bluuebunny/crossref_metadata_2025 huggingface dataset:
Observations on the mass spectrometry of monensin and related compounds
Authors: Chamberlin J. W. , Agtarap A.
Published: May 2005

Monensin and nigericin are structurally related compounds belonging to a family of biologically active, polycylic, monocarboxylic acids produced by Streptomyces. Partial interpretation of their mass spectra has been achieved with the aid of high resolution data and by correlation with spectra of derivatives. These results have been applied to structure elucidation of several minor factors produced along with monensin. An interesting aspect of the mass spectrometry of these compounds is that their alkali‐metal salts are sufficiently volatile to yield mass spectra. Fragmentation of the salts is markedly different from that of the free acids and their derivatives. A scheme is proposed to account for the formation of a number of fragment ions which contain the metal atom.
The mass spectra of meliacins and related compounds—II: Meliacins lacking the ring d epoxide function
Authors: Loudon A. G. , Powell J. W.
Published: May 2005

The mass spectra of some 14,15‐deoxymeliacins are reported and discussed in relation to the previously published fragmentation patterns of the epoxymeliacins. The fragmentation patterns of a few compounds with structures closely related to those proposed for the principal ions in the spectra of the epoxymeliacins are also examined.
Mass spectrometry of piperidine nitroxides—A class of stable free radicals
Authors: Morrison A. , Davies A. P.
Published: May 2005

The 2,2,6,6‐tetramethylpiperidine nitroxides constitute a family of stable free radicals with electronic structures similar to that of nitric oxide. Ionization of the molecules by electron bombardment does not lead to the formation of a radical‐ion, as is the case with even‐electron neutral molecules, but instead yields either a biradical or an even‐electron molecular ion.

The fragmentations of the ions arising from this ionization are described in detail. Accurate mass measurements on most ions (element mapping) and deuterium labelling, where appropriate, have been used to assist in the interpretation of the mass spectra. The observed elimination of nitric oxide from the molecular ions has photochemical analogies.
The electron‐impact‐induced fragmentation of 1,2,3‐benzotriazoles and some related compounds
Authors: Lawrence R. , Waight E. S.
Published: May 2005

The mass spectra of 1,2,3‐benzotriazole and some derivatives with substituents at the 1‐position and in the benzenering have been examined. The loss of N2from the molecularion is characteristic; loss of N2 plus the 1‐substituent is also common. Structures are proposed for these fragment ions. The relative ease of loss of N2, NO and NS from the molecular ions of benzotriazole, 2,1,3‐benzodiazole, 1,2,3‐ and 2,1,3‐benzothiadiazoles is compared.
Fragmentations de Molecules Aliphatiques Bifonctionnelles: Methoxyesters
Authors: Greff Marcel , Wolff Robert E. , Draffan G. H. , McCloskey James A.
Published: May 2005

Certaines des fragmentations des méthoxyesters aliphatiques à longue chaíne nécessitent l'interation des deux fonctions: les deux éliminations d'alcool que subit l'ion par rupture en α de la fanction éther et comprenant le groupe ester, sont trés spécifiques: elles mettent en cause un atome d'hydrogéne en position adjacente au carbone qui porte le groupe méthoxyle.
The application of mass spectrometry to a quantitative characterisation of the electronic and steric effects in organic compounds—I: The transmission of substituent influence through the chain of conjugated double bonds
Authors: Zolotarev B. M. , Yanovskaya L. A. , Umirzakov B. , Chizhov O. S. , Kucherov V. F.
Published: May 2005

The mass spectra of polyenic compounds of the type RC6H4(CH=CH)nCOPh, n=1, R=H,p‐NMe2,p‐OH,p‐OMe,p‐Cl,p‐Br,p‐NO2,m‐NO2; n=2, R=H, p‐NMe2, p‐OMe,p‐Cl,p‐Br, p‐NO2; n = 3, R = H, p‐OMe,p‐Cl, p‐Br,p‐No2 have been measured. The ratio of the intensities of the common ion PhCO (m/e 105) to the intensities of the molecular ions for these series is correlated with the Hammett‐Brown equation with reaction constants p = 0.73 (when n = 1), 0.25 (when n =2), 0.11 (when n = 3). The transmission coefficients were calculated as π'=0.72,0.25 and 0.11 respectively [assuming p=1.01 for benzophenone series‐see M. M. Bursey and F. W. McLafferty, J. Am. Chem. Soc. 89, 1 (1967)]. The contributions of the inductive mesomeric direct polar conjugation and non‐additive interaction were calculated in accordance with the equation log Z/Z0= . It was found that the inductive influence as well as the mesomeric influence of substituents decreases rapidly with the increase in the number of double bonds in the chain. The direct polar effect has a very small value in all series for all substituents with the exeption of NMe2. Non‐additive interaction effects are large. They probably express the general influence of RC6H4(CH=CH)n on COPh.
Mass spectra of photoaddition products from methyl‐substituted maleic anhydrides and thiophen derivatives
Authors: Flores S. E. , Vélez M. , Rivas C.
Published: May 2005

The mass spectra of 1,2‐cycloaddition products obtained from the benzophenone photosensitized irradiation of 2,3‐dimethyl maleic and citraconic anhydride in several thiophen derivatives are prsented and discussed.
Rearrangements in the electron‐impact induced fragmentation of some β‐aroyl‐α‐methylpropionic acids
Authors: Buurmans H. M. A. , Van de Graaf B. , Kieboom A. P. G.
Published: May 2005

A complex rearrangement on electron‐impact for β‐aroyl‐α‐methylpropionic acids, involving both hydrogen and hydroxy migration followed by loss of carbon monoxide and allyl radical, is described and discussed. The rearrangement process, resulting in an ion [ArCOOH2]+, is favoured by electron‐withdrawing substituents in the aromatic ring.
The mass spectra of 1,2,4‐triazines and related compounds
Authors: Palmer M. H. , Preston P. N. , Stevens M. F. G.
Published: May 2005

The mass spectra of monocyclic 1,2,4‐triazines and 1,2,4‐triazines fused to a pyrazole ring through a bridgehead nitrogen have been investigated: fragmentation pathways were elucidated by the use of metastable ions and high resolution mass measurements. The spectra of the monocyclic 1,2,4‐triazines indicate that loss of nitrogen from the molecular ions is a relatively unimportant feature. The decomposition modes of the bicyclic pyrazolo[3,2‐c]‐as‐triazines are sensitive to the nature of the substituent in the triazine ring.
Substituent effects on the mass spectra of substituted phenyl acetates
Authors: Gamble A. A. , Gilbert J. R. , Tillett J. G.
Published: May 2005

The mass spectra of a series of meta‐ and para‐substituted phenyl acetates have been examined. Substituent effects have been correlated with Δ (AP‐IP) values and by using the Harrison and Chin approach. The bond‐cleavage and rearrangement reactions of phenyl accetates are compared with the corresponding reactions of acetanilides and the differences attributed to the degree of transmission of polar effects in the two systems.
Mass spectra of some N‐amino compounds
Authors: Gillis R. G.
Published: May 2005

N‐amino compounds on electron‐impact commonly lose NH from the molecular ion, and frequently lose N, NH2 and NH3. This behaviour contrasts with C‐amino compounds which mainly lose HCN and H2CN. The mass spectra of eight N‐amino compounds are recorded and discussed, together with some data from literature sources.
Comparative studies on photo‐ionization and electron‐impact ionization of peptide derivatives
Authors: Orlov V. M. , Varshavsky Ya. M. , Kiryushkin A. A.
Published: May 2005

Photo‐ionization (PI) mass spectrometry performed with a monochromatic photon beam was applied to a series of peptide derivatives. PI mass spectra of ten N‐acylpeptide methyl esters containing two to four residues of glycine, alanine, valine, leucine, proline, tryptophan, tyrosine, phenylalanine, methionine, carboxymethylcysteine, lysine and ornithine were studied. Comparative analysis of PI (10.2 eV) and electron‐impact ionization (EI) (70 eV) mass spectra shows the total number of peaks on PI to be much less than that obtained with EI, especially in the low m/e region (< 250 to 300). At the same time the relative abundance of ‘heavy’ ions, including molecular ions, is much higher in PI. The amino acid fragmentation pattern followed by N‐acylpeptide esters in PI was found to be the same as for EI.
The ion kinetic energy and mass spectra of isomeric methyl indoles
Authors: Safe S. , Jamieson W. D. , Hutzinger O.
Published: May 2005

The mass spectra of the seven isomeric methylindoles were recorded and the [metastable ion]/[daughter ion] ratios for the reactions m/e 130 → m/e 103 and m/e 103 → m/e 77 have been obtained. The ratios indicate that the decomposing [M — 1] ions (m/e 130) from the 4, 5, 6 and 7 isomers are energetically similar as are the [M — 1] ions from the 2 and 3 isomers. The results observed for the m/e → 103 m/e 77 reaction showed that the decomposing m/e 103 ions from the 2, 3, 4, 5, 6 and 7 isomers all have the same energy distribution. N‐Methylindole gave ratios which were similar to the 4 to 7 isomers at 70eV but different at 20 eV. The ion kinetic energy (IKE) spectra of all the isomeric methylindoles were also obtained and the results compared with the data obtained from the [metastable ion]/[daughter ion] approach. The results from the IKE spectra indicated that the energy distributions of the [M — 1] and [(M — 1) — HCN] ions from 1‐methylindole and the [(M — 1) — HCN] ions from 2‐methylindole could readily be distinguished from other isomers whose [metastable ion]/[daughter ion] ratios were similar. Thus by using both techniques certain ambiguities can be resolved.
Metastable transitions in the mass spectra of methyl and phenylthiohydantoin derivatives of amino acids
Authors: Sun T. , Lovins R. E.
Published: May 2005

The mass spectra of a number of methyl‐ and phenylthiohydantoin amino acid derivatives have been obtained. The major metastable transitions occurring in the mass spectra of these derivatives have been identified and measured. The major fragmentation pathways associated with the metastable transitions have been outlined and are discussed for each group of compounds. Inspection of the metastable data has shown that there is at least one unique metastable transition occurring for each thiohydantoin derivative which may be used to uniquely identify that derivative in the presence of a mixture of thiohydantoin derivatives obtained from the Edman degradation of a peptide or protein. The use of metastable ions to uniquely identify thiohydantoin derivatives in mixtures has proven useful in the identification of the MTH and PTH derivatives of glycine whose molecular ions are not unique and for resolving such ambiguities as occur for example in the mixture of leucine and isoleucine.
High resolution mass spectrometry. Bufadienolides I
Authors: Brown Peter , Kamano Yoshiaki , Pettit George R.
Published: May 2005

Complete low resolution mass spectra and some high resolution data are presented and discussed for a series of naturally occurring 14β‐hydroxy bufadienolides (toad venoms) and their derivatives, but excluding compounds with a 14β,15β‐epoxy group. The bufadienolides employed were bufalin, bufotalin, gamabufotalin, telocinobufagin, arenobufagin, 3β‐acetoxybufotalien, 3β‐acetoxyhellebrigenin, 3β‐acetoxybufalin, 3‐ketobufalin, 14‐anhydrobufalin, 3β‐acetoxy‐15‐ketobufalin and 15α‐hydroxybufalin. The relatively unsaturated 2‐pyrone functionality at C‐17β has been used as an integral label to distinguish (from elemental composition data) ions containing it, from those coming from other parts of the molecule that do not. Structural ‘ion types’ are proposed to interpret this spectral data, and the prognosis for structure elucidation of other bufadienolides by high resolution mass spectrometry appears good.
Variation of fragmentation with ring size in cyclic α‐amino acids
Authors: Coulter A. W. , Fenselau C. C.
Published: May 2005

High resolution mass measurements, defocused metastable ion detection and deuterium labeling experiments have been employed in an investigation of the electron‐impact induced decomposition of a series of carbocyclic amino acids, which varied in ring size from three to eight carbon atoms. About 50 per cent of the total ion current is carried by [M  COOH]+ ions in the spectra obtained from compounds with five to eight carbon atoms in the ring. This is analogous to the fragmentation of the open chain naturally occurring amino acids. The behavior of the compounds with the two smallest rings is anomalous, reflecting to a larger extent the influence of the ring itself. Special attention has been given the loss of H2O and NH4 from ionized species of 1‐aminocyclopropanecarboxylic acid.
The effect of stereochemistry on the mass spectra of the bis(trimethyl‐silyl) esters of maleic and fumaric acids
Authors: Large R. , Saunders K. J.
Published: May 2005

The mass spectra of the bis(trimethylsilyl) esters of maleic and fumaric acids provide a simple and particularly striking example of the influence of stereochemistry on the electron‐impact‐induced fragmentation of organic molecules. The results provide evidence for the structural significance of the m/e 147 ion, which is considerably more intense in the maleate spectrum than in the fumurate spectrum.
Intramolecular amide‐amide interaction in the mass spectra of some geometric isomers
Authors: Holmes J. L.
Published: May 2005

The mass spectra of maleic, fumaric, citraconic, mesaconic and itaconic diamides have been studied. In the molecular ions of the cis isomers, amide‐amide interaction does take place, analogous to but less pronounced than, the carboxyl‐carboxyl interaction of the corresponding acids.

In spite of the weaker interaction a prominent loss of CONH from the molecular ion of a diamide would be strong evidence in support of a cis or similarly rigid geometrical arrangement of the amide groups. The mass spectra of maleic and fumaric nitriles are also reported.
Specific and random processes in the fragmentation of cyclohexanol
Authors: Holmes J. L. , McGillivray D. , Rye R. T. B.
Published: May 2005

The mass spectra of cyclohexanol and eleven deuterated analogues have been studied. Detailed mechanisms, consistent with peak intensity and defocused metastable abundance data, have been proposed for the loss of water from the molecular ion and for the subsequent loss of a methyl radical. The importance of specific eliminations and the absence of any processes involving complete hydrogen atom scrambling in these fragmentations has been demonstrated. Scrambling has also been shown to be absent in the formation of the base peak m/e 57, the [C3H5O]+ ion.
Elektronenstossinduzierte Fragmentierung von Acetylenverbindungen—VI: Struktur und Bildungsenthalpie der Ionen [C11H9]+ und [C9H7]+
Authors: Schwarz Helmut , Bohlmann Ferdinand
Published: May 2005

Die Erscheinungspotentiale für [C11H9]+ aus 1‐bzw, 2‐(Chlormethyl)‐Naphthalin und 1‐Chlor‐phenyl‐(5)‐penten‐(2)‐in‐(4) und für [C9H7]+ aus Inden, Phenylpropin und Phenyl‐(5)‐penten‐(2)‐in‐(4)ol‐(1) werden mit thermochemischen Daten korreliert, um die Bildungsenthalpien der genannten Fragment‐Ionen zu erhalten. Ein Vergleich dieser Bildungsenthalpien mit den Enthapiewerten hypothetischer Modellstrukturen ergibt, dass das IOn [C11H9]+ wahrscheinlich am besten als Benztropylium‐Ion und das Ion [C11H9]+ enweder als ein Äthinyl‐Tropylium‐Ion oder als ein Phenylcyclopropenyl‐Kation wiedergegeben wird. Offenkettige Strukturen Können in allen untersuchten Fällen ausgeeschlossen werden.
Ion‐molecule reactions of a metalloporphyrin with common perfluoro mass standards
Authors: Rosenthal David , Hopf Frederick R. , Whitten David G. , Bursey Maurice M.
Published: May 2005

The ruthenium porphyrin carbonyl (I) reacts with perfluorokerosene and perfluorotributylamine to give ions of the type [M – CO + CnF2n], n = 1 to 4.
Effect of distal positional isomerism on peptide fragmentation. A comparison of dimethylaminobenzylidene and benzoyl derivatives
Authors: Haralambidou E. , Day R. A.
Published: May 2005

The electron‐impact‐induced fragmentation patterns of the positional isomers of N,N‐dimethylaminobenzaldehyde and their Schiff base derivatives of valylisoleucylalanine and leucyltryptophylleucine ethyl esters were determined. The electron‐impact‐induced fragmentation patterns of the positional isomers of N‐hydroxysuccinimido N′,N′‐dimethylaminobenzoate and of the corresponding N,N‐dimethylaminobenzoyl ethyl esters of the above peptides were compared. Significant differences among the isomers were noted between the Schiff base set and the substituted benzoyl set. The N‐blocking groups m‐ and p‐dimethylaminobenzylidene and m‐dimethylaminobenzoyl gave the most useful sets of sequence peaks of relatively uniform intensity with intense molecular ions. Positional isomerism was found to influence cleavage of both proximal and distal bonds.
A study of the fragmentation of cyclopentane‐1,3‐diols and of cyclopentane‐1,2,4‐triols
Authors: Singy Gérard A. , Buchs A.
Published: May 2005

The mass spectra of the two cyclopentane‐1,3‐diol and of the three cyclopentane‐1,2,4‐triol stereoisomers have been studied. Extensive deuterium labelling allows the detection of complex processes, especially for the elimination of water from the [M – H2OO]+· and [M]+· ions.
Fragmentation of 13C Labelled methylcyclohexanes under electron‐impact
Authors: Amir‐Ebrahimi Valia , Gault Franc̨ois G.
Published: May 2005

The methylcyclohexanes labelled with carbon‐13 in the five possible positions have been synthesised and their mass spectra recorded. By comparison of these spectra with those of the corresponding deuterated molecules, it was possible to accurately determine the nature and the contribution of the various fragmentation paths. More than ninety percent of the fragment ions formed from methylcyclohexane result from the rupture, at one stage or another, of one of the CC bonds attached to the tertiary carbon atoms. Besides the elemination of a polymethylene group from the ring, in either one or two steps, the two major fragmentation pathways involve the prior formation of a cyclohexyl or a cyclopentyl ion.
The high pressure nitric oxide mass spectra of aldehydes
Authors: Jardine Ian , Fenselau Catherine
Published: May 2005

The high pressure (0.5 Torr) nitric oxide mass spectra of some aldehydes, obtained using a 10% mixture of NO in N2, are reported. The 10% NO/N2 spectra of the monodeuterated analogs of some of them are compared to the electron‐impact and methane chemical ionization spectra, especially with reference to the process of hydride abstraction by nitrosonium ions.
Stossaktivierungsspektren von 2‐Alkoxybenzoesäuremethylestern
Authors: Levsen Karsten , Schwarz Helmut
Published: May 2005

Die CA‐Spektren der [M – Alken]+·‐ und [M – Alkyl]+‐Ionen aus mehreren 2‐Alkoxybenzoesäremethylestern und zwei2H‐markierten 2‐Äthoxybenzoesäuremethylestern werden diskutiert. Es wird belegt, daß die nach 10−5s durch Stoßaktivierung zerfallenden [M – Alken]+·‐Ionen die Struktur eines ionisierten Salicylsäuremethylesters besitzen. Ferner wird nachgewiesen, daß auch nach 10−5skeineEquilibrierung zu einem strukturidentischen Ion eingetreten ist. Anhand der CA‐Spektren der markierten Derivate werden verschiedene Ionenstrukturen für die durch Stoßaktivierung erzeugten Tochter‐Ionen diskutiert.
Hydrogen shifts in the decomposition of branched chain alkane radical cations
Authors: Howe Ian
Published: May 2005

Heat of formation data are consistent with formation of the t‐butyl ion when C3H7 is eliminated from the molecular ion of 2‐methylhexane. The 1–2 hydrogen shift that must accompany this reaction is confirmed via a deuterium isotope effect upon the low energy metastable decomposition.
Fragmentations de quelques derives thiophosphores sous l'impact electronique. I—migration de groupes phenyles et methyles dans les derives du diphenylthiophosphorane
Authors: Cauquis G. , Divisia B. , Ulrich J.
Published: May 2005

La localisation de la charge d'ionisation dans les diphénylthiophosphoranes substituspar des groupes phényle, méthyle, benzyle, méthylthiométhyle, phénacyle, amino et N‐benzylidèneé amino a permis d'élucider leurs réctions de fragmentation sous l'impact électronique. La composition atomique des divers fragments été déterminée par la mesure précise de leur masse. Ces mécanismes de fragmentation sont confirmés par la présence de nombreux pics d'ions métastables. Les principales fragmentations des composés par la présence de nombreux pics d'ions métastables. Les principales fragmentations des composés phénacyl et aminodiphénylthiophosphoranes s'expliquent par la migration importante de groupes phényles et méthyle du phosphore vers le soufre. Dans les composés benzyl, méthylthiométhyl et N‐benzylidéneamino, l'élimination d'espéces neutres très stables (respectivement le radical benzyle, le thioformaldéhyde et le benzonitrile) favorise d'autres mécanismes de fragmentation.
Die Massenspektren substituierter Succinimide
Authors: Schoch S. , Blos I. , Rüdiger W.
Published: May 2005

Die Massenspektren von Succinimid, vier monosubstituierten und zehn disubstituierten, gesättigten Succinimiden, sowie von sechs ungesättigten (Äthyliden‐substituierten) abgeleitet, die die Identifizierung unbekannter substituierter Succinimide erlauben, welche beim Abbau natürlicher Pyrrol‐Pigmente erhalten werden.
Analyse par Spectrometrie de Masse de Derives Fluores en Serie Pyrimidine et Pyrazine
Authors: Hitzke J. , Guion J.
Published: May 2005

Les dérivés flourés des trichloro‐, dichloropyrimidines et dichloropyrazines ont été synthétisés et analysés par r.m.n. 1H et 19F, associée à la chromatographie couplée avec la spectrométrie de masse. Le comportement de ces composés l'impact électronique est présenté et discurté dans ce travail. Les différences observées pour les spectres masses d'isomérs de position nous permettent de confirmer les grandes voies de dégradation proposées.
Massenspektrometrische Analyse von 2‐Alkoxy‐und 2‐Alkylmerkapto‐(1,3,2)Diox‐, Oxathi‐und Dithi‐Arsolanen
Authors: Adler Oswald , Kober Friedhelm
Published: May 2005

Die Massenspektren der Arsolane (CH2)2XY AsZR (X, Y und Z= O oder S) bei elektronenstoß‐ und Chemischer Ionisation werden verglichen und die Haupt‐Fragmentierungsreaktionen angegeben. Elektronenstoss‐Ionisation‐ und Chemische‐Ionisation‐Spektren zeigen eine Dimeerisierung der Arsolane.
Negative ions in organic mass spectrometry. II—Negative ion mass spectra of simple thio and dithio esters.
Authors: Rullkötter Jürgen , Budzikiewicz Herbert
Published: May 2005

The 70 eV negative ion mass spectra of some simple aromatic and aliphatic thio and dithio esters are discussed. A characteristic fragmentation process, a rearrangement analogous to the nitro‐nitrite conversion of aromatic nitro compounds, is observed for aromatic thio esters.
Fragmentation Sous Impact Electronique de la Pyrrolidine et D'Isoindolines N‐Nitrosees et N‐Aminees
Authors: Denhez Jean Pierre , Ricard Michègle , Dizabo Pierre , Rogic Dunja
Published: May 2005

Les spectres de masse des dérivés N‐aminés de la pyrrolidine, de l'isoindoline et de la diphényl isoindoline ont été étudiés. L'utilisation d'une résolution moyenne et du marquage au deutérium a permis de mécanismes de fragmentation.
Massenspektrometrische Untersuchungen an 1.1‐Difluorcyclopropanen
Authors: Kamel M. , Kimpenhaus  , Riepe W.
Published: May 2005

Die Massenspektren von verschiedenen substituierten 1.1‐Difluorcyclopropanen wurden aufgenommen und ihr Fragmentierungsverhalten untersucht. die Tendenzen in den Bildungswahrscheinlichkeiten der Bruchstükionen bei verschiedenen Difluorcyclopropanen lassen sich qualitativ mit bekanten empirischen Substituenteneffekten erklären.
Mass spectrometry of pyrrolo [2, 3‐ b] pyrazines and pyrazino [2, 3‐ b]indole
Authors: Clark B. A. J. , Parrick J.
Published: May 2005

The first mass spectra of pyrrolo [2, 3‐b] pyrazine and some of its derivatives and of pyrazino [2, 3‐b] indole are reported and compared with those of related compounds. Differences between the spectra of some aryl substituted derivatives are described and discussed.
Mass spectra of substances ionized by fission fragment induced desorption
Authors: Becker Otmar , Fürstenau Norbert , Knippelberg Werner , Krueger Franz R.
Published: May 2005

The mass spectra of substances of physiological and pharmaceutical interest such as steroids, alkaloids, sugars, glycosides and similar, obtained by fission fragment induced desorption as first applied by Macfarlane are presented. The behaviour of organic and inorganic salts is also discussed, including that of mixtures of salts and organic substances. Comparison is made with field desorption data, where available, and electron impact data for those substances of sufficient volatility.
Etude par Spectrométrie de Masse de Silanes et de Stannanes Aromatiques
Authors: Lageot C. , Guillemonat A.
Published: May 2005

Les spectres de masse de six composés du type Et3SiC6H4  ZRxR3−x (Z = Si et Sn, R = Et, R′ = Cl) ont été interprétés. Les résultats ne peuvent être expliqués que par une réorganisation du cycle benzénique sous une forme linéaire.
Hétérocycles des Eléments du Groupe IV. VII—Spectrométrie de Masse de Silacyclopentènes
Authors: Lageot C. , Guillemonat A.
Published: May 2005

Les spectres de masse de nouveaux silacyclopenténes ont été étudiés. Les méchanismes intervenant sont proches de ceux de la série des germacyclopenténes. Ils conduisent principalement à une rétention de la charge sur l'hétéroatome, à une migration d'hydrogéne, à la formation d'ions du type ‘silylénïd’ et à l'expulsin d'un substituant fixé sur l'hétéroatome.
The Use of two scanning modes for the analysis of metastable peaks
Authors: Lacey Michael J. , MacDonald Colin G.
Published: May 2005

Two scanning modes can be used sequentially to determine the relative abundances of a series of daughter ions formed from the same parent ion in the field free region preceding the first sector of a double focusing mass spectrometer. Hydrogen exchange reactions in the molecular ions of benzoic acid and anisole have been analysed by these procedures, and a study of diphenylmethane demonstrates that the usual procedure of single scans gives rise to peaks that might be interpreted erroneously.
Mass spectral hydrogen rearrangements of 1,1′‐bicycloalkyldiols under electron impact
Authors: Deutsch Joseph , Chriki Miriam
Published: May 2005

1,1′‐Bicycloalkyl‐2,2′‐diols (mixtures of stereoisomers) and 1,1′‐diols on electron impact give rise to strong peaks equivalent to [M‐1]+ions, corresponding to cycloalkenone fragments and obviously involving hydrogen atom migrations. Deuterium labelling and substitution techniques reveal the operation of different rearrangement mechanisms for the two series of isomeric compounds. Thus, in the 1,1′‐bicycloalkyl‐2,2′‐diols a ring hydrogen atom is involved in the rearrangement, whereas in the 1,1′‐bicycloalkyl‐1,1′‐diols (pinacols) the hydroxylic hydrogen atoms migrate.
An investigation of the mechanism of single and double hydrogen atom transfer reactions in alkyl benzoates by the ortho effect
Authors: Tajima Susumu , Azami Tadashige , Shizuka Haruo , Tsuchiya Toshikazu
Published: May 2005

Single and double hydrogen atom transfers in reactions (1) and (2) in the mass spectra of ethyl benzoate, isopropyl benzoate, and isobutyl benzoate have been investigated with reference to the ortho effect: (1) [C6H5CO2R]+⋅ → [C6H5CO2H]+⋅ (m/z 122) + (R‐H); (2) [C6H5CO2R]+⋅ → [C6H5CO2H2]+ (m/z 123) + · (R‐2H). It is demonstrated that the intermediate ion [C6H5CO2H2]+ has the protonated benzoic acid structure with the hydrogen atom on the carbonyl group.
Field desorption mass spectrometry of air sensitive transition metal complexes
Authors: McEwen C. N. , Ittel S. D.
Published: May 2005

Field desorption mass spectrometry was used to obtain molecular weight information on a variety of transition metal complexes which are air sensitive and nonvolatile. The base peak for the neutral complexes is the molecular ion and for the salt complexes is the cation.
Electron impact induced fragmentation of steroidal diketones with ‘abnormal’ stereochemistry
Authors: Patterson Donald G. , Lavanchy André , Djerassi Carl
Published: May 2005

The mass spectral fragmentations of steroidal diketones with ‘unnatural’ sterechemistry at positions 8, 9 and 14 have been examined by the use of high resolution, metastable defocusing and isotopic labeling techniques. In addition, the elucidation of fragmentation pathways was greatly facilitated by the use of the INTSUM computer program. In contrast to 14α‐11‐ones, where the McLafferty rearrangement is of minor importance in directing the fragmentation, it is suggested that the ketones in the present study, by virtue of their ring C flexibility, readily undergo the McLafferty rearrangement. If correct, this would represent a further example of available ground state conformations controlling fragmentation after electron impact.
Mass spectrometric fragmentation of the oxetanes of 3,5‐dimethylisoxazole, 2,4‐dimethylthiazole and 1‐acetylimidazole
Authors: Nakano Tatsuhiko , Mart Alfonsoín
Published: May 2005

The mass spectra of the oxetanes of 3,5‐dimethylisoxazole, 2,4‐dimethylthiazole and 1‐acetylimidazole have been studied with the aid of high resolution mass spectrometry. The spectra exhibit characteristic fragmentation patterns which are common to all these oxetanes and are classified as five processes.
Carbene elimination from ionized methanoannulenes
Authors: Wesdemiotis Ch. , Schwarz H. , Budzikiewicz H. , Vogel E.
Published: May 2005

Evidence is produced to demonstrate that loss of CH2 from methanoannulenes is a multistep process initiated by a rearrangement yielding (at least in the case of 1,6‐methano[10]annulene) the isomeric benzocycloheptenes. Loss of CF2, however, apparently is a cheletropic reaction accompanied by rearomatization, thus giving rise to the formation of the molecular ion of naphthalene in the case of 11,11‐difluoro‐1,6‐methano[10]annulene. These findings present further evidence for the parallel behaviour of the bridged annulenes regarding thermal transformations and fragmentation of the molecular ions.
Doubly charged ion mass spectra. 2—aromatic hydrocarbons
Authors: Mathur B. P. , Burgess E. M. , Bostwick D. E. , Moran T. F.
Published: May 2005

Doubly charged ion mass spectra for 15 aromatic hydrocarbons have been obtained using a Nier‐Johnson geometry, Hitachi RMU‐7L mass spectrometer operating at 1.6 kV accelerating voltage. The doubly charged ion spectra have features that are characteristic of the individual compounds. Unsaturated aromatic molecules show intense molecular ions in contrast to saturated, substituted or heteroatom compounds which undergo extensive fragmentation. Ionization energies for forming doubly charged molecular ions and appearance energies for the prominent doubly charged fragment ions have been measured. Calculations of the SCF energies and structures of various doubly charged ions have been carried out. Measured and calculated ionization/appearance energies are in reasonable accord and lend support to the suggested ion structures.
Mass spectrometry of halo‐pyrazolium salts
Authors: Larsen Elfinn , Egsgaard Helge , Pande Umesh C. , Begtrup Mikael
Published: May 2005

Eleven halogen substituted 1‐methyl‐2‐phenylpyrazolium bromides or chlorides were investigated by field desorption, field ionization, and electron impact mass spectrometry. Dealkylation was found to be the predominant thermal decomposition. An exchange between covalent and ionic halogen prior to dealkylation was observed and is discussed in detail.
Ammonia chemical ionization mass spectra of esters and amides of oxyacids of phosphorus
Authors: Cload P. A. , Hutchinson D. W.
Published: May 2005

Chemical ionization mass spectrometry using ammonia as the reagent gas has been carried out with esters and amides of a variety of oxyacids of phosphorus (phosphates, phosphonates, phosphites and phosphoramidates). In all cases, the protonated molecular ion is a major species in the spectrum and the percentage of the total ion current carried by these protonated molecular ions is always considerably greater than that carried by the molecular ions in the corresponding electron impact mass spectra. In the chemical ionization mass spectra only limited fragmentation of the protonated molecular ion occurs from which useful information on the structure of phosphorus derivatives may be inferred.
The mass spectra of some benzyl esters and thioethers
Authors: Corina D. L. , Wright J. N. , Ballard K. E.
Published: May 2005

The electron impact mass spectra of a large number of benzyl esters of carboxylic acids are reported. The fragmentation behaviour is discussed and the esters are divided into groups according to structure and fragmentation. For most esters benzylic cleavage with H transfer competes with simple cleavage.
Electron impact mass spectrometry of some macrocyclic tetraesters
Authors: Traldi Pietro , Vettori Umberto , Podda Gianni , Maccioni Antonio , Corda Luciana
Published: May 2005

The electron impact mass spectrometric behaviour of five recently synthesized macrocyclic tetraesters is described and discussed in detail with the aid of exact mass measurements, linked scans and collisional activation experiments. The unusual primary loss of a dehydrogenated catecholic radical leads to a very stable cation which is the precursor of the most of the fragmentation products.
On the electron impact induced hydroxyl loss from o‐nitrostyrene
Authors: Depke Gisbert , Klose Walter , Schwarz Helmut , Blum Wolfgang , Richter Wilhelm J.
Published: May 2005

Unimolecular hydroxyl (OD˙) loss from regio‐ and stereo‐specifically labelled o‐nitrostyrenes 1a, 1c and 1d results in the formation of an ion which upon collisional activation gives identical mass spectra. Suggestions are made which aim at explaining: (i) the loss of stereochemical integrity of the diastereotopic methylene hydrogens in the course of hydroxyl elimination; and (ii) to account for the collision induced losses of CO and HNC from the [M—hydroxyl]+ ion.
Low energy, low temperature mass spectra: I—selected derivatives of n‐octane
Authors: Bowen Richard D. , Maccoll Allan
Published: May 2005

The low voltage, low temperature mass spectra of a series of octane derivatives n‐C8H17X with X=CH3, OH, OCH3, NH2, NHCH3, N(CH3)2, CO2H, CO2CH3, CO2C2H5, CHO and COCH3 are reported and discussed, using arguments involving thermochemistry where appropriate. The structures of these compounds can be uniquely assigned on the basis of such mass spectra.
Photodissociation of alkane ions in the source of a mass spectrometer: A potential analytical technique
Authors: Kim M. S. , Morgan T. G. , Kingston E. E. , Harris F. M.
Published: May 2005

Alkane ions generated by 70 eV electron ionization are irradiated in the source of a reversed geometry, double focusing mass spectrometer by 2.41 eV (514.5 nm) photons from an argon ion laser. The ions in the chamber are extracted, accelerated to 6 keV and spectra obtained by scanning the field of the magnet. The laser light is mechanically chopped and changes in the peak heights of the mass spectra resulting from photodissociation of ions in the ion chamber are recorded using a phase‐sensitive detector to give what are referred to as photoinduced spectra. The peaks for the molecular ions of alkanes are large relative to other peaks in the photoinduced spectra, a situation which contrasts with that for the mass spectra. The relative photodissociation cross‐sections of several alkanes, C6C10, C12 and C16, have been measured and those of linear and branched [C10H22]+˙ ions are compared. Some of the characteristic features of the photoinduced spectra make the identification of the sample simpler than from mass spectra. The method is applied to the analysis of some alkane mixtures and its potential in analytical work discussed.
Kinetic energy release during CO loss by rearrangement of α‐benzoylcarbenium ions
Authors: Grützmacher Hans‐Friedrich , Dommröse Anne‐Marie
Published: May 2005

Primary α‐benzoylcarbenium ions (a) and tertiary α‐benzoyldimethylcarbenium ions (b) are obtained by chemical ionization of ω‐hydroxyacetophenone and its dimethyl derivative, respectively. Both α‐acylcarbenium ions decompose by a rearrangement reaction and subsequent loss of a CO molecule. The kinetic energy released during this process by metastable ions a and b has been determined under different experimental conditions. The kinetic energy released during the CO elimination from the tertiary α‐benzoyldimethylcarbenium ions b is independent of the experimental conditions and gives rise to dish‐topped peaks with T50=440±20 meV in the MIKE spectra of b. In contrast to this the kinetic energy releases and the peak‐shapes in the MIKE spectra of the primary α‐benzoylcarbenium ion a varies with the experimental conditions. The mechanism of this rearrangement reaction is discussed, and it is shown by a MNDO calculation of the heats of formation of the relevant ions that the different characteristics of the kinetic energy release during the fragmentation of primary and tertiary carbenium ions can be attributed to different types of reaction energy profiles.
Sequence analysis for an unknown peptide by molecular secondary ion mass spectrometry
Authors: Seki Setsuko , Kambara Hideki , Naoki Hideo
Published: May 2005

Positive and negative molecular secondary ion as well as metastable ion mass spectra for various peptides are investigated to clarify their fragmentation regularity. The fragmentation regularity is derived by considering all the possible bond cleavages at the peptide bond or at the adjacent bonds. It is demonstrated that the amino acid sequence for an unknown peptide can be determined by interpreting the positive and negative secondary ion and metastable ion mass spectra using this fragmentation regularity.
Characterization of five [C4H7O]+ Ion structures. Fragmentation of the 2‐pentanone molecular ion
Authors: Laderoute Keith R. , Zwinselman Jan J. , Harrison Alex. G.
Published: May 2005

The [C4H70]+ ions [CH2CHC(OH)CH3]+ (1), [CH3CHCHC(OH)H]+ (2), [CH2C(CH3)C(OH)H]+ (3), [Ch3CH2CH2CO]+ (4) and [(CH3)2CHCO]+ (5) have been characterized by their collision‐induced dissociation (CID) mass spectra and charge stripping mass spectra. The ions 1–3 were prepared by gas phase protonation of the relevant carbonyl compounds while 4 and 5 were prepared by dissociative electron impact ionization of the appropriate carbonyl compounds. Only 2 and 3 give similar spectra and are difficult to distinguish from each other; the remaining ions can be readily characterized by either their CID mass spectra or their charge stripping mass spectra. The 2‐pentanone molecular ion fragments by loss of the C(1) methyl and the C(5) methyl in the ratio 60:40 for metastable ions; at higher internal energies loss of the C(1) methyl becomes more favoured. Metastable ion characteristics, CID mass spectra and charge stripping mass spectra all show that loss of the C(1) methyl leads to formation of the acyl ion 4, while loss of the C(5) methyl leads to formation of protonated vinyl methyl ketone (1). These results are in agreement with the previously proposed potential energy diagram for the [C5H10O]+˙ system.
A mass spectrometric study of the adducts of acetylacetone and cyanogen (Traube's isomers)
Authors: Basato M. , Corain B. , Veronese A. C. , Daolio S. , Pelli B. , Traldi P.
Published: May 2005

The mass spectrometric behaviour of the title compounds has been studied in detail with the aid of deuterium labelling, exact mass measurements, linked scans and collisionally activated decomposition experiments. An interesting conversion reaction of the cyanoenaminedione isomer into the corresponding furane derivative, which appears complete in the second field free region, has been thoroughly investigated.
Stereospecific hydride transfer under NCI/OH− conditions. 2—Origins of the C2H4O elimination from stereoisomeric alkoxyketal derivatives1
Authors: Tabet Jean‐Claude , Hanna Issam , Fetizon Marcel
Published: May 2005

A new stereospecific intramolecular hydride transfer, induced by an alkoxide, has been demonstrated under NCI/OH− conditions using unimolecular and collision‐induced decomposition spectra.
Elemental compositions from daughter ion spectra of m1+ and [m1 + 1]+: Some applications of the method
Authors: Bozorgzadeh M. H. , Lapp R. L. , Gross M. L.
Published: May 2005

The elemental compositions of ions can be determined in tandem mass spectrometry by comparing the daughter ion spectra of the m1+ and [m1 + 1]+ ions. The method is demonstrated for mass‐analyzed ion kinetic energy spectra but is applicable to all types of daughter ion spectra, including complex collisionally activated dissociation spectra. In this work, the method is applied to compounds that produce daughter ions of known elemental compositions, and the errors and limitations are evaluated. Following that test, the procedure is applied to a compound that may produce daughters of more than one possible elemental composition. The method is sometimes useful even if the formula of the parent is not known; that is, the formulae of unknown parent and daughter ions may be found. Locating a specific atom in an isotopically labeled molecule is another capability of the method. The basic equation of the method was generalized and incorporated into a computer program for performing the calculations.
Mass spectra of aliphatic dicarboxylic acids and their dimethyl esters: Cyclic structures for the [M − H2O]+˙ ions from the diacids and [M − MeOH]+˙ ions from the dimethyl esters
Authors: Harrison Alex G. , Kallury R. Krishna Mohan Rao , Krull Ulrich J. , Thompson Michael
Published: May 2005

Methyl 2‐oxocycIoalkane carboxylate structures are proposed lor the [M − MeOH]+˙ ions from dimethyl adipate, pimelate, suberate and azelate. This proposal is based on a comparison of the metastable ion mass spectra and the kinetic energy releases for the major fragmentation reaction of these species with the same data for the molecular ions of authentic cyclic β‐keto esters. The mass spectra of α,α,α′,α′‐d4‐pimelic acid and its dimethyl ester indicate that the α‐hydrogens are involved only to a minor extent in the formation of [M − ROH]+˙ and [M − 2ROH]+˙ ions, while these α‐hydrogens are involved almost exclusively in the loss of ROH from the [M − RO˙]+ ions (R = H or CH3). The molecules XCO(CH2)7COOMe (X = OH, Cl) form abundant ions in their mass spectra with the same structure as the [M − 2MeOH]+˙ ions from dimethyl azelate.
Electron impact ionization of ethylene–methanol heteroclusters: Stable configurations and mechanisms in intracluster ion–molecule reactions
Authors: Choi Chang Ju , Jung Kwang Woo , Kang Wee Kyung , Youn Dae Young , Jung Kyung‐Hoon , Kim Dongho
Published: May 2005

Reactions that proceed within mixed ethylene–methanol cluster ions were studied using an electron impact time‐of‐flight mass spectrometer. The ion abundance ratio, [(C2H4)n(CH3OH)mH+]/[(C2H4)n(CH3OH)m+], shows a propensity to increase as the ethylene/methanol mixing ratio increases, indicating that the proton is preferentially bound to a methanol molecule in the heterocluster ions. The results from isotope‐labelling experiments indicate that the effective formation of a protonated heterocluster is responsible for ethylene molecules in the clusters. The observed (C2H4)n(CH3OH)m+ and (C2H4)n(CH3OH)m–1CH3O+ ions are interpreted as a consequence of the ion–neutral complex and intracluster ion–molecule reaction, respectively. Experimental evidence for the stable configurations of heterocluster species is found from the distinct abundance distributions of these ions and also from the observation of fragment peaks in the mass spectra. Investigations on the relative cluster ion distribution under various conditions suggest that (C2H4)n(CH3OH)mH+ ions with n + m ≤ 3 have particularly stable structures. The result is understood on the basis of ion–molecule condensation reactions, leading to the formation of fragment ions, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_2=\!=\mathop {\rm O}\limits^ + {\rm CH}_3 $\end{document} and (CH3OH)H3O+, and the effective stabilization by a polar molecule. The reaction energies of proposed mechanisms are presented for (C2H4)n(CH3OH)mH+(n + m ≤ 3) using semi‐empirical molecular orbital calculations.
Negative‐ and positive‐ion chemical ionization mass spectra of aromatic amines: Surface‐assisted reactions involving oxygen
Authors: Stemmler Elizabeth A. , Buchanan Michelle V.
Published: May 2005

The O2–N2 and O2–Ar negative‐ion chemical ionization mass spectra of aromatic amines show a series of unusual ions dominated by an addition appearing at [M + 14]−˙. Other ions are observed at [M – 12]−˙, [M + 5]−˙, [M + 12]−˙, [M + 28]−˙ and [M + 30]−˙. Ion formation was studied using a quadrupole instrument equipped with a conventional chemical ionization source and a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. These studies, which included the examination of ion chromatograms, measurement of positive‐ion chemical ionization mass spectra, variation of ion source temperature and pressure and experiments with 18O2, indicate that the [M + 14]−˙ ion is formed by the electron‐capture ionization of analytes altered by surfaceassisted reactions involving oxygen. This conversion is also observed under low‐pressure conditions following source pretreatment with O2. Experiments with [15N]aniline, [2,3,4,5,6‐2H5] aniline and [13C6]aniline show that the [M + 14]−˙ ion corresponds to [M + O − 2H]−˙, resulting from conversion of the amino group to a nitroso group. Additional ions in the spectra of aromatic amines also result from surface‐assisted oxidation reactions, including oxidation of the amino group to a nitro group, oxidation and cleavage of the aromatic ring and, at higher analyte concentrations, intermolecular oxidation reactions.
Differentiation among some isomeric di‐ and trifunctional aromatic amines by plasma desorption mass spectrometry
Authors: Bouchonnet Stéphane , Hoppilliard Yannik , Maret Agnès
Published: May 2005

Isomeric di‐ and trifunctional aromatic amines are easily differentiated on the basis of their plasma desorption (PD) mass spectra. Six series of aromatic amines were studied in the positive‐ion mode. In each series, the differences observed in the PD mass spectra allow each isomer to be characterized. In the formation of molecular ions, these differences proceed from the competition between electron impact ionization and protonation. Several chemoselective or regioselective reactions such as hydrogenation, hydration, dimerization and some fragmentations also allow isomeric aromatic amines to be differentiated.
Stress measurement in graphite/epoxy uniaxial composites by X‐rays
Authors: Barrett Charles S. , Predecki Paul
Published: May 2005

X‐rays can be used to measure residual as well as applied stresses in polymers and reinforced polymeric composites by diffracting from filler particles that are embedded before curing. We have investigated various fillers that exhibit suitable stress‐induced shifts of diffraction angle when embedded in uniaxial graphite fiber/epoxy composites. Stresses in the particles determined by X‐rays are proportional to the corresponding composite stresses, in agreement with the model of H. T. Hahn. Results indicate that the stress sensitivity (change in X‐ray strain per MPa applied to the composite) increases in the order W, CdO, Ni, Ag, Nb, Al. The elastic range terminates at a yield point beyond which the stress sensitivity is markedly reduced for metallic fillers, but no such yield point has appeared with CdO particles. Oppositely directed particle strains are seen after unloading from stress levels that have exceeded the yield point. Theoretical predictions for these findings are discussed. Residual stresses in the particles were determined after curing and storage under ambient conditions. In the fiber direction the residual stresses were always found to be positive and larger than the principal stresses orthogonal to these.