bluuebunny/crossref_metadata_2025_split huggingface dataset:
Massenspektrometrische Untersuchung von Amiden. VIII—Vinyloge α‐Spaltung und Nachbargruppenbeteiligung bei der Fragmentierung von Piperididen α,β‐ungesättigter Carbonsäuren
Authors: Schwarz Helmut , Bohlmann Ferdinand , Altnau Gerald , Hillenbrand Günther 
Published: May 2005

AbstractPiperidide von β‐substituierten α,β‐ungesättigten Carbonsäuren fragmentieren unter Elektronenstoßbedingungen hevorzugt über viergliedrige Übergangszustände. Die für α,β‐ungesättigte Carbonsäureester typische Ausbildung von Sechsringsystemen findet nur untergeordnet statt. Der Mechanismus der Reaktion ist am besten rationalisierbar durch die Annahme einer vinylogen α‐Spaltung und gleichzeitiger Nachbargruppenbeteiligung der Amidfunktion.
Elektronenstossinduzierte Cyclisierung Durch Nachbargruppenwechselwirkung bei N‐(O‐Nitrobenzyl)‐Aminen
Authors: Schwarz Helmut 
Published: May 2005

AbstractEIektronenstoßinduzierte Sauerstoffübertragungen spielen bei der Fragmentierung von N‐(o‐Nitrobenzyl)‐Aminen nur eine untergeordnete Rolle. Durch die Untersuchung 2H‐markierter Verbindungen wird belegt, daß die wichtigsten Ionen durch Nachbargruppenwechselwirkungen erzeugt werden, die zu einer Cyclisierung der Fragment‐Ionen führen.
The mass spectrometric fragmentation of α‐diazosulphones
Authors: Luinenburg O. , Engberts J. B. F. N. , Weringa W. D. 
Published: May 2005

AbstractThe fragmentation of four α‐diazosulphones under conditions of electron‐impact was studied with the aid of high resolution mass measurements and the metastable defocusing technique. An important difference from the spectra of the related α‐diazoketones is the absence of peaks for [M  N2]+˙. Metastables show, however, that these fragments probably exist as intermediates.
On the rearrangement and scrambling of hydrogen in the benzophenone oxime molecular ion
Authors: Kramer V. , Medved M. , Kralj B. , Marsel J. 
Published: May 2005

AbstractThe losses of CO, hydrogen and CO, OH and HNOH radicals from the benzophenone oxime molecular ion have been studied by means of deuterium labelled compounds. Hydrogen scrambling and/or exchange and rearrangement reactions of interest, taking place prior to fragmentation, were observed.
The field desorption mass spectra of some oligosaccharides and their permethylates and peracetylates
Authors: Moor Jacob , Waight E. S. 
Published: May 2005

AbstractField desorption mass spectra have been obtained for a number of di‐, tri‐ and tetrasaccharides, and for some permethyl and peracetyl derivatives. The free sugars usually show intense [M + 1]+ ions thus enabling the determination of molecular weights. The effect of variation of emitter current on the relative intensities of fragment ions has been investigated. Permethylated oligosaccharides show intense molecular ions; in contrast peracetylated oligosaccharides show only weak molecular ions but strong [M  60]+ ions. Information from electron‐impact and field desorption mass spectra is essentially complementary.
The negative ion mass spectra of mixtures of sulphur and organic compounds. I—The formation of [M+Sn]− from the mixture of sulphur and dinitriles
Authors: Hirata Yukio , Matsumoto Kozo , Takeuchi Tsugio 
Published: May 2005

AbstractThe negative ion mass spectra of sulphur, dinitriles and their mixtures were studied. The abundance of negative ions of sulphur was almost comparable to that of positive ions. In the negative ion mass spectrum of a mixture of sulphur and dinitrile, intense and characteristic peaks of [M + Sn]− (n = 2, 3, 4, etc.) were observed resulting from ion–molecule association of dinitrile with the Sn− anions. As a standard sample of a negative ion mass spectrum, sulphur itself has proved useful in the lower mass region (below m/e 256: S8−).
Fragmentation de Benzodioxannes‐1,3 Diversement Substitues en 2,4
Authors: Grunstein J. F. , Dizabo P. , Ricard M. , Brun J. P. 
Published: May 2005

AbstractLes benzodioxannes‐1, 3 diversement substitués en 2,4 subissent deux coupures de ‘rétro’ Diels‐Alder: l'une classique, l'autre avec migration d'hydrogène.
Fragmentation D'azoles Sous L'impact Electronique. V—Isomerisation Du Benzimidazole Avant Degradation
Authors: Maquestiau A. , van Haverbeke Y. , Flammang R. , Pardo M. C. , Elguero J. 
Published: May 2005

AbstractLe spectre de masse du benzimidazole est étudié à l'aide de marquages isotopiques (D et 13C). Après lyionisation il se produit une isomérisation en o‐cyanoaniline, à partir de laquelle deux réactions compétitives conduisent à l'ion [M–HCN]+·. La perte de HCN au niveau de la fonction amino et, par effect ortho, au niveau de la fonction nitrile est confirmée par des mesures d'abondances ioniques. On n'observe pas de réarrangements statistiques d'hydrogènes avant l'élimination de HCN.
Relative activation energies and frequency factors for competing fragmentations of oxetane molecular ions
Authors: Ii Guilford Jones , McDonnell Lorraine P. 
Published: May 2005

AbstractA pair of substituted oxetane mass spectral decompositions exhibit regioselective ring cracking, and single and double hydrogen rearrangement cleavages involving substituent methyl groups. Analysis of ion abundances as a function of ionizing energy provides estimates of relative activation energies and frequency factors for these fragmentations.
MASSENSPEKTREN HETEROAROMATISCHER NITRILE
Authors: Holzmann G. , Rothkopf H. W. , Müller R. , Wöhrle D. 
Published: May 2005

AbstractThe electron‐impact and field ionisation spectra of nineteen di‐ and tetracyanopyrazines are presented. The use of high resolution mass measurement and metastable analysis allows the proposal of some general fragmentation mechanisms. The 5,6‐disubstituted (alkyl or arene) 2,3‐dicyanopyrazines examined show, apart from a less important loss of the nitrile and dicyano groups, fragmentation of the heterocyclic system directed by the nitrogen atoms. In contrast, anellation in the 5,6‐position, leads only to loss of the nitrile and dicyano groups being observed. These general fragmentation mechanisms are also observed for the tetracyanopyrazines examined. A comparison of di‐ and tetracyanobenzene with five ring heterocycles containing four cyano groups shows that fragmentation of nitrile groups is greatly dependent upon the aromaticity of the cyclic system.
Contrasting reactions for conversion of some dihydroaromatic cations to aromatic cations through hydrogen elimination
Authors: Brady Leonard E. , Williams Dudley H. , Traynor Sean C. , Crowley Kevin J. 
Published: May 2005

AbstractComparison of metastable peaks in the mass spectra of the monoterpenes alloöcimene and a‐pyronene shows that they fragment through common ions. It is concluded that the acyclic triene (alloöcimene) undergoes electrocyclic ring closure to the cyclic diene (a‐pyronene) and fragmentation then proceeds from an ionised form of a cyclic diene. The fragmentation proceeds to a series of ions [CnH2n−5]+, the decomposing forms of which are inferred to be protonated benzene (n = 6) and dihydrotropylium ions (n = 7, 8, 9). These ions react via loss of H2, the dihydrotropylium → tropylium conversion being characterised by a relatively large kinetic energy release in both un‐substituted (n = 7) and methyl‐substituted (n = 8, 9) cases.
Kinetic energy release in metastable ion transitions. A study by ion kinetic energy spectrometry and rrkm theory
Authors: Elder J. F. , Beynon J. H. , Cooks R. G. 
Published: May 2005

AbstractAn approach to energy partitioning using experimental data in conjunction with theoretical calculations is presented, with the McLafferty and related rearrangements occurring in the molecular ions of ketones, esters, amides and acid chlorides representing the specific reactions examined. The kinetic energy release associated with statistical partitioning of the nonfixed energy of the activated complex was calculated from unimolecular reaction theory and compared with experimental data. Calculations of the energy dependence of the rate constant and the average statistically released kinetic energy were made for 24 activated complexes corresponding to the two basic structures, cyclic and linear. The frequencies used in the calculations were all modeled upon the 2‐pentanone case with sufficient variation in the frequencies used to allow for any reasonable type of perturbation of the linear and cyclic structures. To further test that the complexes chosen were reasonable, A‐factors were determined. From a comparison of the calculated and experimental results, the contributions of the nonfixed energy of the activated complex and of the reverse activation energy to the energy release were separated. This appears to be applicable, not only to the 2‐pentanone case, but across the series of reactions studied. It is also shown that, despite the fact that these reactions release relatively small kinetic energies, the fraction due to the reverse activation energies may be large. The consequences of these observations for ion enthalpy determinations are emphasized.
Der massenspektrometrische zerfall von naphthalin‐2.1‐diazooxid
Authors: Zeller Klaus‐Peter 
Published: May 2005

AbstractNapthalin‐2,1‐diazooxid eliminiert unter Elektronenstoα‐‐‐wie andere α‐Diazoketone–schrittweise N2 und CO. Das Massenspektrum von 1‐13C‐Naphtalin‐2.1‐diazooxid zeigt, daß keine Oxiren‐Spezies zu den [M  N2]+·‐Ionen beiträgt.
Mass spectrometry of uronic acid derivatives VIII–New processes in the fragmentation of carbohyrate methyle derivatives
Authors: Kováćik VladimíR , Kováč Pavol 
Published: May 2005

AbstractCompared with the fully methylated derivatives the presence of free hydroxyl groups in partially methylated uronic acid derivatives alters drastically the mode of the electron‐impact‐induced fragmentation. Using high and low resolution mass spectrometry with 70 and 12eV electrons and labelling experiments, new fragmentation pathways, having no analogy in any carbohydrate deri‐vatives investigated so far, have been found.
Electron‐impact‐induced rearrangements of organic ions VIUnimolecular reactions of isomeric[C8H9]+ions
Authors: Uccella N. 
Published: May 2005

AbstractMetastable ion spectra and deuterium labelling have been used to investigate a series of gaseous [C8H9]+ ions of isomeric structures. The similarity of the intensities of their metastable loss of hydrogen, acetylene and ethylene molecules and metastable reactions of specifically labelled ions, suggests that the [C8H9]+ reacting ions, formed initially with different structures, isomerise to a common structure or mixture of structures via deep‐seated rearrangement reactions which render all hydrogen atoms equivalent. The isomerisation process involved is controlled by a conversion of a vinyl bond into an allyl‐type bond, thus destroying the aromatic moiety.
Isomerisation of hydrocarbon ions III–[C8H8]+·, [C8H8]2+, [C6H6]+· AND [C6H5]+ IONS
Authors: Borchers F. , Levsen K. 
Published: May 2005

AbstractCollisional activation spectra of [C8H8]+·, [C8H8]2+, [C6H6]+· and [C6H5]+ ions from fifteen different sources are reported. Decomposing [C8H8]+· ions of ten of these precursors isomerise to a mixture of mainly the cyclooctatetraene and, to a smaller extent, the styrene structure. Three additional structures are observed with [C8H8]+· ions from the remaining precursors. [C8H8]2+., [C8H8]+·, [C6H6]+· and [C6H5]+· ions mostly decompose from common structures although some exceptions are reported.
ETUDE DE LA FRAGMENTATION DE N‐ARYL ET DE N‐ALKYL AMINOCETONES EN SPECTROMETRIE DE MASSE
Authors: Audoye Paul , Gaset Antoine , Lattes Armand 
Published: May 2005

AbstractLa comparison des spectres de masse en ionisation chimique et électronique d'alkyl et d'aryl aminocétones a étéréalisée. Elle a surtout permis de mettre en évidence dans tous les cas, la stabilisation particulière du groupe N‐aryl.
Untersuchungen Zum massenspektrometrischen Zerfall des Kawains
Authors: Achenbach H. , Wörth J. , Raffelsberger B. 
Published: May 2005

AbstractIn den Massenspektren von Verbindungen des Kawain‐Typs treten signifikante Ionen auf, deren Bildung nur im Zunge unerwarteter H‐Umlagerungen möglich ist. Die Massen‐spektren spezifisch deuterierter Kawaine geben Einblick in diese elektronenstoß‐induzierten Umlagerungen.
Mass spectra of some substituted imidazoles
Authors: Cooper G. , Irwin W. J. 
Published: May 2005

AbstractComparison of fragmentation pathways and high resolution measurements has revealed that the molecular ions of 1‐(2‐hydroxy‐2‐phenylethyl)imidazoles undergo elimination of benzaldehyde. The parent ions of trans‐1‐styrylimidazoles also cyclise in a manner similar to their photochemical reactivity. A rearrangement involving OH or OMe transfer between the trans‐1‐styryl and 5‐acid or 5‐methyl ester group of an imidazole is also described.
The mass spectra of some aromatic polyketones
Authors: Laćan M. , Vukićević M. , Džanić H. , Stefanović D. 
Published: May 2005

AbstractThe behaviour of some aromatic tri‐ and tetraoxo compounds and of their p‐substituted derivatives under electron‐impact has been investigated by means of high and low resolution mass spectrometry, metastable refocusing and deuterium labelling. Some characteristic fragmentation processes observed with these compounds indicate that their molecular ions exist in the enol form. The formation of principal fragment ions is discussed.
Etude en spectrometrie de masse de la fragmentation de di‐O‐isopropylidene‐1,2‐5,6‐α‐D‐hexofurannoses
Authors: Buchs Armand , Glangetas Alain , Tronchet Jean M. J. 
Published: May 2005

AbstractLa fragmentation de trois stéréoisomères de la classe des di‐O‐isopropylidène‐1,2‐5,6‐α‐D‐hexofurannoses a été étudiée à l'aide de molécules deutériées. Des mécanismes sont proposés pour expliquer la formation des principaux ions.
Mass spectral study of cyclic alkaneboronates of sugar phosphates. Evidence of interaction between the phosphate group and boron under electron‐impact conditions
Authors: Wiecko Jacek , Sherman William R. 
Published: May 2005

AbstractCyclic butane‐ and methaneboronic esters of dimethylphosphates of glucose, galactose, mannose, fructose and methyl gluconate have been examined by mass spectrometry. High resolution information and deuterium labeling of all six carbons of glucose, as well as of the methylphosphate groups, permits elucidation of the origin of various ions, which can be grouped according to their probable mechanism of formation. In each case, the intensity of the [M – R]+ ion can be rationalized, in stereochemical terms, by the ease with which incipient positive charge on boron can be stabilized by the phosphate group. This interaction also gives rise to rearrangement ions containing a BOP linkage. Other effects of structure on fragmentation pattern are discussed. Retention of specific portions of the glucose skeleton in ions with clearly defined label shift behavior, as well as the preservation of intact sugar moieties in intense [M – R]+ ions, suggests applications for stable isotope analyses. These are discussed in terms of their advantages over silicon‐containing derivatives.
Fragmentations de quelques Derives thiophosphores sous L'impact electronique. II—Migration de groupes phenyles et d'atomes de soufre dans quelques derives dithiophosphores
Authors: Cauquis G. , Divisia B. , Ulrich J. 
Published: May 2005

AbstractLes fragmentations de quelques dérivés contenant soit deux groupes diphénylphoshino, soit deux groupes diphénylthiophosphoranyles donnent lieu à diverses migrations de groupes phényles et d'atomes de soufre. Les phényles migrent, suivant le composé, soit d'un phosphore à l'autre, soit d'un phosphore vers le soufre lié à l'autre phosphore. Des migrations d'un phényle du Phosphore vers le carbone ont lieu lorsque ce dernier est fortement électrophile. Dans les composés thiophosphorés, on observe des migrations d'atomes de soufre du phosphore vers le carbone ou la double liaison situé en α de l'atome de phosphore.
Studies in negative ion mass spectrometry. V—A Comparison of positive a positive and negative ion mass spectra of copper(II) complexes of bidentate schiff base ligands
Authors: Wilson J. G. , Fraser I. W. , Garnett J. L. , Gregor I. K. 
Published: May 2005

Abstract70 eV positive and negative ion mass spectra of a series of copper(II) Schiff base complexes have been obtained consecutively under the same ion source conditions. The characteristic feature of the negative ion spectra is their extreme simplicity relative to the corresponding positive ion spectra, the only ions present in significant abundance being the molecular anions and ligand ions. The influence of substituents (R) on positive and negative ion fragmentation patterns is discussed. Metastable peaks have been obtained in all cases for the transition [Cu(Ligand)2]− → [Ligand]−.
Spectrometrie de masse d'heterocycles selenies. IV—comportement de quelques benzo[b]selenophenes 2,3‐disubstitutes
Authors: Croisy Alain , Jacquignon Pierre , Christiaens Léon 
Published: May 2005

AbstractDix huit benzo[b]sélénosphénes disubstitués en 2 et en 3 sont étudiés du point de vue de leur fragmentation sous l'impact electronique. L'influence des substituants sur le comportement du noyau hétérocyclique est examinée en měme temps que la dégradation des chaînes latérales.
Electron impact studies. CI—negative ion mass spectra of the carbonyl group. The ArylCH2CO‐ and Aryl(CH2)2CO‐ systems
Authors: Bowie John H. , Janposri Sompong 
Published: May 2005

AbstractFragmentations of the molecular anions of m‐ and p‐nitrophenyl‐CH2COR yield nitrobenzyl anions in the ion source when R = Ph, but the corresponding ion from the system where R = Me is only formed after collision activation. o‐ and p‐Nitrophenyl parent anions undergo β‐cleavage to the carbonyl centre to produce nitrobenzyl anions. Pronounced rearrangement peaks are noted in the spectra of o‐nitrophenyl‐ compounds. Labelling studies indicate the identity of the eliminated species, but the mechanisms of the rearrangements are complex.
Electron‐impact fragmentation of pentafluorophenyl‐ and pentafluorophenylalkyldimethylsilanes
Authors: Poole C. F. , Morgan E. D. , Pacey N. 
Published: May 2005

AbstractThe mass spectra of pentafluorobenzyl‐ and pentafluorophenylethylsilanes show cleavage to give cyclic fluorohydrocarbon ions of the tropylium type, which, with their fragmentation products, are the principal charge carrying species. In pentafluorophenyldimethylsilanes, exchange of fluorine and methyl between silicon and carbon occurs readily, and again the spectrum is dominated by cyclic fluorohydrocarbon ions. The composition and relative intensities of characteristic ions of diagnostic value in the spectra of pentafluorophenyldimethylsilanes are listed.
Studies in organic mass spectrometry. XXII–Evidence for the existence of cyclic oxonium ions in the gas phase
Authors: Van De Sande C. C. 
Published: May 2005

AbstractThe electron impact induced loss of a phenoxy radical from the molecular ions of α,ω‐bis‐aryloxy alkanes ΦO(CH2)nOΦ (1n; n = 2–7) and F‐p‐C6H4(CH2)nOΦ(2n; n = 2−5) is the result of functional group interaction. Labelling data provide conclusive evidence for the O‐aryl tetra‐hydrofuranium and O‐aryl tetrahydropyranium structures of the resulting decomposing species (lifetimes between 10−6 and 10−5 s) in the case of n = 4 and 5, respectively. Evidence is presented for the occurrence of phenyl participation in the loss of ΦOH from the molecular ions of the lower homologues of 1n and 2n (n = 2, 3).
Studies in organic mass spectrometry. XXIII‐Evidence for the occurrence of cyclic sulphonium ions in the gas phase
Authors: Van De Sande C. C. 
Published: May 2005

AbstractFunctional group interaction occurs in the loss of a phenoxy radical from the molecular ions of ω‐phenylthio alkylphenylethers ØO(CH2)nSØ (n= 2–6). Labelling data provide evidence for the S‐phenyl thietanium, S‐phenyl tetrahydrothiophenium and S‐phenyl tetrahydrothiopyranium structures of the decomposing (lifetimes between 10−6and 10−5s) [M ‐ ØO]+ions in the case ofn= 3, 4 and 5, respectively.
Hydrolysis, methanolysis and ammonolysis of dicarboxylic acids and methyl esters under conditions of chemical ionization mass spectrometry
Authors: Weinkam Robert J. , Gal Joseph 
Published: May 2005

AbstractChemical ionization mass spectra of dicarboxylic acids and methyl esters show fragmentation and unimolecular reactions with reagent gases water, methanol, ammonia and methyl ether, which differ from those observed with hydrocarbon reagents methane and isobutane. These reactions involve exchange of the reagent gas for water or methanol of the dicarboxyl compounds as well as secondary exchange of both functions. An effort has been made to determine the mechanism of these reactions and to determine the structural requirements necessary for their occurrence.
Stepwise retro 1,3‐dipolar cycloaddition induced by electron. Impact on 3,5‐diphenyl‐1,2,4‐oxadiazole
Authors: Selva Antonio , Traldi Pietro , Zerilli Luigi F. , Gallo Gian Gualberto 
Published: May 2005

AbstractThe retro 1,3‐dipolar cycloaddition induced by electron impact on 3,5‐diphenyl‐1,2,4‐oxadiazole is interpreted as a two‐step process on the basis of the energetics and kinetics of the fragments [C7H5NO]+., [C6H5CN]+. and [C6H5CO]+.
Notiz zur intramolekularen WasserstoffbrüCkenbildung bei der Chemischen Ionisation von Ungesättigten C4‐1.4‐Diolen
Authors: Schwarz Helmut , Rapp Uwe , Windel Bernd 
Published: May 2005

AbstractEine durch chemische Ionisation erzeugte intramolekulare Wasserstoffbückenbindung zwischen beiden Hydroxylfunktionen ist nur beim cis‐Buten‐(2)‐diol‐(1.4) nachweisbar, Sowohl das entsprechende trans‐Isomer als auch Butin‐(2)‐diol‐(1.4)zeigen diesen Effekt nicht, was darauf zurückzuführen ist, daß selbst die verwendung starker Protonendonatoren, wie z.B. [CH5]+, keine Symmetrieänderung der Mehrfachbindung herbeiführen kann, was ber Voraussetzung für die intramolekulare Wasserstoffbrücke ist.
The mass spectra of some simple phenylhydrazides and a re‐examination of the fragmentations of phenylhydrazine
Authors: Wolkoff Peder , Hammerum Steen 
Published: May 2005

AbstractThe elimination of small neutral fragments from acetyl‐, formyl‐ and ethoxycarbonyl‐ phenylhydrazines with formation of [C6H8N2]+⋅ ions has been studied. Evidence is obtained from deuterium labelling and from metastable peak intensity ratios, to show that ketene loss from both acetylphenylhydrazines is accompanied (or preceded) by hydrogen transfer to the acylated nitrogen atom to give ions structurally analogous to the phenylhydrazine molecular ion. The decomposing [C6H8N2]+⋅ ions formed from formyl‐ and ethoxycarbonylphenylhydrazines are also suggested to have a phenylhydrazine‐like structure. In the molecular ion of phenylhydrazine interchange occurs between the two ortho hydrogen atoms and two of the three hydrazine hydrogens prior to decomposition; labelling data suggest that the N‐1 hydrogen does not participate in the interchange process.
Fluorinated coal as an internal standard for unit mass assignment
Authors: Huston John L. , Scott Robert G. , Studier Martin H. 
Published: May 2005

AbstractFluorination of bituminous coal by elemental fluorine yields a solid product from which a solid distillate can be made by vacuum pyrolysis. Both fluorinated materials are easily made and are useful for mass spectrometric unit mass assignments. They have certain advantages over the commonly used perfluorokerosene, particularly for use in the high mass region.
Chemical ionization mass spectra of 2, 4, 6‐trinitroaromatic compounds
Authors: Zitrin S. , Yinon J. 
Published: May 2005

AbstractThe methane and isobutane chemical ionization mass spectra of ten 2,4,6‐trinitroaromatic compounds have been recorded. The mass spectra contain intense [M + 1]+ ions and usually little fragmentation. However, in some cases major fragmentation processes have been observed. Some unusual adduct ions have been found with isobutane as the reagent and their temperature dependence has been studied.