bluuebunny/crossref_metadata_2025 huggingface dataset:
The reactive states of ions: Octatrienes and dimethyl substituted cyclohexadienes
Authors: Rennekamp M. E. , Hoffman M. K.
Published: May 2005

The principal decomposition routes of molecular ions of cis, cis, cis‐2,4,6‐octatriene, cis, cis, trans‐2,4,6‐octatriene, trans, cis, trans‐2,4,6‐octatriene, trans‐5,6‐dimethyl‐1,3‐cyclohexadiene and cis‐5,6‐dimethyl‐1,3‐cyclohexadiene were studied using ion kinetic spectroscopy. The loss of radicals from [M]+· appears to proceed via a ground state, while loss of a neutral molecule appears to involve either complete equilibration of structure within the system or both ground state and excited state pathways.
Über die elektronenstossinduzierte phenyl‐Umlagerung bei 4‐Phenyl‐chinuclidinen
Authors: Achenbach H. , Wörth J. , Schneider W. , Bochow H.
Published: May 2005

Die Massenspektren von 4‐Phenyl‐chinuclidinen sind gekennzeichnet durch den bevorzugten Verlust von C7H7 aus dem Molekülion. Dieser unerwartete Fragmentierungsprozeß ist nur im Zuge einer Phenyl‐Umlagerung verständlich.
Silylumlagerungen in den Massenspektren stereoisomerer 5‐Methylcyclohexan‐1,3‐diol‐TMS‐äther
Authors: Winkler F. J. , Robertson A. V.
Published: May 2005

Die Bildung der Silylumlagerungsionen [ROSi(CH3)2]+ aus [M–CH3]+‐Ionen der epimeren 5‐ Methylcylohexan‐cis‐1,3‐diol‐TMS‐äther ist unabhängig von der 5‐ Me‐Konfiguration im Gegensatz zu den stereochmischen Effekten der 5‐Me‐Gruppe bei den Eliminierungen aus [M]+· verwandtr Derivate.
Elektronenstossinduzierte 1.1‐Eliminierung aus Phenylhydroxylamin‐derivaten
Authors: Schwarz Helmut , Zon Gerald , Tsui Fai‐Po
Published: May 2005

Die Reaktivität der Titelverbindungen unter Elktronenstoß ist vergleichbar mit dem thermischen Verhalten. Bei geeigneter Substitution findet eine ungewöhnliche 1.1‐Eliminierung statt, die die Charakteristik einer linear cheletropen Reaktion besitzt.
The concept and rôle of charge localization in mass spectrometry
Authors: Williams D. H. , Beynon J. H.
Published: May 2005

The concepts of charge localization and of radical localization are considered both with regard to their validity and to their usefulness in explaining and predicting the unimolecular fragmentation pathways for positively charged ions formed from organic compounds. It is concluded that there is experimental support for these concepts.
The mass spectra and ionization potentials of the neutral fragments produced during the electron bombardment of aromatic compounds
Authors: Reeher John R. , Flesch Gerald D. , Svec Harry J.
Published: May 2005

A mass spectrometer equipped with a dual ionization chamber ion source has been used to characterize directly the neutral species produced in the dissociative ionization of gases by electron impact. Neutral fragment mass spectra have been obtained for the electron ionization and fragmentation of benzene, toluene, o‐xylene, m‐xylene, p‐xylene, mesitylene and isotopically labeled toluene. The neutral fragment mass spectra correlate well with the structures of the molecules. The abundant species in the neutral fragment mass spectra also correlate reasonably well with the abundant complementary positive ions of the normal mass spectra. Ionization potentials have been determined for the abundant neutral species produced. Where comparisons with values reported elsewhere are possible, the agreement is usually within ±0.2 eV or less.
The mechanism of CO loss in the electron impact‐induced fragmentation of benzoin and its methyl ether
Authors: Klasinc L. , Stefanović D. , Adam S. , Güsten H.
Published: May 2005

The electron impact‐induced fragmentation of benzoin methyl ether gives rise to the formation of an m/e 91 fragment ion which is not present in the mass spectrum of benzoin. Deuterium and 13C labelling, as well as low energy experiments, revealed that this ion is formed from [M – benzoyl]+ by transfer of both the ether methyl group and the hydrogen atom from the α‐position to the adjacent phenyl ring followed by loss of CO and hydrogen.
An evaluation of empirical methods for calculating the ionization potentials of substituted benzenes
Authors: Behan John M. , Johnstone Robert A. W. , Bentley T. William
Published: May 2005

Accurate adiabatic ionization potentials for substituted.
Energetic consideration applied to the mass spectra of some aromatic compounds
Authors: Williams Dubley H. , Bowen Richard D.
Published: May 2005

It is shown that the ‘metastable’ mass spectra of a series of monosubstituted benzenes are consistent with reaction over the lowest available energy surfaces. The non‐occurrence of some qualitatively possible decomposition pathways may therefore be used to place lower limits on the heats of formation of gaseous cations. Conversely, where characterized reactions are preempted by new reactions upon introduction of additional substituents, upper limits may be placed upon the heats of formation of the ionic products of the new reactions. The concepts are employed to deduce that C3H6 elimination from n‐butylbenzence subsequent to ionization leads to ionized toluene rather than ionized methyleneclohexadience.
Field desorption mass spectra of involatile sulphonic acids, sulphonates and dyestuff materials
Authors: Mathias Alan , Williams Albert E. , Games David E. , Jackson Anthony H.
Published: May 2005

Abstract‐Useful field desorption mass spectra can be obtained from involatile sulphonic acids and sulphonates, even when large dyestuff molecules are involved. Unusual cluster ions are commonly found, which can be singly or doubly charged. Most ions can be assigned, however, and the great potential of field desorption mass spectrometry in the identification of these involatile species is clearly established.
Mass spectral fragmentation of functionalized lanostanes‐I
Authors: Dias Jerry Ray
Published: May 2005

Mass spectra of various functionalized lanostanes and their deuterated analogs are compared. It is proposed that the transfer of a hydrogen from the 18‐methyl group to the 11‐oxo group via a McLafferty rearrangement is made geometrically possible by prior ionization of the 13,14 bond which allows an optimum interatomic distance between the oxygen and hydrogen to be acquired; the 8,9 double bond is a requisite for electronic induction of this specific process. Transfer of the hydrogen from the 7β‐hydroxy group to position 14 is implicated in the mass spectrum of 3β‐acetoxy‐7β‐hydroxy‐5α‐lanostan‐11‐one.
The analysis of some heterocyclic compounds
Authors: Borhani R. , Reed R. I.
Published: May 2005

The mass spectra of some relatively simple sulphur compounds have been obtained. Comments upon the McLafferty rearrangement are reported.
The benzoyl ion. Thermochemistry and kinetic energy release
Authors: Elder J. F. , Beynon J. H. , Cooks R. G.
Published: May 2005

The thermochemistry of benzoyl ion formation from a variety of sources has been examined by using the measured kinetic energy release for metastable ions to estimate the excess energy of the activated complex. A correlation is observed between this estimated excess energy and literature values of the heat of formation of the benzoyl ion. From this relationship and the observed correlation between the uncorrected heat of formation and the difference between the appearance potential of [C6H5CO]+ and the ionization potential of the parent compound, the large range of reported values for ΔHf[C6H5CO]+ is seen to be due, at least in part, to variation in the kinetic shift with the critical energy of the reaction. With the exception of the ion generated from trifluoroacetophenone and possibly that from benzaldehyde, the fragmenting [C7H5O]+ ions are shown, from kinetic energy release data, to be structurally identical. The approach adopted here may have general merit in improving or testing the accuracy of thermochemical data based on appearance potential measurements.
Distributions of kinetic energy release in benzoyl ion formation
Authors: Elder J. F. , Cooks R. G. , Beynon J. H.
Published: May 2005

Distributions of the kinetic energy release have been determined for reactions of metastable ions leading to formation of the benzoyl cation. Although the reactions studied were all apparent simple bond cleavages, the shapes of these distributions varied widely, as did the magnitude of the most probable energy release. There is evidence that the shape of the distribution function is related to the mechanism of the reaction. In one case the distribution shows structure not seen in the metastable peak itself, suggesting that at least two reaction pathways are operative. Thus, the present measurements on energy distributions supplement the information concerning different elementary reactions that can be obtained from the study of metastable peaks.
Elimination reactions of ions in the gas phase
Authors: Kuster Th. , Seibl J.
Published: May 2005

The loss of water from the molecular ion of 2‐adamantanol was investigated using specifically labelled deuterium derivatives, and, in particular that stereospecifically labelled in position 4. Water is lost predominantly in a stereospecific 1, 3 fashion by two clearly distinguishable mechanisms. Determination of metastable ion characteristics proved to be essential for drawing this distinction.
An attempt to correlate appearance potentials and semi‐empirical SCF‐LCAO‐MO data
Authors: Sterk Heinz , Heresch Franz
Published: May 2005

Applying the Bell‐Evans‐polanyi principle to mass spectrometric gramentations gives a relationship for calculating their activation energies from various MO data, such as heats of formation and electronic populations. Additionally, a possible extension of the original Bell‐Evans‐Polanyi principle is discussed.
The mass spectrometry of some t‐butyl peresters
Authors: Krull I. S. , Mandelbaum Asher , Mandelbaum Asher
Published: May 2005

Mass spectrometry is suggested as a method for the general characterization of mono‐ and di‐t‐butyl peresters. In many instances it is possible to measure the molecular ion, especially in the mono‐t‐butyl peresters. The fragmentation patterns of various t‐butyl peresters are presented.
Chemical ionization mass spectrum of peroxyacetylnitrate
Authors: Pate Christopher T. , Sprung Jeremy L. , Pitts James N.
Published: May 2005

The chemical ionization mass spectrum of peroxyacetylnitrate, a major component of photochemical smog highly toxic to man and plants, was obtained using both methane and isobutane as reagent gas. The spectrum contains a [M + H]+ ion at m/e 122, intense fragment ions at m/e 43 [CH,CO]+ and m/e 46 [NO2]+, and less intense ions at m/e 61 [CH,ONO]+, m/e 77 [CH30NOz]+ and m/e 88 [+OCCH2ONO] formed by internal rearrangements. These results confirm the commonly accepted structure for peroxyacetylnitrate, CH3(CO)OONO2.
o‐Nitrobenzylidene compounds. I—Competitive ortho interactions in the mass spectra of n‐o‐nitrobenzylidene‐o‐substituted anilines
Authors: Johnston David , Smart Graeme W. , Smith David M.
Published: May 2005

The intense [M – 17]+ ion, which is a characteristic feature of the mass spectra of N‐o‐nitrobenzylideneaniline and its simple derivatives, may be substantially reduced in intensity when the aniline‐derived ring is also ortho substituted: the intensity is lowest when this ortho substituent has a nucleophilic character and can itself interact with the CHN group. The ortho substituents examined are Br, CH3, OH, NH2, SH, SC6H4CH3(p), CO2CH3 and CO2C2H5.
Identification de composes inconnus en spectrometrie de masse par Comparaison a une Bibliotheque sur Cartouches Digitales
Authors: Bachiri Mohamed , Mouvier Gérard
Published: May 2005

An automatic method for interpretation of mass spectra is described. This approach uses the comparison of unknown spectra with those included in a library of standard references. The spectra are stored on digital magnetic tape. Several hundred spectra can be recorded on a cartridge. The tape unit is connected to a minicomputer. This system offers many advantages and is very well suited for medium sized laboratories. The series of compounds studied are the olefins, compounds with very similar spectra, so the method of interpretation has to be powerful. The different parts of the identification algorithm are discussed. The results and experimentation are also presented.
Konstitutionelle Effekte bei der Chemischen Ionisationsmassenspektrometrie di‐ und Trifunktioneller Diterpene
Authors: Schwarz Helmut , Bohlmann Ferdinand , Rapp Uwe , Windel Bernd
Published: May 2005

Die Untersuchung der Chemische‐Ionisations‐spektren von Diterpenen mit zwei bzw. drei Sauerstoffunktionen zeigt, daß die relative Anordnung dieser funktionellen Gruppen für die Abbaureaktionen der Protonierten Molekül‐Ionen vongroßer Bedeutung ist. Auch der Gebrauch von “Direct Analysis of Daughters Ions” und von Defokussierungsaufnahmen durch Variation der Beschleunigungsspannung bei der chemischen Ionisation hibt Einblick in das Fragmentierungsverhalten. die Resultate sind wahrscheinlich auch in anderen Fällen für die Lokalisierung funktioneller Gruppen mit Hilfe der chemischen Ionisation von Bedutung.
Carbon randomization in the fragmentation of [C4H9]+ derived from t‐butyl derivatives
Authors: Leung Hei‐wun , Tsang Chun Wai , Harrison Alex. G.
Published: May 2005

The mass spectrum of 13C centrally labeled neopentane has been re‐examined at a mass resolution sufficient to resolve 13C‐CH mass doublets. Contrary to earlier low resolution results, the [C3H5]+ fragment ion is formed with 75% retention of the central carbon under all experimental conditions, indicating complete carbon scrambling in the fragmentation reaction [C4H9]+→[C3H5]+ + CH4. The higher retention of the central carbon in [C3H5]+ in the mass spectra of (CH3)3CCl and (CH3)3CBr is shown to be due to the occurrence of the reaction sequence

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A study of the ortho effects and rearrangement processes in the mass spectra of 2‐arylaminothiazine and ‐thiazoline derivatives
Authors: Bujtás Gy. , Tamás J.
Published: May 2005

The behaviour of the title compounds under electron impact has been investigated using low and high resolution mass spectrometry and partial 15N and D labelling. A number of ions produced by rearrangement were observed. Abundant ions are formed by intramolecular ortho substitution reactions (cyclizations), as demonstrated by energetic and kinetic considerations and by studying the decomposition pathways of these ions. The ortho substitution processes involve loss or rearrangement of an ortho group of the aromatic ring.
NH3‐Eliminierungen aus 2‐Äthoxybenzoesäureamid und 2‐Äthoxybenzylamin Als Weitere Beispiele [Komplexer] Ortho‐Effekte
Authors: Schwarz Helmut , Wolfschütz Roland
Published: May 2005

Die Mechanismen der Ammoniak‐eliminierung aus den Molekül‐lonen der Titelverbindungen konnten durch die Untersuchung 2H‐markierter Verbindungen aufgeklärt werden. Es wird gezeigt, daß der eigentlichen Fragmentierung ein partilles wasserstoff‐Scrambling vorgelagert ist, das durch die Carbonylfunktion begünstigt wird. Darüber hinaus wird ein weiteres Beispiel einer ungewöhnlichen Äther‐Alkyl‐Spaltung beobachtet, die ebenfalls durch eine nachbargruppenwechselwirkung ermöglicht wird.
Doubly charged fragment ions in the field ionization mass spectra of alkylbenzenes
Authors: Röllgen F. W. , Heinen H. J. , Levsen K.
Published: May 2005

It is shown that the radical [C6H5CmH2m]2+fragment ions found in the field ionization mass spectra of alkylbenzenes are formed via a different adsorption state of the singly charged species than in the case of the formation of [M]2+molecular ions. It is further demonstrated that the primary fragmentation of molecules by the cleavage of CC bonds results not only from decompositions of molecular ions in the gas phase but also from surface reactions.
ÄThylen‐Eliminierung aus dem [C7H11]+‐Ion des 4.4‐Dimethylpentin‐(2)‐Ylchlorids‐(1)
Authors: Bohlmann Ferdinand , Brehm Manfred , Schwarz Helmut
Published: May 2005

Durch die Untersuchung einer 13C‐ und 2H‐markierten Verbindung wird belegt, daß der Äthylen‐Eliminierung aus dem [M‐C]+‐Ion ein vollständiges C‐ und H‐Scrambling vorgelagert ist, Die Isomerisierungsprozesse hängen nicht von der Lebensdauer der zerfallenden [C7H11]+‐Ionen ab.
Lokalisierung von Substituenten bei Porphyrinen: Das Massenspektroskopische Fragmentierungsverhalten von Porphyrinogenen
Authors: Budzikiewicz Herbert , Pesch Reinhold
Published: May 2005

Es wird gezeigt, innerhalb welcher Grenzen aus den Massenspektren von Porphyrinogenen Rückschlüsse auf die Substituentenanordnung gezogen werden Können.
The long‐lived molecular ion of propionitrile: An ion cyclotron resonance study
Authors: Theissling Carla B. , Nibbering Nico M. M. , Meyerson Seymour
Published: May 2005

Evidence has been reported that primary loss of H and of HCN from the molecular ions of propionitrile, isobutyronitrile and butyronitrile in the mass spectrometer is preferentially preceded by hydrogen migration from C‐2 to C‐1. Ion cyclotron double resonance spectra of proton (or deuteron‐) transfer products derived from propionitrile‐2‐d2 and ‐3‐d3 and a series of bases provide evidence that such migration occurs also in long‐lived propionitrile molecular ions.
A comparative study of the pyrolytic and electron impact‐induced fragmentations of 4‐phenylbutanoic acid and some analogues
Authors: Posthumus M. A. , Nibbering N. M. M. , Boerboom A. J. H.
Published: May 2005

By use of deuterium labelling it is shown that the mechanisms of fragmentation of the title compounds upon Curie‐point pyrolysis and electron impact are essentially different. For example, the pyrolytic expulsion of water from 4‐phenylbutanoic acid is a 1,2 eliminations, whereas upon electron impact water is expelled via a 1,4 elimination; the generation of styrene from this acid proceeds via a concerted mechanism upon pyrolysis, but via a stepwise mechanism upon electron impact.
Charge exchange mass spectrometry at high energy
Authors: Hsu C. S. , Cooks R. G.
Published: May 2005

It is shown that charge exchange mass spectra using various reagent ions can be determined on a commercial double focusing mass spectrometer. The experiment relies upon the presence of a collision region held at a potential above ground with the product ions being selected by their unique kinetic energies. Cyclohexene has been studied in detail and the results are in agreement with previous thermochemical and field ionization kinetics data. Agreement with reported charge exchange spectra of n‐propanol, taken at lower energies, is good. The present results, including both the variation of spectra with reagent gas and the small range of kinetic energies present in the charge exchange beam, indicate that a resonant or near resonant process is involved. Thus, the internal energy of the nascent ion is defined within quite narrow limits, just as is the case for charge exchange at lower energy.
Etude en Spectrometrie de Masses des Fragmentations de Derives de la Triazine‐1,2,4
Authors: Lavergne Jean‐Pierre , Viallefont Philippe , Daunis Jacques
Published: May 2005

Les spectres de masse de 49 triazines‐1,2,4 différemment substituées en position 6, possédant les groupes oxo, thioxo, méthylmercapto en position 3 et 5 et de leurs dérivés N‐méthylés sont décrits. Cinq processus de fragementation du cycle traizine, liés á la structure et notamment á la nature du groupement fonctionnel en position 5 sont mis en évidence. L'un d'eux, engageant les ruptures des liaisons N‐1N‐2 et C‐5C‐6, est identifié dans tous les cas. Les pertes d'azote et de monoxyde de carbone ne sont pas observées. Pour certains composés la participation á l'équilibre, á l'état vapeur, de certaines formes tautoméres a été discutée.
Mass spectra of some triaryl derivatives of the group V elements, P, As, Sb and Bi
Authors: Spalding T. R.
Published: May 2005

Triphenyl and tri‐o‐, m‐ and p‐tolyl compounds of the elements P, As, Sb and Bi have been studied as well as tri‐(2,6‐dimethylphenyl)phosphine. The m‐ and p‐tolyl isomers show very similar behaviour and differ significantly from the o‐derivatives. The differences can be largely attributed to steric effects in the o‐isomers. Major fragmentation pathways to Group V element (Mt)‐containing ions involve MtC and CH, and from the tolyl compounds CC bond cleavages. Throughout this paper the symbol Mt is used to refer to the Group V element.
The behaviour of some α,α′‐dibromoketones on electron impact. An analogy to the reductive removal of bromine in solution
Authors: Hoffmann H. M. R. , Loudon A. G.
Published: May 2005

The relative importance of the rearrangement ions [M  Br  CO]+, [M  Br2  CO]+ and [M  HBr2  CO]+ in the mass spectra of the title compounds is compared with the amounts of α‐methoxyketone formed on reduction of these compounds with a Zn/Cu couple in methanol. It is suggested that the quantitative correlation found reflects the electron releasing powers of the substituents on the α carbons.
Mass spectrometry of 3‐methoxy fatty acid methyl esters
Authors: Zirrolli Joseph A. , Murphy Robert C.
Published: May 2005

Fatty acids with a hydroxyl moiety at the C‐3 position are found widely in bacterial lipids, but only rarely in mammalian lipids. The mass spectra of the methyl ether derivative of these hydroxy acids exhibit an intense ion at m/e 75, rather than the rearrangement ion at m/e 74 more typical of fatty acid methyl esters. The mass spectrometric behavior of several 3‐methoxy fatty acid methyl esters were studied, and the origin of the unique ion at m/e 75 was established using 18O and 2H labeled analogs and metastable ion transitions. this ion was shown to arise from the loss of ketene from the 3,4 cleavage ion at m/e 117.
Interpretation Automatique du Spectre de Masse de Complexes Metalliques π Incluant des Derives du Silacyclopentadiene
Authors: Lageot C.
Published: May 2005

Le programme précédemment mis au point pour élucider la structure de composés cycliques saturés et insaturés incluant un atome de groupe IV a été complété pour qu'il sooit applicable aux complexes métalliques π. Leur structure est ainsi déterminée à l'aide du spectre de masse et du programme adéquat en quelques secondes.
Chemical ionization of cyclopropyl ethers II—the nature of the alkyl group fragmentationt
Authors: Andrist A. Harry , Slivon Laurence E. , Wilburn Bruce E.
Published: May 2005

Oxygen‐alkyl cleavage is ruled out in the methane chemical ionization‐ and electron mpact‐induced decomposition of cyclopropyl ethers by the finding that for trans,trans‐2,3‐diethylmethoxycyclopropane the [M  C2H5·]+ ion is more intense than the [M  CH3·]+ ion. The possibility for [M + H  C2H6]+ is discounted by comparison with the methane chemical ionization nass spectrum of tran,tran‐2,3‐dimethylmethoxycyclopropane. The isobutane chemical ionization nass spectrum of the diethylcyclopropyl methyl ether affords nearly exclusive electrocyclic methanol fragmentation, i.e. [M + H  CH3OH]+.
The computer processing and interpretation of mass spectral information. II—computation of the degree of isotope labelling in organic compounds
Authors: Sukharev Yu. N. , Nekrasov Yu. S.
Published: May 2005

The program ISOMETA which processes the low resulution mass spectra and determines the degree of labelling in the molecular and fragment ions is described. The degree of labelling for any stable isotope (D, 13C, 15N, 18O, etc.) in compounds of known molecular formulae can be estimated. The compound may contain any number of elements and atoms of each element. The mass spectra are processed in terms of peak groups of the molecular and fragment ions which have been identified as having one composition. The program is written in ALGOL, runs on a BESM‐6 computer and requires 6.5K core memory.
Study of ions with excess kinetic energy. III—Mass spectra of excess kinetic energy ions of aliphatic amines
Authors: Tsuchiya M. , Tamura K.
Published: May 2005

The mass spectra obtained from ions having excess kinetic energy (named the excess kinetic energy mass spectra) formed by electron impact of several aliphatic amines have been studied. Comparison with the excess kinetic energy mass spectra of the analogous alcohols shows many similarities. For example, the intensity of the [CH2OH]+ ion of an aminoalcohol is about the same as the intensity of the [CH2NH2]+ ion. The excess kinetic energy mass spectra give useful information about the presence or absence of various functional groups, such as CH2NH2, CH2OH, CH3CHNH2 and alkyl groups, and also about rearrangements. The fragmentation mechanisms are straightforward and applicable to a variety of classes of compounds. The molecular weight dependence of excess kinetic energy mass spectra is described.
Electron impact studies. CVII—Negative ion mass spectra of the oxime group. Monoximes derived from α‐dicarbonyl systems
Authors: Bowie John H. , Janposri Sompong
Published: May 2005

Specific losses of water are observed from the molecular anions of monoximes of α‐diketones. Labelling studies, kinetic energy release values and the +E spectra of magnified image ions have been used to aid in the elucidation of the fragmentation pathways. It is proposed that the majority of magnified image ions have α‐keto nitrile structures.
Zur Lokalisierung Funktioneller Gruppen mit Hilfe der Massenspektrometrie. XV—Massenspektren von androstanen mit Hydroxygruppen in den Positionen 3, 16 und 17
Authors: Grote Heinfried , Spiteller Gerhard
Published: May 2005

Die Massenspektren von Androstantriolen mit Hydroxygruppen in den Positionen 3, 16 uund 17 sind im Vergleich zu isomeren Triolen durch hohe Molekülionen gekennzeichnet. Schlüsselionen zeigen den Verlust der C‐Atome 15, 16 und 17 des D‐Ringes als 75 Masseneinheiten schweres Teilchen an. Das verbleibende Spaltstück veliert leicht die 3‐städige Hydroxygruppe als wasser unter Bildung eines [M  93] Ions. Weitere Schlüsselbruchstücke zeigen die Massen 60, 84 und 110. Mit Hilfe dreier deuterierter Androstantriole und der Massenfeinbestimmung läßt sich zeigen, daß diese Ionen Teile des D‐Ringes enthalten.
Structures and formation of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 4}} {\rm H}_{{\rm 8}} } \right]_{}^{_.^ + } $\end{document} ions
Authors: Nishishita Takao , Bockhoff F. M. , McLafferty F. W.
Published: May 2005

Several \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 4}} {\rm H}_{{\rm\ 8}} } \right]_{}^{_.^ + } $\end{document} ion isomers yield characteristic and distinguishable collisional activation spectra: \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm 1-butene} } \right]_{}^{_.^ + } $\end{document} and/or \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm 2-butene} } \right]_{}^{_.^ + } $\end{document} (a‐b), \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm isobutene} } \right]_{}^{_.^ + } $\end{document} (c) and [cyclobutane]+ (e), while the collisional activation spectrum of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm methylcyclopropane} } \right]_{}^{_.^ + } $\end{document} (d) could also arise from a combination of a‐b and c. Although ready isomerization may occur for \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 4}} {\rm H}_{{\rm 8}} } \right]_{}^{_.^ + } $\end{document} ions of higher internal energy, such as d or e → a, b, and/or c, the isomeric product ions identified from many precursors are consistent with previously postulated rearrangement mechanisms. 1,4‐Eliminations of HX occur in 1‐alkanols and, in part, 1‐buthanethiol and 1‐bromobutane. The collisional activation data are consistent with a substantial proportion of 1,3‐elimination in 1‐ and 2‐chlorobutane, although 1,2‐elimination may also occur in the latter, and the formation of the methylcycloprpane ion from n‐butyl vinyl ether and from n‐butyl formate. Surprisingly, cyclohexane yields the \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm linear butene} } \right]_{}^{_.^ + } $\end{document} ions a‐b, not \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm cyclobutane} } \right]_{}^{_.^ + } $\end{document}, e.
Field desorption mass spectrometry of oligosaccharides in the presence of metallic salts
Authors: Prome Jean‐Claude , Puzo Germain
Published: May 2005

In the field desorption mass spectrometry of oligosaccharides, traces of contaminating salts in polar solvents decrease the detection sensitivity, and in some cases no ion could be detected in the molecular range. The present work shows that the addition of alkaline salts (NaI or KI) greatly increases the sensitivity, and cationized molecular ions are obtained. The influence of the molar ratio sugar/salt on the nature and relative intensity of the desorbed species has been studied on mixtures of α‐D‐trehalose and NaI. At the low salt ratio (100:1), high molecular weight clusters [XM + Na]+ are preferentially formed. At the high salt ratio (1:10), mixed clusters [M + NaI + Na]+, doubly charged ions [M + 2Na]2+ and monomeric cationized ions [M + Na]+ are observed along with salt clusters [NaI + Na]+ and [2NaI + Na]+. In the range of molar ratios sugar/salt of 10:1 to 1:1, the field desorption mass spectra exhibit a cationized ion [M + Na]+, which contributes more than 80% of Σ100. This cationization technique has been applied to the field desorption mass spectrometry of several oligosaccharides. In all cases, the salt effect causes the replacement of the [M + H]+ ion by a [M + C]+ ion. (Note: the term [M + C]+ and similar ones mean an association between the whole molecule studied (M) and an alkaline cation [C]+ ([K)]+, [Na]+, [Li]+).) Thus, di, tri‐ and tetrasaccharides exhibit intense [M + Na]+ ions in the presence of NaI and only a few fragment peaks are observed in their field desorption mass spectra. This technique has been applied successfully to the detection of the hexasaccharide ajugose in a natural sample of pentasaccharide, and has also allowed the unambiguous determination of the composition of a mixture of partially methylated trehaloses. The salt effects are dicussed in terms of selective adsorption on the emitter, pre‐existing soluble complexes sugar‐salt, interactions between these species in the electric field and dissociative desorption of ionic complexes.
The formation of a resonance stabilized oxonium ion in isoflavone and 2′‐substituted isoflavones
Authors: Eguchi Shizuko , Haze Machiko , Nakayama Mitsuru , Hayashi Shûichi
Published: May 2005

The predominant elimination of the hydrogen atom or the substituent from the 2′‐position in isoflavone derivatives was confirmed by the use of the metastable ion defocusing technique.
Collisional activation mass spectra of pentene and hexene molecular ions
Authors: Nishishita Takao , McLafferty F. W.
Published: May 2005

The collisional activation spectra of the molecular ions from fourteen pentene and hexene isomers show substantial differences, some of which can be rationalized using known ion fragmentation mechanisms. These differences, and their negligible dependence on ion internal energy, are advantageous for the structural characterization of such isomeric ions, including those produced by fragmentation of larger molecules. The decompositions of metastable ions of the pentenes were nearly identical, but those of the hexenes showed some differences useful for structural charactrization.
Negative ion mass spectra of a series of fluorinated β‐diketones
Authors: Gregor I. K. , Jennings K. R. , Sen Sharma D. K.
Published: May 2005

Electron capture by and the subsequent fragmentation of a series of eleven fluorinated β‐diketones of general formula CF3COCH2COR has been studied in an MS‐50 mass spectrometer. Consecutive loss of two HF molecules from molecular anions occurs with all compounds, as does elimination of CHF3 from [M  H]− ions. Elimination of CO occurs from either \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm M - HF}} \right]_{}^{_.^ - } $\end{document} or \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm M - 2HF}} \right]_{}^{_.^ - } $\end{document} ions for five compounds where R  CF3 or a cyclic substituent. Kinetic energy release in metastable transitions associated with these HF and CO eliminations has been measured. Intensities of various fragment ions are in part influenced by the ion source temperature. Interaction of \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm O}} \right]_{}^{_.^ - } $\end{document} reagent ions with five of the β‐diketones under chemical ionization conditions gave [M  H]− ions as the only significant ion‐molecule reaction product.
Recherches en série azabenzodiazépine. VI—etude en spectrométrie de masse de pyrazolo [3,4‐b]diazépines‐1,4
Authors: Affane‐Nguema Jean‐Paul , Lavergne Jean‐Pierre , Viallefont Philippe
Published: May 2005

Les spectres de masse de 21 pyrazolo[3,4‐b]diazépines‐1,4 dans lesquelles le cycle diazépine peut présenter cinq structures différentes, sont décrits et analysis. Chaque structure a été caractérisée par un ensemble original de ruptures. Parmi celles‐ci un mode de fragmentation commun à tous les composés étudiés a été identifié: il s'agit de la rupture des liaisons C‐5C‐6 et C‐7N‐8 avec formation d'ions pyrazoloimidazoles.
Anionen‐Massenspektroskopie von Naturstoffen. VI—Anionen‐Massenspektroskopische Untersuchungen ausgewählter Gibberellin‐Verbindungen
Authors: Voigt D. , Adam G. , Schmidt J. , Schreiber K.
Published: May 2005

Die Elektronenanlagerungsmassenspektren (2‐4 eV) der Gibberelline A1, A3, A4, A5, A7, A8, A9, 3‐epi‐GA1 und 3‐epi‐GA3 sowie 1β‐Hydroxy‐GA1 werden diskutiert und mit den entsprechenden Kationenmassenspektren verglichen.
Mass spectrometric investigation of stereosomeric 1,2‐dimethyl‐4‐substituted decahydroquinol‐4‐ol N‐oxides. Concerning the configuration of the asymmetric nitrogen atom
Authors: Zaikin V. G. , Bakaev A. A. , Wulfson N. S. , Akhrem A. A. , Ukhova L. I. , Marchenko N. F.
Published: May 2005

The main fragmentation pathways of the N‐1, C‐2 and C‐4 stereoisomers of the 1,2‐dimethyl‐4‐R‐transdecahydroquinoline‐4‐ol N‐oxides (R=CCH, CHCH2 and C2H5) under electron impact are discussed. The correlation between the mass spectrometric chromatographic behaviour and the configuration of polar groups in the N‐oxides examined is discussed. The mass spectra of the N‐1 stereoisomers may be subdivided into two groups, depending only on the orientation of N→O group and not of the 4‐OH group. The spectra of N‐oxides with the axial N‐oxide group reveal less intense ions and much more intense [MCH3]+, [MO]+, [MOH]+ and ions, whereas in the spectra of their equatorial epimers the abundance of the ions exceeds the intensities of the latter ions.
Electron impact studies CX—+E spectra from negative ions. Ortho effects and skeletal rearrangement reactions from sulphur compounds
Authors: Bowie J. H. , White P. Y. , Wilson J. C. , Larsson F. C. V. , Lawesson S.‐O. , Madsen J. Ø , Nolde C. , Schroll G.
Published: May 2005

+E spectra derived from the non‐decomposing anion of some sulphur compounds are independent of the pressure of the collision gas. The compounds chosen for study contain peaks produced from either ortho effects or skeletal rearrangement fragments in their conventional positive ion spectra. The dissociative +E spectra are either devoid of skeletal rearangement ions or alternatiely contain such peaks in small abundance. In contrast, peaks derived from ortho reactions are present in high abundance.
Beiträge zum Studium einiger Heterocyclen. XLIV—Massenspektrometrische Untersuchungen einiger 2‐(p‐X‐Phenyl)‐5‐Y‐4‐acetylthiazole
Authors: Simiti I. , Demian H. , Luputiu Georgeta , Munteanu R.
Published: May 2005

Es wurden massenspektrometrische Untersuchungen einiger neuen 2‐Phenyl‐4‐acetylthiazole durchgeführt. Die Substanzen besitzen hohe Molekülpeaks. Die Substituenten in p‐Stellung des Benzolrings üben keinen Eintluss auf das Fragmentierungsmuster aus, sondern nur auf die relativen Intensitäten von Molekülionen und der Fragmentionen. Die Einführung von Chlor bzw. Brom in Stellung 5 des Thiazols führen zu beträchtlichen Änderungen der Fragmentierung (‘ortho Effekt’). Es findet eine Umlagerung über einen fünfgliedrigen Übergangszustand statt. Ebenfalls sind doppelt geladene Ionen erkennbar, die durch Anwesenheit mehrerer leicht ionisierbarer Gruppen erklärbar sind.
The electron impact induced fragmentation of aromatic aldoximes—II. Substituent effects on the loss of MCN
Authors: Vijfhuizen Peter C. , Dijkstra Geo
Published: May 2005

Loss of HCN from the molecular ion of benzaldoximes occurs via two distinct involving a 4‐membered and a 5‐membered intermediate, respectively. Both low energy high energy molecular ion decomposition were investigated by means of metastable peak shapes and the energetics of further decomposition of ions, respectively. Substituent effects previously held responsible for differences in the behaviour of m‐ and p‐methoxybenzaldoximes are shown to be negligible; the differences are due to the differense in internal energy contents.
Ionic dehydration reactions: The effect of location of the activated complex on kinetic energy release
Authors: Gross M. L. , Deroos F. L. , Hoffman M. K.
Published: May 2005

A broad range of kinetic energy release has been found for the 1,4 elimination of water in a series of ortho substituted benzyl alcohols and benzoic acids. It is suggested that the trend reflects, in part, the position of the activated complex on the reaction coordinate. More specifically, reactions which proceed via an ‘early’ transition state release only small quantities of energy, whereas those processes occurring ‘later’ release a larger fraction of the available energy. Consequently, the o‐ methyl derivatives give large kinetic energy release compared to o‐ amino or hydroxy substituted compounds. Father verification is obtained from the small kinetic energy release observed for the 1,4 ionic dehydration in simple,acyclic alcohols.
Transfert d'un Atome de Chlore lors d'un Réarrangement de Type McLafferty
Authors: Arseniyadis S. , Gore J. , Roumestant M. L.
Published: May 2005

Les spectres de trois allènes ω‐chlorés mettent en évidence deux réarrangements de type McLafferty; l'un s'effectue avec transfert d'hydrogène, I'autre avec transfert de l'atome de chlore.
Fragmentation patterns by fast linked electric and magnetic field scanning
Authors: Millington D. S. , Smith J. A.
Published: May 2005

The fragmentation pattern of the molecular ion of n‐octacosane was obtained, with good resolution, by linked scanning of the electrostatic and magnetic fields in a double focusing mass spectrometer in a total scan time of only 30 seconds.
Mass spectrometric studies on a β‐ketosulfone
Authors: Diller Dov , Bergmann Felix
Published: May 2005

The fragmentation of the β‐ketosulfone‐γ‐methylsulfonyl‐γ‐benzoylbutyronitrile under electron bombardment follows a number of different pathways: formation of the benzoyl ion (Major path); remova of acrylonitrile; liberation of the methylsulfonyl radical or of methylsulfonic acid; and finally elimination of a methylenecyano radical. The fragments observed can be explained by these five degradation paths. The reactions are compared with the photochemical cleavage of this β‐ketosulfone in benzene solution.
Electron impact induced fragmentation of some 1,2,4‐triazole derivatives
Authors: Kallury R. Krishna Mohan Rao , Upadhyaya Pramod V. , Surendra Nath Tumbalam G. , Srinivasan Vankipuram R.
Published: May 2005

The mass spectra of eight 1,2,4‐triazole derivaties have been recorded and found tao reveal extensive hydrogen and skeletal migrations. The structures of the fragments have been confirmed by deuterium labelling and exact mass measurement. The compounds revealed striking differences in their spectra depending on the nature of the substituents.
Pyrolysis mass spectrometry of methionine
Authors: Posthumus M. A. , Nibbering N. M. M.
Published: May 2005

The mechanisms of some fragmentation of methionine upon Curie‐point pyrolysis have been studied by the use of deuterium labelling. They lead to products having the same nominal mass but essentially different elemental compositions compared with ions generated by electron impact on methionine. For exaple, upon pyrolysis the product with mass 116 is due to a 1,2 elimination of hydroxylamine from the title compound, whereas upon electron impact the ion with m/e 116 is generated by successive loss of a molecule of water and of a methyl radical from the molecular ion; the generated of product m/e 101 proceeds via successive loss of a molecule of water, carbon monoxide and of hydrogen upon pyrolysis, but via a one‐step elimination of methanethiol upon electron impact. No evidence has been found for a diketopiperazine formation by a bimolecular process upon pyrolysis, although this type of reaction is well known for α‐amino acids.
Fragmentation of a new type of 6‐phenyl‐2‐pyridone, bearing a 5‐methylsulfonyl substituent, under electron impact
Authors: Bergmann Felix , Diller Dov
Published: May 2005

The mass pectra of 5‐methylsulfonyl‐6‐pyridone and its 3,4‐dihydro derivative show that the most important fragmentations involve the methylsufonyl substituent, which is eliminated in various forms (CH3SO˙; CH3SO2˙; CH3SO2H or SO2H˙). Other fissions like the removal of CO, which is the predominant event in simple 2‐pyridones and in 6‐pyridone, appear only after breakdown of the sulfonyl group. Only 5‐methylsulfonyl‐6‐phenyl‐2‐pyridone eliminates an OH radical from the molecular ion.
The mass spectral rearrangements of aryl propenyl sulfones. An electron impact induced smiles type rearrangement
Authors: Hill Charlotte J. , Thyagarajan B. S. , Bates D. K. , Spangler R. J.
Published: May 2005

The mass spectral behavior of trans‐1‐arylsulfonyl‐2‐arylsulfenyl‐propenes, trans‐1‐arylsulfonyl‐2‐arylsulfinyl‐propenes and trans‐1, 2‐(arylsulfonyl)‐propenes was examined. A Smiles type rearrangement was present in the sulfonyl‐sulfides, but was completely absent in the trans‐1‐arylsulfonyl‐2‐arylsulfinyl‐propenes and trans‐1, 2‐(arylsulfonyl)‐propenes. Vinyl migration to the sulfone oxygen predominates over aryl migration in all of the compounds studied. The mass spectra of the cis and trans isomers of 1‐p‐tolylsulfenyl‐2‐p′‐tolysulfonyl‐propene and 1, 2‐(p‐tolylsulfonyl)‐propene are also described.
Field ionization kinetics: Phenylhexanone
Authors: Patterson Donald G. , Scott Richard B. , Brown Peter
Published: May 2005

A Varian Atlas SMIB double focusing mass spectrometer has been modified for field ionization kinetics measurements. Computer programs have been written for the calculation and display of potential maps, ion trajectories, and the transformation to ion lifetimes and phenomenological rate constants. The previously studied cyclohexene system has been used to check the accuracy of our method. The fragment ions generated by phenylhexanone after field ionization have also been examined by field ionization kinetics, including cleavage and rearrangement reactions, H/D randomization and temperature effects.
Etude par Spectrométrie de Masse du Di‐O‐isopropylidene‐1,2;5,6‐α‐D‐ribo‐hexofurannosul‐3‐ose
Authors: Glangetas Alain , Buchs Armand , Tronchet Jean M. J.
Published: May 2005

La fragmentation du di‐O‐isopropylidène‐1,2:5,6‐α‐D‐ribo‐hexofurannosul‐3‐ose a été étudiée à I'aide de molécules marquées avec du deutérium et de I'oxygéne 18O. Des mécanismes sont proposés pour la formation des principaux ions.
Electron impact induced fragmentation of dibenzo‐18‐crown‐6 polyether and its nitro derivatives
Authors: Gomes Ailton De Souza , Oliveira Clara Marize Firemand
Published: May 2005

The mass spectra of dibenzo‐18‐crown‐6 polyether and three of its nitro derivatives have been determined. The fragmentation pathways of all the compounds suggested that ring contraction was taking place. The molecular ion of the polyether dissociated by three competing processes, mainly through loss of C2H4O units. The molecular ions of the three derivatives dissociated with ring contraction, as well as through losses of O, No and NO2.
Collisional activation of ions formed by [Li]+ ion attachment
Authors: Röllgen F. W. , Borchers F. , Giessmann U. , Levsen K.
Published: May 2005

Since no unimolecular fragmentation is observed with [M+Li]+ ions under normal operating conditions the collisional activation method was used to study the fragmentation behaviour of these ions. It was found that the liberation of the [Li]+ ion is a dominant process only with smaller molecules. In addition, direct bond cleavages and new types of rearrangement reactions lead to fragment ions in which the lithium is normally retained. The decomposition behaviour of [M+Li]+ ions represents an intermediate case between that of [M]+ ions and excited neutral molecules and is quite different from that of [M+H]+ ions.
Unimolekulare CH3‐, CH4‐, C2H4‐ und C3H4‐Eliminierungen aus alkin‐ und arylsubstituierten Isopropylkationen in der Gasphase
Authors: Bobrich Michael , Schwarz Helmut , Levsen Karsten , Schmitz Peter
Published: May 2005

Durch die Untersuchung13C‐ und2H‐markierter Modellverbindungen werden die Methyl‐, Methan‐, Äthylenund Allen (bzw. Propin)‐Eliminierungen aus zwei isomeren [C3H6Y]+‐Ionen studiert (Y =p(HCC)C6H4bzw. C6H5CC−). Es wird belegt daß die Zerfallsprozesse von erheblichen Kohlenstoff‐ und Wasserstoffumlagerungen begleitet werden, deren Ausmaß im allgemeinen nicht einem vollständigen C/H‐Scrambling entspricht, sondern in spezifischer Weise durch die jeweilige Fragmentierung bestimmt wird.
Regiospezifische Wasser‐Eliminierung aus stereo‐ und konstitutionsisomeren Hydroxymethyl‐α‐dekalolen durch chemische Ionisation
Authors: Reich Monika , Schwarz Helmut
Published: May 2005

Die chemische Ionisation (Reaktionsgas i‐Butan) von spezifisch 18O‐markierten, Hydroxymethyl‐α‐dekalolen, die sowohl eine primäre als auch eine sekundäre Hydroxylgruppe enthalten, belegt zum ersten Mal, daß nahezu ausschließlich (>97%) die sekundäre OH‐Funktion an der Bildung des [M + H − H2O]+‐ Ions beteiligt ist. Die Intensität der protonierten Molekül‐Ionen wird durch die Konstituion, die relativen Konfigurationen und die Konformation der Diole beeinflußt.
Massenspektroskopische Untersuchungen an 2,5‐Diaryl‐1‐(arylimino)‐1λ4,2,5‐thiadia‐zolidin‐3,4‐dionen
Authors: Neidlein Richard , Leinberger Peter , Hotzel Alfred
Published: May 2005

Die Massenspektren von 2,5‐diaryl‐1‐(arylimino)‐1λ4,2,5‐thiadiazolidin‐3,4‐dionen wurden untersucht. Das auftreten mehrerer Bruchstücke wird durch die Umlagerung der Titelverbindungen zu 1,3‐(diarylimino)‐5‐aryl‐1λ4,2,5‐thioxazolidin‐4‐onen und 1‐oxo‐2,5‐diphenyl‐3‐(arylimino)1λ4,2,5‐thiadiazolidin‐4‐onen erklärt.