bluuebunny/crossref_metadata_2025 huggingface dataset:
Fragmentation behaviour and ring expansion of 1‐methylimidazole and 1‐methylpyrazole upon electron‐impact
Authors: van Thuijl J. , Klebe K. J. , van Houte J. J.
Published: May 2005

The relative losses of unlabelled vs. labelled HCN from the [M]+˙ and [M – 1]+ ions of a number of specifically labelled 1‐methylimidazoles (I) and 1‐methylpyrazoles (II) have been determined. Hydrogen randomisation in the molecular ions prior to fragmentation is insignificant. Expulsion of HCN follows two distinct pathways: elimination involving positions 2 and 3 (predominant in I) and elimination involving the methyl group and the nitrogen atom at position 1 (predominant in II). The molecular ions eject H˙ from the methyl groups to a high degree of specificity. In both cases some contribution by position 5 is observed. The resultant [M – 1]+ ions exhibit extensive, but incomplete hydrogen randomisation. Loss of HCN from these ions is consistent with intermediacy of ring‐expanded ions, but notably in II a proportion of the HCN is generated from the group. A mechanism for this observation is presented.
Echtzeit‐Datenerfassungssystem mit minimaler hardware für den Einsatz in der Routine‐Massenspektrometrie im organischen Laboratorium
Authors: Schwarzenbach R. , Clerc J. T.
Published: May 2005

Zusammenfassung‐Ein Echtzeit‐Datenerfassungssystem für den Einsatz bei der Routineanwendung der niedring auflösenden Massenspektrometrie im organischen Laboratiorium wird beschrieben. Das Datensystem ist für die Lösung jener Probleme optimiert, die in der Routine am häufigsten auftreten. Die Verwendung aufwendiger Programme erlaubt die Realisierung eines vielseitigen, benützerfreundichen Systems mit minimaler Hardware‐Konfiguration. Datenfluss und logische Struktur der Programme werden eingehend beschrieben.
Skelettumlagerungen unter Elektronenbeschuß–VII: Alkyl‐N‐Phenylcarbamate
Authors: Wünsche C.
Published: May 2005

Die Massenspektren einfacher Alkyl‐N‐Phenylcarbamate werden beschrieben, Die bekannte Skelettumlagerung, die beim Aethyl‐N‐phenylcarbamat zu einem [C6H5NHCH2]+‐Ion2 führt, wird auch bei den Methyl‐, Propyl‐ und Butylhomologen beobachtet. Anhand deuterium‐ und 13C‐markierter Verbindungen wird gezeigt, daß der von Lewis 1964 formulierte Umlagerungs‐ mechanismus die tatsächlichen Verhältnisse nicht richtig wiederzugeben vermag.
Ion structural studies by ion kinetic energy spectrometry: [C7H7]+, [C7H8]+˙, [C7H7OCH3]+˙
Authors: Cooks R. G. , Beynon J. H. , Bertrand M. , Hoffman M. K.
Published: May 2005

The use of kinetic energy release measurements in the structural characterization of ions formed in the mass spectrometer and in the determination of fragmentation mechanisms is demonstrated. In combination with information on the mode of energy partitioning in some of these reactions this allows the following conclusions: (i) The metastable [C7H8]8˙ ions formed from toluene, cyclohepatatriene, n‐butylbenzene, the three methyl anisoles, methyl tropyl ether and benzyl methyl ether all undergo loss of H˙ from a common structure. (ii) The metastable [C7H7]+ ions generated from the same sources and from benzyl bromide, benzyl alcohol, p‐xylene and ethylbenzene appear to undergo loss of acetylene from both the benzylic and the tropylium structures. (iii) The metastable [C7H7OCH3]+˙ ether molecular ions undergo loss of CH3˙ by two types of mechanism, simple cleavage to give the aryloxy cation (not observed for benzyl methyl ether) and a rearrangement process which appears to lead to protonated tropone as the product. (iv) Loss of formaldehyde from the metastable [C7H7OCH3]+˙ molecular ions involves hydrogen transfer via competitive 4‐ and 5‐membered cyclic transition states in the case of the anisoles and in the case of methyl tropyl ether, while for benzyl methyl ether, hydrogen transfer in the nonisomerized molecular ion occurs via a 4‐membered cyclic transition state to yield the cycloheptatriene molecular ion.
Direct chemical ionization of relatively involatile samples. Application to underivatized oligopeptides
Authors: Baldwin M. A. , McLafferty F. W.
Published: May 2005

By direct explosure of the sample to the ion plasma in a chemical ionization source, spectra of many relatively involatile compounds can be obtained with sample temperatures at least 150° below those usually required. A number of peptides that have not been derivatized are shown as examples. Determination of the complete amino acid sequence is possible with samples of 10−7 g.
The activation energy as guiding factor in the fragmentation of substituted diphenylmethanes
Authors: Innorta G. , Torroni S. , Pignataro S. , Mancini V.
Published: May 2005

The mass spectra of a series of substituted diphenylmethanes were obtained. The mass spectral features were compared with those of the corresponding 1,2 diphenylethanes and discussed in terms of the factors which influence the electron‐impact fragmentation. In the series examined, it is shown that the activation energy is the most important factor in determining cracking patterns. The meaning of the averaged rate constants is criticised.
Deuterium isotope effects in mass spectrometry. Mechanism of formation of the [C6H6S]+˙ ion in the decomposition of s‐phenyl methylthiocarbamate
Authors: Stambolija Lj. , Stefanović D.
Published: May 2005

In the [C6H6S]+˙ fragment ion formed from S‐phenyl methylthiocarbamate and undergoing subsequent metastable loss of CS, the hydrogen is not bound to the sulphur atom, as indicated by deuterium isotope effects on competing metastable transitions.
Elektronenstossinduzierte Fragmentierung von Acetylenverbindungen—VIII:. Struktur der stabilen und instabilen Ionen [C9H9]+ aus isomeren C9H10‐Kohlenwasserstoffen
Authors: Köppel Claus , Schwarz Helmut , Bohlmann Ferdinand
Published: May 2005

Die Auftrittspotentiale von [C9H9]+ werden bestimmt und die baraus berechneten Bildungsenthalpien mit verschiedenen Strukturvorschlägen korreliert. Offenkettige Strukturen können in allen Fällen zugunsten von aromatischen (Vinyltropylium‐,bzw. Indanylkation) aus‐geschlossen werden. Die Struktur der instabilen [C9H9]+‐Ionen wird mit Hilfe 13C‐markierter Verbindungen untersucht. Auch hier stehen die Ergebnisse mit der Annahme aromatischer Strukturen im Einklang.
SN2 reactions in the gas phase. Structure of the transition state
Authors: Dougherty Ralph C. , Dalton J. , David roberts J.
Published: May 2005

The alkylhalide‐halide association ions, [RX2]− that are observed in the negative chemical ionization mass spectra of alkyl halides appear to be directly related to the corresponding SN2 transition states in solution. ‘Frontside’ association of halide ions with bridgehead alkyl halides does not occur in our system. The Change in heats and entropies of association for the chloromethane series is consistent with delocalization in the [RX]2− ions.
SN2 reactions in the gas phase. Nucleophilicity effects
Authors: Dougherty Ralph C. , David Roberts J.
Published: May 2005

The heats and entropies of gas phase association of chloride, bromide and iodide with the respective methyl halides are reported. Comparison of these results with results published for SN2 reactions in solution suggests that the solvent is the dominant factor in determining relative halide nucleophilicities for the reactions in solution.
SN2 reactions in the gas phase. Alkyl group structural effects
Authors: Dougherty Ralph C.
Published: May 2005

The gas phase heats and entropies of SN2‐like association of bromide ions with a series of alkyl bromides are reported. Comparison of this data with published data for the same reactions in solution suggests that the alkyl group structural effects on SN2 reactivity in solution are controlled entirely by the solvent.
The chemistry of piperidines—II: The electron‐impact‐induced fragmentation of 3‐AZA‐3‐methylbicyclo[3,3,1]nonanes
Authors: Britten A. Z. , O'sullivan J.
Published: May 2005

The mass spectra of three series of stereoisomeric 3‐aza‐3‐methyl‐6‐cycloalkylaminobicyclo[3,3,1]nonan‐9‐ols and related compounds including deaza analogues are reported and discussed. The spectra of some of the isomers differ characteristically and can be used to assign their configurations.
Fragmentation and rearrangement processes in the mass spectra of perhalogenoaromatic compounds—VIII: Fluoroaromatic heterocyclic derivatives of group IV
Authors: Lanthier G. F. , Miller J. M. , Cohen S. C. , Massey A. G.
Published: May 2005

The metastable ion supported fragmentations and fluorine transfer rearrangements of a series of fluoroaromatic heterocyclic derivatives of silicon, germanium and tin are reported. Of particular interest is the unique loss of neutral SiF4 from the parent ion of (C12F8)Si yielding the [C24F12]+˙ ion. These and similar rearrangements are discussed and structures are proposed for some of the ions observed. The general case of cyclic rearrangement intermediates prior to the loss of neutral metal fluorides from perfluoroaromatic derivatives is discussed. Losses of neutral metal fluorides from the parent ions appear to involve a species with increased co‐ordination number about the central atom as an intermediate. In addition to (C12F8)2M, the following compound types were studied: (C6H5)2Ge(C12F8), (C12F8S)2M and R4Sn2(C6F4)2 (where M = a Group IV metal and R = CH3 or C6H5).
Chemical ionization mass spectrometry—XIX: n‐hexane and n‐octane as reactants
Authors: Yu Tung Yang , Field F. H.
Published: May 2005

The suitability of n‐hexane and n‐octane as reactant gases in chemical ionization mass spectrometry has been investigated. The mass spectra of these substances have been investigated as a function of pressure up to 2·4 Torr for n‐hexane and 1·7 Torr for n‐octane. The major ion present in n‐hexane at 0·8 Torr is [C6H13]+ (m/e 85) with a relative intensity of 0·65. In n‐octane at 0·8 Torr the major ions are [C8H17]+ (m/e 113), [C6H13]+ (m/e 85) and [C5H11]+ (m/e 71). The relative intensities of these ions are 0·38, 0·12 and 0·19, respectively. These alkyl ions in both n‐hexane and n‐octane are thought to have tertiary structures. Rate constants for the rates of reaction of the primary ions in the two compounds have been determined.

The n‐hexane chemical ionization spectra of 26 compounds were determined. The spectra of polar compounds are dominated by proton transfer, whereas those of nonpolar compounds exhibit proton transfer and in addition often surprisingly large amounts of electron transfer. The n‐octane chemical ionization spectra of 15 compounds were determined and the spectra in general are quite similar to those obtained with n‐hexane. n‐Hexane and n‐octane can be used as reagents in analytical chemical ionization mass spectrometry, but except in certain specialized uses they would probably have no advantage over i‐butane.
Apparent charge localization effects in the McLafferty rearrangement of acetate esters: Field ionization kinetic measurements
Authors: Wood Gordon , Falick A. M. , Burlingame A. L.
Published: May 2005

The relative rates of the McLafferty rearrangement in n‐butyl acetate and several related molecules have been examined over the time range 10−11 to 10−5 s by means of a field ionization mass spectrometric technique. It was found that the introduction of a substituent group of low ionization potential (phenyl, dimethylamino) at sites remote from the ester oxygens reduces the rate of the McLafferty rearrangement and that the rate becomes lower as the substituent is moved further away from the ester group. The results suggest that for the cases examined the charge on the molecular ion may be localized on the functional group of lowest ionization potential.
The mass spectra of TMS‐ethers of deuterated polyalcohols. A contribution to the structural investigation of sugars
Authors: Dizdaroglu Miral , Henneberg Dieter , Von Sonntag Clemens
Published: May 2005

Aldoses, ketoses, deoxy‐aldoses, deoxy‐keto‐aldoses, lactones, deoxy‐lactones and other similar compounds are readily reduced by NaBD4 to the corresponding polyalcohol. Their trimethylsilyl ethers show characteristic mass spectra which allow firm assignments of the position of deuteration and hence of the nature of the starting sugar compound. The g.c./m.s. coupling technique even allows trace analysis since full information can be derived from the most intense fragments of the mass spectra.
Collisional activation spectra. Gas phase [C12H10O]+˙ and [C12H9O]+ ions from dephenyl ether, diphenyl carbonate, and o‐, m‐ and p‐phenylphenol
Authors: Levsen Karsten , McLafferty F. W.
Published: May 2005

[C12H10O]+˙ ions in the mass spectra of diphenyl ether and diphenyl carbonate have the same structure, but one which differs from that of these ions from phenylphenol. [C12H9O]+ ions from all three compounds have isomerized to a common structure.
The enolic [C5H10O]+· and [C3H6O]+· ions formed from aliphatic ketones
Authors: Beynon J. H. , Caprioli R. M. , Cooks R. G.
Published: May 2005

The structures of reactive and nonreactive ions formed by McLafferty rearrangement in a variety of ketones are studied using metastable ion abundances and the kinetic energy released in metastable ion fragmentations. The loss of methyl radicals is studied in [C5H10O]+. ions and the mechanism delineated for ions formed in an initial configuration corresponding both to ketonic and enolic forms; the major mechanism in both cases appears to involve a common intermediate. Partial scrambling of hydrogen atoms on the C‐1 and C‐5 carbons and on the oxygen precedes methyl elimination. Loss of neutral ethylene from [C5H10O]+. ions is also studied and again the major mechanism occurs via a common species, intermediate in structure between a ketone and an enol; scrambling of hydrogen is much faster for ions that lose ethylene than for those which lose a methyl radical. Keto ions of formula [C3H6O]+. show no unimolecular loss of methyl. The stable [C3H6O]+. ions generated in the keto and enol forms are shown to preserve their initial structures, confirming the results of ion cyclotron resonance experiments. Reactive [C3H6O]+. ions formed from 2‐pentanone molecular ions by McLafferty rearrangement are shown to have the same structures as reactive ions originally generated as enolic structures from 1‐methylcyclobutanol.

The paper highlights the relationship between hydrogen scrambling and keto‐enol isomerization reactions in aliphatic ketones.
Ionisation et Fragmentation en Spectrométrie de Masse. IV— Appreciation de L'energie D'activation Pour des Fragmentation Simples
Authors: Bouchoux Guy , Fétizon Marcel , Audier Henri‐Edouard
Published: May 2005

L'énergie d'actvation des ruptures simples a été determiné par différents méthodes.
Massenspektrometrische Untersuchung von Amiden: III—Intramolekulare Nucleophile Substitution bei der Methyl‐Abspaltung aus Crotonsaurepiperidid und Vinylogen Derivaten
Authors: Schwarz Helmut , Mathar Wolfgang , Bohlmann Ferdinand
Published: May 2005

Die Methyl‐Abspaltung aus Piperididen des Typs CH3(CHCH)nCONC5H10 verläft bei n = 1 bis 3 nicht über einem Ringverengungsprozeß, wie er früher für n = 0 bewiesen wurde. Die Fragmentierung kann über einen cyclischen Übergangszustand formuliert werden, der unter Nachbargruppenbeteiligung der Amidfunktion entsteht. Sowohl die Untersuchung einer 2H‐markierten Verbindung für n = 1 als auch energetische Messungen (AP, IP, Ek) bei n = 0 bis 3 stimmen mit dieser Vorstellung überein.
Nachbargruppeneffekte bei der Massenspektrometrischen Fragmentierung von Amino‐benzylalkoholen
Authors: Eckhardt G. , Welzel P.
Published: May 2005

Das Fragmentierungsverhalten einer Reihe substituierter Amino‐benzylalkohole wurde mittels hoch‐ und niederauflösender Massenspektrometrei, Defokussierungsmessungen und Deuterium‐Markierungen untersucht. Die o‐, m‐ und p‐Isomeren zeigen charakteristische Fragmentierungsmuster, die bei der Strukturaufklärung solcher Verbindungen von großem diagnostischen Wert sind.
Isomerisation du Benzoxazole et de L'anthranile Sous L'impact Electronique
Authors: Maquestiau A. , van Haverbeke Y. , de Meyer C. , Flammang R.
Published: May 2005

Une isomérisation des ions moléculaires précéde la fragmentation du benzoxazole et de l'anthranile (2,1‐ benzisoxazole) sour l'impact électronique.
Mass spectra of organometallic compounds: XIV—Some monometallic olefing manganese tricarbonyl derivatives
Authors: King R. B. , Ackermann M. N.
Published: May 2005

The metastable ion supported fragmentation process in the mass spectra of the cyclohexadienyl derivative C6H7Mn(CO)3, the cycloheptadienyl derivative C7H9Mn(CO)3, the 1,2,3,4,5‐and 1,2,3,5,6‐pentahaptocyclootadienyl derivatives C8H11Mn(CO)3, the cyclooctatrienyl derivative C8H9Mn(CO)3 and the substituted cyclopentadienyl derivative (CH3)2NCH2C5H4Mn(CO)3, are described. Losses of carbonyl groups, generally stepwise, from the molecular ions to give the corresponding [M – 3CO]+· ions are first observed. Further fragmentation of the carbonyl‐free [M – 3CO]+· ions can involve a variety of processes such as the following: (a) elimination of a neutral manganese atom to give a hydrocarbon fragment; (b) elimination of a neutral hydrocarbon fragment to give an [MnH]+· ion; (c) dehydrogenation; (d) elimination of a 2‐carbon C2H2 or C2H4 fragment; (e) elimination of a C3H4 or C3H6 fragment as a neutral species when it is bridging two carbon atoms bonded to manganese, as in C8H9Mn(CO)3 and 1,2,3,4,5,h5‐C8H11Mn(CO)3, respectively. Fragmentation of the [M – 3CO]+· ion in (CH3)2NCH2C5H4Mn(CO)3 presents the following additional features: (a) elimination of C6H6 with a nitrogen shift from carbon to manganese; (b) elimination of a neutral dimethylamino fragment to give [C6H6Mn]+·, which then loses neutral C6H6, C6H5 or Mn fragments and thus is formulated tentatively as [(fulvene)Mn]+· or [C6H5MnH]+· rather than [(benzene)Mn]+·.
Internal rotation in the molecular ions of benzoic acid and salicylic acid. An INDO molecular orbital approach
Authors: Parker Carol E. , Bursey Maurice M. , Pedersen Lee G.
Published: May 2005

An aspect of the mechanism of the hydroxyl H/ortho H scrambling in the molecular ion of benzoic acid was studied by the open‐shell INDO molecular orbital method. Energies of te unrearranged structure, the planar structure in which H is attached to carbonyl oxygen and rotational conformers of the latter were studied to determine a pathway of minimum energy for rotation. The same calculations were made for salicylic acid, m‐fluorobenzoic acid and p‐fluorobenzoic acid. The results of these calculations agree quite well with experimental results.
Etude de la Fragmentation de Derives Substitues Polycycliques du Benzodioxinne‐1,4
Authors: Ricard M. , Dizabo P. , Dagaut J.
Published: May 2005

Les spectres de masse de cinq dérivés polycycliques du benzodioxinne‐1,4 ont été examinés. Par comparaison avec trois composés dcutériés en position spécifique, les mécanismes de formation des principaux ions ont pû être proposés. Certains réarrangements se font par migration spécifique d'hydrogene, d'autres apres migration au hasard.
An investigation of the decomposition of the intermediate ions produced by electron‐impact. II—[C7H7]+ ions from several halogenotoluenes
Authors: Tajima Susumu , Tsuchiya Toshikazu
Published: May 2005

The structure and decomposition of the [C7H7]+ ions produced by electron‐impact from o‐, m‐ and p‐chlorotoluene, o‐, m‐ and p‐bromotoluence, and p‐iodotoluence, have been investigated. By determining the relative abundance of normal and metastable ions, these [C7H7]+ ions at electron energy of 20 eV are shown to be so‐called ‘tropylium ions’. The amount of the internal energy of the [C7H7]+ ion estimated by the relative ion abundance ratios, † [C5H5]+/[C7H7]+ and m*/[C7H7]+ for the decomposition \documentclass{article}\pagestyle{empty}\begin{document}$ [{\rm C}_{\rm 7} {\rm H}_{\rm 7}]^ + \mathop \to \limits^{m^* } [{\rm C}_{\rm 5} {\rm H}_{\rm 5}]^ + + {\rm C}_{\rm 2} {\rm H}_{\rm 2} $\end{document}, is in the order iodotoluene > bromotoluene > chlorotoluene. The heats of formation of the activated complexes for the reaction \documentclass{article}\pagestyle{empty}\begin{document}$ [{\rm C}_{\rm 7} {\rm H}_{\rm 7}]^ + \mathop \to \limits^{m^* } [{\rm C}_{\rm 5} {\rm H}_{\rm 5}]^ + + {\rm C}_{\rm 2} {\rm H}_{\rm 2} $\end{document} were estimated. The values suggest that the decomposing [C7H7]+ ions from various halogenotoluenes are identical in structure.
Massenspektrometrische Untersuchung von Amiden. IV—Nachbargruppenbeteiligung Bei der Elektronensto‐Ssinduzierten Fragmentierung von O‐Nitrobenzoesaurepiperidid
Authors: Schwarz Helmut , Bohlmann Ferdinand
Published: May 2005

Die Unterschiede bei der elektronenstoßinduzierten Fragmentierung von ortho‐und para‐Nitrobenzoylpiperidin hängen mit einer Nachbargruppenbeteiligung der NO2,‐Gruppe zusammen. Sowohl eine neuartige Sauerstoffwanderung als auch die Ausbildung stabilisierter Radikale über eine intramolekulare Wechselwirkung der beiden Funktionen sind nur bei der ortho‐Verbindung möglich.
Spectrometrie de Masse D'ozonides Aliphatiques
Authors: Bertrand M. , Carles J. , Fliszár S. , Rousseau Y.
Published: May 2005

Un mode primaire de clivage des ozonides aliphatiques par impact électronique, impliquant la rupture de liaisons OO et CC, est mis en évidence. Ce processus (qui n'a pas été observé pour les ozonides aromatiques) est d'autant plus marqué que les substituants portés par le cycle ozonique sont de meilleurs donneurs d'électrons. Les potentiels d'ionisation des ozonides cis et trans du méthyl‐4 penténe‐2 sont respectivement de 8,81 et 8,86 (±0,5) eV. Pour l'ion [RCHO,]+·, on trouve deux seuils d'apparition qui sont probablement reliés à deux modes de formation distincts.
Electron‐impact‐induced fragmentation of some phthalazinone derivatives
Authors: Bruck Péater , Tamás József , Körmendy Kármenoly
Published: May 2005

The mass spectra of 4‐(ω‐hydroxyalkylamino)‐phthalazinone derivatives (I to IV) have been studied. The most important primary fragmentation process is the fission of the alkyl chain β to the amino group, combined with an intramolecular cyclisation reaction. This process results an ion of tricyclic structure, possessing a 4‐membered ring, as was established by partial 15N labelling.
Ungewöhnliche Methyl‐Abspaltungen aus Nicht Endständigen Kohlenstoffpositionen Bei p‐Methylstyrol
Authors: Köppel Claus , Schwarz Helmut , Bohlmann Ferdinand
Published: May 2005

Mit Hilfe 13C‐markiertem p‐Methylstyrol wird der Mechanismus der Methyl‐Abspaltung untersucht. An diesem Prozeß sind nicht nur endständige C‐Atome beteiligt, jedoch erfolgt weder ein vollständiges noch ein partielles C‐Scrambling vor der Fragmentierung.
The mass spectrum of mevalonolactone
Authors: Gray R. T.
Published: May 2005

The principal fragmentation pathways of mevalonolactone are initiated by cleavage α to the hydroxyl function. Each major route has been delineated by using isotopic labelling and metastable analysis. A knowledge of this fragmentation pattern is useful for the calculation of isotopic purity and specificity in samples of mevalonolactone used as substrates in biosynthetic studies.
Mass spectra of porphyrin alkyl esters and their copper complexes. Studies on products from humans and animals with porphyria
Authors: Møller Jørgen , With Torben K.
Published: May 2005

Mass spectra of methyl and higher aliphatic esters of biologically important porphyrins—prepared from human and bovine excreta—were recorded. Variation in the number of esterified carboxyl groups (4 to 8) or in the size of the ester groups causes no change in the fragmentation modes; only the abundances of the fragment ions vary. The conversion of a porphyrin ester to its copper‐complex (chelate) has been achieved in a simple way. The mass spectra of the copper chelates are compared with those of the free porphyrin esters and minor differences are observed.
Etude en Spectrometrie de Masse: VI—Evaluation de l'Induction de la Fragmentation dans les amines β Fonctionnelles
Authors: Rouvier Emile , Cambon Aimé
Published: May 2005

Les spectres de masse de 22 amines β fonctionnelles sont comparés à ceux des amines simples correspondants. L'analyse spectrale montre que l'induction de la fragmentation ne se fait pas uniquement par l'atome d'azote. Les groupements cétone, ester, amide, nitrile l'induisent également dans une proportion qui a pu étre évaluée. Cette approche simple, basée sur la cinétique des réactions unimoléculaires est en accord avec les résultats obtenus à partir des méthoaes basées sur la mesure des potentiels d'ionisation.
The applicability of the defocusing technique in organic mass spectrometry
Authors: Aizawa K. , Yoshida S. , Takahashi N.
Published: May 2005

Defocusing techniques for detecting metastable ions of rather complex molecules were investigated and a generalised procedure, which provides efficient methods in the analysis of fragmentation pathways of complex compounds, was established. Additionally, a new method to differentiate between the transition in the first and the third field free regions, was developed.
Pattern recognition. An application to the identification of some stereoisomeric N‐acetylhexosamines by mass spectrometry
Authors: Vink J. , Heerma W. , Kamerling J. P. , Vliegenthart J. F. G.
Published: May 2005

A method is reported for the identification of trimethylsilylated stereoisomeric N‐acetyl‐hexosamines by application of a pattern recognition procedure to mass spectral data. The selection of characteristic mass spectral data and the pattern recognition procedure are discussed.
Collisional activation spectra of field ionised molecules
Authors: Levsen K. , Beckey H. D.
Published: May 2005

The collision of field ionised molecular ions of high kinetic energy (8 keV) with neutral target atoms (helium) gives rise to a large variety of fragments. In general the types of fragments, as well as their abundance ratios, closely resemble those formed under 70 eV electron‐impact. The differences observed between the collisional activation spectra of several field ionised[C7H8]+. ions, as well as the differences observed between several [C8H8]+. ions can be rationalised assuming different degrees of isomerisation. The usefulness of collisional fragmentation spectra for structure determination of organic compounds has been demonstrated for a variety of compounds and some mixtures.
Elctron‐impact studies of diazadiphosphetidines
Authors: Schlak O. , Schmutzler R. , Gregor I. K.
Published: May 2005

Electron‐impact studies of diazadiphosphetidines,[YF2PNMe]2(YF,Me, Ph, MeO,2,5‐Me2C6H3, and m‐CF3C6H4) are reported, the most abundant fragments corresponding to m/e [M/2–1]+, [M/2]+ and [M/2–1]+. It is concluded from metastable data that formation of the noval rearrangement ion, [M]+→[M/2+1]+is predominantly due to an electron‐impact process. Variable temperature spectra of(F3PNMe)2, (i.e. for Y=F), suggest that ions of m/e [M/2‐1]+are formed, in part, by a thermal process. For the compound [(m‐CF3C6H4)F2PNMe]2 a well resolved negative ion spectrum has been obtained, with the molecular ion present in 100% abundance.
Fragmentation des Closo‐N‐Methyl Phosphorimide, Thiophosphorimides et Arsenimide
Authors: Wolff Anne , Cambon Aimé , Riess Jean
Published: May 2005

Les spectres de masse du closo phosphorimide P4(NCH3)6Sn, où n = 1 à 4, et du closo arsenimide As4(NCH3)6 ont été et des schémas de fragmentations systématiques ont été dégagés, L'introduction des groupes thiophosphoryles se traduit par une superposition des deux types de fragmentations identifiées pour P4(NCH3)6 P4− dérivés ou de l'hexaméthylène tétramine.
Organische Schwefelverbindungen. IX—Ringkontraktion Statt Carben‐Eliminierung von Neutralteilen Bei der Elektronenstossinduzierten Fragmentierung von Thiaspirofuranonen
Authors: Schwarz Helmut , Praefcke Klaus , Höhne Gerhard
Published: May 2005

Bei der elektronenstoßinduzierten Fragmentierung des Thia‐spirofuranons findet ein Prozeß statt, der am besten durch die Annahme einer Ringkontraktion des Neutralteiles C6H10 rationalisierbar ist. Eine Carben‐Struktur für dieses Neutralteil kann ausgeschlossen werden.
Electron‐impact fragmentation of triaryl‐s‐trithianes: A novel skeletal rearrangement involving sulphur‐sulphur bond formation
Authors: Chattopadhyaya Jyoti B. , Rao A. V. Rama
Published: May 2005

The mass spectral fragmentation of seven substituted 2,4,6‐triaryl‐s‐trithianes has been studied and the fragmentation modes confirmed by deuterium labelling. Triphenyl‐s‐trithiane shows some interesting features in its mode of cleavage and does not eliminate S, S2, SH˙, H2S or S2H˙ from its molecular ion. The prominent radical ions in the mass spectrum are at m/e 180 (52.3%) and m/e 186 (45.2%), corresponding to stilbene and PhCHS3. Their compositions have been established by deuterium labelling and accurate mass measurements. The formation of stilbene indicates a relationship between pyrolytic and electron‐impact studies. The origin of [PhCHS3]+˙ suggests that one of the sulphur atoms attaches itself to the other two sulphur atoms in the molecular ion, eliminating a stilbene radical ion. The other important fragmentation corresponds to the monomer radical ion (thiobenzaldehyde) and the thiobenzoyl cation.

Among the other substituted triaryl‐s‐trithianes with substituents such as chloro, methoxy, methylenedioxy and hydroxy groups on the phenyl ring (IV to IX), only the tris‐(p‐chlorophenyl)‐s trithiane shows an insignificant molecular ion. Unlike the triphenyl derivative, the chloro, methoxy and methylenedioxy derivatives show the loss of HS˙ and/or H2S from the molecular ion. The spectrum of tris‐(p‐hydroxyphenyl)‐s‐trithiane corresponds to the spectrum of p‐hydroxythiobenzaldehyde.
Elektronenstossinduzierte Arylwanderungen bei 2.2‐Disubstituierten 1.3‐Dioxolen
Authors: Schwarz Helmut , Schönberg Alexander , Singer Erich , Schulze‐Pannier Heidemarie
Published: May 2005

Bei der elektronenstroßinduzierten Fragmentierung 1.3‐Dioxolen werden im Gegensatz zu sonstigen Arylwanderungen sowohl die nucleophile als auch die elektrophile Gruppe umgelagert. Anßerdem wird in einem Fall eine ungewöhnlich intensive Spaltung geminaler Bindungen am Spiro‐Kohlenstoff beobachtet, die durch die Produkt‐Stabilität des doppelt geladenen Fragment‐Ions erklärbar ist.
Probability based matching of mass spectra. Rapid identification of specific compounds in mixtures
Authors: McLafferty F. W. , Hertel R. H. , Villwock R. D.
Published: May 2005

An automated system is described for computer examination of the mass spectrum of an unknown mixture for the presence of a specific compound. The probability that the compound is present is indicated as a ‘confidence index’ K; 2K should signify the average number of compounds, selected at random, whose mass spectra would have to be examined to find data which match the target spectrum to the same degree as does the unknown. The value of K is determined by the uniqueness U of the m/e value, the abundance A, and the criterion of abundance agreement W of the matching peaks, and of the compound concentration D in the sample. Application to spectra from a variety of compounds, including illicit drugs, indicates that the system has high sensitivity and selectivity, and that the value of K is a useful index of the reliability of the identification. Initial testing of this system has utilized an automated quadrupole mass spectrometer under control of a dedicated microcomputer with sample introduction through a flash evaporator and membrane separator.
Massenspektrometrische Untersuchung von Bromiden: Über den Einfluss der Radikalstabilität auf die Ringgrösse Cyclischer Bromonium‐Ionen
Authors: Schwarz Helmut , Bohlmann Ferdinand , Hillenbrand Günther , Altnau Gerald
Published: May 2005

Die Existenz von füntf‐ oder sechsgliedrigen cyclischen Bromonium‐Ionen, die aus ω‐Phenyl‐alkylbromiden unter Elektronenstoßbendingungen erzeugt werden, hängt in entscheidender Weise von der Stabilität der Phenyl‐Alkyl‐Radikale ab.
Studies in organic mass spectrometry. XVIII—The effect of branching in the sidechain upon the fragmentation of 4,6‐dialkyl‐1,3‐dioxanes
Authors: Monstrey J. , van de Sande C. , Vandewalle M.
Published: May 2005

The presence of a 2′‐tertiary hydrogen atom has a profound influence on the general fragmentation pattern of 4,6‐dialkyl‐1,3‐dioxanes. Branching at the 2′‐position induces a double hydrogen transfer reaction which is absent in the spectra of 4,6‐n‐alkyl‐1,3‐dioxanes.
o‐nitroaniline derivatives. IV—The mass spectra of o‐nitroanils
Authors: Johnston David , Smith David M.
Published: May 2005

The principal feature of the mass spectra of o‐nitroanils, ArCHNC6H4NO2(o‐), is an intense peak corresponding to the [ArCO]+ ion; this implies oxygen transfer from the nitro group to the azomethine carbon during the fragmentation process. In this series of anils, loss of OH from the molecular ion is not apparently an important fragmentation pathway, in contrast to the fragmentation of o‐nitrobenzylideneanilines. Benzylideneaniline derivatives with an o‐nitro substituent in both rings have mass spectra which indicate interaction of both nitro groups with the CHN group, but in this series of spectra the [M—17]+ ion is again of low intensity.
Sauerstoffwanderung vom Phosphor zum Kohlenstoff Beim Massenspektrometrischen Zerfall von α,α‐ Dichloralkylphosphonsäurechloriden
Authors: Schmidtberg G. , Hägele G. , Bauer G.
Published: May 2005

Durch Chlor‐Sauerstoff‐Austauschreaktionen entstehen beim massenspektrometrischen Zerfall von α,α‐Dichloralkylphosphonsäure‐ und ‐phosphinsäurechloriden Carbonyl‐fragmente. Im Spektrum von α.β‐Dichlorvinylphosphonsäuredichlorid bildet Chlorketen CHClCO sogar den Basispeak.
Effects of halogen atoms on the mass spectra of some 3‐phenylpropionyl halides
Authors: Hittenhausen‐Gelderblom R. , Venema A. , Nibbering N. M. M.
Published: May 2005

The mass spectra of the title compounds have been studied by use of deuterium labelling. The character of the halogen atom appears to have a marked influence on the fragmentation pathways. It is shown that the acyl halide group may react with the different active atoms in the molecular ion—the α‐ and β‐hydrogen atoms—as well as with the phenyl ring.
Massenspektrometrische Untersuchungen an Benzophenon und Substituierten Benzophenonen. I‐Ermittlung Thermodynamischer Grössen
Authors: Krenmayr P. , Heller R. , Varmuza K.
Published: May 2005

Es wurden die Ionisieerungspotentiate von Benzophenon und substituierten Benzophenonen sowie die Auftrittspotentiale der häufigsten Fragment‐Ionen gemessen. Ausgehend von berechneten Werten für die Bildungsenthalpien der substituierten Benzophenone, wurden folgende Grüßen ermittelt: Bildungsenthalpien der Molekül‐Ionen; Bildungsenthalpien von Fragment‐Ionen, die in einem einstufigen, und solcher, die in einem zweistufigen Zerfallsprozeß gebildet wurden; Bildungsenthalpien und Ionisierungspotentiale von Radikalen; Dissoziationsenergien des Benzophenons und der substituierten Benzophenone. Die Genauigkeit der Ergebnisse wird diskutiert.
Mass spectrometry of heterocyclic compounds. VI—retro‐1,3‐dipolar cycloaddition and competitive fragmentation reaction of 2,5‐diaryl‐1,3,4‐dioxazoles
Authors: Selva A. , Citterio A. , Pella E. , Tonani R.
Published: May 2005

The process of retro‐1,3‐dipolar cycloaddition of 2,5‐diaryl‐1,3,4‐dioxazoles induced by electron‐impact is discussed. For this purpose, 2‐phenyl‐5‐p‐chlorophenyl‐1,3,4‐dioxazole was prepared, labelled with 18O in position 1; the spectrum of this compound showed clear evidence of retro‐cycloaddition, the dipole fragment retaining the positive charge. This labelled compound also provides a reliable interpretation of other cleavage modes of the heterocyclic ring. The elemental compositions of the ions considered were determined by exact mass measurements and the metastable transitions were detected through the defocusing technique of the electrostatic sector.
Electron‐impact spectra of 2‐acyloxyacetophenones
Authors: Stockburn A. L. , Thomas C. W.
Published: May 2005

The mass spectra of a number of 2‐acyloxyacetophenones (phenacyl esters) are reported. The major fragments in the spectra are due to α‐fission to oxonium ions. A correlation between the intensities of the oxonium ions and Hammett substituent constants is noted. Rearrangements are examined by means of deuterium labelling and low electron voltage studies.
The ionisation potential of some substituted pyridines
Authors: Stefanović D. , Grützmacher H. F.
Published: May 2005

The ionisation potentials of pyridines substituted with electron‐donating and electron‐withdrawing substituents in positions 2, 3 and 4 have been determined.
Collisional activation spectra of the [C9H11O]+ ion from 2‐methyl‐2‐phenylpropane‐1,3‐diol
Authors: Nibbering N. M. M. , Van De Sande C. C. , Nishishita T. , McLafferty F. W.
Published: May 2005

Collisional activation spectra show that the [C9H11O] ion formed by loss of CH2OH from the title compound has rearranged to the protonated phenylacetone structure.
Mechanismus der Amin‐eliminierungen bei der Elektronenstoßinduzierten Fragmentierung von 1.3‐Diaminopropanen
Authors: Eckhardt G. , Goebel K. J. , Tondorf G. , Goenechea S.
Published: May 2005

1,3‐Diaminopropane spalten beim Elektronestoßinduzierten Zerfall in starkem Maße aus den Molekülionen Amine ab. Dem schließen sich Folgereaktionen an, in deren Verlauf Vorzugsweise ein Substituent vom C‐2 der Propankette, in geringerem Maße jedoch auch ein N‐Substituent eliminiert werden. Erniedrigung der Elektronendichte an nur einem Stickstoffaton durch geeignete Substituenten führt Zu einem Intensitätsabfall beider [M–Amin]+˙ Ionen. Die zugrun‐deliegenden Fragmentierungsprozesse wurden mit Hilfe deuterierter Verbindungen untersucht.
Chlorine atom migration in the fragmentation of α‐mesyl sulfonyl chlorides
Authors: Hardstaff W. R. , Langler R. F. , Newman M. J.
Published: May 2005

The mass spectra of alkanesulfonyl chlorides can be rationalized by loss of a chlorine atom from the molecular ion, followed by loss of SO2 with concomitant alkyl cation formation. The mass spectra of two α‐mesyl sulfonyl chlorides exhibit a new fragmentation process in which the chlorine atom initially attached to sulfur migrates to the α‐carbon atom with loss of SO2, thereby resulting in retention of chlorine in the alkyl cation.
Ortho effects in organic molecules on electron‐impact I—Oxidation of olefinic double bond by the ortho nitro group in stilbazoles
Authors: Ramana D. V. , Vairamani M.
Published: May 2005

The electron‐impact‐induced fragmentation in 2′‐nitro‐4‐stilbazole is triggered by the oxidation of the olefinic double bond by the ortho nitro group in the initial step, while such an interaction under the same condition is totally absent in the meta and para isomers. The important fragmentation in 2′‐nitro‐2‐stilbazole is the formation of a cyclised ion with the elimination of the nitro group.
Mass spectrometry of heterocyclic compounds. VII—Evidence for common structure(s) of 1,2‐benzisothiazole and benzothiazole molecular ions produced by electron‐impact
Authors: Selva Antonio , Vettori Umberto , Gaetani Enrico
Published: May 2005

1,2‐Benzisothiazole and benzothiazole ion kinetic energy spectra, and metastable ion relative abundances of the same primary and secondary decomposition processes are compared. The results are interpretable as postulating slow (metastable) process(es) involving common structures and fast process(es)which are structurally dependent. Analogous indications are given by the interring H/D scrambling data, preceding the loss of DCN (or HCN) from 1,2‐benzisothiazole‐3‐d1 and benzothiazole‐2‐d1 molecular ions, measured in either metastable or normal daughter ions at various electron beam energies.
Studies in organic mass spectrometry. XX—Stereospecificity in hydrogen transfer reactions in mass spectra of TMS derivatives of some 2,3‐dialkyl‐1, 4‐cyclopentanediols
Authors: Maenhaut‐Claeys M. , De Clercq P. , Vandewalle M.
Published: May 2005

The mass spectra of TMS ethers of 2,3,‐dialkyl‐1,4‐cyclopentanediols having a 2′‐carboxyl group or 2′‐double bond in one of the sidechains, display a stereospecific rearrangement process. A mechanism is proposed to account for this stereospecificity.
Mass spectral correlations of halogenated 1,1,1,3,3,3‐hexafluoropropanes and 1,1,1‐trifluoroethanes
Authors: Naae Douglas G. , Wiebe Donald A.
Published: May 2005

The mass spectral fragmentation patterns at 20 eV of twelve compounds of the type CF3CXYCF3 (X, Y =F, Cl, Br, I, H) and five compounds of the type CF3 CX2 Y (X, Y= F, Cl, Br) were analyzed. It was noted that the frequency of carbon–helogen and carbon–carbon bond cleavage was quite dependent on the substituents X and Y.
Rearrangement of pentafluoropropionic esters under electron‐impact: Confirmation by stable isotope labelling
Authors: King Graham S.
Published: May 2005

A rearrangement in the mass spectrum of 1‐phenylethyl pentafluoropropionate is discussed together with results obtained by 13c and 18O labelling.
Ortho effects in organic molecules on electron‐impact II– Ortho effects in substituted α,α,α‐trichloracetanilides
Authors: Ramana D. V. , Vairamani M. , Kala S.
Published: May 2005

Elimination of trichloromethyl radical from the molecular ion is the abundant fragment in the mass spectra of most of the thirteen substituted trichloracetanilides studied. Unusual ortho effects of OCH3, NO2 and COOH groups are noticed only after the initial ejection of trichloromethyl radical from the molecular ion.
The behaviour of arylsulfonylmethyl sulfonates under conditions of electron‐impact. The loss of CH2O
Authors: Graafland T. , Engberts J. B. F. N. , Weringa W. D.
Published: May 2005

The mass spectra of ten arylsulfonylmethyl arenesulfonates and two arylsolfonylmethyl trifluoromethanesulfonates are discussed. A notable fragmentation of these compounds is the loss of CH2O from the molecular ions. A probable structure for the [M  CH2O]−. ions, as based on the measurement of metastable rations, is given and a fragmentation mechanism leading to this structure is proposed.
The lowest electronic states of the benzoyl ion. A molecular orbital study with configuration interaction
Authors: Bursey Maurice M. , Kao Jar‐Lin , Pedersen L.
Published: May 2005

A configuration interaction method of molecular orbital theory shown to be accurate for the calculation of excited state energies in several aromatic systems was applied to the problem of excited states of the benzoyl ion. The excited singlet and triplet states of the benzoyl ion lie at least 3.8 eV and 2.6 eV, respectively, above the ground state. These results are not in agreement with a postulated state 20 kcal above the ground state. On the other hand, the charge distribution in excited states does agree with that postulated for the 20 kcal state. The p‐hydroxy and p‐cyano substituents do not greatly influence the charge distribution between the ring and the carbonyl group in either the ground or lowest excited states.
Isomerisation of hydrocarbon ions:II—Octenes and isomeric cycloakanes: Acollisional activation study
Authors: Levsen K.
Published: May 2005

[C8H16]+. molecular ions from alkenes and cycloalkanes differing in their skeletal con‐figuration do not in general isomerise completely to a common structure, except for the molecular ion of n‐propylcyclopentane, the structure of which is identical to that of the normal octene ions. In contrast, decomposing [CnH2n−1]+ fragments are completely or almost completely isomerised after a lifetime of a few μs.
Electron‐impact studies XCV–skeletal rearrangement fragments in the mass spectra of 3,5‐ diphenylisoxazole and 3,5‐ diphenylpyrazole
Authors: Aldous Graham L. , Bowie John H.
Published: May 2005

The ion [C13H9]+ (m/e 165) is produced from the molecular ion of 3,5‐diphenylisoxazole by the process [M  CO  H2CN·] and [M  CO  HCN  H·] and from that of 3,5‐diphenyl‐pyrazole by the eliminations [M  N2H·  C2H2]. These processes have been studied by 2H and 13C labelling. A correlation between photochemical, thermal and electron‐impact decompostions is noted for 3,5‐diphenylisoxazole.
Studies in mass spectrometry. II—A common intermediate in the primary fragmentation process of α‐phenylmethylenecylopropane
Authors: Derocque Jean‐Luc
Published: May 2005

The variation of Z = [(F)+]/[(M)+·] vs electron energy for the loss of H· and CH3· from the molecular ion of 2‐phenylmethylenecyclopropane (I) and α‐phenylmethylenecyclopropane (II) suggests that they both rearrange to a common intermediate before fragmentation occurs. The structure of the intermediate is discussed with regard to the xperimental values found for the Z ratios and to the mass spectra of deuterium labelled compounds.
Electron‐impact studies XCII–Negative ion‐molecule reactions in anhydride systems. Perfluoroacetic anhydride with succinic, maleic and phthalic anhydrides. An ion cyclotron resonance study
Authors: Bowie J. H. , Williams B. D.
Published: May 2005

The trifluoroacetate anion undergoes reaction with succinic, maleic and phthalic anhydrides to yield 1 : 1 adducts. The molecular anions of maleic and phthalic anhydride also undergo reaction with perfluoroacetic anhydride to produce [CF3CO2]−· Maleic anhydride parent ions produce [M + CF3CO·]− ions when allowed to react with perfluoroacetic anhydride.
Stereospecific 1,3 and 1,4 dehydration reactions in the mass spectra of podocarpan‐12‐ and ‐14‐OLS†
Authors: Wahlberg Inger , Karlsson Kerstin , Enzell Curt R.
Published: May 2005

Specific deuterium labelling revealed that podocarpan‐12α‐ and ‐14α‐01, representing conformationally well defined cyclohexanols, eliminate water mainly by stereospecific 1,3 reactions involving cis tertiary hydrogens on electron‐impact. Dehydration of podocarpan‐12ß‐0l, which also involves a cis tertiary hydrogen, occurs almost exclusively by a 1,4 reaction. Subsequent decomposition of the various [M – 18]+· ions was found to lead to different products, thus explaining some of the intensity differences encountered in the lower parts of the spectra of the epimeric podocarpan‐12‐ols and ‐14‐ols.
Mass spectrometry of organic compounds X–Fragementation of 2‐buten‐1‐o1 on electron‐impact
Authors: Kingston David G. I. , Tannenbaum Harvey P.
Published: May 2005

The mass spectra of variously deuterated 2‐buten‐1‐ols (both Z and E) have been examined. Evidence is presented for the formation of the [M – H2O]+· ion via a 6‐membered transition state, and for the occurrence of two distinct reaction pathways for formation of the major ions at m/e 57 and 43.
Substituent effects in mass spectra of monosubstituted benzils
Authors: Richards Kenneth E. , McMaster Blair N. , Wright Graeme J.
Published: May 2005

The mass spectra of a series of thirteenm‐ andp‐substituted benzils have been determined at several ionising voltages below 20 eV and at 70 eV. At ionising voltages up to 5 eV above the ionisation potentials the benzil molecular ions decompose entirely by two pathways to give substituted and unsubstituted benzoyl ions. Fractional intensities of the molecular ion (FM), substituted (FX) and unsubstituted (FH) benzoyl ions were obtained for each benzil as a function of energy from measured ionisation efficiency curves, and ionisation and appearance potentials for all major ions determined from the ionisation efficiency curves by a semilogarithmic method. Various correlations of ion intensity and energy parameters with δ+and δ constants are examined; these are generally poor. Fair correlations are obtained between log (FX/FH) or (AP– AP) and δ or δ+, and these are interpreted in terms of the expected effect of substituents on the stabilities of the product ions in the decompositions. A good correlation is observed between log (FX/FH) and AP· AP; this suggests that substituents affect FX/FHmainly by changing the activation energies for the competing decompositions of the molecular ions. The competitive shift has a marked effect on these appearance potentials so that in this system AP – IP is not a good measure of the activation energy for the primary decompositions.