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  • 2020-2023
  • 2015-2019
  • 1965-1969  (73)
  • Analytical Chemistry and Spectroscopy  (73)
  • 1
    Electronic Resource
    Electronic Resource
    The mass spectra of some C-19 modified cholesteryl derivatives (1968)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1968), S. 567-581 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of twenty one C-19 modified cholesteryl derivatives have been determined and compared with results for related systems. In the case when the hydrogen(s) of the C-19 group have been replaced by other groups the metastable evidence shows that in those molecules with a C-3 hydroxyl group the loss of water followed by the loss of the C-19 group gives rise to an intense ion at m/e 353, whereas the loss of the C-19 group with hydrogen transfer to the ion, followed by the loss of water gives rise to the large ion at m/e 354. In contrast in the case of the C-3 acetates the main fragmentation is the loss of acetic acid followed by the loss of the C-19 group to give the ion at m/e 353. This is rationalised on the basis of results observed in other systems. In the case of the C-3 tosylates evidence for pyrolysis before electron impact fragmentation is presented. The subsequent fragmentation of the large ions at m/e 354, 353 and other m/e values in the high mass region is shown to be in line with earlier work.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210010411
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  • 2
    Electronic Resource
    Electronic Resource
    Non-equivalence Magnetique en Resonance Nucleaire - IV. Influence de Plusieurs Types de Dissymetries sur les Deplacements Chimiques et les Couplages Relatifs a des Systemes —O—CH2—CH3 et —S—CH2—CH3 (1969)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 19-26 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Magnetic non-equivalence of methylenic protons in A—CH2—CH3 groups were studied for several types of compounds. Results are compared with respect (1) to the nature of heteroatom A:A = O and A = S and (2) to the structure of the local dissymmetry element: asymmetric carbon, ketal group and allenic system. Influence of substitution is discussed in relation to conformational problems. Furthermore a variation of the methylene geminal coupling constant with substituents of carbon α to OEt is observed.
    Notes: La non-équivalence magnétique des protons méthyléniques de groupements A—CH2—CH3 est étudiée dans plusieurs séries de composés. Les effets sont comparés d'une part dans les séries A = O et A = S, d'autre part dans les composés présentant un carbone asymétrique, un carbone de type cétal ou une dissymétrie allénique. L'influence de la substitution sur le carbone en α de AEt est discutée en relation avec les conformations. Une variation de la constante de couplage entre les protons méthyléniques géminés en function de la nature des substituants lointains est mise en évidence.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270010106
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  • 3
    Electronic Resource
    Electronic Resource
    Mass spectra of azetidines and 2-azetidinonesThis paper also constitutes Part XXXVIII in the series Electron-Impact Studies. For XXXVII See Ref. 1. (1968)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1968), S. 857-880 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of twenty three azetidines and seventeen 2-azetidinones are reported and discussed. The majority of spectra contain molecular ions. Fragmentation modes are largely dependent upon the substitution pattern and involve specific cleavage of the four-membered ring. Several hydrogen rearrangement reactions occur, and in some cases, cis and trans isomers may be distinguished by large differences in the relative abundances of certain fragment ions.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210010610
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  • 4
    Electronic Resource
    Electronic Resource
    Studies in organic mass spectrometry - VIFor part V, See Ref.2.. The fragmentation of enol derivatives of acyclic β-diketones (1969)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 2 (1969), S. 877-892 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of enol derivatives of β-diketones, such as enol ethers and enaminies are discussed. Their behaviour under electron-impact is in accordance with the fragmentation we suggested for an acyclic β-diketone in the enol form.Rearrangement of the enol functional group is observed in the spectra. This process is a general one, as it show not only migration of oxygen and nitrogen in the enol ethers and enamines, but also migeration of sulphur and chlorine in the thio-ether and in 4-chloro-3-pentene-2-one.Enol derivatives are suitable compounds for determining the branching of alkyl chains in β-diketones.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210020903
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  • 5
    Electronic Resource
    Electronic Resource
    PMR studies of the deuteration and hydration of 4-piperidones (1969)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 389-399 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: PMR spectra of substituted 4-piperidones in base and salt forms in D2O, water and other solvents are reported, and spectral characteristics interpreted in terms of equilibria between free ketone and 4,4-dideuteroxy (or hydroxy) forms. It is shown that 1-mono and 1,3-disubstituted-4-piperidones exist extensively as the corresponding dideuteroxy (or hydrated) species in D2O (or H2O) provided the ring nitrogen atom is positively charged, and that 3-substituents decrease the population of these forms. The facile D/H exchange of α-protons in the piperidone bases is also demonstrated.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270010506
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  • 6
    Electronic Resource
    Electronic Resource
    Mass spectrometry in structural and stereochemical problems. Part CLIII. Electron impact-promoted fragmentation of n-alkyl cyanides (1968)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1968), S. 3-12 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In spite of previous extensive studies on the mass spectrometry of alkyl cyanides, no good mechanistic insight has as yet been gained into the behavior of straight chain alky1 cyanides. For this reason the possible origins for the principal ions in the mass spectrum of a typical alkyl cyanide (n-hexyl cyanide) have been determined using high resolution mass spectrometry anddeuterium labeling of every carbon atom. The results lead to the conclusion that most of the typical fragmentation processes of n-alkyl cyanides proceed through cyclic intermediates.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210010103
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  • 7
    Electronic Resource
    Electronic Resource
    The mass spectra of some triterpenoid dehydration products (1969)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 2 (1969), S. 175-194 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of ten dehydration and solvolysis products obtained from β-amyrin and glycyrrhetic acid were studied. With the exception of those resulting from ‘backbone’ rearrangement, they exhibited conventional fragmentation due to the ring C chromophore, like the parent alcohols. Only those products with a contracted ring A suffered loss of an isopropyl radical. In the latter type, special fragmentation features were exhibited by the isopropylcyclopentene and by the isopropylidene products. These differences enabled the assignment of probable structures for two unknown derivatives.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210020204
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  • 8
    Electronic Resource
    Electronic Resource
    Mass spectrometry of aralkyl compounds with a functional group - VIIFor Part VI, see Ref. 1.. On the structure of the ions C8H9+ from C6H5C2H4X- and C9H11+ from C6H5C3H6X-compoundsSee Ref. 2. (1969)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 2 (1969), S. 157-174 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The C8H9+-ion, formed from the molecular ions of 2-phenyl-1-bromoethane, 1-phenyl-1-bromoethane and of 1-phenyl-1-nitroethane by loss of the bromine atom and of the nitro group, splits off a molecule of acetylene after an almost complete randomization of hydrogens, as proved by deuteration. An eight-membered ring structure for the C8H9+-ion is proposed to explain these results.By loss of the nitro group from the molecular ions of 1-phenyl-1-nitropropane and of 1-phenyl-2-nitropropane the well-known phenylated cyclopropane ion3 (C9H11)+ is generated. Mass spectra of analogues, specifically deuterated in the side-chain, show that in this ion a randomization of hydrogen atoms in the cyclopropane ring as well as a hydride transfer from the cyclopropane ring to the phenyl cation occur.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210020203
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  • 9
    Electronic Resource
    Electronic Resource
    Mass spectrometry in structural and stereochemical problems - CLXIV.For part CLXIII see Ref. 1. Electron impact promoted fragmentation of some thiosemicarbazones (1968)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1968), S. 633-646 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectral fragmentation of thiosemicarbazone derivatives of some typical aliphatic, alicyclic and aromatic aldehydes and ketones has been rationalized using high resolution mass spectrometry supplemented by deuterium labeling. Thiosemicarbazone derivatives of carbonyl compounds yield mass spectra which have little in common with those generated by their semicarbazone analogs.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210010505
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  • 10
    Electronic Resource
    Electronic Resource
    Mass spectometry of aralkyl compounds with a functional group - VI1: Mass spectra of 1-phenylethyanol-1, 2-phenylethanol-1 and 1-phenylpropanol-2Part of the forthcoming thesis of N. M. M. Nibbering. (1968)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 1 (1968), S. 365-390 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of 1-phenylethanol-1 and its analogues, specifically deuterated in the aliphatic chain, suggest that the [M—CH3]+ ion is represented partly by an α-hydroxybenzyl fragment. Moreover, the molecular ion loses successively - after scrambling of all hydrogen atoms, except those of CH3—a hydrogen atom and C6H6, generation the CH3CO+ ion.Diffuse peaks, found in the spectra of of 2-phenylethanol-1 and its analogues, specifically deuterated in the aliphatic chain and in the phenyl ring, show that the molecular ion loses C2H4O, possibly via a four-center mechanism, after an exchange of aromatic and hydroxylic hydrogens.Mass spectra of 1-phenylpropanol-2 and its analogues, specifically, deuterated in the aliphatic chain, demonstrate that in the molecular ion exclusively the hydroxyl hydrogen atom is transferred to one of the ortho-positions of the phenyl ring via a McLafferty rearrangement, generating the [M — C2H4O]+ ion. Furtherore, an eight-membered ring structure is proposed for the [M — CH3]+ ion to explain the loss of H2O and C2H2O from this ion after an extensive scrambling of hydrogen atoms.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210010306
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