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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 1 (1989), S. 493-499 
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of 12 macrocycles containing 4, 6, or 8 N, S, and O heteroatoms (with increasing size from 14 to 24 atoms in the cycle) was studied to ascertain size and heteroatoms effects on the formation and 14 redox characteristics of their mercuric complexes. The concentration dependence of anodic currents at mercury electrodes in solutions of these ligands led to the determination of the formation constants of the complexes generated according to the folling of \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Hg} \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} {\rm Hg}^{{\rm 2 + }} {\rm + 2e}^{\rm - } {\rm,}\,{\rm Hg}^{{\rm 2 + }} {\rm + jL} \mathbin{\lower.3ex\hbox{$\buildrel\textstyle\rightarrow\over {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}}$}} {\rm (HgL}_{\rm j} {\rm)}^{{\rm 2 + }} $$\end{document} In propylene carbonate, the resulting mercuric complexes were stable (log Ks up to 40) mono- and dinuclear species. Their stability depends both on the nature of the heteroatoms and on the size of the macrocycle. For identical ligand sizes, the stability sequence N 〉 S 〉 O was established for mercuric complexes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 217-221 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Sequential daughter-ion-scanning analyses of small peptides have been performed using a hybrid tandem instrument of BEqQ configuration. Precursor ions are selected by B and allowed or induced (by high-energy collisional activation) to decompose in the region preceding E. Decoupling of E from the accelerating voltage permits the selection of the first-generation daughter ion whilst retaining appropriate float voltages for the quadrupole assemblies. The daughter ion selected by E is further subjected to low-energy collisional-activation dissociation (CAD) in q and the fragment-ion spectrum is obtained by scanning Q. The sequential daughter-ion-scanning technique has been used to establish that ‘internal’ fragments of the types, (AY′) and (BY′), are formed via initial Y-type cleavage. Fragmentation of a protonated peptide (angiotensin III) by loss of the C-terminal amino acid residue, yielding a (Bn′ + OH) ion, is reported for the first time. This process is analogous to that previously described for metal-cationized peptides.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 4 (1992), S. 19-26 
    ISSN: 1040-0397
    Keywords: Amalgam electrode ; cadmium ; macrocyclic complexes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical oxidation of cadmium amalgam was studied in the nonaqueous solvents CH2Cl2, 1,2-C2H4Cl2 and propylene carbonate. Significant coordination effects were observed between the electrogenerated Cd(II) ions and 18-membered macromonocyclic ligands, each containing six Lewis bases heteroatoms: 18-O6, 18-S6, 18-N2O4, and 18-N6. The stoichiometries and the stabilities of the resulting complexes were determined. These stabilities increase from 18-O6 or 18-S6 to 18-N6.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1979), S. 474-481 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New experimental data on the rearrangement reaction of various phenoxyethyl halides to give [C6H6O]+· are presented and compared with previous studies so that a coherent picture of this process can be developed. By examining the metastable kinetic energy release for low energy decomposing molecular ions of the phenoxyethyl halides, it has been concluded that formation of [C6H6O] occurs by competitive 1,2 and 1,3 hydrogen shifts from the alkyl carbons to oxygen followed by a rate determining C—O bond cleavage. This is substantiated by the absence of a primary hydrogen isotope effect. For more highly activated molecular ions, a new mechanism comes into play as evidenced by the appearance of a small hydrogen isotope effect. It is postulated that this third mechanism involves transfer of the alkyl hydrogen to the ortho position of the ring by a rate determining 1,5 shift, followed by a 1,3 hydrogen shift from the ortho methylene group to oxygen and rapid C—O bond cleavage. This 1,3 hydrogen shift to oxygen appears to be ‘catalysed’ by the halogen atoms yielding phenol ions. No indications have been found for the formation of tautomeric 2,4-cyclohexadienone ions. Furthermore, highly activated molecular ions produce [C6H6O]+· which can undergo metastable decomposition to lose carbon monoxide. Kinetic energy release measurements for the latter reaction show that the majority of these [C6H6O]+·ions have been formed as phenol ions as well. These arguments are supported by energetic measurements and by comparisons with previous ion cyclotron resonance and collisional activation studies.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1982), S. 269-273 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Water and acetic acid eliminations from 1-tetralin radical cations have been shown previously to be highly regiospecific 1,4 processes. Utilizing deuterium labeling, high resolution peak ratio measurements and metastable ion defocusing techniques, the stereochemistry of these processes has been investigated. cis-4-d1- and trans-4-d1-1-Tetralol both lose HOH and DOH in appreciable amounts; similarly, both acetoxy derivatives lose HOAc and DOAc. These results are interpreted in terms of an ionic epimerization which operates in competition with a stereospecific 1,4 elimination mechanism. A hydrogen exchange process which occurs between the 4-carbon and the oxygen atom situated on the 1-carbon of 1-tetralol has also been observed. This process accounts for observed H/D ratios in the ethene elimination reaction of various deuterium labeled 1-tetralols.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1983), S. 542-546 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Additional evidence for the rearrangement of the 1- and 3-phenylcyclobutene radical cations, their corresponding ring-opened 1,3-butadiene ions and 1,2-dihydronaphthalene radical cations to methylindenetype ions has been obtained for the decomposing ions by mass analysed ion kinetic energy spectroscopy (MIKES). The nature of the [C9H7]+ and [C10H8]+· daughter ions arising from the electron ionization induced fragmentation of these [C10H10]+· precursors has been investigated by collisionally activated dissociation (CAD), collisional ionization and ion kinetic energy spectroscopy. The [C9H7]+ produced from the various C10H10 hydrocarbons are of identical structure or an identical mixture of interconverting structures. These ions are similar in nature to the [C9H7]+ generated from indene by low energy electron ionization. The [C10H8]+· ions also possess a common structure, which is presumably that of the maphthalene radical cation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 19 (1984), S. 519-520 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1988), S. 712-718 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The elemental compositions of ions can be determined in tandem mass spectrometry by comparing the daughter ion spectra of the m1+ and [m1 + 1]+ ions. The method is demonstrated for mass-analyzed ion kinetic energy spectra but is applicable to all types of daughter ion spectra, including complex collisionally activated dissociation spectra. In this work, the method is applied to compounds that produce daughter ions of known elemental compositions, and the errors and limitations are evaluated. Following that test, the procedure is applied to a compound that may produce daughters of more than one possible elemental composition. The method is sometimes useful even if the formula of the parent is not known; that is, the formulae of unknown parent and daughter ions may be found. Locating a specific atom in an isotopically labeled molecule is another capability of the method. The basic equation of the method was generalized and incorporated into a computer program for performing the calculations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 19
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Major factors which determine the distribution of internal energy of a primary product ion A+, P(E)A+, at formation are delineated in terms of the quasi-equilibrium theory and a variety of experimental evidence is offered to support these conclusions. These major factors include: the P(E) of the molecular ion, the rate constants as a function of energy, κ(E), for M+·→A+ + N0 and for competing reactions of M+·, and the partitioning of excess internal energy between A+ and N0. The ‘fluctuation effect’ on this partitioning makes P(E)A+ relatively insensitive to many structural and energy changes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 12 (1977), S. 55-62 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to provide a comparison with the extensive research on the mechanism for elimination of water from various cyclohexanols, the mass spectra of 1-tetralol(1,2,3,4,-tetrahydro-1-naphthalenol) and 2-tetralol(1,2,3,4-tetrahydro-2-naphthalenol) have been investigated. Deuterium labeling experiments show that the 1-tetralol molecular ion expels water by a highly specific 1,4 elimination, whereas 2-tetralol undergoes a 1,3 elimination. Both of these processes are competitive with cycloreversion reactions. The ionization potentials and appearance potentials for the major fragments \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm M - H}_{\rm 2} {\rm O}} \right]_{}^{_.^ + } $\end{document} and the cycloreversion products hae been measured using the Electron Distribution Difference method. In addition, the kinetic energy release in the metastable decompositions to lose water have been measured. It has been found that the 1,4 elimination for 1-tetralol releases over 50% of the available energy in the transition state, which is unexpected in view of the 6-membering ring transition state involved. This research also includes an investigation of the nature of the various \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 10}} } \right]_{}^{_.^ + } $\end{document} ions formed in the rearrangement reaction to lose water.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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