bluuebunny/crossref_metadata_2025 huggingface dataset:
Mass spectrometry of organic compounds. VIII—Remote group interaction in hydroxyorganotins
Authors: Kingston David G. I. , Tannenbaum H. P. , Kuivila H. G.
Published: May 2005

Hydroxyorganotins of the general formula R3Sn(CH2)nOH undergo rearrangement on electron‐impact to yield ions in which oxygen has become directly bonded to the tin atom. The scope of this rearrangement is discussed, and it is shown that steric and structural factors play a significant but not decisive effect in its occurrence.
Phosphates D'énols: XI—Étude en Spectrométrie de Masse des Dérivés Diméthyliques
Authors: Gaydou Emile M. , Peiffer Gilbert , Etienne Marc
Published: May 2005

L'étude d'une série de phosphates énoliques du type A an spectrométrie de masse conduit à des schémas de rupture influencés par la nature des substituants R, R′ et R″, On observe généralement à côte de la perte du groupement énolique, des phénomènes des phénomènes de double ou simple réarrangement d'hydrogène. Lorsque R et R′ sont des groupements alcoyles, ce sont les atomes d'hydrogène magnified image du groupement fixé en 1 qui migrent. En l'absence de groupement alcoyle en 1, ce sont les atomes d'hydrogène du groupment en 2 qui provoquent le réarrangement. Enfin si R, R′ et R″ sont des atomes d'hydrogène, on a essentiellement perte de l'enchaînement éolique sans réarrangement.
Structure and mechanism of fragmentation of [C2H5O]+
Authors: Keyes B. G. , Harrison A. G.
Published: May 2005

The decomposition reactions of [C2H5O]+ ions produced by dissociative electron‐impact ionization of 2‐propanol have been studied, using 13C and deuterium labeling coupled with metastable intensity studies. In addition, the fragmentation reactions following protonation of appropriately labeled acetaldehydes and ethylene oxides with [H3]+ or [D3]+ have been investigated. In both studies particular attention has been paid to the reactions leading to [CHO]+, [C2H3]+ and [H3O]+.

In both the electron‐impact‐induced reactions and the chemical ionization systems the fragmentation of [C2H5O]+ to both [H3O]+ and [C2H3]+ proceeds by a single mechanism. For each case the reaction involves a mechanism in which the hydrogen originally bonded to oxygen is retained in the oxygen containing fragment while the four hydrogens originally bonded to carbon become indistinguishable.

The fragmentation of [C2H5O]+ to produce [CHO]+ proceeds by a number of mechanisms. The lowest energy route involves complete retention of the α carbon and hydrogen while a higher energy route proceeds by a mechanism in which the carbons and the attached hydrogens become indistinguishable. A third distinct mechanism, observed in the electron‐impact spectra only, proceeds with retention of the hydroxylic hydrogen in the product ion.

Detailed fragmentation mechanisms are proposed to explain the results. It is suggested that the [C2H5O]+ ions formed by protonation of acetaldehyde or ionization of 2‐propanol are produced initially with the structure [CH3CH\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^ + $\end{document}H] (a), but isomerize to [CH2CH\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^ + $\end{document}H2] (e) prior to decomposition to [C2H3]+ or [H3O]+. The results indicate that the isomerization a → e does not proceed directly, possibly because it is symmetry forbidden, but by two consecutive [1,2] hydrogen shifts.

A more general study of the electron‐impact mass spectrum of 2‐propanol has been made and the fragmentation reactions proceeding from the molecular ion have been identified.
Massenspektrometrische Untersuchung von Amiden. VI—Mechanismus der Methyl‐Abspaltung aus Crotonsä;urepiperidid
Authors: Bohlmann Ferdinand , Mathar Wolfgang , Schwarz Helmut
Published: May 2005

Durch die Untersuchung 2H‐markierter Verbindungen wird belegt, daß im Falle von Crotonsäurepiperidid nur die Wasserstoffe der Methylgruppe an der CH3·‐Abspaltung teilnehmen.
Electron‐impact studies. LXXXIV—Substituent effects in the negative ion mass spectra of aryl esters
Authors: Bowie J. H. , Nussey B.
Published: May 2005

Linear plots may be obtained for the fragmentations of aryl p‐cyanobenzoates using the McLafferty approach, but the correlations are not as satisfactory as those observed1 for aryl nitrobenzoates. Some satisfactory correlations of substituent effects are noted in the negative ion spectra of substituted benzyl‐p‐nitrobenzoates and substituted phenyl‐(p‐nitrophenyl)acetates. Pronounced rearrangement peaks are observed in the spectra of substituted phenyl‐(p‐nitrophenyl)acetates. Appearance potential studies suggest that the similarities in ρ values obtained1 for the fragmentations of aryl m‐ and p‐nitrobenzoate molecular anions are probably due to the correspondence between Hammett σ values and appearance potentials in the two series.
Analyse en Spectrometrie de Masse de Derives Fluores en Serie Pyrimidine et Triazine
Authors: Hitzke J. , Cambon A. , Guion J.
Published: May 2005

Nous avons synthétisé tous les dérivés fluorés de la perchloropynmidme, de la 2,4,6 trichloropyrimidine et de la perchloro s‐triazine. La r.m.n. du fluor associée au couplage chromatographie en phase vapeur‐spectrométrie de masse, nous ont permis de séparer et d'identifier les produits obtenus. Nous presentons et discutons le comportement de ces composes sous l'impact électronique.
Mass spectrum of nitromethane
Authors: Meyerson Seymour , Fields Ellis K.
Published: May 2005

The mass spectrum of nitromethane points to rupture of the CH3NO2 bond as the dominant primary reaction, as also observed in pyrolysis, photolysis and radiolysis. Isomerization of the molecular ion to the nitrite configuration seems to contribute little in the mass spectrum of nitromethane, in contrast to those of nitrobenzene and other nitroarenes. The nitrite ion is probably the immediate precursor of [NO]+ at its appearance potential, but most of the [NO]+ yield seems to stem from secondary decomposition of excited [NO2]+.
Phosphates d'enols. XII—Etude en Spectrometrie de Masse de Derives Diethyliques et di‐n‐Butyliques
Authors: Gaydou Emile M. , Peiffer Gilbert
Published: May 2005

L'étude des fragmentation en spectrométrie de masse de phosphates diéthyliques (1) et di‐n‐butyliques (2) est grandement influencée par la nature des substituants R, R′, R″ fixés sur la double liaison
magnified image
Lorsque R = H on observe une perte prépondérante d'éthylène ou de butène‐1. Dans le cas où R = CH3 le procesus de double réarrangement se produit avec participation des groupements alcoyles de l'enchaînement énolique.
The internal energy of product ions formed in mass spectral reactions
Authors: McAdoo D. J. , Bente P. F. , Gross M. L. , McLafferty F. W.
Published: May 2005

Major factors which determine the distribution of internal energy of a primary product ion A+, P(E)A+, at formation are delineated in terms of the quasi‐equilibrium theory and a variety of experimental evidence is offered to support these conclusions. These major factors include: the P(E) of the molecular ion, the rate constants as a function of energy, κ(E), for M+·→A+ + N0 and for competing reactions of M+·, and the partitioning of excess internal energy between A+ and N0. The ‘fluctuation effect’ on this partitioning makes P(E)A+ relatively insensitive to many structural and energy changes.
Mass spectrometry in structural and stereochemical problems: CCXXXVI—corrected electron‐impact‐induced migratory aptitudes in aryl phenyl carbonates
Authors: Jaeger David A. , Tomer Kenneth B. , Woodgate Paul D. , Gebreyesus Tarekegn , Djerassi Carl , Shapiro Robert H.
Published: May 2005

Corrected relative migratory aptitudes for aryl groups in the electron‐impact‐induced rearrangement of aryl phenyl carbonates have been determined.
Studies in organic mass spectrometry. XVI—A combined approach to the structures of ions generated from the molecular ions of acyclic β‐diketones through loss of small neutral molecules
Authors: Conrath K. , Van Sande C. De , Vandewalle M.
Published: May 2005

The structures of ions produced from acyclic 1,3‐diketones by loss of carbon monoxide, ketene or olefins are investigated. Structural inference is made by comparison of the heats of formation of these ions with data for ions of known structure generated from other precursors. All assignments are confirmed by a study of metastable transitions. Loss of carbon monoxide yields ions in the keto form. Expulsion of a ketene or olefin moiety results in enol type ions.
Thermochemistry and metastable energy release for the dissociation [C3H7]+ → [C3H5]+ + H2
Authors: Holmes J. L. , Weese G. M.
Published: May 2005

The reverse activation energy, Erev, for the dissociation [C3H7]+ → [C3H5]+ + H2 has been determined as 0.24 ± 0.06 eV from measurements of the AP of [C3H5]+ produced by electron‐impact from thermally generated sec‐C3H7 radicals. The energy release observed in the corresponding metastable dissociation is 0.21 ± 0.01 eV, indicating that virtually all of Erev is partitioned as translational Kinetic energy of the fragmentation products. The metastable ion peak shape is also discussed with respect to the evaluation of the energy release.
Differentiation of tautomers by ion cyclotron resonance spectrometry: \documentclass{article}\pagestyle{empty}\begin{document}${\rm (CH}_{\rm 3} {\rm)}_{\rm 2} \mathop {\rm N}\limits^{\rm + } {\rm = CH}_{\rm 2} {\rm vs H}_{\rm 3} {\rm C}\mathop {\rm N}\limits^{\rm + } {\rm H = CHCH}_{\rm 3}$\end{document}
Authors: Tomer Kenneth B.
Published: May 2005

Ion cyclotron resonance spectrometry and deuterium labeling have been used to determine that nondecomposing \documentclass{article}\pagestyle{empty}\begin{document}${\rm (CH}_{\rm 3} {\rm)}_{\rm 2} \mathop {\rm N}\limits^{\rm + } {\rm = CH}_{\rm 2}$\end{document} ions do not isomerize to \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} {\rm CH = }\mathop {\rm N}\limits^{\rm + } {\rm HCH}_{\rm 3}$\end{document}.
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

Piperidide 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

EIektronenstoßinduzierte 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

The 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

The 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

Field 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

The 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

Les benzodioxannes‐1, 3 diversement substitués en 2,4 subissent deux coupures de ‘rétro’ Diels‐Alder: l'une classique, l'autre avec migration d'hydrogène.
Mass spectra of bicyclic terpenoid ketones
Authors: Wheeler J. W. , Shonowo O. O.
Published: May 2005

Examination of fragmentation patterns of five bicyclic ketones containing cyclopropane rings and their deuterated analogs indicates that similarity in structure gives minimal similarity in fragmentation. No generalizations can be made concerning either the loss of similar fragments or their deuterium content.
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

Le 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

A 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

The 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

Comparison 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

An 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

Napthalin‐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

Compared 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

Metastable 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

Collisional 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

La 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

In 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

Comparison 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

The 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

La 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

Cyclic 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

Les 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

70 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

Dix 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

Fragmentations 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

The 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.
On the formation of doubly charged ions in field ionization
Authors: Derrick Peter J.
Published: May 2005

The observation of doubly charged ions in field ionization with blade or wire emitters does not in itself indicate that high excitation energies (≥ 17 eV) are accessible through gas phase ionization with such emitters.
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

The 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

Functional 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

Chemical 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

The 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

Eine 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

The 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

Fluorination 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

The 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.
Fragmentation paths ofO‐ andS‐phenylN‐phenylbenzohydrazonates, and the isomericN,N‐diphenylbenzohydrazides upon electron impact
Authors: Wolkoff Peder
Published: May 2005

The 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

The 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

Fragments 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

The 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

The 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

Les 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

Ion 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

The 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

Fragmentation 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

Upon 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

Les 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

The 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

Diagnostic 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

The 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

The 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

Les 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

An 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

Ion 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

Complete 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

Les 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.