bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fragmentation paths ofO‐ andS‐phenylN‐phenylbenzohydrazonates, and the isomericN,N‐diphenylbenzohydrazides upon electron impact
Authors: Wolkoff Peder 
Published: May 2005

AbstractThe mass spectra of O‐ and S‐phenylbenzohydrazonates and the isomeric N, N‐diphenylbenzohydrazides have been examined. The benzohydrazonates decompose by expulsion of a phenoxy (thiophenoxy) radical, or by elimination of phenol (thiophenol); the latter is a new example of the mass spectral retro 1, 3‐dipolar cycloaddition reaction. There are no indications of a mass spectral Chapman rearrangement in these compounds, while evidence is adduced for a mass spectral retro Chapman rearrangement in the spectrum of N, N‐diphenylthiobenzohydrazide.
Electron impact studies. CIII—Negative ion mass spectra of naturally occurring compounds: Nitrobenzoyl derivatives of amino esters
Authors: Stapleton B. Jane , Bowie John H. 
Published: May 2005

AbstractThe negative ion mass spectra of p‐nitrobenzoyl derivatives of amino esters show pronounced molecular anions and characteristic fragmentation patterns. Fragment anions observed in the spectra of o‐nitrobenzoyl analogues arise by various interactions between the nitro and amino ester groups. No fragmentation of the amino ester residue is observed for the m‐nitrobenzoyl derivatives, but the +E spectra of these systems can be used to provide definitive structural information.
Ortho effects in organic molecules on electron impact. IV—Ortho interaction of the carboxyl group with the olefinic bond in substituted benzoic acids
Authors: Ramana D. V. , Vairamani M. 
Published: May 2005

AbstractFragments ions involving hydrogen migration from the –COOH group to the olefinic bond in the mass spectra of stilbene‐2‐carboxylic acid and ortho‐carboxylbenzalaniline are discussed.
The mass spectra of alkyl phenyl tellurides
Authors: Busse P. J. , Grigsby R. A. , Kolar F. L. , Irgolic K. J. 
Published: May 2005

AbstractThe mass spectra of several alkyl phenyl tellurides, C6H5TeR (R = CH3, CD3, C2H5, n‐C3H7, i‐C3H7 and n‐C4H9) have been studied with special emphasis on the fragmentation patterns involving cleavage of the alkyl and aryl tellurium–carbon bonds. Each compound exhibited intense parent ions. The rearrangement ions [C6H6Te]+⋅ and [C6H6]+⋅ were found in the spectra of phenyl ethyl and higher tellurides. Two other rearrangement ions [HTe]+ and [C7H7]+ were observed in the spectrum of each compound. Examination of the mass spectrum of phenyl methyl‐d3 telluride demonstrated that the [HTe]+ ions derive hydrogen from the phenyl group.
The use of labelled analogues for the determination of mass spectrometric fragmentation mechanisms of cannabinoids. A re‐investigation of the formation of the most abundant fragment ion [C15,H19,O2]+ in Δ1(6)tetrahydrocannabinol
Authors: Boeren Edward G. , Heerma Wigger , Terlouw Johan K. 
Published: May 2005

AbstractThe routes leading to the formation of the most prominent fragment ion [C15H19O2]+ (m/e 231) in the cannabinoid Δ1(6) tetrahydrocannabinol were investigated with the aid of deuterium labelled compounds. A previously proposed mechanism for the two‐step process could be confirmed, but the mechanism for the one‐step route had to be revised.
Recherches en Serie Azabenzodiazepine. III—Fragmentation en Spectrometrie de Masse de Quelques Pyrido, Pyrimido, Pyrazolodiazepinones, Triazino et Triazolotriazepinones
Authors: Lavergne Jean‐Pierre , Viallefont Philippe , Daunis Jacques 
Published: May 2005

AbstractLes spectres de masse des pyrido[2,3‐b], pyrimido[3,4‐b], pyrimido [4,5‐b], pyrazolo[3,4‐b]‐ diazépinones‐1,4 et des as‐triazino[4,3‐b] et s‐triazolo[4,3‐b]triazépinones‐1,2,4 sont décrits et analysés. Cinq processus de fragmentation de l'ion moléculaire sont le plus souvent identifiés, le mode principal d déradation étant l'expulsion d'une moléule de cétène avec formation des ions méthyl‐2 azabenzimidazoles ou méthyl‐2 azabenzotriazoles. Le comprotement particulier des triazolotriazépines, présentant deux antres types de rupture, est mis en évidence.
Unexpected course of olefin loss from some alkylcyclopentanone ions. Gaseous ion structure by ion cyclotron resonance spectrometry, mass‐analyzed ion kinetic energy spectrometry and collision‐induced dissociation
Authors: Hass J. Ronald , Cooks R. Graham , Elder James F. , Bursey Maurice M. , Kingston David G. I. 
Published: May 2005

AbstractIon cyclotron resonance results show that the ions formed by single and by double McLafferty rearrangement in 2‐ethyl‐5‐propylcyclopentanone have neither keto nor enol structures. Collision‐induced dissociations confirm that these ions are structurally distinct from the keto ions formed directly by electron impact upon the corresponding neutral molecules. It is suggested that the major reaction path for olefin loss from 2‐ethyl‐5‐propylcyclopentanone and from 2‐ethylcyclopentanone involves ring opening followed by hydrogen transfer to carbon in the alkene elimination step. Only in metastable ions is there evidence for the occurrence of the normal McLafferty rearrangement. The techniques mentioned in the title, together with conventional low and high resolution mass spectrometry, have been used to characterize the sometimes complex mixtures of cyclic and acyclic ions formed from cyclopentanone and some of its alkyl derivatives. Use of a number of different techniques of ion structure characterization allowed corroboration of particular results by quite distinct methods and it also allowed the effects of ion internal energy and lifetime upon structure to be partly elucidated.
Mass spectra of sulfur compounds: Alkyl phenoxythioacetates
Authors: Tomer Kenneth B. , Gleich Joan , Biderman Mitchell 
Published: May 2005

AbstractThe mass spectra of some alkyl phenoxythioacetates have been examined. An unusual rearrangement ion [M  C6H5O  CO]+ was observed. The structure is confirmed by high resolution mass measurement and isotopic labeling studies.
Constituents of cannabis sativa L. XII—mass spectral fragmentation patterns for some. Cannabinoid acid as their TMS derivatives
Authors: Billets Stephen , El‐Feraly Farouk , Fetterman Patricia S. , Turner Carlton E. 
Published: May 2005

AbstractFragmentation schemes for a number of TMS derivatized cannabinoid acids are described. Specific fragmentation pathways and rearrangement mechanisms were determined based on the ion composition of deuterium labeled derivatives. Significant differences in the mode of fragmentation of the two isomeric Δ9‐tetrahydrocannabinolic acids are described. These results are based on information obtained from deuterium labeling and high resolution data or by the extension of previously reported mechanisms for neutral cannabinoids. Comparisons of the fragmentation schemes between the neutral and acidic cannabinoids are used to confirm many of the fragmentation mechanisms.
endo‐cyclobutane ring strain in the cyclic isomers of 7‐coumarinyl diesters rooc(CH2)nCOOR
Authors: Compernolle F. , De Schryver F. C. 
Published: May 2005

AbstractUpon electron impact the open form diesters ROOC(CH2)nCOOR where R = 7‐coumarinyl and 4‐methyl‐7‐coumarinyl and their cyclic isomers obtained by photolysis react via common fragmentation pathways. The cyclic isomers derived from 7‐coumarinyl by photolysis resist heating to 250oC, but a thermal ring opening was observed for the more crowded cyclic isomers derived from 4‐methyl‐7‐coumarinyl. Differences in the appearance potentials for the ions [M  OR]+ produced from 7‐coumarinyl and its photocyclization isomers can be attributed to their different ground state enthalpies. The strain in the endo‐cyclobutane ring of the photocyclization isomers derived from 7‐coumarinyl (ring strain and strain due to nonbonded interactions) amounts to 38 ± 1 kcal mol−1.
Spectres de Masse de la Methyl‐2 Thiazolidinethione‐2 et de la Dimethyl‐2,4 Δ2‐Thiazoline
Authors: Llinares Jeanine , Vincent Emile‐Jean , Salmona Gérard 
Published: May 2005

AbstractLes spectres de masse des composés étudiés montrent que la processus prinncipal de fragmentation est le méme dans les deux cas: rupture des liaisons SC‐2 et NC‐4 marquage sélectif au carbone 13 en und position du cycle a permis de vérfier les mécanismes de rupture de ces moléules sous l'impact électronique.
Evidence for an ortho specific loss of OH· in some aromatic aldoximes from examination of metastable peak shapes
Authors: Vijfhuizen Peter C. , Terlouw Johan K. 
Published: May 2005

AbstractThe mechanism for loss of an OH radical from the molecular ions of the ortho substituted compounds 2‐methyl‐, 2‐hydroxy‐, 2‐amino‐ and 2‐methoxybenzaldoxime has been studied. It is inferred from the examination of the first field free region (composite) metastable peak shapes that two distinct mechanisms are operating. Based upon additional deuterium labelling experiments it is proposed that loss of OH involves both participation of the ortho substituent in the formation of a 5‐membered heterocyclic ring and the formation of a protonated isocyanide type ion via a 3‐membered ring transition state. Loss of OCH3 from the corresponding O‐methyl ethers probably occurs by similar mechanisms. The formation of a 5‐membered ring is also proposed to be the driving force for the loss of H2NO in the spectrum of 2‐methoxybenzaldoxime.
Diagnostic trends in the mass spectra of some mono methyl alkanes
Authors: Scammells D. V. , Hickmott B. 
Published: May 2005

AbstractDiagnostic trends have been observed in the electron bombardment mass spectra of certain mono methyl alkanes. These trends can lead to specific identification, via the ratios of certain peaks in the spectra of such isomers as the 2‐ and 4‐methyl alkanes which under normal conditions give very similar spectra.
A comparison of electron impact and field ionization spectra of some 2,5‐diketopiperazines
Authors: Szafranek Janusz , Palacz Zbigniew , Grzonka Zbigniew 
Published: May 2005

AbstractThe mass spectra of cyclo‐(Gly‐Leu), cyclo‐(Gly‐Tyr), cyclo‐(Ala‐Tyr), cyclo‐(Leu‐Tyr), cyclo‐(Val‐Phe) and cyclo‐(Leu‐Phe) are presented. The use of high resolution mass measurements and metastable analysis allows the proposal of some general fragmentation mechanisms. The dominant features in the mass spectra of 2,5‐diketopiperazines are fragments corresponding to cleavages of sidechains and the rupture of the piperazine‐2,5‐dione ring. The characteristic fragments may be used in the identification of any 2,5‐diketopiperazines by mass spectrometry.
Electron impact mass spectra of some enamines
Authors: Moskal Janusz , Nagraba Krzysztof , Moskal Aleksandra 
Published: May 2005

AbstractThe mass spectra of α,β‐diarylaminocrotonic acid anilides have been determined and the fragmentation pathways are now discussed. The proposed pathways have been confirmed by deuterium labelling, the spectrum of the model compound, or the appropriate metastables. The detailed electron impact data are given.
Mecanismes de Fragmentation de l'Oxazole
Authors: Audier Henri‐Edouard , Fetizon Marcel , Henry Yannik , Prange Thierry 
Published: May 2005

AbstractLes mécanismes de fragmentation de l'oxazole ont été précisés par diverses techniques expérimentales (refocalisation des ions métastables, deutériation, mesures de PA) et par le calcul.
Ion formation by [Li]+ ion attachment in high electric fields
Authors: Giessmann U. , Röllgen F. W. 
Published: May 2005

AbstractAn improved method for ionization by [Li]+ ion attachment in high electric fields is described in which gaseous molecules collide with a tungsten wire covered with a lithium salt. The simple mass spectra of a number of compounds which exhibit only [nM + Li]+ ions demonstrate the particular advantage of this ionization method. So far, additional peaks resulting from reactions of the molecules with the salt on the emitter surface have been found only in the mass spectra of acids.
The effect of ion preparation on kinetic energy release: Substituent and leaving group effects on the reactivity of the [C6H5CO]+ ion
Authors: Hoffman Michael K. , Friesen Marlin D. 
Published: May 2005

AbstractIon kinetic energy spectrometry has been utilized to investigate the loss of CO from [p‐Z‐C6H4‐CO]+ and [C6H5CO]+ ions generated from substituted acetophenones and benzo‐phenones. The variation of the leaving group in forming the [C6H5CO]+ ion has no detectable effect on the kinetic energy release observed in the subsequent decomposition reaction. A substituent effect consistent with the assumption that substituted benzoyl ions have no memory of their origin is also observed.
Mass spectrometry in structural and stereochemical problems. CCLVI—electron impact induced fragmentation of juvenile hormone analogs
Authors: Dunham Loren L. , Henrick Clive A. , Smith Dennis H. , Djerassi Carl 
Published: May 2005

AbstractComplete high resolution mass spectra of several analogs of the juvenile hormones have been analyzed with the aid of our recently developed INTSUM program and mass spectra of deuterated analogs. Representative compounds chosen for study included the biologically interesting (2E, 4E)‐3,7,11‐trimethyl‐2,4‐dodecadienoates (1,2), (2E,4E)‐11‐methoxy‐3,7,‐11‐trimethyl‐2,4‐do‐decadienoates (3,4) and three analogs (5‐7) of the trans‐trans‐farnesoate skeleton. These compounds display characteristic fragmentations which can be used to detect the presence of the compounds in complex mixtures using mass fragmentography or aid in the structure elucidation of related compounds.
Etude en Spectrometrie de Masse de bis Heterocycles Ethers du Resorcinol
Authors: Sacquet Marie‐Claude , Graffe Bernadette , Maitte Pierre 
Published: May 2005

AbstractLes spectres de masse e quelques bis hétérocycles, éthers dud résorcinol, sont étudiés ici, Nous interprétons les résultats à partir des fragmentations des monhétérocycles parents. Aucune mesure de haute résolution n'a été faite, Dans le cas des cétones benzyliques, l'hétérocycle fonctionnel se fragmente avant l'autre. Au contraire, dans la fragmentation des hétérocycles non fonctionnels, chaque hétérocycle semble participer en méme temps aux ions résultants.
The nature and fragmentation pathways of the molecular ions of some arylureas, arylthioureas, acetanilides, thioacetanilides and related compounds
Authors: Baldwin Michael A. , Loudon Alexander G. , Maccoll Allan , Webb Kenneth S. 
Published: May 2005

AbstractEvidence as to the nature of the molecular ions of the title compounds near the ionization thresholds and of their fragmentation processes is presented and discussed. The mode of formation of 5‐membered rings, involving the loss of an ortho substituent, is compared and contrasted with the formally similar process reported for the N‐dimethyl N'‐(o‐X‐phenyl) formamidines.
Bicyclic oxonium ions with an oxygen bridgehead
Authors: Van de Sanded C. C. , Vanhooren M. , Van Gaever F. 
Published: May 2005

AbstractElectron impact induced fragmentation of 4‐(ω‐phenoxymethyl and ‐ethyl)tetrahydn pyranes results in abundant [M  93] + ions through loss of a phenoxy radical. These ions are all produced in high yields by isobutane chemical ionization through loss of phenol from the quai molecular ions. Labelling data (2H, 13C) provide evidence for the l‐oxoniabicyclo[2.2.1]heptane ai l‐oxoniabicyclo[2.2.2]octane structures of the electron impact produced decomposing (ion sour and first field free region) ions [M  93]L in the case of the methyl and ethyl compounds, respective.
Mass spectra of sulfur compounds: alkyl thiophenoxyacetates and thiophenoxythioacetates
Authors: Tomer Kenneth B. , Gleich Joan 
Published: May 2005

AbstractThe mass spectra of some alkyl thiophenoxyacetates and S‐alkyl thiophenoxythioacetates have been examined. Several rearrangement processes have been identified by high resolution mass measurement and isotopic labeling studies.
Interpretation Automatique des Spectres de Masse de Composes Organiques. Mise au Point
Authors: Bachiri Mohamed , Mouvier Gérard 
Published: May 2005

AbstractComputerized methods for interpretation of mass spectra are increasing and many papers have now been published. Three different approaches can be used to identify an unknown compound. These methods are reviewed and discussed. First, the heuristic technique which tries to simulate the reasoning of the chemist and deduce the formulae. The only information needed are the mass spectra, the empirical formulae and the n.m.r. spectra. Some promising results have been obtained but the method has important restrictions. Another approach represents the mass spectra as points in a hyperspace. By developing decision surfaces it is possible to classify an unknown compound. This is called pattern recognition and the different empirical methods for recognizing patterns in mass spectral data are explained and reported. The last and simplest technique is to match an unknown spectrum against a library of standard references. When the unknown spectrum is in the library, this approach gives the best results.
The stereospecific loss of water from 1,4‐dihydroxy‐Δ6,7‐octalins under electron impact
Authors: Tureček F. , Vystrčil A. , Hanuš V. 
Published: May 2005

AbstractThe mass spectra of four of the six 1,4‐dihydroxy‐ Δ6,7‐octalins are reported. The spectra differ considerably, depending on the configuration of the hydroxyl groups. The relative amounts of 1‐3,1‐4, transannular 1‐3 and hydroxyl‐hydroxyl elimination of water from the molecular ions were determined by using specificaliy labelled compounds. Effects of configuration and conformation are discussed.
Metastable ions in chemical ionization
Authors: Cameron D. , Clark J. E. , Kruger T. L. , Cooks R. G. 
Published: May 2005

AbstractThe ion [C3H5]+ generated in a chemical ionization source by a variety of methods, including protonation and charge exchange, exhibits a metastable peak for H2 loss which is two orders of magnitude weaker than that formed in an electron impact source. The stable [C3H5]+ ions generated by electron impact and chemical ionization undergo collision‐induced dissociation to a comparable extent, both losing H2 by only one of the two competitive mechanisms observed for metastable ions. In contrast to the behavior of [C3H5]+, the molecular ions of p‐substituted nitrobenzene, generated by charge exchange at high source pressure, yield composite metastable peaks for NO loss which are very similar in shape and intensity to those generated by electron impact. The contrasting behavior of the metastable ions extracted from high pressure ion sources in the two systems may be due to differences in the efficiencies of quenching of the ionic states responsible for fragmentation as metastable ions. It is noteworthy that the NO loss reactions require considerably lower activation energies than does the H2 loss reaction.
Isomerization of hydrocarbon ions. VI—parameters determining the isomerization of aliphatic hydrocarbon ions
Authors: Leven Karsten , Heimbrecht Jörg 
Published: May 2005

AbstractThe radical or non‐radical character of aliphatic hydrocarbon ions determines the extent to which these ions equilibrate to a mixture of interconverting structures prior to decomposition. It is suggested that the radical (odd electron) ions have both lower thresholds for decomposition and higher barriers for isomerization that non‐radical (even electron) ions, thus explaining their reduced tendency for isomerization. Moreover, the molecular size seems to be a major influencing factor for the isomerization of unsaturated hydrocarbon molecular ions. With decreasing molecular size isomerization prior to decomposition becomes more pronounced. Collisional activation spectra of fragment ions (formed by loss of H2O from the corresponding alcohols) and of [C5H10]+and [C4H8]+molecular ions are reported in support of these conclusions.
Etude des fragmentations en spectrographie de masse de dithiolannes‐1,3 substitués en 2 par des groupements insaturés
Authors: Dedieu Michel , Pascal Yves‐Louis , Dizabo Pierre , Basselier Jean‐Jacques 
Published: May 2005

AbstractLes spectres de masse des produits étudiés montrent un ion moléculaire toujours abondant. Certaines fragmentations mettent en jeu la perte du groupement éthylénique; d'autre correspondent à des coupures du cycle dithiannique, suivies éventuellement de recyclisations impliquant la chaine éthylénique et les possibilités de résonance qu'elle permet. La présence d'un noyau phényle dans la chaine éthylénique modifie les spectres par formation d'un ion benzothiopyrylium très stable.
Ortho effects in organic molecules on electron impact. V—ortho effects of the nitro group in n‐substituted anilines
Authors: Ramana D. V. , Vairamani M. 
Published: May 2005

AbstractSome very interesting ortho effects are observed in the mass spectra of N‐benzyl‐o‐nitroaniline and N,N‐dibenzyl‐2,4‐dinitroaniline. Fragment ions arising from the transfer of oxygen from the nitro group to the benzylic carbon are seen in these spectra.
Stabile ‐Ionen in der Gasphase—eine CA‐Studie
Authors: Schwarz Helmut , Wesdemiotis Chrysostomos , Heimbach Heinz , Levsen Karsten 
Published: May 2005

Abstract[C11H9]+‐Ionen aus sechs verschieden strukturierten Vorläufern werden mit Hilfe der Stoßaktivierungsspektren untersucht. Die Ergebnisse zeigen, daß die stabilen Ionen weitgehend als Benztropylium‐Ionen oder als eine Mischung rasch interkonvertierender Strukturen vorliegen.
The electron impact induced fragmentation of geminal dialkanoates
Authors: Ingram John G. K. , Barry Thomas C. 
Published: May 2005

AbstractThe mass spectra of representative 1,1‐dicarboxylates have been studied in order to identify fragmentation patterns typical of such compounds and thus to aid their characterization in complex mixtures. Two typical decomposition pathways were noted. One invoves the loss of a carboxylate group, and the other the ejction of an sliphatic sidechain. It is suggested that a similar gragmentation scheme is to be expected of the much more labile dialkanoates derived from ketones.
The electron impact induced fragmentation of aromatic aldoximes—III. On the loss of HCNO, OH⋅ and substituents and the role of substituent effects in the decomposition of cyclohexadiene type intermediate ions
Authors: Vijfhuizen Peter C. , Terlouw Johan K. 
Published: May 2005

AbstractThe mechanisms for loss of HCNO, OH˙ and the substituent X˙ from aromatic aldosimes were elucidated with the aid of deuterium labelling, metastable ion characteristics and substituent effects. It is proposed that the loss of HCNO occurs through a cyclohexadiene type intermediate ion generated via a 6‐membered ring hydroxyl hydrogen transer to the ortho position of the phenyl ring. This is followd by a second step which involves the trnsfer of a hydrogen atom from the ortho position to C‐1. It is inferred from the corelation with the mesomeric effect (σR+) of substituents that this step is rate determining. Loss of OH˙ and X˙ proceed via the same cyclohexadiene type intermediate ion but, depending upon the substituent, other pathways are also followed.
Stereochemistry and mechanism of electron impact induced elimination reactions in acenaphthenol and acetoxyacenaphthene
Authors: Manhart Daryl D. , Brown Peter , Hunter Duncan H. 
Published: May 2005

AbstractThe mechanisms for elimination of H2O from acenaphthenol and of AcOH from acetoxyacenaphthene under low energy conditions have been determined, using regiospecific and stereospecific deuterium labeling probes, and by measurement of ionization and appearance potentials for alternative pathways. Both concerted and stepwise processes must be invoked in order to explain the experimental data. Proximity effects appear to be the most important factors in determining mechanistic type.