field theory was used to calculate the variation of ΔG with solvent polarity. The calculated solvent shifts δΔG are small and in agreement with the values determined experimentally.
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    URL: http://dx.doi.org/10.1002/poc.610080206
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    A remarkably bent allene. X-Ray crystal structure and ab initio calculations (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 94-96 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: X-ray data on the crystal and molecular structure of bis(biphenyl-2,2′-diyl)allene, reveal a remarkably strong deviation from linearity (170·1°) of the allene unit of the molecule. Ab initio calculations involving dimers of molecules yield good correlation with this geometry, showing that the non-linearity is due to packing effects in the crystal.
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    Kinetics of the reaction of amines with 1,1,1-trichloro-4-methoxy-3-penten-2-one (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 97-102 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the reaction of 1,1,1-trichloro-4-methoxy-3-penten-2-one with various aliphatic and aromatic amines was studied at 25°C in water, dimethyl sulphoxide, methanol, ethanol, chloroform, toluene and hexane. The formation of the corresponding 1,1,1-trichloro-4-amino-3-penten-2-one is explained in terms of an addition-elimination mechanism.
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    Are kekulene, coronene, and corannulene tetraanion superaromatic? Theoretical examination using hardness indices (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 103-107 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The superaromaticity concept is examined and developed, taking into account what is known about aromaticity. Three new hardness indices indices are defined, and shown to be excellent parameters for characterizing superaromaticity. High superaromaticity indicates significant global annulenoid conjugation relative to local benzenoid conjugation in circularly annealed benzenoid molecules. Kekulene, coronene and corannulene tetraanion all are predicted to be superaromatic. The prediction for the corannulene tetraanion strongly supports the “annulene-within-an-annulene” structure derived from NMR data.
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    Enthalpies of micelle formation by hexadecyltrimethylammonium bromide in aqueous solution containing pentanol (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 108-112 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Titration calorimetric data show a dramatic change from endo- to exothermic deaggregation when pentanol-hexadecyltrimethylammonium bromide (CTAB) mixed solutions are injected into an aqueous solution containing pentanol. The results are interpreted in terms of a change in the structures of the aggregates in solution from simple CTAB micelles to mixed amphiphilic microheterogeneities when pentanol is added.
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    Amines as leaving groups in nucleophilic aromatic substitution reactions. III.For Part II, see Ref. 2. Hydrolysis of 1-amino-2,4-dinitrobenzenes (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 113-120 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetic study of the reaction of 1-pyrrolidino-2,4-dinitrobenzene, 1-piperidino-2,4-dinitrobenzene and 1-morpholino-2,4-dinitrobenzene with NaOH in the presence and absence of the amine leaving group was carried out in aqueous solutions at 25°C, giving 2,4-dinitrophenol as the only product. A mechanism involving the formation of σ complexes by addition of HO- or the amine to the unsubstituted positions of the aromatic ring is proposed. These complexes were found to react faster than the original substrates.
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    Masthead (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080301
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    Efficient and/or selective methylation by diazomethane of alcohols, halo alcohols, glycols, amino alcohols and mercapto alcohols with the use of a proton-exchanged X-type zeolite as an acid-base bifunctional catalyst (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 121-126 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Reactions of diazomethane with butanol, allyl alcohol and β- and γ-halo alcohols led to efficient methylation (giving the corresponding methyl ethers) with the use of a proton-exchanged X-type zeolite compared with H2SO4. The reactions with propylene and isobutylene glycols using the zeolite provided regioselective methylation of the primary OH rather than the secondary or tertiary OH, whereas regioselectivity was not observed in the reactions using H2SO4. The reactions with 2-aminoethanol and 2-mercaptoethanol showed high chemoselective S-methylation and N-monomethylation, respectively, in the presence of the zeolite instead of H2SO4. The mechanism for the reactions is proposed to involve acid-base bifunctional catalysis of the zeolite in which the acidic site reacts with diazomethane to form its conjugate acid, and the nucleophilicity of OH and SH groups is enhanced by the interaction of the basic site with the proton of the groups.
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    URL: http://dx.doi.org/10.1002/poc.610080212
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    Theoretical studies on the acid-catalysed aromatization of benzene-cis-1,2-dihydrodiolsDetermination of Reactivity by MO Theory, Part 92. For Part 91, see Reference 1. (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 127-131 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Theoretical studies on the acid-catalysed dehydration of 15-substituted dihydrodiols were carried out using the AM1 method. In agreement with the experimental results, the rate-limiting step is dehydration of the protonated diols, R+, and the o-phenol-forming pathway (path 1) is favoured both kinetically and thermodynamically over m-phenol product formation. The transition state for path 1 (TS 1) is found to be at an early position (ca 23% progress) along the reaction coordinate and a better correlation of the rate constant is obtained with σ+. Three resonance forms can exist for the benzenonium intermediate but the contribution of one form is dominant in the later TS, which resembles the cationic intermediate. The contribution of the other two, however, weakens the σ+ effect of +M subsituents. The σP correlation of the rate constant in acid solution is therefore suggestive of a later TS resembling the cationic intermediate which is stabilized by solution.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080213
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    Several mechanisms in the elimination kinetics of ω-chlorocarboxylic acids in the gas phase (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 133-138 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the gas-phase pyrolysis of ω-chlorocarboxylic acids were examined in a seasoned static reaction vessel and in the presence of at least twice the amount of the free radical inhibitor cyclohexene or toluene. In conformity with the available experimental data on rate determination, these reactions proved to be unimolecular and obeyed a first-order rate law. The presence of the primary chlorine leaving group in Cl(CH2)nCOOH (n = 1-4) showed a change in mechanism from intramolecular displacement of the Cl leaving group by the acidic hydrogen of the COOH to anchimeric assistance of the carbonyl COOH to the C—Cl bond polarization in the transition state. This mechanistic consideration is nearly the same for the series of 2-, 3-, and 4-chlorobutyric acids. The chlorine atom at the 2-position of acetic, propionic and butyric acids is dehydrochlorinated through a prevailing reaction path involving a polar five-membered cyclic transition state.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080302
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    First successful correlation of the UV spectra of three kinds of styrenes with spin-delocalization substituent constants σ. (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 143-148 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: UV spectra of 17 para-Y-substituted styrenes, 8 para-Y-substituted α-methylstyrenes and 20 para-Y-substituted α,β,β-trifluorostyrenes were measured and correlated against spin-delocalization substituent constants (σ.) with confidence levels above 99·9%.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080304
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    Kinetic studies on the pyramidal inversion of optically active selenonium imides (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 139-142 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Kinetic studies were carried out on the thermal epimerization by pyramidal inversion of optically active (S)-(-)Se- and (R)-(+)Se-4-[(-)-menthyloxycarbonyl]phenyl(2′,4′,6′-triisopropylphenyl)selenonium-N-toluene-4″-sulphonimides (1). The first-order rate constants for the pyramidal inversion of (S)-(-)Se-1 and (R)-(+)Se-1 were determined and the activation enthalpies and entropies were calculated. A fairly large difference was found in the activation parameters between optically active (S)-(-)Se-1 and (R)-(+)Se-1, i.e. a large negative activation entropy was obtained in the case of (R)-(+)Se-1.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080303
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    Nature of the highest occupied molecular orbitals of trans- and cis-bicyclo[4.1.0]hept-3-enes (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 149-158 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Photoelectron spectra of trans-bicyclo[4.1.0]hept-3-ene and two methyl derivatives, 1-3, and cis-bicyclo[4.1.0]hept-3-ene and three of its derivatives, 4-7, were measured. Ab initio molecular orbital (MO) and density functional theory (DFT) calculations were performed on these compounds. By combining the results of the experimental and computational trends, it was established that the highest occupied molecular orbitals (HOMOs) of 1-3 are the ‘twist’ bent σ bond at the fusion between the two rings whereas for 4-7 the HOMOs are the π orbital in the six-membered ring. The DFT ordering is the same as that suggested by the photoelectron spectra whereas at the MO level the HOMO always corresponds to the π orbital. The intensities of the photoelectron spectra were calculated at the DFT level and good qualitative agreement with experiment was found.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080305
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    The question of pentaphenylethyl: An AM1 study (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 171-174 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Semi-empirical AM1 theoretical calculations were carried out on the pentaphenylethyl and 9-trityfluorenyl free radicals, related radicals and their precursor hydrocarbons. Previous reports of the preparation of the former radical have been questioned, although the existence of the second is on secure ground. Based on simple energy considerations, it is concluded that pentaphenylethyl should be as readily prepared. However, the acidity of the precursor hydrocarbon is considerably less than that of 9-tritylfluorene, and possible radical decomposition via dissociation to triphenylmethyl and diphenylcarbene is calculated to be more facile than the corresponding decomposition of 9-tritylfluorenyl. A previous postulation of a rapid phenyl equilibration of the pentaphenylethyl radical is shown to be untenable.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080307
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    Dicarboximide-based clathrate design. Host synthesis, inclusion formation and x-ray crystal structures of a free host and of inclusion compounds with 2- and 3- methylcyclohexanone, 3-methylcyclopentanone, butyronitrile, propan-1-ol and (-)-fenchone guests (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 159-170 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystalline host compounds consisting of a roof-shaped dicarboxinide framework and pendant diarylethanol analogous subunits were synthesized and shown to form inclusion complexes with small organic molecules such as alcohols, amines, ketones or polar and apolar organic solvents. Clathrate efficiency and selectivity depend on the particular host structure. The crystal and molecular structures of a free host compound (2a) and inclusion compounds [2a·3-methylcyclohexanone (1 : 1), 1a·3-methylcyclopentanone (1 : 1), 1a·2-methylcyclohexanone (1 : 1), 1b·butyronitrile (1 : 1), 1b·propan-1-ol (2 : 1) and 1b·(-)-fenchone (1 : 1)] were determined by x-ray diffraction analysis. In all the structures, the hydroxyl group is involved in intramolecular hydrogen bonds and the host and guest molecules are held by lattice forces only. The channels and cavities left in the host matrix are large enough to allow disorder or high thermal displacement parameters of the guest molecules. The local packing coefficients for all guests are 0·42 on average.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080306
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    Unusually large kinetic deuterium isotope effects on oxidation reactions. 1. The mechanism of hydroxide-catalysed permanganate oxidation of PhCD(CF3)OH and PhCD(CH3)OH in WaterPresented in part at the 12th IUPAC Conference on Physical Organic Chemistry, Padova, 1994. (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 186-190 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The oxidation of 1-phenyl-2,2,2-trifluoroethanol (ROH) with potassium permanganate in 0.2 M aqueous sodium hydroxide solution at 25 °C provides 2,2,2-trifluoroacetophenone as the sole product. The reaction rate constant, which was measured under pseudo-first order conditions by following the decrease in substrate concentration as a function of time, was found to be substantially smaller than previously reported. The primary kinetic deuterium isotope effect was measured as k2H/k2D = 14·7 ± 1·0. A hydrogen-transfer mechanism involving significant tunnelling is proposed. The oxidation of 1-phenylethanol under similar reaction conditions yields acetophenone as the initial product. The kinetic deuterium isotope effect was found to be k2H/k2D = 5·2 ± 0·8.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080309
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    The search for the ethynylcation: Nitrosation of N,N-bis(trimethylsilyl)ynamines (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 191-194 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of bis-silylated ynamines with different nitrosyl reagents affords products derived from an electrophilic attack at the β-carbon atom and not the expected alkynyldiazonium salts.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610080310
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    Masthead (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080401
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    Guest Editorial (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 195-195 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080402
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    Introduction to living polymeriz. Living and/or controlled polymerization (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 197-207 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of various imperfections such as slow initiation, termination, transfer and slow exchange on kinetics, molecular weights and polydispersities in chain growth polymerizations are simulated. The simukations demonstrate that well defined polymers polymers can be prepared in systems with chain-breaking reactions. Thus, under carefully selected conditions, non-living polyumerizations may provide controlled polymers. On the other hand, polymers with unpredictable molecular weights and broad and even polymodal molecular weight distributions can be formed in living systems without irreversible transfer and termination. In some living systems molecular weights may stay constant or even decrease with conversion. Therefore, a clear distrinction should be made between living and polymerizations.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080403
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    Living carbocationic copolymerizations. I. Synthesis and characterization of isobutylene/p-methylstyrene copolymers (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 258-272 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The isobutylene (IB)-p-methylstyrene (pMeSt) monomer pair readily produces by living copolymerization nearly random copolymers with up to M̄n ≈ 50,000 g mol-1 and M̄w/M̄n ≈ 1·4. The livingness of the copolymerization process and the compositional homogeneity of the copolymers have been demonstrated by the following four diagnostic plots: (A) M̄n (number-average molecular weight) and corresponding N (number of moles of copolymer formed) vs Wp (weight of copolymer formed) for the diagnosis of chaintransfer; (B) -ln (1 - C) (C = conversion of monomers) vs time for the diagnosis of termination; (C) copolymer composition vs molecular weight; and (D) cumulative copolymer composition vs conversion for the diagnosis of true homogeneous copolymers. The theory for the use of the -ln(1 - C) vs time plot for the quantitation of irreversible termination in copolymerization has been developed. The exact conditions (i.e. nature of reagents, reagent concentrations, temperature, etc.) which lead to desirable products in terms of conversion, molecular weight, molecular weight distribution (MWD) and copolymer composition, were developed systematically by analyzing the results of a large number of experiments. The following combination of chemicals was found to lead to living copolymerization, and uniform high molecular weight, narrow MWD copolymers: IB-pMeSt 97 : 3 mol/mol with 5-tert-butyl-1,3-dicumyl methyl ether (5-tBu-1,3-DiCumOMe) initiator, TiCl4 coinitiator, ethyl chloride (EtCl) solvent, triethylamine (TEA) electron pair donor (ED) and 2,6-di-tert-butylpyridine (DtBP) proton trap at -52, -65 and -85°C.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080409
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    Living carbocationic copolymerizations. II. Reactivity ratios and microstructure of isobutylene/p-methylstyrene copolymers (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 273-281 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel method was developed for the quantitative description of copolymerization behavior, specifically for the derivation of reactivity ratios and micro- and macro-compositions of monomer pairs with significantly different reactivities. The novelty of the method lies in the manner of generating instantaneous feed and copolymer composition data from experimentally readily obtainable cumulative copolymer compositions, although the latter drifts with progressing copolymerization. It is demonstrated that such copolymer systems can be described by two reactivity ratios, albeit the values are valid only over the narrow feed composition range within which they were determined. The great advantage of this method is that whereas the differential copolymer composition equation is strictly valid only at 0% conversion, the method produces corresponding instantaneous feed and copolymer compositions at any conversion. Assumptions or approximations are unnecessary to calculate reactivity ratios. Subsequently the procedure was applied to obtain reliable monomer reactivity ratios of isobutylene (IB)-p-methylstyrene (pMeSt) copolymers, rIB and rpMest, prepared by living carbocationic copolymerizations with [IB]/[pMeSt] feeds compositions of 90:10 and 97:3 mol/mol, i.e., with feed compositions of industrial importance. According to our procedure, rIB = 0·74±0·11 and rpMeSt = 7·99±3·34. These reactivity ratios were then used to calculate overall IB-pMeSt copolymer compositions over the entire comonomer conversion range and to compare calculated with experimental compositions. The good quantitative agreement between calculated and experimental compositions indicates that the description of both macro- and micro-compositions of IB-pMeSt copolymers obtained in the 90:10 and to 97:3 mol/mol feed composition range is satisfactory.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080410
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    Nitroxide mediated free radical polymerization process - autopolymerization (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 301-305 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The autopolymerization of styrene in the presence of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy free radical), with and without organic acids, such as benzoic acid and camphorsulfonic acid, was studied. Broad polydispersities are obtained in the absence of acid, whereas narrower polydispersities are obtained in their presence. The significance of these results for the synthesis of narrow polydispersity polystyrene by the TEMPO-mediated living polymerization process is discussed.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080413
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    Nucleophilic substitution at nitrogen-centered radicals: Reactions of diphenylphosphide ions with N,N-dibutyl-p-toluenesulfonamide by the SRN1 mechanism (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 356-358 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photostimulated reaction of N,N-dibutyl-p-toluenesulfonamide with diphenylphosphide ions in liquid ammonia leads to the corresponding phosphinic amides after oxidation Inhibition experiments with p-dinitrobenzene and 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO) and the fact that the reaction is retarded in the dark suggest that it proceeds by the SRN1 mechanism.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610080507
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    Complexation of tropylium ions with crown ethers and acyclic polyethers examined by fast atom bombardment mass spectrometry (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 377-384 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular complex formation of six macrocyclic and six acyclic polyethers with tropylium and 4-methoxyphenyltropylium tetrafluoroborates was observed and characterized in the gas phase by fast atom bombardment mass spectrometry (FABMS), to obtain information on intrinsic molecular interactions in the absence of the complicating effect of solvation. The stoichiometry of the complexes was assessed on the basis of corresponding peaks in FAB mass spectra. In addition to the expected 1 : 1 complexes between polyether and tropylium ion, some 2 : 1 complexes were also formed. The stability order of selected complexes was studied in competition experiments. The complexation equilibrium constant and thermodynamic parameters for the interaction of dibenzo-18-crown-6 with tropylium ion were determined in 1,2-dichloroethane solution by UV-visible spectrophotometry. Complexation of polyethers with tropylium salts has not been reported previously.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080511
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    Masthead (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080601
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    Aqueous solvation effect on the prototropic tautomerism of 2-thiocytosine (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 395-399 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Free energies of solvation were calculated for the four most stable gas-phase tautomeric forms of 2-thiocytosine (TC) using a local field SCF procedure with the solvation model SM2. The calculated changes in the free energies for each pair of tautomers reveal that all six possible equilibria tend to produce the thione-amino TC(1, 8, 8) and TC(3, 8, 8) species. This is in agreement with UV and ionization constant data.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080603
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    Radiolytic studies of the reductive cyclization of 2-nitroarylamides: Cyclization via hydroxylamine intermediates (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 587-596 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reductive cyclization of several 2-nitroarylamides was studied by radiolytic reduction, examining the effects of substituents on the nitrophenyl ring and on the leaving aniline and variations in the nature of the link between the nitrophenyl ring and the leaving aniline. The stoichiometry of the reduction and the identification of N-hydroxylactam and aniline products suggest that the major initial products of such a reduction of the nitroamides are the corresponding hydroxylamines. Under anaerobic conditions, cyclization via the hydroxylamines was considerably faster (up to 160-fold) than via the corresponding amines under comparable conditions, but was similarly influenced by changes in geometry. Unlike cyclization via the amines, rates of cyclization via the hydroxylamines were sensitive to substitution on the leaving aniline, being accelerated by electron-withdrawing groups. The rate-determining step in the cyclization of the hydroxylamines is proposed to be breakdown of the tetrahedral intermediate.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080904
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    Mono-, bis- and tetra-acridine ligands: Synthesis, X-ray structural determination and dynamic fluorescence microscopic studies on the modification of the higher order structure of DNA (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 597-604 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A series of mono-, bis- and tetra-acridine ligands were prepared and their effects on the higher order structure of DNA were studied by dynamic fluorescence microscopy. The single-crystal structure of the bis-acridine derivative N-[2-(dimethylamino) ethyl]-4-[2-(9-acridinylamino)benzamido]-2-(9-acridinylamino)benzamide trihydrochloride (4) was determined, and shows that the molecule is sufficiently flexible to fold into an intramolecular stacking interaction in the crystal, supporting earlier hydrodynamic evidence that this compound can bis-intercalate into DNA forming a single base pair (bp) sandwich complex. The corresponding tetra-acridine analogue 1,11-bis[4-[2-(9-acridinylamino)benzamido]-2-(9-acridinylamino)phenyl]-1,11-dioxo-6-methyl-2,6,10-triazaundecane pentahydrochloride (6) was synthesized, and dynamic fluorescence microscopy was used to study the effects of 4 and 6 on the higher order structure of large T4 DNA molecules (166 kbp), by measuring the average long-axis legth (persistence length, l) of the complexes. The mono-intercalating ligand acridine orange (5) increase l, whereas the bisintercalating diacridine 4 has no apparent effect and the putative multi-intercalating tetracridine derivative 6 decreases l by compacting the higher order DNA structure. These results demonstrate the usefulness of the technique for directly observing ligand-DNA complexes, and show that ligands with suitably positioned multiple binding sites can influence the higher order structure of DNA (and thus possibly gene expression).
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080905
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    Metal ion complexation by the phosphoryl and the carbonyl groups probed by 17O NMR spectroscopy (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 605-609 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Interactions between compounds containing phosphoryl, carbonyl, or hydroxyl groups (or combinations of these groups) with metal ions (Na+, Mg2+) were probed in CD3CN solutions by 17O NMR spectroscopy. For all phosphoryl and carbonyl substrates a strong high - field shift of the P=O and C=O signals was observed on the addition of a salt; no shift was observed, however, for the OH group signal, indicating that no chelation takes place in the hydroxyphosphoryl (or hydroxycarbonyl) derivatives. For 2-hydroxy-3-benzoylpropylphosphonic diester the 17O NMR studies, together with conformational analysis based on the 1H spectroscopy, demonstrated the chelation of a metal ion by the P=O and C=O functions (fermation of an eight-membered cyclic structure) with the OH group involved in the intramolecular hydrogen bonding, but not in the complexation to the metal ion.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080906
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    Aminolysis and hydrolysis of sulphamate esters: Substantial N=S bonding in the transition state leading to N=sulfonylamines (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 610-616 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The aminolysis and hydrolysis of several sulphamate esters, RNHSO2ONp (R = PhCH2, Ph, 4-MeC6H44, 3-MeC6H4, 4-FC6H4, 4-ClC6H4, 3-ClC6H4, H; Np = 4-NO2C6H4) were been studied in 50% (v/v) aqueous acetonitrile at various temperatures. Reaction of the esters with an amine (R1NH2) gives -ONp and both sulphamide, (RNHSO2NHR1) and sulphamate (RNHSO2O-R1NH3+) products. First-order rates were determined by the appearance of -ONp and sometimes also by the disapperance of ester. The reaction was found to be independent of amine type and concentration and at the high pHs that obtain the substrate esters are fully ionized. A Hammett ρacyl of -;1·8 was obtained for the decomposition of the sulphamate anions and this is consistent with substantial N=S bonding in the transition state leading to N-sulphonylamine, RN=SO2. This intermediate then partitions very rapidly, reacting with R1NH2 and H2O respectively. ΔH
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080907
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  • 83
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    Crystal structure of the poly(ethylene oxide)-p-nitrophenol molecular complexPresented at ‘MacroAkron '94, 35th IUPAC Symposium on Macromolecules’, Akron, Ohio, 11-15 July 1994. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 36 (1995), S. 117-125 
    Details
    ISSN: 0959-8103
    Keywords: poly(ethylene oxide) ; p-nitrophenol ; molecular complexes ; crystal structure ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A crystalline complex of poly(ethylene oxide) (PEO) and p-nitrophenol (PNP) was studied by differential scanning calorimetry, X-ray diffraction, and FTIR spectroscopy, The phase diagram of this system is characterized by a peritectic reaction, and reveals the formation of a new crystal form different from those of PEO, and PNP. The triclinic unit cell of the complex was determined from the X-ray diffraction patterns of differently oriented samples obtained by mechanical deformations or spherulitic crystallizations. Finally, the molecular packing and the conformation adopted by the PEO chains were determined by FTIR spectroscopy. Polarization measurements have shown that the aromatic rings are very nearly normal to the c parameter (chain axis) and that the 1-4 axes of PNP molecules are parallel to the a* reciprocal parameter (spherulitic growth direction). Finally, a new (t2 gt2 gt3) conformation is proposed for the PEO chains on the basis of a normal mode analysis and the calculation of the intramolecular energy.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210360202
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  • 84
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    Kinetics and mechanism of reaction of acridine orange with bromateion at low pH (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 175-185 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction between acridine orange hydrochloride [3,6-bis(dimethylamino)acridine hydrochloride] and potassium bromate in dilute sulphuric acid was studied by monitoring the absorbance change at 492 nm. The reaction exhibited complex kinetic behaviour. In excess bromate the reaction had an induction period with slow depletion of acridine orange (AC) followed by a fast depletion step. The initial reaction step was found to be first order with respect to both AC and bromate and second order with respect to H+. The stoichiometric ratio of AC to bromate was 3 : 2. At the end of the induction period, the redox potential of the reaction mixture has shown a distinct rise, while the Br- concentration dropped sharply. The dual role of bromide ion both as an inhibitor and autocatalyst is discussed. A 16-step reaction mechanism is proposed and the simulated curves agreed well with the kinetic curves.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080308
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  • 85
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    Living cationic polymerization of isobutyl vinyl ether by the CF3CO2H-SnCl4-nBu4NCl system: In situ direct analysis of the growing species by 1H, 13C and 19F NMR spectroscopyThis work was presented in part at the 42nd Annual Meeting of the Society of Polymer Science, Tokyo, Japan, September 1993, paper 20D151 and at the International Conference on Frontiers in Polymerization, Liège, Belgium, October 1993.2 (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 282-292 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Direct 1H, 13C and 19F NMR spectroscopic analysis was carried out on the carbocationic intermediate generated in the interaction of tin(IV) chloride (SnCl4) with the adduct [4, CH3CH(OiBu)OCOCF3] of isobutyl vinyl ether (IBVE) and trifluoroacetic acid (CF3CO2H), either in the presence or in the absence of tetrabutylammonium chloride. The reactions were to mimic the living cationic polymerization of IBVE by the 4-SnCl4 initiating system (with added nBu4NCl) that was also found in this study. In CD2Cl2 solvent at -78°C, the 1H and 13C NMR analysis revealed the formation of a carbocationic intermediate [CH3C+H(OiBu)] that is in a rapid exchange equilibrium with the covalent counterpart 4. For the first time, the cation formation was further supported by 19F NMR analysis on the counteranionic part (CF3COO-) in 4, where, with SnCl4, the CF3 group gave a broadened signal that appeared clearly downfield relative to that in the covalent form. These and other results, which are in close correlation with the corresponding polymerizations, demonstrated the following: (i) the SnCl4-assisted generation of carbocationic species from the covalent ester 4; (ii) a rapid exchange between the cation and its covalent precursor 4; (iii) the relatively high cationic concentration in the salt-free system, where no living polymerization occurs; and (iv) the effective suppression of the cationic species in the presence of the salt, which proved to be the prime key factor for living polymerization.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080411
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  • 86
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    Nature and concentration of active species in cationic polymerization of vinyl ethers: A kinetic investigation (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 293-300 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Kinetics of the polymerization of isopropyl vinyl ether, isobutyl vinyl ether (IBVE) and chloroethyl vinyl ether initiated by HI in CH2Cl2, in the presence and in the absence of tetrabutylammonium iodide as common anion salt, were investigated. The polymerizations proceed directly through the carbon-iodide termini without any necessary electrophilic activator. As previously observed with cyclohexyl vinyl ether, it was found that the addition of small amounts of salt, (0·5-10% with respect to initial [HI], depending on the monomer) drastically reduces the polymerization rate and leads to living-type polymerizations. Higher amounts of salt have no influence on the polymerization rate which remains constant over a broad range of [NBu4I]/[HI] ratios. This general behaviour, observed for the all vinyl ethers, suggests a common ion salt effect and therefore an ionic polymerization mechanism involving ion pairs and free ions. In the absence of salt, both ion pairs and free ions of higher reactivity participate in the propagation, whereas only ion pairs contribute to the propagation in the presence of a common ion salt. According to this scheme, the living character of the polymerization is assumed to result from a propagation reaction governed by undissociated ionic species. The validity and the implications of this reaction scheme, in terms of active centre concentrations, are also discussed.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080412
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    Masthead (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080501
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  • 88
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    Polymerization of acrylates and methacrylates to make homopolmers and block copolymers initiated by N-alkoxyphthalimides and succinimides (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 316-324 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Various N-alkoxyphthalimides were prepared and tested as initiators for polymerization of a variety of monomers. Acrylates and methacrylates polymerized at 40-50°C. Vinyl acetate and styrene were moderately reactive at 60-65°C. Rates of reaction were sensitive to the choice of solvent. THF generally gave the highest conversions, with much reduced reactivities in solvents of higher polarity, such as acetonitrile, acetone, DMSO or DMF. In aliphatic hydrocarbon solvents or di-n-butyl ether no polymers were obtained. Bulk polymerizations proceeded well, depending on the monomer. Rates of polymerization were sensitive to the structure of the group attached to nitrogen. OR groups, where R contained α-electron-withdrawing esters, benzylic or allylic groups, were more reactive than when R was an aliphatic group. A-B block copolymers were readily prepared, starting with PMA, PBA or PMMA. However, because the rates of initiation were slow, relative to rates of propagation, N-alkoxyphthalimide initiators survived mostly intact. Consequently, final A-B block copolymers were invariably contaminated with indeterminate amounts of homopolymer from polymerization of the second monomer.
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    URL: http://dx.doi.org/10.1002/poc.610080415
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  • 89
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    Theoretical studies on the reactions of substituted phenolate anions with formate estersDetermination of Reactivity by MO Theory. Part 91. For Part 90, see Ref. 1. (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 325-334 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Semiempirical MO (PM3) studies are reported on the reactions of 18 substituted phenolate anions with m-(MNPF), p-(PNPF) and 3,4-dinitrophenyl formates (DNPF). The mechanistic change from rate-limiting formation to breakdown of the anionic intermediate (T-) can occur in the gas phase, especially for MNPF, at approximately an equal proton affinity (PA) of the nucleophile and leaving group phenolates, i.e. ΔPA = 0 as the PA of the phenolate anion is decreased. In solution, however, owing to the low stability of T and a greater stabilization by solvation of the transition state for the breakdown step (TS2), all three formate esters are predicted to proceed by a concerted mechanism, which is in agreement with the experimental results. The low stability of T can be ascribed to the relatively high electron affinity of the phenolate anions.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080502
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  • 90
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    Oscillations of electrical potential differences across the interface in phase-transfer catalytic systems (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 341-343 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Oscillations of electrical potential differences across the liquid-liquid interface in phase-transfer catalyst systems are reported. The occurrence of the oscillations is consistent with the Starks' shuttling mechanism.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080504
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  • 91
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    Complexation of spiropyrans with cyclodextrins: Effects of β- and γ-cyclodextrins on the thermal isomerization of 6-SO3--spiropyran (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 335-340 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal isomerizations of 1′,3′,3′-trimethyl-spiro[2H-1-benzopyran-2,2′-indoline]-6-sulphonic acid (6-SO3--SP) between its spiro (SP) and merocyanine (MC) forms were followed spectrophotometrically in the presence of cyclodextrins (β- and γ-CDs) at various pressures. From the pressure dependence of the isomerization rate, the activation volumes for the thermal isomerization of 6-SO3--SP were estimated to be 17·1 cm3 mol-1 for MC → SP and 8·5 cm3 mol-1 for SP → MC. The equilibrium constants (K) for the inclusion complex formation of CDs with 6-SO3--SP were determined at various pressures. It was found that the stability of the 1:1 inclusion complex between 6-SO3--SP and CDs decreases in the order β- 〉 γ- 〉 α-CD. From the pressure dependence of K, the reaction volumes were estimated to be -0·9 cm3 mol-1 for the 6-SO3--SP-β-CD system and 4·0 cm3 mol-1 for the 6-SO3--SP-γ-CD system. Based on the activation volumes, the structure of the transition state for the thermal isomerization is discussed and an explanation for the effect of CDs on the reaction rate is given. The difference in the reaction volumes for the inclusion complex formation of β- and γ-CDs is explained in terms of the difference in the number of water molecules excluded from the CD cavity.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080503
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  • 92
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    Mechanism of bimolecular substitution reactions of hydroximoyl halides with amines in actonitrile solution (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 344-350 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction in acetonitrile solution of (Z)-O-methylbenzohydroximol chlorides [ArC (Cl)=NOCH3] with morpholine, pyrrolidine and azetidine gives the corresponding (Z)-amidoximes [ArC(NR1R2)=NOCH3] in acetonitrile. The rates of these reactions were measured under pseudo-first-order conditions (excess amine). The reactions were found to follow overall second-order kinetics (first order in amine). The Hammett ρ-value (with σ) for the reaction with pyrrolidine is +0·92. The reaction of the p-nitro compound with pyrrolidine gives a significant element effect [k(p-nitrobenzohydroximoyl bromide)/k(p)-nitrobenzohydroximoyl chloride = 10]. A Brφonsted β-value of 0·38 was estimated from the reactions of morpholine and piperidine with the p-nitrohydroximoyl chloride. The slower reaction of (E)-O-methyl-p-nitrobenzohydroximoyl chloride with azetidine gives primarily the (E)-amidoxime (E:Z ≈ 98:2) This reaction also follows second-order kinetics. The kinetic observations made in this study are compared with the corresponding results obtained in earlier work in benzene solution. It is suggested that in acetonitrile solution the reactions proceed by an addition-elimination mechanism with rate-determining loss of chloride ion (AN + DN#). It is further suggested that acetonitrile is assisting in the breakdown of the tetrahedral intermediates formed in these reactions.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080505
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  • 93
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    Solution electron affinity changes via the deuteriation of the methyl groups of p-xylene (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 371-376 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: EPR techniques, including spectral double integration, were utilized to measure the equilibrium contants in dimethoxyethane at 195 K for electron transfer between perdeuteriated p-xylene and xylene, α-d3-p-xylene and α,α′-d6-p-xylene. The results, coupled with the law of Hess, yield all the relative solution electron affinities (EA). It was found that methyl deuteriation lowers the solution EA by 160 J l mol-1 per deuterium, whereas ring deuteriation in these systems lowers the solution EA by about 370 J l mol-1 per deuterium, which is about the same effect as is observed in the benzene system. The results are discussed in terms of hyperconjugative, inductive and solvation effects.
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    URL: http://dx.doi.org/10.1002/poc.610080510
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    Correction (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 385-385 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080512
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  • 95
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    Kinetic study of proton/deuteron transfer reactions of 2,4,6-trinitrotoluene and its derivatives with tertiary amines (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 387-394 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rate of proton/deuteron transfer reactions of 2,4,6-trinitrotoluene (TNT), 2,2′4,4′6,6′-hexanitrobibenzyl (HNBB) and 2,4,6-trinitrobenzyl chlorides (TNB) with tertiary amines was followed spectrophotometrically. The rate constants obtained under various conditions were interpreted in terms of isotope, solvent and steric effects. The Arrhenius plots curved upward at low temperatures for TNT and TNB, indicating clearly the intervention of tunnelling. The tunnelling parameteres were calculated semi-empirically on the basis of Bell's theory. The observed rate constants at low temperatures agreed well with the predicted values. In the present systems, some side and consecutive reactions involving the formation of 2,2′,4,4′6,6′-hexanitrostilbene took place, and in some cases interrupted the rate measurements in the proton/deuteron transfer steps.
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    URL: http://dx.doi.org/10.1002/poc.610080602
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    Prediction of hydrogen bond basicity in nitriles from dipole moments, mesomeric effects and electrostatic potentials (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 421-428 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Measured molecular dipole moments and theoretical percentages of mesomeric zwitterionic forms were used to calculate the attractive electrostatic potentials at short, V(s), medium, V(m), and long, V(I), distances. Values of an attraction power function Φ (H) = A + BV (s) V(m) V(I) was then deduced for 18 nitriles and cyanamide vinylogues or iminologues along the C≡N direction. The satisfactory agreement observed between Φ (H) and the hydrogen bond basicity scale pKHB indicates that the method can be a useful tool for the prediction of hydrogen bonding, needing only simple calculations and allowing easy interpretation.
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    URL: http://dx.doi.org/10.1002/poc.610080606
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    Kinetics and mechanism of oxidation of (arylthio)acetic acids by pyridinium hydrobromide perbromide (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 429-434 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Oxidation of several monosubstituted (phenylthio)acetic acids (PTAA) by pyridinium hydrobromide perbromide (PHPB) was studied in aqueous acetic acid. The reaction is first order with respect to PHPB. Michaelis-Menten type kinetics are observed with respect to (arylthio)acetic acid. The effect of solvent composition indicates that the transition state is more polar than the reactants. The formation constants of the intermediate substrate-PHPB complexes and the rates of their decomposition were determined at different temperatures. The rates of oxidation of para and meta-substituted (phenylthio)acetic acids were correlated with Hammett's substituent constants. The ρ value is -1·60 at 35°C. The rates of oxidation of ortho substituted compounds are correlated with Charton's triparametric equation. A mechanism involving the decomposition of the intermediate complex in the slow rate-determining step affording a sulphonium ion which hydrolyses in a subsequent fast step to the sulphoxide is proposed.
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    URL: http://dx.doi.org/10.1002/poc.610080607
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    Ab initio molecular orbital study of the O + C6H5O reaction (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 407-420 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An ab initio molecular orbital study of the potential energy surface of the C6H5O + O reaction was performed at the (PUMP3/6-31G*//UHF/6-31G*) level of theory. Various reaction channels were considered. The most favorable mechanism, la and Ib, start from the attachment of the oxygen atom to the carbon atom of the C6 ring in the ortho- or para position with respect to CO, taking place without activation energy. Then, either hydrogen elimination by mechanism Ia or 1,2-H shift from the C(H)(O) group takes place; the latter process leads to the formation of the very stable C6H4(O)(OH) radical, which can also eliminate H by mechanism Ib. Thus, the main products of the C6H5O (2B1) + O(3P) reaction are o/p-benzoquinones and the hydrogen atom. At low temperatures, however, the system may be trapped in the potential well of the C6H4(O)(OH) intermediate. At high temperatures, the reaction may proceed by the formation and decomposition of o/p-benzoquinones. Because of their higher activation energies, the reaction mechanisms giving rise to other products-the attachment of the oxygen atom to the bridging position to form an epoxy intermediate, followed by insertion of O into the CC bond and dissociation to give C5H5 and CO2 (channel IIc), in addition to the attachment of oxygen to the terminal O atom of C6H5O followed by elimination of O2 (channel III) - cannot compete with channel Ia or Ib. RRKM calculation was carried out for the total and individual rate constants for channels Ia and Ib. The three-parameter expression for the total rate constant, fitted by the least-squares method for the temperature range of 300-3000 K, is given as ktot = 5·52×10-17 T1·38 e+148/T cm3 mol-1 s-1.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080605
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  • 99
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    Multinuclear, variable-temperature NMR study of hydrogen bonding in two ortho-Mannich bases (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 463-467 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1H and 13C NMR data for 2-diethylaminomethyl-3,4,6-tri- and -tetrachlorophenols in CH2Cl2 solutions at a variety of temperatures are reported. The results are consistent with intramolecular hydrogen bonding and proton transfer as shown in the structure 3. Concentration dependence of the NMR data for the perchloro compound shows an additional hydrogen bonding process attributed to the solute self-association. The 1H, 13C and 15N NMR data support the proposed proton transfer structure.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610080704
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  • 100
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    Effects of the ring size and solvent polarity on the stability of the cyclic intramolecular excimer of saturated diamines (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 484-489 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The fluorescence of some aliphatic diamines was studied in the gas phase and in some solvents at several temperatures. It was found that N,N,N′,N′-tetramethylpropane-1,3-diamine (TMPD) and N,N,N′,N′-tetramethylbutane-1,4-diamine (TMBD) have two emission bands in the gas phase. TMBD also shows two bands in solution. These bands were assigned previously to an excited monomer and an intramolecular excimer. From the temperature dependence of the intensity ratio of the two bands, the enthalpy changes for the excimer formation were evaluated. The stability of the cyclic excimer is discussed in terms of the ring size effect and the solvent effect on the band positions.
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    URL: http://dx.doi.org/10.1002/poc.610080707
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