bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractBy 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

AbstractThe 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

AbstractIn 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

AbstractDie 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractAldoses, 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

Abstract[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

AbstractThe 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.
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

AbstractDie 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

AbstractDas 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

AbstractUne 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

AbstractThe 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

AbstractAn 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

AbstractLes 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

AbstractThe 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

AbstractDie 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

AbstractUn 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

AbstractThe 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

AbstractMit 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

AbstractThe 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

AbstractMass 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

AbstractLes 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

AbstractDefocusing 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

AbstractA 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

AbstractThe 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.