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  • 1965-1969  (318)
  • 1920-1924
  • Analytical Chemistry and Spectroscopy  (318)
  • 1
    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.
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  • 2
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Activation energies Eα and free enthalpies of activation ΔG
    Notes: Mittels der Temperaturabhängigkeit der Protonenresonanzsignale wurden für 1.3-Dioxane, 1.3-Oxathiane und 1.3-Dithiane mit ein und zwei Paaren geminaler Methylsubstituenten Geschwindigkeitskonstante k, freie Aktivierungsenthalpie ΔG
    Additional Material: 2 Ill.
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  • 3
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 88-89 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 90-92 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969) 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 93-99 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The theory for deceptive simplicity in the NMR spectra of oriented molecules is discussed in terms of degeneracy of subspectra. The conditions for the degeneracy of AB, AB2 and AA′BB′ spectra leading to deceptive simplicity in the spectra of the type ABX, AB2X, AA′BB′X and AA′XX′ are reported.It is shown that the conditions for deceptive simplicity are easily fulfilled for ABX, AA′BB′X and AA′XX′ cases. It is further demonstrated that deceptive simplicity is not so common in AB2X spectra.The proton spectra of partially oriented 2,4,5-trichloronitrobenzene (AB) and 2,6-dibromo-pyridine (AB2) are use to illustrate degeneracy and those of p-chloro- and p-bromo-fluorobenzenes are reported to demonstrate deceptive simplicity.
    Additional Material: 3 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 101-108 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An NMR study of some bridged bicyclo and tricyclo compounds yielded unusual spectra with respect to solvent effects and virtual coupling. As is the general case for most large polycyclic systems a complete analysis of the spectrum is not possible and the structural details derived from NMR are based on a partial analysis of the spectrum. If the accessible resonances correspond to protons adjacent to methylene groups, the resonance patterns and the chemical shifts may be strongly dependent upon solvent. For 6-endo-hydroxy, bicyclo[2.2.1]heptane-2,endo-carboxylic acid lactone (1), 6-endo-hydroxy, 2-exo-methyl-bicyclo[2.2.2]octane-2-endo-carboxylic acid lactone (2), and exo-3,4,exo-8,9-diepoxy, endo-tricyclo[5,2,1,02,6]decane (3), resonances for each fall in this class and the change induced by solvent are attributed to virtual coupling as well as a change in the overall splitting pattern.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 109-123 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The barriers to rotation about the C—N bond in eighteen substituted N,N-dimethylbenzamides have been determined by complete line shape analysis of the NMR spectra of the N,N-dimethyl protons. The barriers have been correlated with the substituent constants σ and σ+. It has been shown that polar solvents increase the barrier in N,N-dimethylbenzamide.Acid catalysis of rotation about the amide C—N bond in N-(p-N,N-dimethylcarboxamidobenzyl)-pyridinium bromide has been investigated. 18O exchange studies show that catalysis is due to N-protonation rather than the formation of a tetrahedral intermediate. The rate of rotation is a function of the Hammett acidity function, H0, and the water activity, and it is shown that proton exchange between the N- and O-protonated species involves the intermediacy of a water molecule.The differences in chemical shifts for the non-equivalent N, N-dimethyl groups of the benzamides are also a function of the substituents. Possible explanations of this phenomenon are discussed.
    Additional Material: 6 Ill.
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  • 11
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variable temperature, proton magnetic resonance study has been made of complexes of pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, and 2,6-dimethylpyridine with borane and boron trifluoride. By lowering the temperature and slowing ligand exchange, separate resonance signals can be observed for bulk and complexed molecules of the base. A direct comparison of the complexing abilities of these ligands was made by studying them in pairs with borane or boron trifluoride. The complexing abilities, as estimated from the NMR data, decreased in the order: 4-MePy 〉 3-MePy 〉 Py 〉 2-MePy 〉 2,6-MePy. This trend was interpreted in terms of steric effects and the basic strengths of these molecules towards boron trifluoride.
    Additional Material: 3 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969) 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The ring inversion of cyclohexane derivatives with one, two and three pairs of geminal methyl and alkoxyl groups has been studied by investigations of the temperature dependence of the NMR signals.The rate of the inversion depends on the number and the relative positions of the ligand pairs as well as on their size. A single pair of geminal ligands has only a very slight effect on the inversion rate. Two ligand pairs hinder the inversion when they are in the 1 and 4 positions relative to one another, but facilitate it when they are in the 1 and 3 positions. In both cases the effects are smaller with methoxyl groups than with methyl groups.Three ligand pairs significantly increase the inversion rate when they are in the 1, 3 and 5 positions, but reduce it when they are in the 1, 2 and 4 positions.The effect of 1,3 substituents is attributed to an increase in the energy of the ground state of the molecules whereas the effect of 1,4 arranged substituents is attributed to an increase in the energy of the transition state of the chair inversion.
    Notes: Mittels der Temperaturabhängigkeit der Protonenresonanzsignale wurde die sesselinversion von Cyclohexanderivaten mit ein, zwei und drei Paaren geminaler Methyl- und Alkoxylgruppen untersucht.Die Geschwindigkeit der Sesselinversion hängt von der Zahl und der relativen Stellung der Ligandenpaare sowie von der Größe der Liganden ab.Ein Paar geminaler Liganden verändert die Inversionsgeschwindigkeit nur unwesentlich.Zwei Liganden-Paare erschweren die Inversion, wenn sie in 1- und 4-Position zueinander stehen, erleichtern sie jedoch, wenn die in 1- und 3-Position zueinander angeordnet sind. Beide Effekte sind bei Methoxylgruppen kleiner als bei Methylgruppen.Drei Liganden-Paare erhöhen die Umklapphäufigkeit besonders stark, wenn sie in 1-, 3- und 5- Position zueinander stehen, vermindern sie hingegen, wenn sie in 1-, 2- und 4-Position angeordnet sind.Der Effekt 1,3-ständiger Substituenten wird auf Erhöhung des Energieinhaltes des Grundzustandes der Molekeln, der Effekt 1,4-ständiger Substituenten auf Erhöhung des Energieinhaltes des Übergangszustandes der Sesselinversion zuriückgeführt.
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  • 14
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    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 189-189 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 15
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: For the interpretation of experimental data on the activation energy and free activation enthalpy for the inversion of cyclohexane and its di-, tetra- and hexa-methyl derivatives, model calculations were made to determine the ‘relative’ energies of the ground, intermediate and transition states of the molecules. For this purpose Hendrickson's model was extended so that with internal molecular variables (bond lengths, valence and torsional angles) the topography and the ‘relative’ energy of every possible unsymmetrical conformation could be included.To obtain optimal agreement between the calculated values and the experimental results a total of 17 different combinations of potential functions for deformation of valence angles, torsional angles and H—H interactions were used. By application of the extended calculating procedure it was found that for cyclohexane the half-chair conformation is not, as until now assumed, the only transition conformation in chair inversion, but that there are numerous other unsymmetrical transition conformations with similar energies.The calculations for methyl cyclohexanes showed that for molecules with synaxial arrangement of methyl groups the relative energy of the chair form is considerably increased. The chair form is however still the most stable, even in the case of 1,1,3,3,5,5-hexamethylcyclohexane. The most favourable twist conformations are about 2.6 to 6.5 kcal/mole energy richer.Calculation of activation energies showed that, with synaxial arrangement of two or more methyl groups, the relative energy of the transition conformation is less markedly increased than is that of the ground state, with the result that the activation energy is reduced in comparison with that for cyclohexane.
    Notes: Zur Interpretation der experimentell bestimmten Werte der Aktivierungsenergie bzw. der freien Aktivierungsenthalpie der Ringinversion wurden für Cyclohexan, 1,1-Dimethyl-, 1,1,3,3- und 1,1,4,4-Tetramethyl- sowie 1,1,3,5,5-Hexamethylcyclohexan Modellberechnungen des ‘relativen’ Energieinhalts von Grund-, Zwischen- und Übergangskonformationen durchgeführt. Dazu wurde das Hendrickson'sche Rechenmodell so erweitert, daß mit molekülinternen Variablen (Bindungsabständen, Valenz- und Torsionswinkeln) die Topographie und der ‘relative Energieinhalt’ jeder beliebigen unsymmetrischen Konformation berechnet warden können.Zur optimalen Anpassung der berechneten Daten an die experimentellen Ergebnisse wurden insgesamt 17 verschiedene Kombinationen von Potentialfunktionen für Deformation von Valenzund Torsionswinkeln und H—H-Wechselwirkung verwendet.Bei Anwendung des erweiteren Rechenverfahrens auf die Cyclohexanmolekel ergab sich, daß die halbsesselähnliche Konformation nicht, wie bisher angenommen, einzige Übergangskonformation der Sesselinversion ist, vielmehr gibt es außerdem unendlich viele unsymmetrische Übergangskon-formationen gleichen Energieinhalts. Die Rechnungen ergaben für die Methylcyclohexane, daß bei Molekülen mit synaxialer Anordnung von Methylgruppen der relative Energieinhalt des Sessels zwar stark angehoben ist, der Sessel ist jedoch in allen Fällen selbst bei den Molekeln des 1,1,3,3,5,5-Hexamethylcyclohexans die stabilste Konformation. Die günstigsten Twistkonformationen sind um 2,6 bis 6,5 kcal/mol energiereicher. Bei der Berechnung der Aktivierungsenergie wurde gefunden, daß bei synaxialer Stellung von mindestens zwei Methylgruppen der relative Energieinhalt der Übergangskonformation weniger stark angehoben ist als derjenige der Sesselform, wodurch die Aktivierungsenergie im Vergleich zum Cyclohexan erniedrigt wird; bei 1,4-Stellung der Substituenten wird dagegen der relative Energieinhalt der Übergangskonformation stärker angehoben als der des Grundzustandes, die Aktivierungsenergie wird erhöht.
    Additional Material: 6 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 209-212 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two stereochemically distinct two-bond carbon-13- hydrogen coupling constants J(13C—CH), for α-chlorostyrene-α-13C have been shown to be of similar magnitude but opposite sign (-6.3 and +5.6 Hz). A simple additivity relationship which adequately reproduces all the reported J(13C—CH) values for chloroethylenes has been found.
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  • 17
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 213-227 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton NMR spectra of 1-substituted 2,4-dimethylbenzenes (2), 1-substituted 2,6-dimethylbenzenes (3) and 1-substituted 2,4,6-trimethylbenzenes (4) were determined and the SCS values compared with those of monosubstituted benzenes (1). SCS of 1 are assumed to be primarily due to the effects of π-electron charge density, substituent electric field and substituent diamagnetic anisotropy, and the van der Waals interaction: thus \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm SCS = SCS}_{\pi {\rm}} + {\rm SCS}_{\rm E} + {\rm SCS}_{\rm A} + {\rm SCS}_{\rm V} $$\end{document} When, however, the substituent is sterically hindered, then: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm SCS}^{\rm '} {\rm = SCS}_{{\rm \pi}^{\rm '}} {\rm + SCS}_{{\rm E}^{\rm '}} {\rm + SCS}_{{\rm A}^{\rm '}} {\rm + SCS}_{\rm V} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ = {\rm c}_{\rm \pi} {\rm SCS}_{\rm \pi} {\rm + c}_{\rm E} {\rm SCS}_{\rm E} {\rm + c}_{\rm A} {\rm SCS}_{\rm A} {\rm + c}_{\rm V} {\rm SCS}_{\rm V} $$\end{document} where cπ∼V may be constants predictable from the theories associated with each component. By estimating SCSπ∼V or cπ∼V, a quantitative separation of SCS into their components was attempted. It is shown, however, that the data available, as well as the nature of this approach, cannot necessarily be sufficient for this purpose.Various effects which might also contribute to the proton NMR chemical shifts of sterically hindered molecules are also discussed.
    Additional Material: 4 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 229-237 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proton and 13C—H satellite spectra of five diethyl haloacetals have been analyzed and their spectral parameters obtained. The parameters for the ethoxy methylene protons indicate the extent of their magnetic nonequivalence. It has been found that these parameters are dependent on the degree of halogen substitution in the group Z, which is bonded to the central carbon atom, and correlate well with the corresponding group electronegativity values, a′ z, proposed by Huheey. The parallel behavior of the methylenic J(C—H) and chemical shifts indicates that a primarily through-bond mechanism is responsible for propagation of both the electronic and symmetry effects observed. Transmission factors calculated from the spectral data agree with independent estimates reasonably well, thus supporting the conclusions reached here.
    Additional Material: 3 Ill.
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  • 19
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The non-equivalence of ethyl, benzyl and isopropyl groups fixed on nitrogen atoms in 2-and 3-pyrazolines, pyrazolidines and pyrazolidones depends on the assymetry existing in the molecule. The asymmetric centres are either a ring carbon atom, a quaternary nitrogen atom (protonation, quaternarization) or a tertiary nitrogen atom (slow nitrogen inversion). The nitrogen inversion process was observed only in the case of pyrazolidines (possibility of inversion at the two adjacent nitrogens) and of pyrazolidones (inversion of the ‘non-amidic’ nitrogen). The inversion is temperature-dependent and is affected by substituents.
    Notes: La non-équivalence de groupements éthyle, benzyle et isopropyle fixés sur les azotes de pyrazolines-2 et 3, de pyrazolidines et de pyrazolidones est fonction de l'asymétrie existant dans la molécule. Celle-ci peut provenir soit d'un carbone du cycle, soit de l'un des azotes rendu asymétrique par protonation, quaternarisation ou simplement par ralentissement de son inversion, Ce dernier phénomène n'a été observé que dans le cas des pyrazolidines (possibilité d'inversion de deux azotes adjacents) et des pyrazolidones (inversion de l'azote non amidique): il est fonction des substitutions et des variations de température.
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  • 20
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    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 278-278 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 21
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    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 279-280 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 22
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969) 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 23
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    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 281-293 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have examined the 19F NMR spectra of a number of oxygen-containing fluorocarbon products and obtained a comprehensive set of 19F chemical shift values, which enabled us to determine the influence of an oxygen atom bonded to a fluorocarbon group on the 19F chemical shift. The influence of neighbouring fluorocarbon groups, either directly connected or separated by an oxygen atom, was also considered.Our results may be summarized as follows. An oxygen atom bonded by a single bond (ether type bond) to a fluorine substituted carbon atom decreases the 19F chemical shift, as does the introduction of a further fluorine atom. Considering two adjacent fluorocarbon groups, a variation of x ppm in the 19F chemical shift of one of the two groups gives a variation of 0·12 x ppm in the opposite sense on the 19F chemical shift of the other group. If the two groups are connected by an ether oxygen atom, the effect is only about 0·06 x ppm.
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  • 24
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    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 295-303 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-precision line measurements and tickling were shown to yield information, often not accessible, on the assignment and signs of spin coupling constants. For pentafluorothiophenol-d, this information was obtained for the three meta-JFF's. Relative to C6F5SH, the 19F resonances in C6F5SD experienced an upfield ‘isotope’ shift.
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  • 25
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two C-4 protons of reduced nicotinamide adenine dinucleotide (NADH) produce an AB NMR spectrum at 100 MHz as well as at 220 MHz. This observation allows an upper limit of 50 sec-1 to be placed on the mean rate of interconversion of the two folded forms of NADH invoked to account for the magnetic non-equivalence of the C-4 protons. The interpretation of non-equivalence of the C-4 protons in terms of the various equilibria among folded and unfolded forms of NADH and its possible significance in the mechanism of action of dehydrogenase enzymes is discussed. It is suggested that one folded form of NADH is strongly favored thermodynamically over the other and that the resulting magnetic non-equivalence of the C-4 protons is of doubtful significance in explaining the stereospecificity of dehydrogenase enzymes toward the nicotinamide ring.
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  • 26
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NMR spectral parameters are reported for benzofurazan, 1,2,3- and 2,1,3-benzothiadiazole, and 1-methyl- and 2-methyl-benzotriazole. The coupling constants are discussed in connection with the aromaticity of these compounds and the occurrence of partial bond fixation.
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  • 27
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    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 319-327 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The NMR spectra of fifteen para-substituted acetanilides, XC6H4·NH·CO·CH3 (X = NH·CO·Me; NH2; CO·OEt; COOH; Cl; OEt; F; H; OMe; CH3; NO2; C6H5; —N=N—C6H5; Me3Si), have been recorded. δCH3 and δNH are linearly related to Hammett's σp constant. The coupling J (o-H—H) between aromatic protons is mainly dependent on σR0. J(13C—H), in methyl group is approximatively constant in the series.
    Notes: Les spectres de RMN de quinze acétanilides para-substitués XC6H4·NH·CO·CH3 (X = NH·CO·ME; NH2; CO·OEt; COOH; Cl; OEt; F; H; OMe; CH3; NO2; C6H5;—N=N—C6H5; Me3Si) ont été étudiés. Il y a une relation linéaire entre δCH3 et δNH et les constantes σP de Hammett. Le couplage J(o-H—H) entre les protons aromatiques est relié plutôt à σR0. La constante J (13C—H) dans le groupe CH3, est indépendante de X.
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  • 28
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    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 1 (1969), S. 329-335 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton magnetic resonance spectra of methylene dichloride solutions containing N-methyl morpholine and sulphur dioxide have been studied as a function of temperature. Complex formation reduces the rate of interchange of magnetic sites via inversion at nitrogen but increases the rate of ring inversion. The conformational preference of the complex is discussed. It is suggested that interaction with SO2 may be a useful general method of studying nitrogen inversion.
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  • 29
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    Organic Magnetic Resonance 1 (1969), S. 341-342 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 30
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    Organic Magnetic Resonance 1 (1969), S. 337-340 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The meso or threo configuration of diastereoisomeric molecules is elucidated on the basis of respective NMR spectra of either isomers. The symmetry relationship (according to Raban and Mislow) between protons or groups are not identical in each isomer, and the consequent differences in chemical shifts and spin-coupling constants permit assignment of configurations.
    Notes: La configuration meso ou thréo de molécules diastéréoisomères est déterminée à partir des spectres RMN respectifs xde chaque isomère. Les relations de symétrie (Raban et Mislow), qui existent entre protons ou groupes de ces molécules sont différentes par chaque diastéréoisomère d'un couple donné et ces différences se traduisent dans les déplacements chimiques et constantes de couplage mis en jeu. Des attributions de configuration sont ainsi rendues possibles.
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  • 31
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    Organic Magnetic Resonance 1 (1969), S. 343-344 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 32
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    Organic Magnetic Resonance 1 (1969), S. 344-344 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 33
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    Organic Magnetic Resonance 1 (1969), S. 344-344 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 34
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    Organic Magnetic Resonance 1 (1969) 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 35
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    Organic Magnetic Resonance 1 (1969), S. 467-470 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The NMR spectrum of phenylacetylene has been studied in the nematic phase of a mixture of 50% 4-methoxy benzylidene 4-amino-α-methyl cinnamic acid-n-propyl ester and 50% anisole-p-azophenyl-n-capronate at 30°C. Ratios of interproton distances have been derived.
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  • 36
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The substituent effect on proton resonances and vicinal H, H-coupling constants in benzene derivatives is studied using linear regression analysis. The change in shielding observed on substitution, relative to the proton resonance in benzene, Δσ, can be expressed as \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta\sigma = - 1.04 \times 10^{- 12} {\rm E}_{\rm Z} - 1.08 \times 10^{- 18} {\rm E}^{\rm 2} + 9.17\Delta \rho + 0.18. $$\end{document}. This equation enables calculations of substituent effects on the basis of the dipolar and quadratic field effect (Ez, E2) and the π-charge density changes on the neighbouring C-atom (Δρ).The vicinal coupling constants show no correlation with the HMO-π-bond order. A linear regression using the well known dependence of the coupling constant on substituent electronegativity yields \documentclass{article}\pagestyle{empty}\begin{document}$$ ^3 {\rm J = 7}{\rm .63 + 0}{\rm .508}\Delta \alpha - 0.096\Delta \beta $$\end{document} where ΔEα and ΔEβ are the changes in electronegativity caused by substitution in α- or β-position, respectively, to the HCCH-fragment considered.
    Notes: Der Einfluß von Substituenten auf die Protonenresonanzen und die vicinalen H, H-Kopplungskonstanten in Benzolderivaten wird mit Hilfe linearer Ausgleichsrechnungen untersucht. Für die relativ zur Protonenresonanz des Benzols auftretende Abschirmungsänderung Δσ bei der Substitution wird die Beziehung \documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta\sigma = - 1.04 \times 10^{- 12} {\rm E}_{\rm Z} - 1,08 \times 10^{- 18} {\rm E}^{\rm 2} + 9,17\Delta \rho + 0,18. $$\end{document} angegeben, die eine Berechnung der Substituenten-Effektes mit Hilfe des dipolaren und quadratischen Feldeffektes (Ez, E2) und der π-Ladungsdichte-Änderung am benachbarten C-Atom (Δρ) erlaubt.Die vicinalen Kopplungskonstanten lassen sich mit der HMO-π-Bindungsordnung nicht korrelieren. Eine Ausgleichsrechnung unter Benutzung der bekannten Abhängigkeit der Kopplung von der Substituenten-Elektronegativität liefert \documentclass{article}\pagestyle{empty}\begin{document}$$ ^3 {\rm J = 7}{\rm .63 + 0}{\rm .508}\Delta \alpha - 0.096\Delta \beta $$\end{document} wobei ΔEα und ΔEβ die durch Substitution bedingte Änderung der Elektronegativität in α- bzw. β-Stellung zum betrachteten HCCH-Fragment bedeuten.
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  • 37
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The confromations of the unsaturated seven membered ring in 4,4,6,6-tetradeuterium-1,2-benzocycloheptene-(1) (1) and five benzocycloheptene derivatives were determined by NMR spectroscopy. For all investigated compounds at -80°C only one conformer was present in detectable quantity. By analysis of the NMR data - molecular symmetry, coupling constants and chemical shift - it can be shown that the conformation is always the chair form. The free conformational enthalpy of both the other conformations with boat or twist form of the ring is for all six compounds more than 1.8 kcal/mole.The experimental results agree with those from model calculations: thus for benzocycloheptene, the 5,5-dimethyl derivative (2) and the 4,4,6,6-tetramethyl derivative (4) the lowest energy was found for the chair conformation; the second most stable conformations were found to be the boat for 1 and 4, and the twist form for 2.
    Notes: Für 4.4.6.6-Tetradeuterium-1.2-benzocyclohepten-(1) (1) und fünf Benzocyclo-heptenderivate wurde PR-specktroskopisch die Konformation des ungesättigten Siebenringes bestimmt. Bei allen untersuchten Verbindungen liegt bei -80° nur ein Konformeres in nachweisbarer Menge vor. Durch Auswertung PR-spektroskopisch bestimmter Daten - Molekel-Symmetrie, Kopplungskonstanten, chemische Verschiebungen - kann gezeigt werden, daß dieses Konformere Sesselform hat. Die freie Konformationsenthalpie der beiden anderen Konformeren mit Wannen- bzw. Twist-Form des Siebenringes beträgt bei allen sechs Verbindungen mehr als 1,8 kcal/Mol.Mit den experimentellen Ergebnissen stimmen diejenigen von Modellrechnungen überein: Für die Molekeln des Benzocycloheptens sowie des 5.5-Dimethylderivates (2) und der 4.4.6.6-Tetramethylverbindung (4) wurde für die Sesselkonformation der niedrigste Energieinhalt berechnet; als zweitstabilste Konformation wurde bei 1 und 4 die Wanne, bei 2 hingegen die Twist-Form ermittelt.
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  • 38
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Various complexes of boron trifluoride and typical organo-phosphours compounds have been investigated using proton and fluorine resonance (at variable temperature) and boron and phosphorus resonance. In BF3, boron resonance is insensitive to the complex strength, but fluorine resonance suggests the possibility of various types of complexes on the phosphorus group or, additionally on the heteroatoms (e.g. oxygen, nitrogen) of the molecule. These complexes are probably σ type. Proton chemical shifts in the organo-phosphorus compounds follow the same trends as in similar complexes of amines, esters etc.; these perturbations may be mainly due to magnetic anisotropy effects; proton-phosphorus couplings conversely follow changes in phosphorus electronegativity.
    Notes: On a étudié, en résonance du proton et du fluor (à température variable) ainsi qu'en résonance du bore et du phosphore, un certain nombre de complexes entre BF3 et des composés organo-phosphorés typiques. En ce qui concerne BF3, la résonance de bore reste insensible à la force du complexe; par contre, la résonance du fluor suggéère l'existence de plusieurs types de complexes, soit sur le groupe phosphoré, soit sur les hétéroatomes (par example N, O) de la molécule. Ces complexes sont vraisemblablement de type σ pur. Le déplacement chimique des protons dans la molécule organo-phosphorée subit sensiblement les mêmes perturbations que dans les autres molécules complexables (amines, esters, etc.); ces perturbations peuvent provenir avant tout d'effets d'anisotropie magnétiques; par contre, les couplages proton-phophore suivent la modification de l'électronégativité de ce dernier.
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  • 39
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    Organic Magnetic Resonance 1 (1969), S. 491-491 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 40
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    Organic Magnetic Resonance 1 (1969), S. 481-489 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of line width and chemical shift vs. temperature for amide and hydroxyl proton magnetic resonance signals from: barbituric acid, dialuric acid, parabanic acid, alloxan and alloxan monohydrate dissolved in anhydrous dimethyl sulfoxide-d6 are reported. The behavior of the amide signals shows that, between 20 and 65°C, none of the compounds listed exhibits lactim-lactam tautomerism. The amide proton resonance in uracil has also been investigated. The signal is a closely spaced, equal intensity, doublet due to the non-equivalence of H(1) and H(3). Again, no evidence of tautomerism is observed. Activation energies for the hydroxyl resonances in dialuric acid and alloxan monohydrate indicate hydrogen bonding between solute and solvent. The results of simple LCAO-MO calculations are in accord with the experimental conclusions concerning tautomeric equilibria.
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  • 41
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    Biological Mass Spectrometry 2 (1969) 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 42
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A system is described in which computer techniques are used to carry out major steps in the procedure for interpretation of high-resolution mass spectral data. These steps include identification and evaluation of the molecular ion, neutral fragments lost from the molecular ion, and characteristic ion series, followed by elucidation of specific structural details using a sub-routine for the particular compound class selected. The technique shows promise of not only increasing the interpreter's efficiency, but of providing more specific and detailed structural information from the spectral data.
    Additional Material: 12 Ill.
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  • 43
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    Biological Mass Spectrometry 2 (1969), S. 17-31 
    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-six commercially available medicinal phenothiazines have been determined at high resolution. In each compound, the side chain attached to the 10-position of the phenothiazine ring contains nitrogen and fission of the C—C bond α to this nitrogen gives in most cases the base peak. Some of the compounds are also substituted at the 2-position and this substituent generally remains intact, though some substituents such as acetyl, propionyl, methoxyl and methylthio can undergo fragmentation. Fragmentations fall into three groups; those which give ions representing a part of the side chain; those which give ions representing the intact phenothiazine ring with part of the side chain attached; those which give ions representing a partially fragmented ring system.
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  • 44
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    Biological Mass Spectrometry 2 (1969), S. 33-36 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Under electron-impact, N-alkyl trifluoracetamides exhibit peaks due to [CF3]+ and [M — CF3]+. Ions corresponding to [COCF3]+ are absent. The base peak in many straight chain derivatives occurs at m/e 126 due to alkyl radical loss from the molecular ion; the mass of this ion rising to m/e 140 in the α-substituted N-sec-butyltrifluoracetamide and to m/e 154 in the tert-butyl derivative. High resolution measurements on a number of peaks indicate that they originate by loss of HF from other fragment ions.
    Additional Material: 3 Ill.
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  • 45
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    Biological Mass Spectrometry 2 (1969), S. 37-47 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectral fragmentations of 3-indazolone (I), 1-acetyl-3-acetoxyindazol (II), 1,2-diacetyl-3-indazolone (III), 1-methyl-3-indazolone (IV), 2-methyl-3-indazolone (V), 2-methyl-3-indazolone-N-d-1 (VI), 3-methoxy-indazole (VII), 1-ethyl-3-indazolone (VIII), 1-carbethoxy-3-indazolone (IX), 1-carbethoxy-2-methyl-3-indazolone (X), 2′-carboxyethyl-3-indazolone (XI), 1-oxo-2,3-dihydropyrazolo-(1,2-α)-3-indazolone (XII) and 1-ethyl-3-indazolone-N-d-2 (XIII) are reported. The loss of an ·N2R radical from the parent radical ion in indazolone and the alkyl indazolones occurs more readily than the loss of a formyl radical, and no loss of HCN is observed from the parent radical ion. Mass spectral data can be used to distinguish between N-methyl and O-methyl derivatives of 3-indazolone.
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  • 46
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    Biological Mass Spectrometry 2 (1969), S. 81-103 
    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 exo-2-norbornyl chloride, 1- and 2-methyl exo-2-norbornyl, exo-camphenilyl, apoisobornyl, bornyl and isobornyl chloride, and camphene hydrochloride, α- and β-fenchyl chloride and fenchene hydrochloride, and exo-isofenchyl chloride and 2,5,5-trimethyl exo-2-norbornylchloride, and camphene and α-fenchene have been examined at 12 to 16 and 80° eV and at 30 to 49 and 80°, or higher temperatures. Wagner-Meerwein rearrangements occur very readily in the ion source and compounds related by these rearrangements give very similar fragmentation patterns. Thermal decompositions are important with the tertiary chlorides especially at higher source temperatures. The rates of methanolysis of some of these chlorides were measured.
    Additional Material: 7 Ill.
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  • 47
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    Biological Mass Spectrometry 2 (1969), S. 63-79 
    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 several fluoroalkyl, fluoroalkenyl and fluoroacyl complexes of manganese, rhenium, iron and ruthenium carbonyls are described. After loss of carbonyl groups, fluoroalkyl compounds eliminate an olefin, with formation of metal halide species. A trifluorovinyl complex shows a novel elimination of a carbon atom to give an ion postulated to be a difluorocarbene-metal fluoride; the occurrence of difluorocarbene-metal ions in the spectra of some related complexes is also discussed. The spectra of the acyl complexes show little evidence of elimination of the acyl carbonyl group; the major process is fission of the CO—Rf bond with loss of a fluoroalkyl radical and formation of the cationic metal carbonyl, e.g. π-C5H5M(CO)3+ (M = Fe or Ru). The relevance of thermal or photochemical model reactions to processes occurring in the mass spectrometer is discussed.
    Additional Material: 4 Ill.
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  • 48
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    Biological Mass Spectrometry 2 (1969), S. 49-61 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Changes in the mass spectra with inlet temperature were used in this work to demonstrate the dependence of keto-enol tautomerism of acetylacetone, 3-methyl acetylacetone and 3-allyl acetylacetone on temperature.The largest dependence of temperature were shown by the ion [M — 42]+. arising from a McLafferty type rearrangement and by the ion [M — Me]+ resulting from simple α-cleavage. The ion [M — 42]+. peak increases with the temperature of the inlet system while the ion [M — Me]+ peak decreases. By assuming that the ion [M — 42]+. represents the keto form and that the ion [M — Me]+ represents the cis-enol form (stabilized by the hydrogen bond) one sees that the direction of the intensity variation of these peaks with temperature is in accord with the expected change of keto-enol tautomerism with temperature. A quantitative correlation on the basis of the above assumptions is also approached.Recording of the mass spectra of these three β-diketones at different energies of the incident electrons enables us to estimate whether or not the particular ions present in the mass spectra result from energetically favourable processes.The variation of the intensities of the peaks with the temperature of the inlet at different electron energies is also discussed.
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  • 49
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    Biological Mass Spectrometry 2 (1969), S. 105-119 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: α-Trifluoracetamino carbon ions are important fragments in the mass spectra of N-Trifluoracetyl α-amino acids and their derivatives. They fragment by eliminating neutral molecules. This breakdown is mainly influenced by the structure of their substituents. Several of these ions show some remarkable skeletal rearrangements.
    Notes: α-Trifluoracetaminocarbonium-Ionen treten als charakteristische Bruchstücke in den massenspektren von N-Trifluoracetyl-α-aminosäuren und deren Derivaten auf. Sie zerfallen unter Eliminierung stabiler Neutralmolekeln, wobei in erster LInie die Struktur ihres Substituenten entscheidenden Einfluß ausübt. Im Zuge dieser Fragmentierungen kommt es bei einer Reihe von Ionen zu bemerkenswerten Strukturumlagerungen.
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  • 50
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    Biological Mass Spectrometry 2 (1969), S. 135-135 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 51
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    Biological Mass Spectrometry 2 (1969), S. 136-136 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 52
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    Biological Mass Spectrometry 2 (1969), S. 121-134 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: As a result of high resolution mass measurements, calculation of metastable ions, and investigation of specifically deuterated compounds the fragmentation is discussed of some α-substituted N-methyl benzylamides containing different N-acyl groups. α-Cleavage leads to the formation of N-methyl α-acylamino carbon ions which show skeletal rearrangement. The intensity of the rearranged ions depends on the structure of the N-acyl group. Migration of the α-methyl group is observed in the mass spectra of N-acetyl and N-p-Cl-benzoyl N-methyl-α-phenylethylamide.
    Notes: Der massenspektrometrische Zerfall einiger α-substituierter N-Methylbenzylamide mit verschiedenen N-Acylgruppen wird anhand der Ergebnisse aus hochauflösender Massenbestimmung, Berechnung der metastabilen Ionen Untersuchung spezifisch deuterierter Verbindungen diskutitert. Dabei wird die Strukturumlagerung der durch α-Spaltung entstandenen N-Methyl-α-acylaminocarboniu-Ionen nachgewiesen. Sie ist von der Art der N-Acylgruppe abhängig. In den Massenspektren von N-Acetyl-bzw. N-p-Cl-Benzoyl-methyl-α-phenyläthylamid wird die Wanderung der α-Methylgruppen beobachtet.
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  • 53
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    Biological Mass Spectrometry 2 (1969) 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 54
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    Biological Mass Spectrometry 2 (1969), S. 137-156 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 55
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    Biological Mass Spectrometry 2 (1969), S. 175-194 
    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.
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  • 56
    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.
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  • 57
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    Biological Mass Spectrometry 2 (1969), S. 209-212 
    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 deuterated species shows that both the isomeric ions [CH2=SH]+ and [CH3—S]+ are formed in the ratio 2:1 from CH3SH; the ions [CH3CH=SH]+ and [CH3CH2S]+ in the ratio 0·8:1 from CH3CH2SH; and [CH2=OH]+ and [CH3—O]+ in the ratio 6·7:1 from methanol.The heats of formation of [CH3S]+ and [C2H5S]+ are of the order of 222 and 203 Kcal.mole-1 respectively. The isomeric ions cannot be distinguished on thermodynamic grounds.
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  • 58
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    Biological Mass Spectrometry 2 (1969), S. 195-207 
    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 several compounds obtained during the process of Stork's isoxazole synthesis9 as well as the related isoxazoles have been investigated. The fragmentations of simple alkyl isoxazoles are nicely formulated via azirine intermediates. A striking difference between the spectra of isoxazoles and those of methylfurans as to the relative abundance of [M  -  l] peaks is noteworthy. The very low abundance of these peaks in the former reflects the unique character of isoxazole nucleus due to the preferential cleavage of N—O linkage rather than a benzylic C—H bond rupture. If an alkyl substituent is present at 4-position in 3,5-dimethylisoxazoles, strong peaks at m/e 110, 68 and 43 are common in their spectra. The analyses of metastable transitions and high resolution measurements have demonstrated that the formation of these ions can be interpreted by a mechanism involving the cleavage of N—O linkage.
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  • 59
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    Biological Mass Spectrometry 2 (1969), S. 213-221 
    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 two series of aliphatic polynitro compounds are reported and discussed. The fragmentation patterns of aliphatic nitro and polynitro compounds are similar in that no appreciable molecular ion current is observed; however, there are several other features in the fragmentation of aliphatic polynitro compounds which differ from that of nitroalkane spectra. Both series of compounds studied-C(NO2)x(CH3)4-x, where x = 4 to 0 and C2(NO2)x(CH3)6-x, where x = 6,4,2-show a decrease in the number and intensity of alkylions with an increase in the NO+ and NO2+ ion current as x increases. The main ions resulting from the more nitrated compounds are [NO]+, [NO2]+, [CO2]+. and [CH3CO]+, whose noncharged counterparts are the principal species produced in the detonation of these compounds. This similarity of the products of the two processes suggests the use of mass spectroscopy for the investigation of the initial explosive processes. The principal fragmentation pathways of the polynitroalkanes have been elucidated by exact mass measurements and the observation of metastable ion transitions.
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  • 60
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    Biological Mass Spectrometry 2 (1969), S. 223-239 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In 2,6-di-unsaturated carbonyl compounds, two successive, site-specific hydrogen transfers are necessary to account for the loss of carbon atoms 1, 2, 3 and 4, together with one hydrogen from C-8. The deuterated methyl geranate required for this study was readily converted to pseudo-ionone, in which a similar fission was shown to occur. Previous predictions about the β-ionone mass spectrum2 have been shown to be substantially correct, and its similarity to the mass spectra of benzylidence acetones is pointed out.
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  • 61
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    Biological Mass Spectrometry 2 (1969), S. 241-248 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass-spectral and n.m.r. analysis of thiophenes labeled by exchange with deuteriosulfuric acid establishes that exchange at the 2 and 5 positions is essentially complete before any deuterium is incorporated at positions 3 and 4. Thus, such exchange is a satisfactory procedure for position-specific labeling. Mass spectra of the labeled thiophenes show that about 60% of the [CHS]+ ion yield is derived from molecular ions that have not undergone prior rearrangement. The remaining 40% arises by a path or paths in which the four hydrogen atoms lose position identity. Other decomposition paths contributing to the mass spectrum are characterized by more nearly complete scrambling of hydrogens.
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  • 62
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of a series of 2-substituted 8-hydroxyquinolines and related compounds are reported. Fragmentation pathways based upon interpretation of spectra and metastable transitions for 8-quinolinol; 2-methyl-8-quinolinol; 4-methyl-8quinolinol; 2-hydroxymethyl-8-quinolinol; 2-aminomethyl-8-quinolinol; 8-quinolinol-2-carboxaldehyde; 8-quinolinol-2-carb-oxaldehyde oxime; and 8-quinolinol-2-carboxaldehyde tert-butylimine are discussed, as are dissociations in the related compounds 2-hydroxymethyl quinoline and quinoline-2-carboxaldehyde oxime. It is suggested that the molecular ions of 2-substituted-8-quinolinols undergo rearrangement to a substituted azatropylium ion prior to dissociation. An ion of m/e 89 has been observed in these spectra and is considered to be characteristic of the quinoline nucleus bearing an X-substituent in any position, where X = OR, SR, NH2 etc. (R = H, CH3, etc).
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  • 63
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    Biological Mass Spectrometry 2 (1969), S. 283-298 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: When a fragmentation takes place in mass spectrometry, the positive charge remains on the fragement with the lowest ionization potential. This criterion, which has been indicated previously for the alkane series is shown to be generally true.
    Notes: Lors d'une rupture en spectrométrie de masse, la charge positive demeure préférentiellement sur le fragment de potentiel d'ionisation le plus bas. Ce critère, qui fut mis en évidence sur les alcanes, a été généralisé à divers types de fragmentations.
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  • 64
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    Biological Mass Spectrometry 2 (1969), S. 299-308 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron-impact-induced ionization and fragmentation of six C6H10 structural isomers have been studied in order to determine the effect of isomerism upon their mass spectrometric behavior. The 70 eV mass spectra, metastable transitions and appearance potentials of the principal ions are reported. Significant differences between the mass spectra of the six isomers were observed; however, metastable transition and appearance potential data indicate that the fragmentation path-ways are the same for all the C6H10 molecules. Experimentally determined ionization potentials for the structural isomers are presented and compared to ionization potentials calculated by the bond orbital method. Utilizing fragmentation pathways deduced from general features in the mass spectra and from observed metastable transitions, we calculated heats of formation (ΔHf) for the observed principal ions and compared these values to ΔHf values for isomeric ions from other molecules.
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  • 65
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    Biological Mass Spectrometry 2 (1969), S. 309-315 
    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 the non-benzenoid aromatic heterocycles 2H- and 2-methyl-2H-cyclopenta[d]pyridazine and several deuterated analogs have been analyzed. The majority of the nitrogen lost from these heterocycles occurs as HCN OR H2CN. The deuterium labeling suggests a rearrangement of the molecular ion prior to fragmentation.
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  • 66
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    Biological Mass Spectrometry 2 (1969), S. 325-330 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The formation of the styryl ion \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm PhCH = }\mathop {\rm C}\limits^{\rm + } {\rm H} $\end{document} in the mass spectra of some cinnamic compounds is shown to occur via the intermediate formation of the cinnamoyl ion \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm Ph} - {\rm CH} = {\rm CH} - {\rm C} \equiv \mathop {\rm O}\limits^{\rm + } $\end{document} rather than by direct cleavage of the bond α to the double bond.
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  • 67
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of allphatic ketones are drastically altered following substitution of a trifluoromethyl entity adjacent to the carbonyl group (II and III) or attachment to the γ-carbon atom (V). Loss of the trifluoromethyl group by α-cleavage far exceeds the alternative elimination of an alkyl radical. Virtually complete repression of the McLafferty rearrangement process (I → a) occurs when a CF3 group is attached to the γ-carbon atom. A fluorine atom is not transferred in lieu of hydrogen in the McLafferty rearrangement as demonstrated by the mass spectrum of 1,1,1,7,7,7-hexafluoroheptan-4-one (IV). Rationalization for these results are presented as is a description of the syntheses of several hitherto unknown fluorinated ketones.
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  • 68
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    Biological Mass Spectrometry 2 (1969), S. 331-333 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a series of straight chain aliphatic ketones which has been studied, it has been shown that the structural requirement for loss of water from the molecular ions produced by electron-impact is an alkyl group of seven or more carbon atoms attached to the carbonyl function.
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  • 69
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    Biological Mass Spectrometry 2 (1969), S. 425-426 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 70
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    Biological Mass Spectrometry 2 (1969), S. 427-429 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that FI mass spectra can serve to elucidate some structural features and determine the molecular weights of mono- and oligosaccharides.
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  • 71
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mass spectra of thioglycollic acids and esters are reported and discussed. The spectra of compounds of the type X·CH(Y)·S·CH2·COOR(X 〉 Y) contain skeletal rearrangement fragments with the composition R·Y·C2H3SO+. Ions produced by simple cleavage processes may be usefully correlated with structure.
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  • 72
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    Biological Mass Spectrometry 2 (1969) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 73
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure elucidation of organic compounds is only one of the applications of mass spectrometry to chemistry. Important subjects are also mass spectrometric quantitative analysis of mixtures of inorganic and of organic compounds, determination of isotopes and related problems. In ‘Massenspektrometrie’, edited by H. Kienitz, all these applications are discussed together with an excellent introduction to the function of mass spectrometers and the techniques of measurement. This book contains a lot of information and stimulation for mass spectroscopists and chemists, and is especially recomended for use in analytical laboratories.
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  • 74
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    Biological Mass Spectrometry 2 (1969), S. 433-445 
    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 tetrazole, all isomers of monomethyl- and dimethyltetrazole, several trifluoromethyl substituted tetrazoles, as well as deuterated analogs, were recorded. Loss of N2 was the important fragmentation of the molecular ions of tetrazole and 2-methyl substituted tetrazoles; however, HN2 loss was more important for 1-methyl substituted tetrazoles. The 1-methyl-tetrazoles showed molecular ion peaks while the 2-methyltetrazoles exhibited an unprecedented [M + 1] peak with no molecular ion.
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  • 75
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    Biological Mass Spectrometry 2 (1969), S. 481-519 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 76
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    Biological Mass Spectrometry 2 (1969), S. 447-466 
    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 25 triphenylmethyl (trityl) substituted compounds have been recorded. The trityl cation m/e 243 appears as a peak of major intensity for all classes of compounds examined; these contained trityl-carbon, trityl-nitrogen, trityl-oxygen or trityl-sulfur bonds. Fragmentation of the non-trityl portion of the molecules produced simple ions whose origin was predictable or of low intensity. A mechanism for the decay of the trityl cation is presented which is based upon retention of the α-carbon. Supporting evidence was afforded by mass spectral analysis of (C6H5)313CH in which all fragments from the trityl cation appear to retain nearly all of the 13C.
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  • 77
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    Biological Mass Spectrometry 2 (1969), S. 467-479 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanisms for the major fragmentations obtained with selected substituted uracils are discussed. Interpretation of data was facilitated by use of metastable peaks, high-resolution data, and low-voltage spectra.The major fragmentation obtained with N-alkyl substituted uracils, when the alkyl group contains 2 or more carbons, is due to cleavage of the alkyl substituent. This cleavage is accompanied by a rearrangement of 1 or 2 hydrogens from the alkyl group to the uracil ring. Possible mechanisms for the rearrangements are discussed. It was found that the molecular ion of 1- and 3-alkyl substituted uracils (where the alkyl group has 2 or more carbons) does not undergo the expected ‘retro Diels-Alder Reaction’. Instead, the odd-electron ion formed by loss of the alkyl substituent with a single hydrogen rearrangement undergoes this reaction (loses HNCO). Since it is formed as a secondary reaction product, the relative abundance of the ‘retro Diels-Alder’ fragment is low compared to what is obtained in the spectra of the simple uracils.The ‘retro Diels-Alder Reaction’ can be used to differentiate between 2- and 4-thiouracils, and between 1- and 3-methyl and phenyl substituted uracils. It was found that 1- and 3-alkyl substituted uracils (alkyl group of 2 or more carbons) can be differentiated by the mass of the M-alkyl fragment since the 3-substituted compounds give predominantly a double hydrogen rearrangement and the 1-substituted compound gives mainly a single hydrogen rearrangement. In addition the intensity of the molecular ion, relative to the M-alkyl ion, is considerably stronger in the 1-substituted uracils.
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  • 78
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    Biological Mass Spectrometry 2 (1969), S. 567-577 
    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 reactions of twenty-one 1,1-dichlorocyclopropanes prepared from various isomeric octenes are discussed. The most characteristic reaction may be represented as follows: The importance of this fragmentation and the distribution of the positive charge between the species produced is a function of the degree of branching in the molecule. The more highly branched isomers produce less characteristic fragmentation patterns.The identification of isomeric octenes from the fragmentation patterns of the corresponding 1,1-dichlorocyclopropanes is discussed.
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  • 79
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    Biological Mass Spectrometry 2 (1969), S. 579-590 
    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 a group of m- and p-substituted acetanilides were measured to determine the effect of the substituents, if any, on the rate of C2H2O expulsion (rearrangement) vs. the rate of [CH3CO]+ formation (simple cleavage). Our results agree with observations of others in that substituents which raise the ionization potential of the aromatic ring appear to localize, on the average, less charge density on this locus, and conversely. The atomic composition of the substituent, however, irrespective of its position, seems to determine the relative rates of the competing reaction. Although in several cases Zm/Zp values were close to unity, rearrangement of isomeric molecular ions to a common species is shown not to occur.
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  • 80
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    Biological Mass Spectrometry 2 (1969), S. 603-609 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of the four stereoisomeric 1-methyldecalins and the four 2-methyldecalins have been measured. For each set of stereoisomers, the order of relative intensity of the parent-less-CH3 ion, but not of the parent ion, parallels the order of relative stability of the molecules. The correlation suggests that loss of the methyl group from the members of each set of stereoisomers leads to a common product, with the differing conformational energies converting into differences in vibrational energy, which in turn lead to differing extents of further decomposition.
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  • 81
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    Biological Mass Spectrometry 2 (1969), S. 591-601 
    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 maleic acid, maleic acid-2,3-d, fumaric acid and fumaric acid-2,3-d have been examined and fragmentation mechanisms are proposed for these compounds. The molecular ion of the cis-acid fragments via H atom transfer from one carboxyl group to the other followed by loss of CO2. The trans acid does not fragment significantly by this route and the former effect may be characteristic of molecules containing two carboxyl groups cis-oriented to each other. This hypothesis was successfully tested by examining the mass spectra of citraconic, itaconic and phthalic acids. Itaconic and mesaconic acids show some of the fragmentation characteristics of fumaric acid.
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  • 82
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    Biological Mass Spectrometry 2 (1969), S. 611-623 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fragmentation patterns in the spectra of 2-aryl-1,3-dithianes and -1,3-dithiolanes have been elucidated by deuterium labelling studies. Ortho effects are observed in the spectra of 2(o-alkoxyphenyl)-1,3-dithianes. The molecular ions of the 1,3-dithianes eliminate S2H· and metastable kpeaks substantiate these eliminations. The hydrogen involved in this elimination randomises (C-4, 5 and 6) Prior to elimination in the spectrum of 2-phenyl-1,3-dithiane, but originates mainly from C-5 in that of the bis propane-1,3-dithioacetal of terephthaldehyde.
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  • 83
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the α-cleavage processes of aliphatic amines (using RLCH2N(R)CH2Rs and RLCH(NR)RsRL represents the larger Rs the smaller alkyl group throughout this paper and both, unless indicated to the contrary, have similar degrees of lsubstitution on the α-carbon atom. as typical substrates) at several ionizing voltages indicates that the loss ratio of large and small alkyl radicals, [M — RL]/[M — Rs], decreases with ionizing voltage. This ratio, greater than 1·0 at 70 eV, may become less than unity at low voltage (15 eV, 10 eV) in some cases. Comparison of similarly structured compounds with nitrogen or oxygen as the heteroatom suggests that the effects of ionizing voltage are lessened when the fragment is of greater stability (e.g. amine vs. ether or imine vs. ketone). The effects of lowering the ionizing voltage became much less pronounced as the alkyl groups become larger or similar in size.
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  • 84
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 3,4-, 3,5-, 3,6-, and 4,5-dichlorobenzyne and 3,4,5,6-tetrachlorobenzyne are generated by high vacuum pyrolysis of the corresponding 1,2-diiodobenzenes or phthalic acid anhydrides in a mass spectrometer. The ionization potentials are measured by the RPD-method and the heats of formation of these substituted benzynes are estimated.
    Notes: 3,4-, 3,5-, 3,6-, und 4,5-Dichlordehydrobezol sowie 3,4,5,6-Tetrachlordehydrobenzol wurden durch Hochvakuumpyrolyse aus den entsprechend substituierten 1,2-Dijodbenzolen bzw. Phthalsäureanhydriden erzeugt und massenspektrometrisch nachgewiesen. Die Ionisationspotentiale wurden nach dem RPD-Verfahren gemessen und die Bildungsenthal pien der substituierten Dehydrobenzole abgeschätzt.
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  • 85
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    Biological Mass Spectrometry 2 (1969), S. 835-842 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of substituents on the fragmentation of N-aryl trifluoracetamides has been investigated. The base peak in all ring-monosubstituted derivatives is the molecular ion. Other important ions arise by loss of CF3 and COCF3 from the molecular ion, and the latter daughter ion fragments further, by loss of the aromatic substituent and by expulsion of small neutral molecules. The effects of substituents on the intensity of these ions is discussed. 1-Phenylethyl trifluoracetamide exhibits a base peak which is the molecular ion, wheras the corresponding 2-phenyl derivative has a molecular ion of very low intensity.
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  • 86
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    Biological Mass Spectrometry 2 (1969), S. 865-876 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: In contrast to the olefins I and II, olefins alkylsubstituted at the double-bond(III to IX) suffer no isomerization by hydrogen migration before fragmentation occurs. Almost the only degradation-reaction of the molecular ions of the olefins III to VIII is the McLafferty-rearrangement. From the isomers III and IV, respectively V and VI, the same McLafferty-rearrangement product is formed, therefore the spectra are nearly identical.A general scheme for the occurrence of identical mass spectra of isomeric compounds is given.The olefin IX in which the McLafferty-rearrangement is not possible shows preferential cleavage of the ally1 bond. If the chain contains a futher alky-substituent, bond-rupture at the branched c-atom competes with the McLafferty-rearrangement.
    Notes: Im Gegensatz zu den Olefinen I und II unterliegen die an der Doppelbindung alkylsubstituierten Olefine II bis IX keiner der Bruchstückbildung vorausgehenden Isomerisierung unter Wasserstoffwanderung. Bei den Olefinen III bis VIII ist die McLafferty-Umlagerung die nahezu einzige Abbaureaktion der Molekülionen. Aus den Isomeren III und IV bzw. V und VI entsteht das gleiche McLaffetty-Abbauprodukt, so daß die Spektren praktisch identisch sind.Es wird ein allgemeingültiges Schema für das Auftreten identischer Massenspektren isomerer Verbindungen angegeben.Ein Olefin der Struktur IX, bei dem die McLaffetty-Umlagerung nicht möglich ist, zeigt bei Electronenbeschuß vorzugsweise. Befindet sich ein weiterer Alkylsubstitutent in der Kette, so tritt als Konkurrenzreaktion zur McLaffety-Umlagerung der Bindungsbruch an der Verzweigungsstelle ein.
    Additional Material: 9 Ill.
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  • 87
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    Biological Mass Spectrometry 2 (1969), S. 877-892 
    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.
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  • 88
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    Biological Mass Spectrometry 2 (1969), S. 893-900 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The main fragmentation sequences of glycollide and its homologues are initiated by fission of a CO—O bond, leading to the formation of fragment ions of low, m/e, such as [R1CO]+ and [CR1R2CCO]+. When a hydrogen atom is present on a ring carbon atom, 1,3 hydrogen migration occurs to produce [CHR2OH]+. In case where a ring carbon atom carries an alkylchain ≥ C2H5, a McLafferty rearrangement occurs with the adjacent carbonyl group. When both ring carbon atoms are dimethyl substituted, a 1,4 hydrogen migration must be invoked to account for the observed fragmentation sequence.
    Additional Material: 2 Ill.
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  • 89
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    Biological Mass Spectrometry 2 (1969), S. 915-917 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 90
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    Biological Mass Spectrometry 2 (1969), S. 901-906 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cortisol is thermally unstable. It is easily decomposed by loss of ketence and water. The spectrum of the resulting 11β-hydroxy-Δ4-androsten-3,17-dion can be superimposed upon the spectrum of the undecomposed cortisol, which only can be obtained free of the decomposition product under carefully controlled conditions. The thermal degradation product can be eaisly detected by its molecular peak at mass 302 and a key fragment at mass 163, which are nearly absent in the spectrum of cortisol. Cortisol is therefore an excellent testing material for the quality of inlet systems.
    Notes: Cortisol ist thermisch instabil. Es zersetzt sich leicht unter Verlust von Keten und Wasser, Das Spektrum das entstehenden 11β-Hydroxy-Δ4-androsten-3,17-dions überlagert sich dem Cortisolspektrum, das man frei von Zerstezungsprodukt nur unter sorgfältiger Einhaltung der Aufnahmebedingungen erhält Das thermische Zersetzungsprodukt läßt sich leicht an seinem Molekül-Ion der Masse 302 und einem Schlüsselbruchstück der Masse 163 erkennen, die im Cortisolspektrum nahezu völlig fehlen, so daß Cortisol eine ausgezechnete Testsubstanz zur Qualitätsprüfung vonEinlass-Systemen darstellt.
    Additional Material: 8 Ill.
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  • 91
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    Biological Mass Spectrometry 2 (1969), S. 947-952 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The trifluoroacetyl derivatives of alditols are convenient compounds for mass spectrometric investigation as they are easily obtainable and highly volatile. They show simple fragmentation patterns with intensive peaks in the high mass range. Trifluoroacetates of alditols may be used for detection and location of deoxy groups in the molecule.
    Additional Material: 6 Ill.
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  • 92
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    Biological Mass Spectrometry 2 (1969), S. 953-963 
    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 thirty sydnoes have been interpreted; the types investigated include 3-aryl, 3-alkyl-, substituted 3-alkylsydnones; and bis sydnones. A characteristic fragmentation mode involves initial loss of NO and CO from the molecular ion, but peaks corresponding to alkylcarbonium ions dominate the spectra of 3-alkylsydnones; a cyclic mechanism is suggested for weak transitions involving loss of sydnone neutral molecule from the molecular ion. A mechanism is proposed for loss of chlorine radical from the molecular ion of 3-(2,4-dichlorophenethyl)sydnone. An unusual feature in the mass spectrum of trimethylenebis sydnone is rationalised on the basis of a precursor 1,2,3-oxadiazole ion. The effect of substituents in the aryl ring on the fragmentation of 3-arylsydnones is discussed.
    Additional Material: 5 Tab.
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  • 93
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    Biological Mass Spectrometry 2 (1969), S. 1039-1039 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 94
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    Biological Mass Spectrometry 2 (1969), S. 1042-1042 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 95
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    Biological Mass Spectrometry 2 (1969) 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 96
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 97
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    Biological Mass Spectrometry 2 (1969), S. 1043-1048 
    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 aluminum isopropoxide show that polymers, [Al(OC3H7)3]x where x = 1 to 7, can be present in the vapor and are, therefore, probably present in the bulk sample. The polymeric composition of the vapor depends on the previous history of the sample. Exact mass measurements on many of the ions along with data on a number of metastable peaks support the proposed fragmentation mechanisms. Loss of 102 mass units between intense peaks in the mass range above 500 a.m.u. leads to the suggestion that the higher polymers may be used as high mass marking substances.
    Additional Material: 2 Ill.
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  • 98
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    Biological Mass Spectrometry 2 (1969), S. 1049-1060 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The composition of solid saturated hydrocarbons from slack-wax after reaction with urea has been investigated by electron-attachment (EA) mass spectrography with negative ions. From the spectra of the samples the content of paraffin hydrocarbons, monocyclic, dicyclic and other polycyclic naphthenes was calculated. The presence of n-paraffins up to C46, isoparaffins and cycloalkanes up to C52 has been confirmed. In the paraffin series the concentration of normal paraffin hydrocarbons containing one and two 13C atoms was determined. On the basis of the results obtained the constitution of the samples and the possible structures of the hydrocarbons were discussed. The results obtained have shown that the solid hydrocarbons which react with urea not only consist of one- or two-ring systems, but also of systems with up to five and six rings.
    Additional Material: 8 Ill.
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  • 99
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    Biological Mass Spectrometry 2 (1969), S. 1067-1072 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes a direct appearance potential difference method, which is employed to determine, qualitatively, relative free radical stabilities. The method appears to be of general value since the starting materials (β-substituted N-ethylanilines) are relatively simple to prepare and because the dominant electron-impact reaction is the one which releases the free radical under investigation.
    Additional Material: 3 Tab.
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  • 100
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    Biological Mass Spectrometry 2 (1969), S. 1103-1115 
    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 the alkyl cyanides up to n-pentyl cyanide were studied. Using metastablel ion transitions, appearance potentials and deuterium labelling, the fragmentation patterns, spectral characteristics and trends for this series can be given. The investigation of labelled compounds demonstrates the specificity of rearrangement and normal decomposition processes. Alkyl ions in nitriles are produced by simple cleavage of the carbon-carbon bond, while ions of the type [M -alkyl]+, which at the first sight could originate in the same way, are presumably formed via cyclic intermediates and are in fact rearrangement ions.Apart from the known γ and δ-hydrogen rearrangements, there is novel evidence for a β-hydrogen rearrangement via a five-membered ring transition state.
    Additional Material: 7 Tab.
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