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  • 1990-1994  (218)
  • 1980-1984
  • 1993  (218)
  • Physical Chemistry  (218)
  • Nuclear reactions
  • 1
    Electronic Resource
    Electronic Resource
    Micelle-induced change in the rate-limiting step of substituted benzoate ester thiolysis (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 7-14 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of hexadecyltrimethylammonium bromide (CTAB) micelles on the acid dissociation constant of para-substituted benzenethiols, α-toluenethiol and n-heptanethiol was determined. The effect of CTAB on the rate of thiolysis by the thiols was measured using para-substituted p-nitrophenyl benzoates. The effects of micelles were analysed using a pseudophase ion-exchange (PIE) model. The Brønsted plot for ester thiolysis showed discontinuity at the pKa of the leaving group in water and was linear in micelles. Micelles increased the Hammett ρ value for thiolysis of esters by α-toluenethiol from 2·08 to 2·68. The Hammett plot for the rection of benzenethiol with esters in water is linear with σ- and displays a ρ value of 0·87, whereas in micelles the plot is linear with σ and presents a ρ of 2·83. Taken together, these data indicate that micelles produce a change in the rate-limiting step of thiolysis of substituted benzoate esters, leading exclusively to rate-limiting thiolate attack. In micelles thiolysis may be concerted and the effect of the aggregate on the reaction mechanism can be ascribed to the interaction of the thiolate ions, and the transition states, with the head groups as well as a medium effect.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060103
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  • 2
    Electronic Resource
    Electronic Resource
    Generation of vinyl cations by nitrosation of N-silylated imines and enaminesPresented as a poster at the 10th IUPAC Conference on Physical Organic Chemistry at Technion, Haifa, Israel, August 5-10, 1990. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 44-46 
    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 monosilylated imines and a disilylated enamine with nitrosyl salts in dichloromethane at -78°C is shown to proceed via intermediate vinyl diazonium salts and vinyl cations.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060107
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  • 3
    Electronic Resource
    Electronic Resource
    Phosphonic systems. Part 8. Solution and solid-state conformation of diastereomeric adducts of diethyl prop-2-enylphosphonate to p-nitrobenzaldehyde (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 64-70 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A mixture of siastereomeric adducts of lithiated diethyl prop-2-enylphosphonate to p-nitrobenzaldehyde was separated and the solution and the solid-state structures of the individual stereoisomers were studied. Conformational analysis demonstrated that in solution the most populated rotamer involves in both cases trans orientation of the PO3Et2 and O2NC6H4 groups and a gauche relationship of the phosphoryl and hydroxyl groups. In the solid state the crystal structure determination demonstrated that the molecules exist in the same conformation as in solution, although the P=O⃛H—O hydrogen bonding changed from intramolecular to intermolecular (dimeric) interactions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060111
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  • 4
    Electronic Resource
    Electronic Resource
    Conformational interconversion of [1.1] ferrocenophane: A molecular mechanics study (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 107-112 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A molecular mechanics scheme developed for bridged ferrocene derivatives was applied to study the conformational energy surface of [1.1] ferrocenophane (1). The mechanism of the intramolecular interconversion of 1 is shown to be different from the mechanism of the syn-syn exchange proposed earlier for this ‘molecular acrobat’.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060207
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  • 5
    Electronic Resource
    Electronic Resource
    Acidity constants of benzamide and some Ortho-substituted derivatives (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 101-106 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Acidity constants of benzamide and seven ortho-substituted derivatives were determined. Except for o-nitrobenzamide, all the amides exhibit medium effects. The data were treated by vector analysis. o-Aminobenzamide displays two protonation equilibria. The second acidity constant was determined by vector analysis and by the excess acidity function, since the acid strength provided by perchloric acid is insufficient for complete protonation. Different acidity functions and the ortho substituent effect on ionization of the amide group are compared.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060206
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  • 6
    Electronic Resource
    Electronic Resource
    Carbon and hydride migrations of cyclobutylhalocarbenes (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 126-131 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photolysis of cyclobutylchlorodiazirine affords chlorocyclopentene and chloromethylenecyclobutane by direct rearrangements from the diazirine's excited state (65%) and by competitive formation and subsequent rearrangement of cyclobutylchlorocarbene. The involvement of excited diazirine in the analogous cyclobutylfluorodiazirine photolysis is much reduced (12%).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060210
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  • 7
    Electronic Resource
    Electronic Resource
    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    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.610060101
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  • 8
    Electronic Resource
    Electronic Resource
    Zn2+ complexes with N-(2-pyridyl)cinnamides: Characterization and UV studies (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 15-22 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Zinc(II) complexes of N-pyridylcinnamides (H, m-OCH3, p-OCH3 and p-OH derivatives) were studied by spectrophotometric methods in aprotic media, and represent a chemical model inhibition by cinnamides of coniferyl alcohol dehydrogenase (CAD), a zinc enzyme involved in the lignification process. The complexation of N-pyridylcinnamide and m-methoxy-N-pyridylcinnamide with zinc ion is effected according to a 1 : 1 stoichiometry (ML), whereas a two-step equilibrium (M + L ⇌ ML \documentclass{article}\pagestyle{empty}\begin{document}$ V_{\rm m} = 4 \cdot 45C_0 + 6 \cdot 44C_1 - 3 \cdot 33C_2 + 0 \cdot 46C_4 + 52 \cdot 9{\rm (}n = 300,r = 0 \cdot 999,s = 0 \cdot 81) $\end{document} ML2) is preferred with p-methoxy and p-hydroxy compounds. These ligands are mainly bonded through the carbonyl oxygen atom and the nitrogen of the pyridyl ring. Molar absorptivities for these complexes, not directly available, were calculated from analysis of the experiemental data. The UV complexation results are also supported by the stoichiometry of the complexes, which were synthesized and characterized.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060104
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  • 9
    Electronic Resource
    Electronic Resource
    Precipitation of strong uncharged organic acids with various crown ethers or with acyclic polyethers from aqueous medium. Characterization of adducts in the solid state (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), 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: It was found that substituted picric acids form slightly soluble 1 : 2 : 2 adducts with several simple crown ethers or with tri-, tetra-, or pentaethylene glycol dimethyl ether (glymes 4, 5 and 6) in water, whereas 2,4,6-trinitrobenzenesulfonic acid forms a 1 : 1 : 1 adduct with dicyclohexano-18-crown-6 (cis-syn-cis). The ability of a crown ether to precipitate a given acid follows the order dicyclohexano-18-crown-6 (cis-syn-cis) 〉 benzo-15-crown-5 〉 dicyclohexano-24-crown-8 〉 18-crown-6 〉 21-crown-7, 15-crown-5 ≫ 12-crown-4, roughly in the order of its base strength. Precipitation can occur even when the concentration(s) of one or more of the components are 〈 10-4 M. The solubility products of the 18-crown-6 complexes with dichloro- or dimethylpicric acids were estimated. In the solid state the 1 : 2 : 2 dicyclohexano-18-crown-6 (cis-anti-cis)-dichloropicric acid-water complex, which reportedly has two pseudohydronium ions lacking C3v symmetry of H3O+, exhibits an IR spectrum in the OH stretching region characteristic of an aqua complex.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060108
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  • 10
    Electronic Resource
    Electronic Resource
    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    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.610060201
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  • 11
    Electronic Resource
    Electronic Resource
    Crystal and moecular structure of N-nitro-N-methyl-p-nitroaniline: Analysis of substituent effects on the ring geometry and estimation of the Hammett substituent constant for the N-methylnitramino group (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 257-260 
    Details
    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 structure of N-nitro-N-methyl-p-nitroaniline was solved with good precision: R = 0·058 and average estimated standard deviation for bond lengths = 0·003 Å. Analysis of the geometry reveals that the NO2 attached to the N atom is strongly conjugated. Application of the HOSE model to its geometry and to geometries of 12 other para-substituted nitrobenzenes yields good linear regressions between canonical structure weights and Hammett σ values by interpolation, σ for the N(Me)NO2 group is estimated to 0·36.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060502
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  • 12
    Electronic Resource
    Electronic Resource
    Acid-catalysed solvolysis of optically active 1-Phenyl-1-methoxythane. The role of ion- molecule pair intermediates (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 287-292 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The acid-catalysed solvolysis of (R)-1-phenyl-1-methoxyethane was studied in mixtures of dilute aqueous perchloric acid and acetonitrile at 50°C. The rate of loss of optical activity (kα) was found to be the same as the rate of solvolysis (ksolv) at both low and high water contents of the solvent. These results are not in accord with literature data on racemization and oxygen exchange of 1-phenylethanol in water, which has been discussed in terms of interconversion of chiral ion-dipole pair intermediates. The mechanistic implications of the results are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060506
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  • 13
    Electronic Resource
    Electronic Resource
    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    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.610060601
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  • 14
    Electronic Resource
    Electronic Resource
    Conformational analysis of substituted perhydro-1,2-oxazolo[3,2-c] [1,4]oxazines by NMR spectroscopy (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 326-332 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 13C NMR spectra of most of the substituted perhydro-1,2-oxazolo[3,2-c] [1,4]oxazines (3) at low temperature showed the presence of two isomers of unequal populations. The major isomer is shown to be the cis isomer {except in 2-hydroxymethyl-2-methylperhydro-1,2-oxazolo[3,2-c] [1,4] oxazine (3e)}, which is in equilibrium with the minor isomer (trans conformer) by a relatively slow nitrogen inversion. Intramolecular hydrogen bonding in oxazines, having 2-hydroxymethyl substituents, is shown to be an important factor in determining the population ratio of the two isomers. The barrier to nitrogen inversion was determined by detailed band-shape analysis of proton and carbon NMR spectra and were in the range 66·3-72·9 kJ mol-1. The chair inversion had been slowed down, in one case, trans-dimethylperhydro-1,2-oxazol[3,2-c] [1,4]oxazine-2,3-dicarboxylate (3j), to show the presence of the two forms of the cis isomers. The barrier to chair inversion is 41·5 kJ mol-1 as determined by proton NMR band-shape analysis of 3j.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060603
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  • 15
    Electronic Resource
    Electronic Resource
    Kinetic solvent isotope effect studies on the methanolysis of 1-phenylethyl chlorides (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 361-366 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The negative slope (ΔρY+ 〈 0) of the Hammett-type plot using kinetic solvent isotope effect, log kSOH/kSOD versus σ+, for methanolysis of 1-(Y-phenyl)ethyl chlorides is rationalized by an ion-pair mechanism in which a solvent molecule attacks the relatively stable carbocation formed in the pre-equilibrium.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060608
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  • 16
    Electronic Resource
    Electronic Resource
    Theoretical studies of substituent effects on thermal eliminations of aryl ethyl carbonates and S-aryl O-ethyl thiocarbonatesDetermination of Reactivity by MO Theory. Part 82. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 215-222 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Substituent effects on the thermal elimination reactions of carbonates and thiocarbonates were investigated MO theoretically using the AM1 method. For both substrates, an electron-withdrawing group is found to facilitate the decomposition. A two-step process is favoured by carbonates, whereas one- and two-step processes can compete in the pyrolysis of thiocarbonates. The ability to transmit substituent effect is greater with oxygen (carbonates) than with sulphur (thicarbonates) in contrast to the experimental results of Taylor and co-workers. Modelling studies with replacement of the phenyl ring with a vinyl group are found to be justified in this type of work.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060404
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  • 17
    Electronic Resource
    Electronic Resource
    Ab initio studies of the reaction between diazonium ions and water (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 243-250 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ab initio calculations, using the 6-31G* basis set, were performed in order to study the energetics of the electrophilic attack on water by such diazonium ions as methyl-, ethyl- and fluroethyldiazonium. For the first case, an indication of a transition state appears at the Hartree-Fock level, whereas for the other two, the energy is continuously decreasing from reactants to products. When correlation energy was taken into account via single-point MP2/6-31G* calculations, a deep ion-dipole energy minimum was observed for the methyldiazonium ion followed by a low transition state, whereas the other two did not change their energy pattern. On performing the MP2/6-31G* optimization for the methyl species, the Hartree-Fock results were confirmed, with a slight displacement of the transition state toward a shorter CO distance.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060408
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  • 18
    Electronic Resource
    Electronic Resource
    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    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.610060501
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  • 19
    Electronic Resource
    Electronic Resource
    Structure, stabilization energies and chemical shifts of the cyclobutenyl cation. Does it have ‘aromatic’ homocyclopropenium ion character? An ab initio study (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 445-464 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relatively high stability and the structure of the simplest homoaromatic carbocation, the cyclobutenyl cation 1, was established ab initio by using correlated wave functions at HF 6-31G*, MP2(full)/6-31G*, MP2(full)/6-311G** and MP4(SDQ,full)/6-31G* geometries. The stability of 1 was estimated using homodesmotic and isodesmic reactions. The heat of formation of 1 was estimated to be 244 kcal mol-1 (1 kcal = 4·184 kJ). Chemical shift calculations were carried out at correlated levels and are in good agreement with the experimental values. At all levels of theory chemical shift calculations confirm the bent structure of 1. The MP4(SDTQ,fc)/6-311G**//MP2(full)/6-311G** + ZPE(MP2/(full)6-31G*), QCISD(T,fc)/6-31 + G*//MP2(full)/6-31G* + ZPE(MP2(full)/6-31G*) and MP4(SDQ,full)/6-31G*//MP4(SDQ,full)/6-31G* + ZPE(MP2(full)/6-31G*) ring inversion energies of 9·1, 9·3 and 9·0 kcal mol-1, respectively, agree with experiment (8·4 ± 0·5 kcal mol-1). Triplet electronic states are not competitive energetically. The homoaromatic character of the cyclobutenyl cation is shown by the nearly equal charges on C-1, C-2 and C-3, the considerable 1,3-bond order, the short 1·74 Å C-1—C-3 distance and the large stabilization energy relative to the allyl cation.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060803
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  • 20
    Electronic Resource
    Electronic Resource
    Interaction of 3,4-diphenyl-1,2,5-thiadiazole 1,1-dioxide with proton donor solvents (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 341-346 
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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 UV spectra of 3,4-diphenyl-1,2,5-thiadiazole 1,1-dioxide (I) and that of its thiadiazoline and thiadiazolidine derivatives were measured in several aprotic and protic solvents. Strong specific interactions of I with protic solvents are observed and the formation of stable carbinolamine type derivatives of I with methanol or ethanol is proposed. Spectroscopic data (UV, 1H and 13C NMR) and electrochemical evidence for their formation are given and a new thiadiazoline derivative of I (3-ethoxy-2-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide) was synthesized. The equilibrium constant for the reaction of I with ethanol is reported.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060605
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  • 21
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    Electronic Resource
    Dipole moments and electronic structure of 2,6-bis(dialkylamino) derivatives of 4H-pyran-4-one(thione) and 4H-thiopyran-4-one(thione) (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 489-493 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dipole moments of a series of 2,6-bis(dimethylamino) and 2,6-bis(pyrrolidino) derivatives of 4H-pyran-4-one (2), 4H-thiopyran-4-thione (3), 4H-pyran-4-thione (4) and 4H-thiopyran-4-thione (5) were determined in benzene and dioxane solutions at 25°C. High values of the dipole moments (6·44-8·44 D) and mesomeric moments originated from delocalization of the nitrogen lone pairs into the π-system of the heterocyclic moieties (1·11-3·08 D) indicate a strong polarization of the molecules 2-5 due to a tendency to stabilize pentamethinium and pyrylium (thiopyrylium) ionic structures. The MNDO-calculated electronic distribution in 2-5 compared with that for the parent 4H-pyran(thiopyran)-4-one(thione)s is in line with this conclusion.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060902
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  • 22
    Electronic Resource
    Electronic Resource
    Reactions of cycloalkyl chlorides and bromides with diphenylphosphide ions in liquid ammonia (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 421-426 
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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 reactions of cycloalkyl (butyl, pentyl, hexyl and heptyl) chlorides and bromides with diphenylphosphide ions were studied in liquid ammonia. Cyclobutyl chloride was unreactive, whereas the bromide reacted giving the substitution product cyclobutyldiphenylphosphine (isolated as the oxide) in good yields; this reaction was catalysed by light and partially inhibited by p-dinitrobenzene (p-DNB). Cyclopentyl, cyclohexyl and cycloheptyl chlorides did not react in the dark, but the substitution products were formed under irradiation, and these reactions were inhibited by p-DNB. The bromides reacted in the dark or under irradiation, and these reactions were partially inhibited by p-DNB. It can be then concluded that the reactivity of cycloalkyl halides depends on the ring size and the nucleofugal group. In addition, as the overall reactivity decreases, there is an increase in electron transfer reactions.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060707
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  • 23
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    Electronic Resource
    Nucleophilic catalysis in deoxymercuration: The beta effect of mercury (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 555-560 
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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: Deoxymercuration was examined in the antiperiplanar stereochemistry of trans-2-acetoxycyclohexylmercury(II) acetate (6). The presence of the mercury group accelerates the departure of the beta leaving group by a factor of about 1010. This beta effect is larger than that of silicon and comparable to that of germanium. In contrast to these latter cases, the rate for 6 was found to increase with the nucleophilicity of the solvent. It is concluded that a molecule of solvent is coordinated with mercury in the transition state. This nucleophilic assistance raises the polarizability and nucleophilicity of the mercury group, enhancing its ability to stabilize the developing positive charge or to form a bridged intermediate.
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    Stereochemical structures of (8,8-ethylenedioxy-2-oxo-)- and (8,8-ethylenedioxy-2-hydroxy-)-6-phenylsulphonylbicyclo[3·3·0]octanes (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 583-589 
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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: Cyclopentannulation of 4-tert-butyldimethylsilyloxy-2-cyclopenten-1-one from a β-metallated dioxolane-type orthoester affords 4-tert-butyldimethylsilyloxy-8,8-ethylenedioxy-6-phenylsuiphonyl-2-oxobicyclo [3·3·0] octanes as a mixture of two diastereoisomers. Their stereochemical structures were established by NMR and x-ray analysis. The minor product possesses a cis ring fusion, the sulphonyl and the tert-butyldimethylsilyloxy groups being endo and exo, respectively. The major isomer also has a cis ring fusion but an exo position for both dimethylsilyloxy and sulphonyl groups. Both cyclopentannulation products result from an anti addition with respect to the 4-tert-butyldimethylsilyloxy group on the enone.
    Additional Material: 5 Ill.
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    Attractive interactions between negative charges and polarizable aryl parts of host-guest systemsSupramolecular Chemistry, Part 40. Part 39: A. V. Eliseev and H.-J. Schneider, Angew. Chem., in press. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 590-594 
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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: NMR measurements of associations between simple organic host and guest molecules bearing alternatively negatively charged groups and electroneutral π-moieties show in aqueous solutions weak but distinct attractions reaching approximately 2 kJ mol-1 and X-/arene unit. A similar value is observed for the complex between a calixarene with 4-sulfonato groups and toluene, for which the NMR shifts indicate an orientation with the guest methyl substituent upwards. The conformational fit of the selected complexes is checked by molecular mechanics simulations.
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  • 26
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    Oxidation kinetics of p-aminodiphenylamine with peroxydisulphate (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 609-614 
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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 oxidation of p-aminodiphenylamine with the peroxydisulphate ion were investigated spectrophotometrically. The oxidation was accompanied by the appearance of a wine-red colour, which changed to become colourless. The reaction rate was measured by the stopped-flow technique with a UV spectrophotometer. The reactions proceeded with second-order kinetics, first-order for each individual reactant. Cationic micelles (cetyltrimethyl ammonium bromide) caused an enhancement in the reaction rate followed by inhibition at higher concentrations. Anionic micelles (sodium dodecyl sulphate), on the other hand, had a slightly retarding effect. The effects of radical scavenger, pH and ionic strength on the fast oxidation rate were examined. A mechanism consistent with the observations is discussed.
    Additional Material: 8 Ill.
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    Protonation of 2-(2-thienyl)pyrrole and 2-(2-thienyl)-1-vinylpyrroles (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 471-477 
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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: 2-(2-Thienyl)pyrrole and its 3-alkyl-1-vinyl derivatives have been shown (1H NMR) to be protonated by HSO3F, CF3COOH, HCl and HBr at the pyrrole C-5 atom. Reaction with the superacid system HSO3F—SbF5-SO2 results in the equilibrium between pyrrolium and thiophenium ions. The heats of formation (ΔH), charges and HOMO partial electron densities for 2-(2-thienyl)pyrrole and its protonated forms have been calculated by the MNDO method. The calculated ΔH values of thienylpyrrolium and pyrrolythiophenium ions are in agreement with the experimentally observed ratio.
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    Zero-field splitting versus interelectronic distance in triplet electron spin resonance spectra of localized dinitrenes (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 483-487 
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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: Triplet zero-field splitting parameters were obtained in 2-methyltetrahydrofuran glass at 77 K for phenylene-1,4-dinitrene (1), biphenyl-4,4′-dinitrene (2), (E)-1,2-bis(4′-nitrenophenyl)ethene (3), 1,4-bis(4′-nitrenophenyl)buta-1,3-diene (4) and 1,8-bis(4′-nitrenophenyl)octa-1,3,5,7-tetraene (5). The results were (1) |D/hc| = 0·169 cm-1 |E/hc| = 0·004 cm-1, (2) |D/hc| = 0·189 cm-1, |E/hc| = 0·00 cm-1, (3) |D/hc| = 0·122 cm-1, |E/hc| = 0·00 cm-1, (4) |D/hc| = 0·0865 cm-1, |E/hc| = 0·00 cm-1 and (5) |D/hc| = 0·0442 cm-1, |E/hc| = 0·00 cm-1. All these biradicals are ground-state singlets. Based on the observed decrease in triplet signal intensities as temperature decreases. The substantial magnitudes of |D/hc| for 3-5, despite the large distance between localized nitrene electrons, is much more than can be explained by a simple dipolar interaction between localized electrons, and is attributed at least partly to spin polarization effects on the π-electron clouds of these systems.
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    Theoretical studies of the effects of ortho-methyl substitution on SN1 and SN2 processes at primary and secondary benzylic carbonsDetermination of Reactivity by MO Theory, Part 84. For Part 83, see Ref. 1. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 499-508 
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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 effects of o-methyl substitution on the transition-state (TS) structure and reactivity of SN1 and SN2 processes were investigated for primary and secondary benzyl (α-tert-butyl) derivatives MO theoretically using the AM1 method. The o-methyl groups have both stabilizing (by electron donation) and destabilizing (steric) effects on the SN2 TS; the former prevails for the primary whereas the latter effect becomes dominant for the secondary compounds. In contrast, complex interplay of the two effects are operative in the SN1 TS of both primary and secondary derivatives leading to the reactivity order which is consistent with that observed by solvolytic experiments, o,o′-dimethyl 〈 H 〈 o-methyl. The bond length-reactivity rule applies only for the primary benzyl SN2 series for which steric effects are insignificant. For reactions of benzyl derivatives is general the coplanarity between the carbenium sp2 centre and the benzene ring, π-σc-x*, is of the utmost importance in stabilizing TS structure for which other structural requirements may be relaxed.
    Additional Material: 9 Tab.
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    Multinuclear NMR and ab initio MO studies of 7-methyl-7H-pyrrolo [2,3-b]pyridine and related compounds (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 139-144 
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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 contribution of the polarized resonance structures to 7-methyl-7H-pyrrolo[2,3,-b]pyridine and 4-methyl-4H-pyrrolo [3,2-b] pyridine, which have recently attracted much attention in physico-chemical studies, was considered based on multinuclear (1H, 13C and 15N) NMR spectroscopy and MO calculation. Comparison of the chemical shifts of the compounds with those of other relevant compounds and the effects of concentration and solvents observed by multinuclear NMR suggested that the contribution of the non-polarized structures to both compounds predominates over that of the polarized structures. This result was also supported by ab initio MO calculations using the 6-31G basis set.
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    URL: http://dx.doi.org/10.1002/poc.610060303
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    [4] Metacyclophane: STO-3G molecular structure, strain energy and CNDO/S—Cl electronic transition energies (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 163-170 
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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 structure of [4] metacyclophane is optimized at the ab initio STO-3G SCF level and a genuine minimum is located. In the STO-3G structure the benzene ring is less bent and geometrically distorted than in the previously reported MNDO structure. Although some bond alternation is calculated for the carbon-carbon bond lengths of the bent benzene ring, their values still fall in the range of highly delocalized compounds. Despite the fact that the STO-3G strain energy [SE(tot.)] is larger than the corresponding MNDO strain energy, the distribution of SE(tot.) over the bent benzene ring [SE(bb.)] and the oligomethylene bridge [SE(br.)] is similar. To facilitate the hitherto unsuccesful identification of [4] metacyclophane, its electronic transition energies were calculated with CNDO/S-CI using the STO-3G geometry as input geometry. The reliability of the CNDO/S-CI results was assessed by a comparison of calculated and experimental electronic transition energies for p- and, m-xylene, [5] para- and [5] metacyclophane and [4] paracyclophane following the same approach.
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    Kinetics and mechanism of electron transfer reactions of aquo-thallium(III) and coordinated thallium(III). Reduction of thallium(III) and chlorothallium(III) complexes by L-ascorbic acid in aqueous acid medium (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 179-186 
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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 stoichiometry of the reaction of TIIII with ascorbic acid (H2A) in the presence and absence of chloride ion conforms to TIIII + H2A 〉 TII + 2H+ + A. where A is dehydroascorbic acid. The reaction exhibits complex kinetics and the reactivity of various chlorothallium (III) species decreases in the order of [TIOH]2+ 〉 TI3+ 〉 [TICI]2+ 〉 [TICI2]+ 〉 TICI3 〉 [TICI4]-. The mass balance relationship was employed to calculate the equilibrium concentration of the chloride ion for evaluation of the rate constants.
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    Ring-opening reactions. 6.For part 5, see ref. 1. eliminative ring fission of aziridinium and azetidinium ions (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 187-192 
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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 reactivity ratio between the three- and four-membered cyclic ammonium ions in ring-opening elimination reactions was measured. The comparison with the analogous ratio obtained in a previous study on ring-opening substitution reactions suggests a substantial difference in the effect of the stereochemical factors governing the two ring-opening reactions and confirms the anomalous behaviour of small rings in the ring-opening substitution reaction.
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    URL: http://dx.doi.org/10.1002/poc.610060310
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    3-Methylcarboxy-1H-indazole. Theoretical study of its formation via intramolecular aliphatic diazonium coupling and x-ray crystal structure (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 201-214 
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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 methyl ester of 1H-indazole-3-carboxylic acid (2-Me) is formed in the diazotization of o-aminophenylacetic acid to o-diazoniumphenylacetic acid (1) in an intramolecular aliphatic diazonium coupling. 2-Me was identified and characterized by single-crystal x-ray diffraction and found to crystallize as hydrogen-bonded trimers of crystallographically independent molecules. The methylcarboxy groups are rotated slightly out of the best plane of the trimer resulting in only a pseudo-threefold axis. The crystal structure of 2-Me is compared with other indazoles and pyrazole. Regioselective electrophilic diazonium ion addition to the enol tautomer of 1 and subsequent hyrazone-azo tautomerization are proposed as a possible mechanism for indazole formation under acidic conditions. The tautomerization equilibrium between acetic acid and its enol 1,2-dihydroxyethene was studied and the effects of phenyl and o-diazoniumphenyl substitution on this equilibrium were explored with semi-empirical quantum mechanical methods. The performance of the semi-empirical method was assessed by comparison with ab initio and/or experimental data. It was found that the enol of o-diazoniumphenylacetic acid is stabilized greatly owing to extended conjugation and push-pull interactions in the enol form. These results suggest that the enol tautomer might be a viable reactive intermediate that warrants considerations in discussions of reaction mechanisms.
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    URL: http://dx.doi.org/10.1002/poc.610060403
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    Relative stability of crowded isomeric enols: 2-Mesityl-2-phenylethenols and their methyl ethers (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 233-242 
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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 structure of 2-mesityl-2-phenylethenol (7) obtained by reduction of mesityl phenyl ketene with LiAlH4 and by acid-catalysed rearrangement of 1-mesityl-2-phenylethylene glycol was determined by x-ray crystallography to be Z [(Z)-7]. In contrast with a literature report, the reduction of 2-acetoxy-2-mesityl-2-phenylacetaldehyde did not provide the E isomer [(E)-7], but a mixture of (Z)-7 and 2-mesityl-2-phenylethenol. An (E)-7-(Z)-7 mixture of 1:5 was obtained starting from pure (Z)-7 at 80°C in dimethyl sulphoxide. The lower stability of (E)-7 was ascribed to higher steric effects due to a smaller Ph-C=C compared with Mes-C=C torsional angle and a preferred intramolecular π(Mes)-OH in (Z)-7 over π(Ph)-OH hydrogen bonding. In order to dissect the effects, the corresponding 2-mesityl-2-phenylvinyl methyl ethers (E)-15 and (Z)-15, where hydrogen bonding is absent, were prepared and equilibrated in chlorobenzene. The (Z)-15: (E)-15 ratio of ca 3:1 between 58° and 132° (ΔG=0·8 kcal mol-1) gives ΔH ≈ 0·6 kcal mol-1 and ΔS ≈ 0·5 e.u. It was concluded that steric effects contribute ca 1 kcal mol-1 and hydrogen bonding ca 1·5 kcal mol-1 to the higher stability of (Z)-7 over (E)-7. The unknown mesitylphenylacetaldehyde 16 was obtained from (Z)-7 at 135°C in 31% yield.
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    Stereochemical features of the (2+2) cycloaddition reactions of chiral allenes. V. Cycloaddition of 1-tert-butyl-3-methylallene with 1,1-dichloro-2,2-difluoroethene (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 95-100 
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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 (2 + 2) cycloaddtion reactions of 1-tert-butyl-3-methylallene (tBMA) with radicophiles were investigated. The attempted cycloaddition reactions with N-phenylmaleimide, acrylonitrile and methyl acrylate produce only (4 + 2) cycloadducts of 1-tert-butyl-1,3-butadiene which is formed by the more rapid [1.3] hydrogen sigmatropic rearrangement of the tBMA. The (2 × 2) cycloaddition of tBMA with 1,1-dichloro-2,2-difluoroethene (1122) occurs more rapidly than does the sigmatropic rearrangement, and produces a mixture of the four cycloadducts 1-4. The cycloaddition of 1122 with enantioenriched tBMA produces one cycloadduct (3) in which ca 91% of the enantiomeric excess (ee) of the tBMA is transferred to the cycloadduct. The other three cycloadducts are formed retaining much less of the ee of the starting tBMA. The results are interpreted on the basis of molecular modeling calculations carried out on the 1122-1,3-dimethylallene system reported previously. It is suggested that cycloadduct 3 is formed by essentially only one continuous minimum-energy reaction pathway, while cycloadducts 2 and 4 are formed by two competitive minimum-energy reaction pathways which result in the formation of cycloadducts possessing opposite absolute configurations. The combined contributions of the two competitive pathways result in much lower overall degrees of transfer of the ee of the tBMA to the diradical intermediates and cycloadducts.
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    Erratum (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 132-132 
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    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.610060211
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    Study of initial- and transition-state solvation in the solvolysis of tert-butyl halides in alcohols from infinite dilution activity coefficients (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 133-138 
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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 Gibbs energies of activation of the solvolytic reactions of tert-butyl halides (chloride, bromide and iodide) in eight mono-alcohols and eight di-alcohols were dissected into contributions from the initial state and transition state. The unified approach proposed by Abraham was applied and the various factors making up the overall solvent effect in both states were identified and compared. To perform this study, the Gibbs energies of transfer of the initial state were calculated using the infinite dilution activity coefficient values of the solutes in the solvents, γ∞. These values were determined from the UNIFAC group-contribution method, with the modified Flory-Huggins equation in the combinatorial term and with group interaction parameters from the Parameter Table exclusively based on experimental γ∞ data reported in the literature. It is concluded that solvent polarizability and polarity-HBD acidity and cavity effects during the activated process are mainly due to transition-state contributions.
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    Stern-Volmer quenching kinetics for use of a dualistic quencher (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 160-162 
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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 Stern-Volmer quenching equation for use of a dualistic quencher, which serves not only as the quencher for an excited starting molecule but also as the promoting agent for product formation, was obtained by applying the steady-state approximation to the photoreaction system. The equation was applied to the kinetic analysis of the Norrish type II photoreaction of valerophenone using triethylamine, which serves as the excited-state quencher and as the promoting agent for product formation.
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    IUPAC Commission on Physical Organic Chemistry (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 193-194 
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    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.610060311
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    Intramolecular photoinduced electron transfer (PET) bond cleavage in some sulfonium salt derivatives. Effect of distance and thermodynamics on PET rate (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 333-340 
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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 rate of intramolecular photoinduced electron transfer (PET) between a naphthacene electron donor (D) and a sulfonium electron acceptor (A) was found to be dependent on the thermodynamics for PET and distance between D and A. The slopes of In kET vs through-bond and through-space distance plots was found to be -0·60 and -0·91 Å-1, respectively. The product distribution obtained from the photolysis of regioisomeric naphthacenyl sulfonium salt derivatives was found to be independent of distance. Photolysis of three regioisomeric naphthacenyl phenylmethyl-p-cyanobenzylsulfonium salts produced unsubstituted thiomethylphenylnaphthacene and mono-, di- and tri-p-cyanobenzyl-substituted thiomethylphenylnaphthacene. The appearance of the out-of-cage di- and trisubstituted photoproducts suggests that secondary photochemistry and intermolecular electron transfer bond-cleavage reactions are occurring when the concentration of the sulfonium salt in acetonitrile is 10-2 and 10-3 M and the degree of conversion is high. The primary photoproduct is the mono-substituted naphthacene derivative.
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    Nucleophilic substitution reactions of isopropyl benzenesulphonates with anilines and benzylamines (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 357-360 
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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 nucleophilic substitution reactions of isopropyl arenesulphonates with anilines and benzylamines in acetonitrile at 65·0°C were investigated. The cross-interaction constants ρxz (and βxz) between substituents in the nucleophile (X) and leaving group (Z) are positive and relatively small. The transition state (TS) variation is consistent with that predicted by the More O'Ferrall-Jencks diagram, as expected from the positive ρxz. The small magnitude of ρxz correctly reflects a relatively loose TS structure, in contrast to the tight TS for ethyl (or methyl) derivatives under similar reaction conditions.
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    Ion-molecule pairs as intermediates in solvolysis. Catalysis by the pyridine leaving group on the elimination reaction (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 374-375 
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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: Solvolysis of the 1-(1-methyl-1-phenylethyl)pyridinium cation (1-P+) in 25% (v/v) acetonitrile in water at 60°C provides the alcohol 2-hydroxy-2-phenylpropane (1-OH) as the main product along with the alkene 2-phenylpropene (3). The formation of the elimination product 3 is promoted by the leaving pyridine. Thus, eight times more 3 is obtained from 1-P+ than from the protonated ether 1-OMeH+. Hydron abstraction by the leaving pyridine is only two times less efficient than with AcO- as leaving group. The results indicate that the ion-molecule pair 1+ -P has a significant lifetime. The elimination product is formed mainly from the ion-molecule pair. The free carbocation yields almost exclusively the substitution product.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060610
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    Simultaneous determination of primary and secondary thermodynamic isotope effects in tautomeric equilibria (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 367-373 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: NMR determination of site-specific hydrogen isotope ratios at natural deuterium abundance (SNIF-NMR) provides the basis for simultaneous access to primary and secondary thermodynamic fractionation factors in exchange reactions and avoids the need for selective isotope labelling of the reagents. The method was applied to the measurement of fractionation parameters involving OH, CH2, CH3 and =CH groups in keto-enol tautomeric equilibria. The fractionation factors relating the =CH and OH sites of the enol species are simply derived from 2H NMR spectra whereas the determination of isotope parameters which relate keto and enol positions exploits a combination of 2H and 1H NMR experiments. Since only monolabelled isotopomers have to be considered at natural abundance, the method also offers the advantage of avoiding the occurrence of complex equilibria associated with multi-labelled species possibly introduced by deuterium enrichment. The primary equilibrium isotope effects illustrate a preference of deuterium for the methylene fragment of the keto form with respect to the ethylenic position of the enol tautomer. Since the enol species is itself engaged in a fast tautomeric equilibrium associated with a symmetric or unsymmetric double minimum potential, the thermodynamic parameters are averaged over the exchanging partners. It is shown that the average thermodynamic fractionation factor relating the OH and =CH hydrogens of the enol are significantly influenced by the nature of the substituents at both carbonyl positions of the β-diketones. Moreover, methyl and chlorine substitution increases by a factor of about 1·1 the thermodynamic isotopic fractionation factor relating the -COCHCO- position of the keto form to the hydroxyl position of the enol.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060609
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  • 45
    Electronic Resource
    Electronic Resource
    Magnetic field effects upon photochemistry of bifuctional chain molecules (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 381-392 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: External magnetic field effects are discussed for three typical examples of photoreactions involving biradical intermediates: photo-induced intramolecular electron transfer in chain molecules D—(CH2)n—A consisting of an electron donor (D) and an acceptor (A), intramolecular hydrogen abstraction in bifunctional species :X—(CH2)n—YH containing a hydrogen donor (YH) and an acceptor (:X in the excited triplet state) and photochemical homolytic ring opening of a cyclic ketone which yields a biradical consisting of an acyl and an alkyl group. There has been progress in the elucidation of reaction mechanisms through the analysis of magnetic field effects on lifetimes of reaction intermediates and product yields in radical reactions involving biradicals. Extremely small interactions such as the Zeeman energy and hyperfine interaction may give rise to a large change in the distribution of photo-products derived from bifunctional chain molecules.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060702
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  • 46
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    Evidence for the presence of the CH-π-interacted ap-conformers of benzyl formates (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 399-406 
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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: In order to examine the preferred conformations of benzyl, 1-phenylethyl and cumyl formates, lanthanoid-induced shifts (LIS) of 1H and 13C NMR and difference NOE spectra of these esters were measured. The measurements showed that a folded conformer capable of forming intramolecular CH-π interaction are predominant with all three series of formate esters. The LIS and other experiments suggested the coexistence of considerable amounts of extended conformers, however. As the ester group is enforced to take supposedly unfavourable ap-conformation in the CH-π contiguous folded conformer, the predominance of the conformer was a surprise and needed explanation. The NOE experiments on a series of para-substituted benzyl formates, XC6H4CH2OCHO (X = CH3O, CH3, H, Cl, NO2), showed that the enhancement of aromatic proton signals (ortho and meta) induced by the irradiation of formyl proton increases gradually as the substituent becomes more electron donating, whereas the enhancement of benzylic (α) proton signal remains constant irrespective of the nature of the substituent. This can be explained by assuming that the CH-π contiguous folded conformer is in equilibrium with the extended conformer. The trend of the substituent effect supports the hydrogen bond-like nature of the CH-π interaction. A similar trend was also observed with substituted 1-phenylethyl formates. Hence the unexpected stability of the ap-conformer of benzyl formates could be ascribed to the stabilization due to the CH-π interaction.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060704
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    Vibrational spectra of C4H7+ isomers in low-temprature antimony pentafluoride matrices (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 427-432 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The IR spectra of isomeric bicyclobutonium (1), delocalized cyclopropylcarbinyl (2) and 1-methylally (3) cations were recorded at 180 K in SbF5 matrices. Cations 1 and 2 generated from cyclopropylcarbinyl and cyclobutyl chloride, respectively, rearrange to 3 at temperatures above 230 K. The structures 1, 2 and 3 were confirmed by comparison of the recorded frequencies with the MP2/6-31G*-calculated values. These results are in accord with prediction that ions 1 and 2 are rapidly equilibrating non-classical structures.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060708
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  • 48
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    Multinuclear NMR study of a five-membered ring ditellurium derivative (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 520-522 
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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: 125Te, 1H and 13C NMR data are presented for a five-membered ring ditellurium derivative. The signals are assigned by means of integration and correlation spectroscopy. The NMR data are most consistent with the presence of one of the two possible structures.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060906
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    Solvation and metal ion effects on structure and reactivity of phosphoryl compounds. 2. β,γ-Substituted alkylphosphonic esters (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 523-530 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: NMR spectroscopic and conformation analyses ware carried out for five dimethyl β,γ-disubstituted propylphosphonates, YCH2CHXCH2PO3Me2, in five solvents and in acetone containing sodium and magnesium ions. Conformational preferences observed for the rotation about the C1—C2 bond are determined by the attractive interactions between the oxygen containing substituents X (X = OH, OMe) and the phosphoryl group, and are enhanced by the metal ions, presumably via chelation effects. The rotation about the C2—C3 bond yields statistical distribution of the rotamers. For Y = benzoyl, there was no evidence for a competition of the carbonyl group for the intramolecular interactions with X or with a metal ion.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060907
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  • 50
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    A comparison of the relative magnitudes of the interaction energies between functional groups with zero, one and two intervening 2p AOs on Carbon, and substituent effects on the relative ground-state energies of E-1,2-disubstituted ethenes (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 621-626 
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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: Ab initio theoretical calculations have been carried out on directly bonded donor-acceptor (Ẍ-Y) species and on variously substituted E-1,2-disubstituted ethanes, and π interaction energies have been estimated. In conjunction with the previously calculated radical stabilization energies of mono- and disubstituted methyl radicals, a comparison is made of the relative magnitudes of the π interaction energies between groups with zero, one and two intervening 2p AOs on carbon atoms. It is concluded that the stabilizing effect of the π interaction between directly bonded donor Ẍ and acceptor Y groups (zero intervening 2p AOs) is approximately 2·1 times that in the disubstituted methyl radicals (one intervening 2p AO), while in the E-1,2-disubstituted ethenes (two intervening 2p AOs) the stabilizing effect is ˜ 0·7 of that calculated for the disubstituted methyl radicals for both acceptor-donor and acceptor-acceptor disubstituted systems. No correlation is observed with the π stabilization energies of the ‘cross-conjugated’ 1,1-disubstituted ethenes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061105
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    Cationic and anionic halochromism (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 637-641 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The spectral changes of organic solutions of N,N,N′,N′-tetramethylenediaminoacetylacetonatocopper(II) perchlorate and a merocyanine dye in the presence of NaI or LiClO4 provide examples of anionic and cationic halochromism, respectively. The observed changes are interpreted as arising from all possible interactions in the three-component system of the dye, the salt and the solvent.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061108
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    AM1 and polarized-π frontier molecular orbital (PPFMO) studies of facial selectivity in hydrogen transfer to substituted adamantyl radicals (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 690-695 
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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: Fully optimized transition states for hydrogen transfer from methane and propene to substituted 2-adamantyl radicals were calculated using the AM1 molecular orbital method. Methane and propene were chosen to provide an early (propene) and a late (methane) transition state. For 5-substituted radicals (F, Cl, Ph, CH3, CF3) the enthalpic differences between syn and anti reactions was found to be small [〈0·1 kcal mol-1 (1 kcal = 4·184 kJ)]. Other radicals with nitrogen or boron included directly in the adamantyl fragment showed greater selectivities, with aza substitution favoring syn and bora substitution favouring anti attack, as did the 4,9-difluoro derivative. The calculated selectivities are all in qualitative agreement with experimental results (where available) on bromine atom transfer. PPFMO calculations showed the polarization of the SOMO to be generally in accord with the AM1 results, whereas the polarization of the LUMO's was less indicative. The bond orders for the bonds syn and anti to the incipient C—H bond in the adamantyl fragments indicated that the anti bonds were always weaker than those syn, in agreement with the suggestion by Cieplak that has been used to explain the experimental selectivities. However, the bond lengths of the incipient C—H bonds are always shorter for the side of preferred attack, in apparent agreement with the suggestion by Anh.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610061206
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    Alkaline hydrolysis of substituted benzyl substituted benzoates (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 23-28 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics and mechanism of the alkaline hydrolysis of both acyl- and aryl-substituted benzyl benzoates were studied in 80% (v/v) aqueous acetone at 20, 34, and 40 °C. Each of the substituted benzyl alcohols generated an independent σ-ρ plot which was correlated well with the Hammett equation (R = 0·996-0·999). The values of ρ for the acyl moiety showed no tendency either to increase or to decrease with the intrinsic reactivity of the parent benzyl alcohol and were all within ±0·098 of the mean of 2·236. However, the Hammett ρ values for the leaving groups decreased from H to p-NO2 substituents of the acyl part, in which the values were smaller than those of acyl moieties and fairly accurately obeyed the σ0 values rather than the σ values. The rate data for benzyl-substituted benzoates were correlated by the Yukawa-Tsuno equation, log k/k0 = 1·72(σ0 + 0·49ΔσR-) - 0·020, R = 0·996. The results suggested that the alkaline hydrolysis of benzyl benzoates showed a greater sensitivity to acyl than aryl activation, and the rates and activation parameters were largely determined by the addition step. The results are attributed to the preferential partitioning of an unstable tetrahedral intermediate to the products.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060105
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    Elimination kinetics and mechanism of primary, secondary and tertiary α-hydroxycarboxylic acids in the gas phase (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 54-58 
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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 rates of elimination of primary, secondary and tertiary α-hydroxycarboxylic acids were determined in a seasoned, static reaction vessel over the temperature range 280-390°C and the pressure range 30-201 Torr. The reactions, in the presence of a free radical inhibitor, are homogeneous, unimolecular and follow a first-order rate law. The rate coefficients are given by the following equations: for glycolic acid, log k1 (s-1) = (14·03 ± 0·24) - (209·3 ± 1·5) kJ mol-1 (2·303RT)-1; for lactic acid, log k1 (s-1) = (12·24 ± 0·11) - (182·8 ± 1·3) kJ mol-1 (2·303RT)-1; and for 2-hydroxyisobutyric acid, log k1 (s-1) = (12·91 ± 0·13) - (174·7 ± 1·5) kJ mol-1 (2·303RT)-1. The basicity and the ease with which the hydroxy group is removed from primary to tertiary α-hydroxycarboxylic acids are reflected in rate enhancement. The mechanism of these eliminations appears to proceed through a semi-polar five-membered cyclic transition state.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060109
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    Kinetics and mechanism of the oxidation of substituted benzaldehydes by ethyl N-chlorocarbamate (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 1-6 
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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 oxidation of a number of para- and meta-monosubstituted benzaldehydes by ethyl N-chlorocarbamate (ECC) were studied in aqueous acetic acid solution in the presence of perchloric acid. The main product of the oxidation is the corresponding benzoic acid. The reaction is first order with respect to the aldehyde, ECC and hydrogen ions. The oxidation of benzaldehyde exhibits a substantial primary kinetic isotope effect (kH/kD = 5·20 ± 0·10). Addition of ethyl carbamate has no effect on the rate. [EtOC(OH)NHCI]+ is postulated as the reactive oxidizing species. The rates of oxidation of para-substituted benzaldehydes exhibit an excellent correlation with Taft's σ1 and σR+ values whereas those of the meta-substituted compounds compounds correlate best with σ1 and σR0 values. The reaction constants are large and negative. A mechanism involving transfer of a hydride ion from the aldehyde to the oxidant, in the rate-determining step, is proposed.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060102
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  • 56
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    Effects controlling the conformational selectivity and association parameters of H-bonded assemblies between di- and triaminotriazines and bemegride (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 29-43 
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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: 2,4,6-Tris(aminocyclohexyl)triazine (1) and 2,4-bis(aminocyclohexyl)-6-methoxytriazine (2) are present in solution in two and three equilibrating conformations, respectively. The activation barrier for interconversion of the conformers 1a ⇌ 1b is 14·55 ± 0·2 kcal mol-1 (1 kcal = 4·184 kJ) and the activation barrier for interconversion of the conformers 2a ⇌ 2b ⇌ 2c is 14·2 ± 0·2 kcal mol-1. The conformational analyses of 1 and 2 were also followed by molecular mechanics calculations. Compounds 1 and 2 form H-bonded intermolecular complexes with bemegride (3). Association of 3 proceeds by selection of a specific conformation of 1 and 2, i.e. 1b and 2a, respectively. The association constants of 3-1b and 3-2a are to Ka = 915 and 450 l mol-1, respectively. Molecular mechanics calculations for the H-bonded intermolecular assemblies support the experimental observations of the selective conformational association.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060106
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    Ambident reactivity of aryloxide ions towards 1,3,5-trinitrobenzene, low-temperature characterization of the elusive Oxygen-bonded σ-complexes by 1H and 13C NMR spectroscopy (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 71-82 
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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 ambident reactivity of phenoxide ion towards 1,3,5-trinitrobenzene (TNB) was re-examined by means of a novel reaction system(CD3CN-glyme-d10) which allows the investigation of species formed at low temperatures (-40°C), contrasting with previous studies in dimethyl sulfoxide (DMSO) at ambient temperature. The new method coupled with 400 MHz NMR spectroscopy has allowed the definitive observation of both O- and C-bonded phenoxide σ-complex adducts for the first time, confirming the formation of the former through kinetic control and of the latter through thermodynamic control. The corresponding O-bonded σ-adduct in the TNB-mesitoxide system (whereC-bonded σ-adduct formation is not possible but where there is competing nitro group displacement) has also been characterized by 1H and 13C NBR. Another O-bonded aryloxide adduct characterized is that from the reaction of TNB with3,5-di-tert-butylphenoxide; in this system there is also competing NO2 displacement. Stereoelectronic factors in the O-bonded σ-adducts and aryl ethers are discussed.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060202
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    Nucleophilic solvent intervention in the solvolysis of 2-aryl-2-Chloropropanes. An example to demonstrate the advantage of using the YBnCl scale in correlation analysis (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 122-125 
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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 advantage of using the YBnCl scale over the YCl scale in Grunwald-Winstein-type correlation analysis was demonstrated by the kinetic evidence of a significant nucleophilic solvent intervention in the solvolysis of 2-aryl-2-chloropropanes. A depression of log k values measured in ethanol-trifluoroethanol mixtures and a positive azide salt effect were observed.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060209
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    Acid-base equilibria and kinetics between triarylmethane dye carbinols and organic acids in apolar aprotic solvents: Relative basicities of dye carbinols in toluene (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 145-152 
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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: Equilibria and kinetics of acid-base reactions in toluene between a carboxylic acid (m-toluic, salicylic acid) and a set of carbinol bases (derived from basic triarylmethane dyes) were studied spectrophotometrically. The results for the equilibrium and kinetic parameters were critically analysed. The rate constant of the forward step of the acid-carbinol base equilbrium was found to provide a suitable scale of basicities in toluene. The basicities of the dye carbinols chosen decrease in the order Ethyl Violet- 〉Crystal Violet- 〉Methyl Violet- ≈ Victoria Pure Blue BO- ≫ Brilliant Green- 〉Malachite Green-carbinol. This is fairly consistent with the order observed in water. A fairly good correlation between base strengths of the carbinols and σR+ parameters of their para-alkylamino substituents was obtained.
    Additional Material: 6 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060304
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    Stereochemistry of aminolysis of N-pentafluorophenylcarbonimidoyl dichloride. Crystal and molecular structures of N2-pentafluorophenyl-N1,N1-dibenzylchloroformamidine (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 319-325 
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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: It has been established that the product of the reaction of N-pentafluorophenylcarbonimidoyl dichloride (1) with dibenzylamine, viz. N2-pentafluorophenyl-N1,N1-dibenzylchloroformamidine (4a) is a Z-isomer, whereas according to the concept of stereoelectronic control one might have expected a product with E-configuration. The heat of formation and the geometry of Z- and E isomer of N2-pentafluorophenyl-N1,N1-diethylchloroformamidine (4b) (the latter is a product of the reaction of 1 with diethylamine) were calculated with the semi-empirical MNDO method. The calculated geometry of (Z)-4b was found to be in a good agreement with the experimentally determined structure of 4a. The formation of (Z)-4b is more preferable energetically than that of (E)-4b; the calculated difference in the heats of formation is 2·8 kcal mol-1. Thermodynamic control of the reaction stereochemistry is proposed.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060602
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    Temprature dependence of the deuterium isotope effect in the deprotonation of some nitroalkanes by anionic bases (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 393-398 
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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 temperature dependences of rates and deuterium isotope effects were determined for the deprotonation of 1-phenyl-1-nitroethane (1), its analogue 1-d, 1-phenyl-2-nitropropane (2) and its analogue 2-d by methoxide in methanol, ethoxide in ethanol, hydroxide/methoxide in 50% (v/v) methanol-water and hydroxide in water. The isotope effects varied little with substrate or solvent-base combination. kH/kD at 30°C was between 6·0 and 7·1 in all cases. The temperature dependences varied considerably [AaH/AaD = 0·14-1·35 and EaD - EaH 0·95-2·29 kcal mol-1 (1 kcal = 4·184 kJ)]. AaH/AaD was lower with 1-phenyl-1-nitroethane than with 1-phenyl-2-nitropropane, but there was no consistent variation with solvent/base.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060703
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    Adsorption at the liquid-liquid interface: An important factor in phase-transfer catalysisReactions of Organic Anions, Part 200. For Part 199, see Ref. 1. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 412-420 
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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: A new rationalization of some phenomena in the phase-transfer catalysed processes promoted by concentrated aqueous alkali solutions, such as alkylations and β-eliminations, is proposed. It is predicted on the basis of adsorption theory and subsequently evidenced experimentally that the size of the interfacial area, controlled by the rate of stirring, affects the position of the extraction equilibrium of various anions with quaternary ammonium cations supplied by the phase-transfer catalysts.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060706
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    Steric deuterium isotope effect in the solvolysis of (Z)-[Methyl-D3]-2-ethylidene-1-adamantyl iodide accelerated by F-strain (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 293-301 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The deuterium isotope effect in the solvolysis of (Z)- and (E)-[methyl-d3]-2-ethylidene-1-adamantyl mesylates [(Z)- and (E)-1d-OMs] and iodides [(Z)- and (E)-1d-I] was studied in 2,2,2-trifluoroethanol at 25·0°C for mesylates and at 50·0°C for iodides. For the mesylates, which show a relatively small F-strain effect, the (Z/E)H rate ratio (117 ± 1) is essentially identical with the (Z/E)D rate ratio (116 ± 1) at 25·0°C. On the other hand, for the iodides, which show a larger F-strain effect, the (Z/E)H rate ratio (5413 ± 57) is greater than the (Z/E)D rate ratio (5040 ± 58) at 50·0°C. This indicates that (Z)-1h-I has greater F-strain than (Z)-1d-I in the ground state. These results again confirm that the F-strain effect in the (Z)-2-ethylidene-1-adamantyl derivatives exists between the (Z)-methyl group and the leaving group atom directly attached to the reaction centre.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060507
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    Homoaromaticity of decamethyl[5]pericyclyne (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 316-318 
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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: It is shown that a theoretical computation of the Dewar resonance energy of decamethyl [5] pericyclyne should give the same value for the homoaromaticity of this compound as that calculated earlier from heat of hydrogenation measurements. Both methods show this quantity to be small, but the accuracy of the methods appears insufficient for more exact agreement.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060510
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  • 65
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    Base catalysed photochemically induced hydrogen isotope exchange in o-methylbenzophenone (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 465-470 
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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: Photochemically induced hydrogen-deuterium and hydrogen-tritium exchange between o-methylbenzophenone and labelled methanol is shown to be catalysed by sodium carbonate. Both the (E) and (Z)-photoenols participate in the exchange reaction whereas in absence of the catalyst only the (E)-photoenol is reactive. Analysis of the measured quantum yields for hydrogen isotope exchange reaction allowed the determination of the relative population of transient photoenols and to its comparison with that obtained from the flash photolysis experiments. Both hydrogen kinetic and solvent isotope effects are discussed.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060804
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    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.610060901
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  • 67
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    Photoreaction of 2-benzoylcyclohexanones on a silica gel surface: Deviation from their solution photochemistry (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 494-498 
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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: On irradiation on a dry silica gel surface, 2-benzoylcyclohexanones which have the lowest n, π* state and are devoid of methyl substituents on their cyclohexanone rings, undergo an oxidative cleavage to give adipic acid and subsituted benzoic acid along with the Norrish Type II product. Irradiation of 2-chlorocylohexanone and cyclohexane-1,2-dione on silica gel also gives adipic acid. The cyclohexanonyl radical on the surface, which is produced from the α-cleavage of the 2-benzoyl group of the 2-benzoylcyclohexanones or the cleavage of the C—Cl bond of 2-chlorocyclohexanone, is suggested as the precursor of adipic acid; the radical is probably converted into cyclohexane-1,2-dione, which undergoes a secondary photoreaction to give adipic acid on the surface.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060903
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  • 68
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    Efficient formation of some amidines by the reactions of aryliminodimagnesium with weakly electron-accepting benzonitrile, N,N-dimethylformamide and related compounds. Features of reactions governed by σ-complexationAryliminodimagnesium Reagents, Part XXIII. For Part XXII, see Ref. 1. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 509-519 
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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: In many reactions of magnesium reagents, including Grignard and aryliminodimagnesium [ArN(MgBr)2, IDMg], the formation of abnormal products via reactions such as radical dimerization, hydrogen abstraction and conjugate 1,4-addition orginating from efficient single electron transfer (SET) is not excluded. In IDMg reactions with benzonitrile and N,N-dimethylformamide in tetrahydrofuran, however, clean reactions took place affording N-arylbenzamidine and N,N′-diarylformamidine via exclusive 1,2-addition and condensation plus replacement, respectively. Some alkyl and arylvinyl cyanides gave the corresponding amidines without 1,4-addition or hydrogen abstraction. These results are the first observation of such reactions of magnesium reagents, and are attributed to a combination of the weak electron-donating ability (EDA) of IDMg with the weak electron-accepting ability (EAA) of nitriles. Although ESR is therefore inapplicable, factors governing the product yields were studied on the basis of effects caused by the addition of strongly coordinating hexamethylphosphoramide and pyridine to the reagent solution, and by addition of nitrobenzenes having a strong EAA. From the results, a large participation of σ-complexation followed by implicit SET in the inner sphere of the complex is proposed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060905
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  • 69
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    Calculation of non-linear optical properties of pyridinium cyclopentadienylides (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 531-534 
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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: Finite field/PM3 calculations of the dipole moments, polarizabilities, hyperpolarizabilities, and second-order hyperpolarizabilities of pyridinium cyclopentadienylide and some nitro and amino derivatives suggest that these compounds are good candidates for non-linear optical materials.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060908
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  • 70
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    Photochlorination of tetrachloroethene in carbon tetrachloride solutions (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 545-550 
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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: Validation of the mechanism of tetrachloroethene photochlorination at low C2Cl4 concentrations was investigated. The reaction was examined in carbon tetrachloride solution. For initial tetrachloroethene concentrations below 2 mol I-1, the solvent participates in a free-radical chain photochlorination. The presence of CCl4 disturbs the course of this particular chain reaction and influences the duration of the induction period.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610061003
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  • 71
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    Solvent effects on initial and transition states in the reaction of m-fluorophenyltriethyltin with mercuric chloride in methanol and methanol-water mixtures (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 561-566 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have investigated solvent effects on the aromatic electrophilic substitution reaction of m-fluorophenyltriethyltin, 1, with mercuric chloride in order to obtain information about the polarity of the transition state. Second-order rate constants have been determined for the reaction of 1 with mercuric chloride in methanol and methanol-water mixtures at 25·0°C, allowing determination of δΔG
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610061006
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  • 72
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    Use of the multifunctional autocorrelation method to estimate molar volumes of alkanes and oxygenated compounds. Comparison between components of autocorrelation vectors and topological indices (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 574-582 
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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 Multifunctional Autocorrelation Method (MAM) derived from the autocorrelation method of Moreau et al. was used to calculate molar volumes for 300 linear or branched alkanes from C6 to C11 and 104 oxygenated compounds including 40 alcohols, 30 ethers and 34 ketones. Components Ci of a MAM connectivity vector were compared with several topological descriptors. MAM descriptors were generally more efficient than topological descriptors but good regressions were obtained for alkanes only when more than two components Ci were used. An excellent regression was obtained with four components (C0 to C4): \documentclass{article}\pagestyle{empty}\begin{document}$$ V_{\rm m} = 4 \cdot 45C_0 + 6 \cdot 44C_1 - 3 \cdot 33C_2 + 0 \cdot 46C_4 + 52 \cdot 9{\rm (}n = 300,r = 0 \cdot 999,s = 0 \cdot 81) $$\end{document} Models obtained using descriptors based on connectivity were good enough for many practical purposes. However, to derive models adapted to estimate molar volumes for alkanes, an autocorrelation vector V based on Van der Waals volumes (as given by Bondi) was considered. The best equation obtained again includes three components: \documentclass{article}\pagestyle{empty}\begin{document}$$ V_{\rm m} = 1 \cdot 750V_0 - 0 \cdot 123V_3 - 0 \cdot 037V_4 + 17 \cdot 97{\rm (}n = 300,r = 0 \cdot 999,s = 0 \cdot 85) $$\end{document} To extend the use of MAM to compounds containing heteroatoms, a set of alcohols, ketones and ethers, were each functional group represents a different interaction type, was considered. Chemical families were first studied individually, then the total set was considered. The components of an autocorrelation vector V based on Van der Waals volumes were used as molecular descriptors. Oxygenated compounds are correctly described by only one component V0. The correlation coefficient is 0·993 for all the chemical families studied, and the standard error of the estimate is low (s = 2·56). Comparison of standard errors of the estimate for Wiener's indices (s = 17·38) and autocorrelation components (s = 3·95), for all chemical families, shows that components of MAM are more efficient as molecular descriptors. The quality of regression equations was not significantly changed when 104 oxygenated compounds and 141 alkanes were studied in a global set.
    Additional Material: 7 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610061008
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    Study of initial state and transition state solvation in the Menschutkin reaction of triethylamine with ethyl iodide in alcohols from infinite dilution activity coefficients (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 595-599 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Gibbs energies of activation of the Menschutkin reactions of trethylamine with ethyl iodide in 10 monoalcohols and nine dialcohols, were dissected into contributions from the initial state and transition state. To perform this study, the infinite dilution activity coefficient values of the solutes in the solvents, γ∞, were determined by the UNIFAC group-contribution method, using the modified Flory-Huggins equation in the combinatorial term. For triethylamine, the γ∞ values were calculated using group-interaction parameters from the VLE Parameter Table, due to the nonavailability of specific γ∞ UNIFAC interaction parameters for the relevant groups. For ethyl iodide, the γ∞ values were calculated using the group-interaction parameters from the specific γ∞ UNIFAC Parameter Table, except for the solvents diethylene glycol and triethlene glycol, where VLE parameters were used for the same reasons as explained above for the triethylamine. The results were compared with those obtained for the unimolecular decomposition of tert-butyl halides. For the Menschutkin reaction, we conclude that solvent disruption and reorganization to a state appropriate to solvating the molecular species is a dominant interaction mechanisim.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610061011
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    Structure-odour relations for bitter almond odorants (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 627-633 
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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: Structure-bitter almond odour relations are established for a set of 65 organic compounds (40 having the bitter almond character) belonging to benzene, pyrrole, thiophene, acyclic and cyclic compounds. Compounds are described using components of autocorrelation method, and the odour is described with a binary variable. Data were analysed using principal component analysis followed by a linear discriminant analysis. The obtained model gives satisfactory classification and prediction of the training set and the test set, respectively. In addition, obtained structure-odour relations were translated to structural elements (and rules) necessary for a stimulus to have bitter almond character.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610061106
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    Theoretical solute parameters and correlations of log P and pKa. A comment on a recent development and statistical protocol (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 634-636 
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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: Physical-chemical properties can be correlated and predicted using linear free energy or linear solvation energy relationships (LSER). Procedures to obtain theoretical parameters from calculated molecular structures that can be used in LSER have recently been evaluated [G R. Famini, C. A. Penski and L. Y. Wilson, J. Phys. Org. Chem. 5, 395-408 (1992)]. Among other applications, these procedures were applied to correlate octanol-water partition coefficients and pKa values for two groups of structurally diverse solutes with very good reported results. In this paper, the statistical results of those studies are re-examined. The corrected statistical parameters do not provide tenability for the appropriateness of the methodology in these applications. However, valid multilinear relationships of the theoretical LSER parameters with the experimental properties are found which do substantiate the original conclusions of Famini et al.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610061107
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    α-Versus β-carbon nucleophilic attack in vinylic substitution (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 59-63 
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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 mechanism of substitution of the bromine atom in (Z)-α-bromo-β-arylthiovinyl phenyl sulphones, PhSO2CBr = CHSAr, with arylthiolates, Ar′S- was studied. The same mixture of the four possible products, PhSO2C(SAr′) = CHSAr (Ar, Ar′ = p-Tol, p-CIC6H4), was formed in both cross-experiments (Ar ≠ Ar′). A mechanism involving 1,2-intramolecular migration of the arylthio group is suggested.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060110
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    Interaction of dichlorocarbene with imines (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 83-84 
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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 interaction of dichlorocarbene with imines and ketene imines was studied by means of the MNDO method. The results indicate that the lack of ylide cyclization products in the reactions of dichlorocarbene with ketene imines is due to a high reactivity of ketene imine ylides in intermolecular reactions, rather than stereoelectronic factors preventing cyclization. It was shown that the dichlorocarbene reaction with N-benzylideneaniline resulting in gem-dichloraziridine proceeds through transient formation of ylide.
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    URL: http://dx.doi.org/10.1002/poc.610060203
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    Molecular rearrangements in homogeneous gas-phase elimination reactions. Pyrolysis kinetics of alkyl methanesulphonates (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 85-94 
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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 rates of elimination of several alkyl methanesulphonates were determined in a seasoned, static reaction vessel over the temperature range 300-420°C and the pressure range 28-163 Torr. The reactions are homogeneous, unimolecular and follow a first-order rate law. The overall rate coefficients are given by the following equations: for isobutyl methanesulphonate, log k1 (s-1) = (12·51 ± 0·38) - (177·0 ± 2·1) kJ mol-1 (2·303RT)-1; for 2-phenyl-1-propyl methanesulphonate, log k1(s-1) = (12·62 ± 0·04) - (176·2 ± 0·5) kJ mol-1 (2·303RT)-1; for neopentyl methane-sulphonate, log k1(s-1) = (13·35 ± 0·42) - (198·2 ± 5·2) kJ mol-1 (2·303RT)-1; and for 3-chloro-2,2-dimethyl-1-propyl methanesulphonate, log k1(s-1) = (13·87 ± 0·42) - (218·2 ± 5·4) kJ mol-1 (2·303RT)-1. Rearrangements in these methanesulphonate pyrolyses may proceed via an intimate ion-pair type of mechanism. Consequently, the results appear to confirm that intramolecular migration through autosolvation is possible in gas-phase elimination reactions of certain types of organic molecules.
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    URL: http://dx.doi.org/10.1002/poc.610060204
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    Catalytic activity of polypodands and glymes under solid-liquid phase-transfer catalysis conditions. Amolecular mechanics study (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 113-121 
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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 molecular mechanics study of cyclophosphazenic polypodands and of glymes, of their complexes with ion pairs (IPs) M+ I- (M+ = Li+, Na+, K+, Rb+) and IP aggregates (M+ I-)n was carried out to investigate the catalytic activity of these ligands in solid-liquid phase-transfer reaction. This activity is explained by their ability to bind IP aggregates effectively and to activate the anion by increasing the interionic distance in the single IP.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060208
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    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.610060301
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    π-Complexes of naphthalene and its derivatives with nitrosonium cation (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 153-159 
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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: 1H, 13C, and 15N NMR studies, including the use of the 13C NMR deuterium perturbation method, showed that the interaction between naphthalene or its methylated derivatives and the nitrosonium cation result in the formation of π-complexes. The chemical behaviour of these complexes was investigated; in particular, their ability to be converted into binaphthyl derivatives was established.
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    URL: http://dx.doi.org/10.1002/poc.610060305
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    Versatile packing modes of 9-substituted 9-fluorenols. X-ray crystal structures of 9-methyl-, 9-phenyl-, 9-(1-naphthyl)- and 9-(2-biphenylyl)fluoren-9-ol (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 171-178 
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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 four studied semi-rigid fluorenol derivatives differ only in the size of the 9-substituents. All four compounds crystallize with two molecules per asymmetric unit and with relatively low crystallographic symmetry [P1 for the 9-methyl derivative (1) and P21/n for the 9-(1-naphthyl) (3) and 9-(2-biphenylyl) (4) derivatives]. Crystal data: 1, a = 8·779(1), b = 11·570(1), c = 11·747(1), α = 91·197(5), β = 104·345(4), γ = 105·848(6)° 2, a = 8·425(1), b = 13·819(1), c = 23·902(2)Å, β = 95·87(1)° 3, a = 15·679(4), b = 8·567(2); c = 23·884(17)Å, β = 92·60(6)° 4, a = 7·770(6), b = 33·766(10), c = 13·649(4)Å, β = 95·30(1)°. Nevertheless, the packing modes are different. The 9-methylfluoren-9-ol molecules, forming H-bonded tetramers with full H-bond saturation, give rise to the lowest packing coefficient among the four compounds. The crystals of the 9-phenyl derivative are built up of H-bonded dimers, whereas those of the bulky 9-naphthyl and 9-diphenylyl derivatives consist of single molecules only. The latter two compounds, however, have a denser packing than the two that contain H-bonded aggregates. The crystal structures are held together mainly by ordinary Van der Waals forces. In the case of 9-biphenylyfluoren-9-ol, the structure seems to be stabilized also by weak H-bond-type interactions from the alcoholic hydroxyl group to the π-electron cloud of an aromatic ring in the neighbouring molecule the O…centroid distances are 3·182(3) and 3·248(4)Å, and in the 9-naphthyl derivative the OH groups are involved in some short (˜3·3Å) intermolecular approach, possibly indicating an electrostatically favourable packing for the compound.
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    URL: http://dx.doi.org/10.1002/poc.610060308
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    Mechanism of SYN addition of molecular fluorine to ethylene. An ab initio MO studyCycloaddition in Synthesis, Part 64. For Part 63 see Ref. 9. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 195-200 
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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 whole process for the syn addition of molecular fluorine to ethylene was analysed at the MP2/6-31 + G level with IRC calculation. The analysis indicates that fluorine approaches the C—C double bond vertically to form a perpendicular complex as the intermediate, which then reorientates to a rhombic-type complex as the transition state to give the final syn addition product. This shows that the square-type complex previously proposed is not involved in any stage of the reaction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060402
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    Radical reactions of epoxides. 2.For Part 1, see Ref. 1. intramolecular competition between cyclopropylmethyl and oxiranylmethyl radical ring-opening rearrangementsInitial results presented at the 46th Northwest Regional Meeting of the American Chemical Society, LaGrande, OR, 1991. Taken from the Thesis of K. W. Krosley.2 (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 228-232 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The erythro-thioimidazole precursor to the cyclopropyloxiranylmethyl radical has been prepared. Treatment with 7-19 equiv. of triphenyltin hydride at 70°C gave only 3-cyclopropylprop-2-en-1-ol, the product of epoxide ring opening. No product in which the cyclopropyl ring had opened was observed. Kinetic analysis allowed the assignment of a lower limit for the rate of oxiranylcarbinyl radical rearrangements of 1 × 1010 s-1 at this temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060406
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  • 85
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    Photochemical and radiolytic cleavage of 10-methylacridine dimer in solutions and cryogenic glasses (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 254-256 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 10-Methylacridine dimer [(AcrH)2] dissociates into a pair of 10-methylacridyl radicals (AcrH·) on laser excitation (308 nm) in solvents of various polarities. Exposure of (AcrH)2 in methylcyclohexane glass at 77 K to γ-rays of 60Co generates the radical cation (AcrH)2+·. Thermal annealing of the matrix to 90 K results in dissociation of (AcrH)2+· into AcrH· and 10-methylacridinium cation (AcrH+).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060410
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    Hydrogen bonding of aromatic amines in hydroxylic solvents. Part 1. Absorption spectroscopy of substituted anilines and hydrogen bond-induced rehybridization of trivalent nitrogen atoms.This paper is dedicated to Professor Jiro Tanaka on the occasion of his 63rd birthday. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 261-272 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The longest wavelength absorption band of substituted anilines containing electron-accepting groups is characterized as an intramolecular charge-transfer (ICT) transition. Dual absorption peaks observed for the ICT transition of some para-substituted anilines in a strongly hydrogen-bonding solvent, hexafluoropropan-2-ol (HFP) can be attributed to two inequivalently hydrogen-bonded species with differently hybridized aniline nitrogens in HFP. The hydrogen bond-induced rehybridization causes appreciable changes in the ICT absorption spectra of highly polar aromatic amines. Rehybridization of aromatic amino nitrogens depends on the OH acidity in the solvent molecule and the basicity of the substituted anilines. The geometry of trivalent nitrogens in aryl amines is critically dependent upon the ionization potential of the amino group, the electron affinity of the electron-accepting substituent and the substitution site of the electron-withdrawing group with respect to the amino moiety.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060503
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  • 87
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    The Marcus cross relation for hydrogen-transfer reactions (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 281-286 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Marcus cross relation provides a tool to calculate cross rates from the corresponding identity rates and the equilibrium constant. Assumptions made in deriving the Marcus cross relation and conclusions which can be drawn from agreement or disagreement between experimental and calculated cross rates are discussed. For a small variation in identity rate constants, agreement between experimental and calculated cross rates are discussed. For a small variation in identity rate constants, agreement between experimental and calculated cross rates simply means that the rate constant of a hypothetical thermoneutral cross reaction has a value within the range covered by the identity rates. Whether or not this value corresponds to the mean value of logarithmic identity rate constants can only be checked for a large variation in identity rates. Therefore, a newly defined index M is used to relate the difference in experimental and calculated logarithmic rate constants to the variation in the logarithmic identity rates. Provided that the Marcus cross relation is not obeyed, this indicates non-additivity of kinetic parameters. Applying this analysis to protontransfer reactions between different transition metal acids and between 9-alkylflourenes and (9-alkylfluorenyl)lithium shows that claims about agreement or disagreement of experimental rate constants with the rate constants calculated by means of the Marcus cross relation have to be revised in part.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060505
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  • 88
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    Substituent effects in carbon-13 NMR spectra of aminopyridines (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 307-315 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 13C NMR spectra of 45 vicinally substituted 2-, 3- and 4-aminopyridines were investigated. The substituent effects are evidently sensitive to the position of both the substituent and the fixed amino group. In the para position with respect to the substituent, long-range electronic effects are expressed by the dual substituent parameter treatment (DSP), and the resonance contribution is more important than the inductive contribution. Correlation results for the ipso and ortho carbon atoms using the more sophisticated extended DSP equation suggest non-electronic effects of unknown origin.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060509
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    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.610060401
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  • 90
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    Substituent effects on the kinetic solvent isotope effect in solvolyses of arenesulphonyl chloridesLimitation of the Transition State Variation Model, Part 6. (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 223-227 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Hammett type plot of kinetic solvent isotope effect (KSIE = kSOH/kSOD), log(KSIE) vs σ, can be a useful mechanistic tool for solvoltic reactions. The slopes of such straight line plots for para-substituted benzenesulphonyl chlorides in methanol (0·15), water (0·05) and methanol-water (0·05) are interpreted in terms of different reaction channels (general base-catalysed and SN2), in contrast to simple Hammett plots, log kSOH (or log kSOD) vs σ, invariably exhibiting non-linear concave curves.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060405
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    Calorimetric study of human serum albumin in water-dioxane mixtures (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 251-253 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The calorimetric isotherm of water sorption by solid human serum albumin (HSA) was measured in water-dioxane mixtures. This isotherm has been successfully described at low water contents in the solvent within the framework of the presented model. The adsorption equilibrium constant and the monolayer formation energy were estimated from this model. The interaction enthalpies of solid HSA with the solvent in water-rich mixtures do not differ essentially from the solution enthalpy of HSA in water. This means that the solvent water content may be sufficient for the intermolecular interactions of HSA suspended in a water-organic mixture to be similar to those in aqueous protein solution.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060409
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    Determination of the existence, value and uncertainty of the compensation or isokinetic temperature (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 273-280 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The demonstration of the existence of a compensation effect, the linear dependence of the enthalphy on the entropy for a series of chemical reactions, is often complicated by an apparent linear dependence arising solely from experimental errors. A non-linear least squares method has been developed for establishing the existence or non-existence of a compensation effect and for determining the value of the compensation temperature if the effect exists. The uncertainty in the value of the compensation temperature can be determined by means of a Monte Carlo procedure. If a compensation effect does not exist, three cases can be distinguished: (1) the relationship between the enthalpy and entropy is linear, but the compensation temperature is 0 K; (2) the various reactions cannot be distinguished from each other because of experimental errors; and (3) the reactions do differ, but the relationship (if one exists) between the enthalpy and entropy is not linear. The method is illustrated using both hypothetical and experimental examples.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/poc.610060504
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    Erratum (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 433-433 
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    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060709
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  • 94
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    Hydrogen-bond basicity of nitriles (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 302-306 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A thermodynamic hydrogen-bond basicity scale, pKHB, and a spectroscopic hydrogen-bond basicity scale, Δν(OH), were measured which permitted the construction of the solute hydrogen-bond basicity scale, β2H, for 71 nitriles embracing a wide range of structures from trichloroacetonitrile to cyanamides. Field, resonance, and polarizability contributions of the X substituents to the hydrogen-bond basicity of XCN compounds were established. Steric effects do not contribute to the hydrogen-bond basicity of nitriles.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060508
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    Metal ions that promote the hydrolysis of nucleoside phosphoesters do not enhance intramolecular phosphate migration (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 347-356 
    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 several metal ions and metal ion complexes on the hydrolysis and interconversion of uridylyl(2′,5′)uridine and its 3′,5′-isomer were studied as a function of pH and metal ion concentration. The hydrolysis was shown to be markedly accelerated by Zn2+, Cd2+ and trivalent lanthanide ions and by tri- and tetraaza complexes of Zn2+. In contrast, none of these species appreciably promotes the interconversion of the 2′,5′- and 3′,5′-isomers, in spite of the fact that this reaction proceeds through the same pentacoordinated intermediate as the hydrolysis. Lanthanide ions also promote the hydrolytic dephosphorylation of uridine 2′- and 3′-monophosphates, but have a barely noticeable effect on their interconversion. The mechanisms of the metal ion-promoted reactions are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060606
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    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.610060701
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  • 97
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    Tuning intramolecular carbenic insertions (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 376-379 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The 1,2-carbenic hydride shift of neopentylmethoxycarbene was suppressed by the methoxy substituent. Thermally activated hydride shifts were observed with phenoxymethylmethoxycarbene and phenoxymethyltrifluoro-ethoxycarbene, where appropriate potentiating substituents were introduced at both the migration origin and the migration terminus. Similarly, the 1,3-CH insertion reaction of tert-butylfluorocarbene could be induced by thermal activation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610060611
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  • 98
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    Microwave activation of the mutarotation of α-D-glucose: An example of an interinsic microwave effect (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 407-411 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mutarotation reaction of α-D-glucose in ethanol-water solvent in a modified commercial microwave oven, when compared with control reactions carried out at identical temperatures, shows a non-thermal microwave effect, evidenced both by a more rapid reaction and by a change in relative amounts of α- and β-D-glucose over time.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/poc.610060705
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    Masthead (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993) 
    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.610061001
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  • 100
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    Using theoretical descriptors in structure-activity relationships: Solubility in supercritical CO2 (1993)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 6 (1993), S. 539-544 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The use of quantitative structure-activity relationships (QSAR) in correlating biological phenomena to chemical structure, and the use of linear free energy relationships (LFER) and linear solvation energy relationships (LSER) for correlating physical phenomena are becoming standard occurrences. In this work the empirical LSER solvatochromic descriptors were replaced with a computationally derived set to aid in a priori property prediction. This paper deals with the application of this descriptor set to correlating the solubilities of 22 compounds in super critical CO2. A reasonable correlation, consistent with previous correlations by other researchers, was found.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610061002
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