bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elektronenstoss‐Induzierte Molekülumlagerungen—I. Massenspektrometrische Fragmentierungen von Azinen und Phosphazinen
Authors: Zeeh Bernd , Beutler Rolf 
Published: May 2005

AbstractDie Massenspektren von 15 Azinen sowie 5 Phosphazinen werden mittels deuterium‐Markierung und exakten Massenmessungen untersucht. Azine von Aldehyden eliminieren HCN und (HCN + H) aus dem Molekülion, was mit einer Umlagerung verbunden ist. Azine von Ketonen spalten zuerst ein Aryl‐bzw. Akylradikal ab und lagern sich anschliessend um unter eliminieung von CN. oder (CN. + H). Analogien zur photolytischen oder termischen Abspaltungvon Stickstoff aus Azinen wurden nicht gefunden. o, o′‐Dinitro‐benzaldazin erleidet unter Elektronenstoss eine doppelte Sauerstoffumlagerung, bei de CO2 eliminiert wird. Phosphazine zeigen bei Elektronenbeschuss ein ähnliches Verhalten wie bei der Thermolyse.
Chemistry of lichen constituents—VII: Mass spectra of some pulvic acid derivatives
Authors: Letcher R. M. 
Published: May 2005

AbstractThe mass spectra of three methoxypulvic dilactones, four methyl esters of methoxypulvic acids and five methyl ethers of pulvic acid derivatives have been measured and rationalised employing accurate mass measurements and metastable peak assignments to substantiate the proposed fragmentations and rearrangements. In particular, the mass spectral differences and similarities between the isomeric methoxypulvic dilactones, between their methanolysis products and between the isomeric methyl ethers, are rationalised.
Mass spectrometric studies on o‐terphenyl‐2‐13C: Identification of compounds related to its synthesis and fragmentation processes
Authors: Copet A. , Facchetti S. 
Published: May 2005

AbstractAfter identification of the impurities, separated from synthesized orthoterphenyl (I) labelled in position 2 with 13C, i.e. o‐xenylcyclohexanol (II), o‐xenylcyclohexene (III), hexahydrotriphenylene (IV) and o‐xenylcyclohexane (V), the fragmentation processes under electron‐impact of molecules I, II and IV have been studied, advantage being taken of their 13C labelling.Mass spectrometric studies were carried out on an AEI MS‐9 for determination of the atomic composition of the main ions and on a MAT CH‐4 instrument for quantitative determination of 12C and 13C species, at low energy, assuming an equal sensitivity.The 13C labelling of position 2 in I, has not yet given clear evidence of a formerly assumed rearrangement into phenanthrenic structure after ring opening.The fragmentation of molecule II occurs in two ways, i.e. into a series of hydrocarbon fragments, produced from the molecular ion by loss of H2O or into fragments still containing the oxygen atom. The difference between the fragmentation processes of the two series depends on the fact that the loss of H2O from the molecule stabilizes the two carbon atoms adjacent to the C carrying the hydroxyl group. This is shown by the relatively higher 13C content of the hydrocarbon fragment in C15 compared with that of the equivalent oxygenated fragment.The labelling in IV shows how the rupture of the saturated ring occurs under electron‐impact, the first C removed being the one nearest to the central ring.
Zum Verhalten von Trimethylalkoxysilanen bei Elektronenstoss
Authors: Dube G. , Kriegsmann H. 
Published: May 2005

AbstractEs werden die Massenspektren von Trimethylaklkoxysilanen dr Typen (CH3)3SiO(CH2)nCH3 (n = 0‐8) und (CH3)3SiO(CH2)nCH(CH3)2 (n = 0‐3) wiedergegeben und die meisten Abbaureaktionen der Verbindungen bei Elektronenstoß durch metastabile Ionen belegt. Die von Diekman, Thomoson und Djerassi für Trimethypentoxysilane angegebenen Zerallsmechanisman laufen auch bei den untersuchten Substanzen ab. Es werden Besonderheiten beim Ablauf dieser Reaktionen bei Trimethylalkoxsilanen mit längerer und kürzerer Alkoxykette diskutiert und einige weitere Zerfallsreaktionen mitgeteilt.
The question of hydrogen and randomization in phenyl isocyanide
Authors: Yeo Adrian N. H. , Cooks R. Graham , Williams Dudley H. 
Published: May 2005

AbstractThe loss of HCN and DCN from 2,4,6‐d3‐phenyl isocyanide is preceded by H/D randomization in the large majority of k‐states which could be sampled in this study.
Electron‐impact studies—XVIII. Fragmentation of some epimeric 7‐substituted norbornenes
Authors: Das K. G. , Nayar M. S. B. , Chinchwadkar C. A. 
Published: May 2005

AbstractThe fragmentation modes of some epimeric 7‐substituted norbornenes have been established from deuteration and high resolution studies. Stereochemical differences were found to have very little influence in directing the fragmentation modes of these epimers. Formation of common intermediates or transition states by ring opening process has been proposed to rationalise the mass spectral behaviour of these compounds.
Bridgehead nitrogen heterocycles—II: The mass spectra of some pyrazolo[1,5‐a]pyridines
Authors: Potts K. T. , Singh U. P. 
Published: May 2005

AbstractPyrazolo[1,5‐a]pyridine undergoes fragmentation upon electron‐impact by loss of HCN or C2H2N·. In the 2,3‐dimethyl derivative loss of HCN and CH3CN were both observed from the [M – 1]+ ion and, in the 3‐methyl‐2‐phenyl derivative, loss of PhCN occurred from the corresponding [M – 1]+ ion. Loss of methyl and phenyl radicals was also observed. In 3‐acetyl‐2‐methyl and 3‐benzoyl‐2‐phenyl derivatives, characteristic losses of the CH3CO· and PhCO· groups were noted. The introduction of a 7‐methyl substituent into the six‐membered ring had little effect on the fragmentation pattern.
Mass spectrometry in structural and stereochemical problems—CLXXXIV: Charge localization in fragment ions of amino ketones and esters
Authors: Cable J. , Adelstein G. W. , Gore J. , Djerassi Carl 
Published: May 2005

AbstractThe mass spectral fragmentation of a number of specially synthesized amino esters and ketones has been studied in which the distance between the two functionalities has been varied. The principal fragments formed following initial ionization are the even‐electron immonium ions a and b. Further fragmentation of ion a in the amino esters occurs via non‐specific processes. Therefore it is difficult to establish the degree of mobility of the positive charge in the fragment ions, notably whether the species with the charge present on the oxygen atom makes a significant contribution to the fragmentation. The β‐(IIb) and γ‐(IV) amino ketones show no McLafferty rearrangements after α‐fission, thus demonstrating that uncoupling of the carbonyl π electrons is not a feasible trigger in lieu of charge localization.
The ion kinetic energy spectra of some aromatic hydrocarbons
Authors: Beynon J. H. , Caprioli R. M. , Baitinger W. E. , Amy J. W. 
Published: May 2005

AbstractThe technique of ion kinetic energy spectroscopy has been applied to the study of the aromatic hydrocarbons benzene, toluene, naphthalene, 2‐methyl naphthalene, biphenyl and anthracene. The method is illustrated by a complete study of naphthalene in which transitions of metastable doubly‐ and singly‐charged ions are listed, including reactions in which singly‐charged ions are formed by collision induced charge‐exchange reactions of doubly‐charged ions and by the double process of charge‐exchange and metastable decomposition with loss of one or two hydrogen atoms. Decompositions of doubly‐charged ions into two singly‐charged ions, together with the kinetic energies released in these decompositions, are also given for all the compounds studied.
Metastable ions of methane and their use in calibrating a low mass scale
Authors: Beynon J. H. , Caprioli R. M. , Baitinger W. E. , Amy J. W. 
Published: May 2005

AbstractThe decomposition of metastable positive ions of methane formed by electron bombardment is discussed. Some new collision‐induced decompositions involving the formation of H+, H2+˙ and H3+ have been found in the ion kinetic energy spectrum as well as in the mass spectrum of methane. In the latter case, the ‘metastable peaks’ occur below mass 1 on the mass scale and can be used for mass calibration in this region of the mass spectrum.
Mass spectra of maleimides, isomaleimides, bis‐maleimides, bis‐isomaleimides and the intramolecular photocyclization products of bis‐maleimides
Authors: Feast W. J. , Put J. , De Schryver F. C. , Compernolle F. C. 
Published: May 2005

AbstractThe mass spectral fragmentation of some maleimides, isomaleimides, bis‐maleimides, bis‐isomaleimides and diazatetracyclotetraones (intramolecular photocyclization products of bis‐maleimides) have been investigated. The elimination of carbon dioxide from the molecular ions of these compounds is not generally an important process. Fragment ions arising from the transfer of one or more hydrogen atoms from the eliminated to the charge retaining moiety (and vice versa) are prevalent and the variation in fragment ion intensity with changes in structure is consistent with the mechanisms of the analogous fragmentations of succinimides established by Djerassi's group. The apparently unusual fragmentations of the diazatetracyclotetraones may be rationalized on the basis that the molecular ion consists of three or more different species.
Mass spectra of β‐quinuclidones and β‐benzquinuclidones
Authors: Ermakov A. I. , Sheinker Yu. N. , Mikhlina E. E. , Mastafanova L. I. , Ya. Vorobjova V. , Yanina A. D. , Yakhontov L. N. , Kostyanovsky R. G. 
Published: May 2005

AbstractThe mass spectra of quinuclidone‐3, benzquinuclidone‐3, 2‐azaquinuclidone‐3, 2‐azabenzquinuclidone‐3 and some of their functional substituted derivatives have been investigated. Fragmentation of the compounds investigated has been shown to proceed through the open form of the molecular ion with cleavage of a bridgehead bond containing the carbonyl group and subsequent elimination of carbon monoxide.
Strukturspezifischer Massenspektrometrischer Abbau von mono‐ und di‐n‐alkyl‐substituierten Acetylenverbindungen
Authors: Luftmann H. , Spiteller G. 
Published: May 2005

AbstractMassenspektren mono‐n‐alkyl‐substituierter Acetylene vom Typ 1, die zumindest 7 Kohlenstoffatome in gerader Kette des Restes R enthalten, sind durch Schlüsselbruchstücke der Masse 82 und 96 gekennzeichnet. Sie zerfallen weiter unter Verlust eines Methylradikals. In den Spektren di‐n‐alkyl‐substituierter Acetylene sind diese Schliiüsselbruchstücke urn eine entsprechende Zahl von Masseneinheiten verschoben. Sie werden unter Eliminierung von C5H10 Teilchen weiter abgebaut. Daneben entstehen auch aus di‐n‐alkyl‐substituierten Acetylenverbindungen Schlüsselbruchstücke der Masse 67, 81, 82 und 95,96.
Preference factors and isotope effects in the loss of H. (D.) and HCN (DCN) from deuterated pyrazoles upon electron‐impact
Authors: Van Thuijl J. , Klebe K. J. , Van Houte J. J. 
Published: May 2005

AbstractThe mass spectra of deuterated pyrazoles show that loss of H. and of HCN from the molecular ion occurs with a very high specificity from the 3(5)‐position. For the two processes isotope effects and preference factors have been determined. Metastable ion decompositions involving the loss of HCN from the [M ‐ H] ‐fragment indicate that the identity of the hydrogen atoms in this fragment is lost to a large extent.
Electron impact studies—LXV: Negative‐ion mass spectrometry of functional groups 2‐aryl‐1,3‐dithianes
Authors: Bowie J. H. , White P. Y. 
Published: May 2005

AbstractThe negative‐ion mass spectra of 2‐aryl‐1,3‐dithianes contain pronounced molecular anions together with fragment ions which are produced by both simple and complex cleavage reactions. These spectra contain further examples of specific hydrogen scrambling processes in negative ions. Nitroaryldithianes give intense negative‐ion spectra, and that of the o‐nitro derivative exhibits an unusual proximity effect. The fragmentation patterns have been examined using both 2H and 13C labelling and the metastable defocusing technique.
Mass spectrometric studies of 4‐oxo‐4,5,6,7‐tetrahydrobenzofurans
Authors: Cortés E. , Salmón M. 
Published: May 2005

AbstractThe mass spectra of alkyl and aryl 4‐oxo‐4,5,6,7‐tetrahydrobenzofurans have been determined and the fragmentation patterns are established unambiguously by deuterium labelling in the 5,5,7,7‐d4 position.
Mass spectra of N and O methyl and methylthiomethyl derivatives of benzophenone oxime
Authors: Leyshon W. M. , Wilson D. A. 
Published: May 2005

AbstractThe mass spectra of benzophenone oxime O‐methyl and O‐methylthiomethyl ethers, α,α‐diphenyl‐N‐methyl and methylthiomethyl nitrones, and some deuterated analogues, are reported. Fragmentation pathways are discussed, with particular reference to the structures of ion m/e 211 found in all the spectra. Some evidence suggests nitrone → O‐ether rearrangement at either neutral molecule or molecular ion level.
Fragmentation de Triazoles Sous L'Impact Electronique—II 1,2,3‐Triazole
Authors: Maquestiau A. , Van Haverbeke Y. , Flammang R. , Elguero J. 
Published: May 2005

AbstractLa similitude de comportement des 1,2,4‐ et 1,2,3‐triazoles sous l'impact électronique est attribuée à la formation de structures ioniques communes. L'étude des transitions métastables correspondant à al perte d'une molécule d'azote semble indiquer que, dans le cas du 1,2,3‐triazole, les deux formes tautoméres coexistent à l'état gzaeux et qu'une isomérisation partielle de l'ion moléculaire se produit dégradation.
The study and characterization of nucleosides by mass spectrometry—II: Comparisons between the mass spectra of 3′,5′‐substituted, isomeric pairs of 2,2′‐anhydrouridines
Authors: Westmore J. B. , Lin D. C. K. , Ogilvie K. K. 
Published: May 2005

AbstractThe mass spectra of 2,2′‐anhydrouridines substituted in the 3′ and 5′ positions were studied. When the substituents were acetyl, pivaloyl, trifluoroacetyl or trimethylsilyl, it was found that specific fragmentations occured which could identify the position of the substituent. The specific fragmentations often resolve earlier ambiguities in the interpretation of mass spectra of 2,2′‐anhydropyrimidine derivatives. Mono‐acetyl and mono‐pivaloyl 2,2′‐anhydrouridines are not easily distinguished because of thermal reactions in the sample probe. They may be readily distinguished, however, by acetylation (with acetic anhydride‐d6 for the mono‐acetyl isomers), trifluoroacetylation or trimethylsilylation, followed by mass spectral analysis of the reaction product.
Mass spectrometry in structural and stereochemical problems—CCXXIII:ortho interactions of nitro groups
Authors: Tomer Kenneth B. , Gebreyesus Tarekegn , Djerassi Carl 
Published: May 2005

AbstractThe mass spectra of C13 labeled o‐ nitrobenzoic acid and o‐nitrobenzaldehyde were studied. Earlier proposed fragmentations involving group migration to a charge‐carrying vacant ortho position were verified. A completely unexpected interaction in o‐ nitroanisole was uncovered by O18labeling.
Gas phase studies of N‐nitrosamines by ion cyclotron resonance spectroscopy
Authors: Billets Stephen , Jaffe H. H. , Kaplan Fred 
Published: May 2005

AbstractThe gas phase basicities of a series of cyclic and acyclic N‐nitrosamines were determined by ion cyclotron resonance techniques. The fragmentation pattern and ion‐molecule reactions of these compounds are discussed in terms of high resolution mass spectrometry and deuterium labeling. The presence of a unique rearrangement of the molecular ion is discussed in terms of specific ion‐molecule proton transfer reactions and fragment ion products.
Chemical ionization mass spectrometry studies—VII: Deuterium labeled decanes
Authors: Hunt D. F. , McEwen C. N. 
Published: May 2005

AbstractCI mass spectra of the five isomeric vicinal d2‐decanes have been recorded using methane and d4‐methane as reagent gases. In contrast to earlier suggestions, we find that a large fraction of the alkyl fragment ions from n‐decane are formed by elimination of olefins from the abundant [M – 1] ion. Only the C9 and C8 fragment ions are produced completely by a one‐step reaction between the decanes and the methane reagent ions. Isotope exchange does not occur between the hydrocarbon and the reagent ions derived from d4‐methane but extensive scrambling of the deuterium label in the d2‐decanes does take place in the [M – 1] ion.
Internal energy effects on the mass spectral fragmentations of some phosphorus heterocycles
Authors: Weringa W. D. , Granoth I. 
Published: May 2005

AbstractIn addition to the elimination of C6H5· and C7H7·, 2,8‐dimethyl‐10‐phenyl‐ and 10‐(p‐tolyl)‐phenothiaphosphines lost C6H5S· and C7H7S·, respectively from high internal energy molecular ions, while the low internal energy ions eliminated C6H5PH and C7H7PH, respectively. 2,8‐Dimethyl‐10‐phenylphenoxaphosphine lost C6H5·, C6H5P and C6H5PH· both in the source and in the first field‐free region, but the expulsion of C6H5O· was not observed.
Etude de la Fragmentation des bis Alkylthio‐3,5 Isothiazoles en Spectrometrie de Masse
Authors: Julien Jacques , Vincent Emile‐Jean , Poite Jean‐Claude , Roggero Jean 
Published: May 2005

AbstractL'étude du schéma de rupture de 26 bis alkylthio‐3,5 isothiazoles permet de mettre en évidence des modes de rupture assezy pen connus dans la série des isothiazoles. On reconnaît dans le cas des bialkyl thio‐3,5 isothiazoles deux modes importants correspondant respectivement à la perte du radical mercapto et à la perte de deux atomes de soufre. Nous démontros à l'aide des spectres des dérivés deutériés dans chaque position et du dérivé perdeutérié correspondant, le rôle spécifique des substituants alkylthio dans le mécanisme de fragmentration correspondant ` la perte des radicaux alkyle, thioalkyle et mercapto. Un mécanisme de transposition de l'ion moléculaire est envisagé pour expliquer la présence de deux schémas compétitifs de rupture.
Massenspektrometrische Fragmentierungen β‐Substituierter Adamantanone und Adamantandione
Authors: Eckhardt G. , Fehlhaber H.‐W. 
Published: May 2005

AbstractDurch hoch‐und niederauflösende Massenspektrometrie und durch Bestimmung emtastabiler Ionen mittels Defokussierung wurde die elektronenstoß‐induzierte Fragmentierung einer Reihe β‐substituierter Adamantanone und Adamantandione untersucht. Während die isomeren Brom‐, Jod‐ und Thiocyanato‐adamantanone fast identische Spektren liefern, ist das Fragmentierungsverhalten der Fluor‐ und Chlor‐Verbindungen davon abhängig, ob die Substituenten in Bezug auf den die Carbonyl‐Gruppe enthaltenden Ring axial oder äquatorial angeordnet sind. Hydroxyund Acetoxy‐adamantanone liefern ziemlich komplexe Massenspektren. Adamantandione, die in β‐Stellung durch verschiedene COR‐bzw. NR1R2‐Gruppen substituiert sind, geben charakteristischen Peaks von Ionen, die durch McLafferty‐Umlagerung bzw. α‐Spaltung und anschließende Eliminierung von Kohlenmonoxid und Allyl‐Spaltung gebildet werden Das Fragmentierungsverhalten der isomeren Hydroxycarbomethoxy‐adamantanone und Dihydroxy‐carbomethoxyadamantane wird durch die Orientierung der funktionellen Gruppen bestimmt.
On the correlation between emitter heating current and emitter temperature in field desorption mass spectrometry
Authors: Kümmler D. , Schulten H.‐R. 
Published: May 2005

AbstractCalibration curves have been established that give an estimate of the temperature in the emission region of high temperature activated field desorption emitters. Two characteristic types of field anodes have been investigated: (1) emitter wires carrying microneedles of 25 to 30 μm length, preferentially used for field desorption of organic compounds; (2) emitters with microneedles of 50 to 60 μm length, which are used for the investigations of polymers by pyrolysis field desorption mass spectrometry.
Stereochemical effects in the electron impact mass spectra of some 2,6‐dideoxy‐3‐c‐methylhexopyranoses
Authors: Gioia B. , Vigevani A. 
Published: May 2005

AbstractThe electron impact mass spectra of the methyl α‐and β‐glycosides of axenose, of a number of derivatives, and of mycarose, display substantial differences, characteristic of their stereochemistry. In order to interpret this behaviour the structures of the fragments and the main features of the fragmentation patterns have been established, and the methyl glycosides of some related monosaccharides (arcanose, cladinose and idose) have been examined. The experimental results allow the observed differences to be attributed to the presence of an intramolecular hydrogen bond between the hydroxyl group at C‐3 and the oxygen atom of the methoxy group in the methyl α‐glycosides of axenose and mycarose.
Applications of artificial intelligence for chemical inference. XIX—Computer generation of ion structures
Authors: Smith Dennis H. , Konopelski Joseph P. , Djerassi Carl 
Published: May 2005

AbstractThe purpose of this paper is to discuss an interactive computer program which can be used to study questions of plausible ion structures. The program can be constrained in a variety of ways by the user, based on information inferred from (i) the structure of the intact molecule which gave rise to the ion, (ii) metastable defocusing experiments to identify progenitors, and (iii) existing knowledge of the fragmentations and rearrangements of related molecules, including deuterium labeled analogs. Implementation of these constraints is discussed primarily with the example of triethylamine, an apparently simple compound whose behavior is examined in detail with the aid of the program because of the complexity of its fragmentation.
Deconvolution of composite metastable peaks: A new method for the determination of metastable transitions occurring in the first field free region
Authors: Evers E. A. I. M. , Noest A. J. , Akkerman O. S. 
Published: May 2005

AbstractThe masses of daughter ions resulting from metastable transitions in the first field free region of a “reversed geometry” mass spectrometer can be accurately determined through a mass analysed ion kinetic energy scan at the apparent mass at which these daughter ions travel through the magnetic sector. A combination of these mass analysed ion kinetic scans with scanning the magnetic flux allows the resolution of overlapping metastable diffuse peaks.
Conjugated Schiff bases. VII—Decarbonylation of some 1,3‐hetrodienes under electron impact
Authors: Moskal Janusz , Nagraba Krzysztof , Pálonek Elzbieta 
Published: May 2005

AbstractThe mass spectra of some 1,3‐ heterodienes containing the 1‐oxa‐4‐aza‐butadiene system have been determined and the characteristic fragmentation pathways are discussed. The pathways suggested are supported by the appropriate metastables, the spectra of model compounds and by deuterium labelling. The 1, 3‐heterodienes substituted by the thioarylamide group from ions involving participation of the sulphur atom.
Determination of daughter ion elemental compositions in charge separation reactions
Authors: Vijfhuizen Peter C. , Van Der Schee Henk , Terlouw Johan K. 
Published: May 2005

AbstractIt is shown that the elemental composition of a product ion generated from a multiply charged ion in a charge separation reaction can be determined with a double focusing instrument under conditions of high mass and energy resolution. Results for a number of charge separation reactions in benzylamine are briefly discussed.
The mass spectra of halogenated β‐sultones and a comparative study with vinyl methanesulfonates
Authors: Kao Liu Lilian 
Published: May 2005

AbstractThe mass spectra of some halogenated β‐sultones which have been determined show some common features. These include the absence of molecular or ions and the presence of abundant trihalomethyl and [M‐ trihalomethyl]+ ions. The latter can subsequently lose sulfur dioxide, ions are also observed in high abundance.
Notiz zur elektronenstoßinduzierten Ringkontraktion von Cycloalkanonen und zur Struktur der ‐Ionen
Authors: Schwarz Helmut 
Published: May 2005

AbstractDurch CA‐Untersuchung wird nachgewiesen, daß Cyclooktanon‐Ionen vor der Äthylen‐Eliminierung nicht zu ionisiertem 2‐Äthylcyclohexanon isomerisieren. Außerdem wird gezeigt, daß die durch einfache und doppelte McLafferty‐Umlagerung aus einigen Cycloalkanonen erzeugten Ionen m/e 98 je nach Konstitution der Vorläufer in verschiedenen Strukturen existieren können.