bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fragmentation and rearrangement processes in the mass spectra of perhalogenoaromatic compounds. XII‐pentafluorophenyl derivatives af phosphorus (V) halides
Authors: Jones Timothy R. B. , Miller Jack M. , Fild Manfred 
Published: May 2005

AbstractThe Mass spectral fragmentation processes for a number of alkyl and aryl subtituted phosphinyl and phosphonyllk halides and their thio analogs are discussed with respect to two intramolecular rearrangment processes. The first is aryl fluorine transfer to phosphorus and the second concerns a rearrangement depicted as follows, i.e. a reverse Arbuzov reaction RR′XPS→RXPSR′. Both pathways are supported by evidence obtained form metastable ions and mass analyzed ion kinentic energay spectra. The previously observed phenomenon of subtituent coupling is also describedc where ita occurs in the phosphinyl compounds. The mass spectra of a number of mixed fluoro‐pebtafkuorophenyl phosphorances are also discussed.
Structure and fragmentation mechanism of [C3H7S]+ ions
Authors: Broer W. J. , Weringa W. D. 
Published: May 2005

AbstractFrom a comparison of the metastable ion bundance ratios for loss of C2H4 and H2S from [C3H7S]+ ions in a series of alkyl thio ethers and thiols it was concluded that in most compunds these ion s isomerize to a common structure prior to decomposition in the first field free region. The mechanism for C2H4 loss from the [C3H7S]+ ion gen erated from CH3SCH2CH3 was investigated in detail using 13C and 2H labelling. A rearrangement with formation of a cyclic intermediate prior to the decompistion reaction is proposed. The fragmentation is preceded by extensive hydrogen scrabling. The carbon atoms of the expelled C2H4 molecule are those of the CH2CH3 moiety.
Cyclization‐elimination reactions in the mass spectra of aminopyridine derivatives II‐aryl sulfonamides of 2‐aminopyridine and related compounds
Authors: Broxton Trevor J. 
Published: May 2005

AbstractThe mass spectra of aryl sulfonamides of some 2‐aminopyridines and 2‐aminopyrimidine show abundant peaks corresponding tothe loss of SO2 and HSO2 from the molecular ion. Evidence in favour of a cyclization‐elimination reaction involving bond formation between the pyridine ring nitrogen and the ortho position of the benzene ring is presented.
Effect of ortho substituents in the electron impact induced fragmentation of 2,2′‐disubstituted stilbenes
Authors: Mintas M. , Jakopčić K. , Klasinc L. , Güsten H. 
Published: May 2005

AbstractThe effect of ortho substituents NH2, OCH3, CH3, Cl and NO2 on the fragmentation of five symmetrically and five unsymmetrically 2,2′‐disubstituted stilbenes under electron impact was investigated. The fragmentation patterns deduced were supported by metastable transitions in the first and second field free regions and by exact mass measurements of prominent ions. In general, the fragmentation was found to be in accord with that of stilbene and the corresponding monosubstituted stilbenes. There are, however, some deviations from the general fragmentation scheme caused by direct through‐space interactions of the ortho, ortho′ substituents with concomitant loss of neutral fragments. It is supposed that the formation of 7‐membered cyclic or heterocyclic ions is the result of such through‐space reactions.
Durch Nachbargruppenbeteiligung induzierte (1,2)‐Chlorwasserstoff‐Eliminierung aus ionisiertem 2‐(β‐Chloräthyl)‐ benzoesäuremethylester
Authors: Borchers F. , Heimbach H. , Levsen K. , Morhenn H. , Schwarz H. 
Published: May 2005

AbstractDurch die Untersuchung deuterierter Verbindungen und die Benutzung von Stoßaktivierungsspekten werden sowohl der Mechanismus der ungewöhnlich intensiven HC1‐Eliminierung aus 2‐(β‐Chloräthyl)benzoesäuremethylester als auch die Struktur des resultierenden Produkt‐Ions aufgeklärt. Es wird belegt, daß die stabilen magnified image‐Ionen (Lebensdauer τ ∼ 10−5s) als ionisierte 2‐Vinylbenzoesäuremethylester vorliegen, während die reaktiven Spezies (τ < 10−6s) wenigstens teilweise cyclisieren. Die HCL‐Abspaltung aus 2‐(β‐Chloräthyl)benzosäuremethylester stellt nur formal eine simple (1,2)‐Eliminierung dar. In Wirklichkeit handelt es sich um eine besondere Nachbargruppenbeteiligung der Esterfunktion.
Hydrogen migrations in mass spectrometry. IV—formation of [C6H7]+ in the chemical ionization mass spectra of alkylbenzenes
Authors: Leung Hei‐Wun , Harrison Alex. G. 
Published: May 2005

AbstractUsing specific deuterium labelling the mechanisms of the olefin elimination reactions leading to formation of [C6H7]+ in the H2 and CH4 chemical ionizatin mass spectra of ethylbenzene and n‐propylbenzene (and to [C2H5C6H6]+ in the CH4 chemical ionization mass spectra) have been investigated. The results show that the reaction does not occur by specific migration of H from the β position of the alkyl group to the benzene ring. For ethylbenzene 23–29% of the migrating H originates from the α‐position, while for n‐propylbenzene H migration from all propyl positions is observed in the approximate ratio, position 1:position 2:position 3=0.30:0.22:0.48. It is proposed that the results can be explained on the basis of competing H migration from each alkyl position involving cyclic transition states of different ring sizes, rather than by H randomization within the alkyl chain.
Collision induced dissociations of radical cations
Authors: Maquestiau André , Van Haverbeke Yves , Flammang Robert , De Meyer Claude , Das K. G. , Reddy G. Sudhara 
Published: May 2005

AbstractThe collision induced dissociation spectra of ions generated by ionization or fragmentation of various samples reveal at least five non‐decomposing structures. In contrast, the kinetic energy release measurements for the loss of carbon monoxide from the metastable ions are in agreement with the occurrence of a common reactive species. Isomerization into an ‘α,β‐unsaturated aldehyde‐like’ structure prior to fragmentation is proposed to accommodate these collision induced dissociation and mass analysed ion kinetic energy data. Some resuts suggest also that carbon monoxide loss from the phenol molecular ion may not occur via the cyclohexadienone tautomer.
Fragmentation sous l'Impact Electronique de Diamino‐4,5 Triazoles‐1,2,4 et d'Amino‐4 Mercapto‐5 Triazoles‐1,2,4
Authors: Aouial Mohamed , Bernardini Antoine , Viallefont Philippe 
Published: May 2005

AbstractLes spectres de masse d'un certain nombre d'amino‐4 triazoles −1,2,4 porteurs d'un substituant amino, méthylamino, mercapto ou méthylmercapto en position 5 sont décrits et analysés. Cinq processus de fragmentation du cycle triazole, liés à la nature du groupement fonctionnel en position 5, sont mis en évidence; l'un d'eux, identifié dans tous less cas, résulte de la rupture des liaisons N‐2C‐2 et N‐4C‐5.D'autres dégradation sont également observées à partir du groupment amino en position 4.
Etude par Spectrométrie de Masse d'une Série de Phényl‐1 Naphtalènes Substitués et des Dihydro‐1,4 Naphtols‐1 Correspondants
Authors: Pfau Michel , Heindel Ned D. , Gülaçar Fazil O. , Buchs Armand 
Published: May 2005

AbstractUne étude par spectrométrie de masse d'une série de phényl;‐1 naphtalenes substitués et des dihydro‐1,4napthols‐1 correspondants permet de proposer des modes de formation plausibles pour tous les ions importants. L'élimination de méthanol, qui aboutit à des ions majeurs, fait probablement intervenir le transfert d'un atome d'hydrogène par un état de transition à huit atomes.
Rearrangements in the electron impact induced fragmentations of sulfonyl chlorides
Authors: Davis Paul P. , Grossert J. Stuart , Langler Richard F. , Mantle William S. 
Published: May 2005

AbstractThe major fragmentation pattern obsrved in the mass spectra of simple alkane‐ and arylsulfonyl chlorides may be rationalized by loss of a chlorine atom from the molecular ion, followed by loss of SO2 with concomitant carbocation formation. The mass spectra of α‐mesyl sulfonyl chlorides and napthalenesulfonyl chlorides exhibit ions resulting from chlorine atom migration to the α‐carbon atom with concomitant loss of SO2. The mass spectra of α‐mesyl sulfonyl chlorides also show ions which involve chlorine atom migration to the β‐sulfonyl group.
Analogie Photochimique. II—Cyclisation des Aldéhydes δ,ε Insaturés sous Impact Electronique
Authors: Morizur Jean‐Pierre , Mercier Jacqueline , Furth Bernard , Kossanyi Jean 
Published: May 2005

AbstractLes spectres de masse des aldéhydes δε‐insaturés gem‐diméthylés en 4 présentent un ion m/e 126 résultant de l'élimination d'une oléfine à partir de l'ion moléculaire. Cette élimination implique la cyclisation intermédiaire des aldéhydes insaturés en cyclohexanone, comportement analogue à celui observé en photochimie. Les abondances relatives des décompositions unimoléculaires d'ion m/e 126 (observées par balagyage combiné) confirment le mécanisme proposé.
Synthèse et Propriétés d'Alkylidénehydrazono‐2 Méthyl‐3 Dihydro‐2,3 Benzothiazoles
Authors: Richer Jean‐Claude , Beljean Martine , Pays Michel 
Published: May 2005

AbstractThe synthesis and the spectral properties of 2‐alkylidenehydrazono‐3‐methyl‐2,3‐dihydrobenzothiazoles are reported. In the mass spectra of each of these compounds, the main fragmentation implies the breaking of the N‐Nbond of the azine.
Collisional ionization of monocharged positive ions
Authors: Maquestiau André , Van Haverbeke Yves , Flammang Robert , De Meyer Claude , Menu Alain 
Published: May 2005

AbstractCompetitive fragementations of doubly charged ions formed by charge stripping have been observed for some hydrocarbon ions. The reproducibility of the abundance ratios indicates that they may be used to characterize the structural identity or non‐identity of non‐decomposing monocharged positive ions.
The mass spectrum of 1‐heptyl iodide
Authors: Stahl Daniel , Gäuumann Tino 
Published: May 2005

AbstractThe mass spectra of twelve 13C labeled compounds have been measured in order to investigate the fragmentation of the 1‐heptyl iodide molecular ion. A mechanism is proposed for each reaction leading to the ions containing the iodine atom. The loss of olefin from the heptyl ion derived from the 1‐heptyl iodide proceeds via extensive rearrangement of the linear ion. A non‐linear intermediate structure obtained via protonated substituted cyclopropane is suggested to explain the major fragmentation reactions of the heptyl ion.
Untersuchung von 2.4.6‐substituierten s‐Triazinen durch Gaschromatographie‐Massenspektrometrie
Authors: Zeman Alfred , Wörle Rudolf 
Published: May 2005

AbstractZahlreiche 2.4.6‐Trialkoxy‐s‐triazine wurden mittels Gaschromatographie‐Massenspektrometrie untersucht. Die Fragmentierung dieser Verbindungen bei Elektronenbeschuß wird diskutiert. Die Methode erlaubt, komplexe Triazingemische, die bei der Umsetzung von 2.4.6‐Trichlor‐s‐triazin mit Alkoholgemischen entstehen, schnell und sicher zu identifizieren.
Aliphatic chain–sugar interactions under electron impact. The loss of methanol from acylated methyl glycopyranosides
Authors: Puzo G. , Tichadou J. L. , Prome J. C. 
Published: May 2005

AbstractUnder electron impact, long chain acylated methyl glucopyranoside derivatives lose a methanol molecule from the molecular ion. The hydrogen atom which is transferred arises from the aliphatic chain. This reaction is important when the aliphatic chain contains four or more carbon atoms. The results may be explained by a two‐step hydrogen transfer: hydrogen transfer to the oxygen carbonyl of the ester group, and then to the methoxy glycosidic group prior to fragmentation.
The mass spectrometric fragmentation of some diastereoisomeric 4‐methyl‐1,3,2‐dioxaphosphorinanes
Authors: ZielińSka Barbara , Stec Wojciech J. 
Published: May 2005

AbstractThe mass spectra of nine diastereoisomeric pairs of 4‐methyl‐2‐X‐2‐Y‐1,3,2‐dioxaphosphorinanes have been examined. The differences between the intensities of particular ions in the mass spectra of geometrical isomers are reported and rationalized in terms of the conformations adopted by compounds.
Hydrogen rearrangement in molecular ions of alkyl benzenes: Appearance potentials and substituent effects on the formation of [C7H8]+ ions
Authors: Kuck Dietmar , Grützmacher Hans‐Fr. 
Published: May 2005

AbstractThe mechanism of the formation of [C7H8]+ ions by hydrogen rearrangement in the molecular ions of 1‐phenylpropane and 1,3‐diphenylpropane has been investigated by looking at the effects of CH3O and CF3 substituents in the meta and para positions on the relative abundances of the corresponding ions and on the appearance energies. The formation of [C7H8]+ ions from 1,3‐diphenylpropane is much enhanced at the expense of the formation of [C7H7]+ ions by benzylic cleavage, due to the localized activation of the migrating hydrogen atom by the γ phenyl group. A methoxy substituent in the 1,3‐diphenylpropane, exerts a site‐specific influence on the hydrogen rearrangement, which is much more distinct than in 1‐phenylpropane and related 1‐phenylalkanes, the rearrangement reaction being favoured by a meta methoxy group. The mass spectrum of 1‐(3‐methoxyphenyl)‐3‐(4‐trideuteromethoxyphenyl)‐propane shows that this effect is even stronger than the effect of para methoxy groups on the benzylic cleavage. From measurements of appearance potentials it is concluded that the substituent effect is not due to a stabilization of the [C7H7X]+ product ions. Whereas the [C7H7]+ ions are formed directly from molecular ions of 1‐phenylpropane and 1,3‐diphenylpropane, the [C7H8]+ ions arise by a two‐step mechanism in which the s̀ complex type ion intermediate can either return to the molecular ion or fragment to [C7H8]+ by allylic bond cleavage. Obviously the formation of this s̀ complex type ion, is influenced by electron donating substituents in specific positions at the phenyl group. This is borne out by a calculation of the ΔHf values of the various species by thermochemical data. Thus, the relative abundances of the fragment ions are determined by an isomerization equilibrium of the molecular ions, preceding the fragmentation reaction.
Excitation in ion–molecule collisions. A study of protonated aromatic molecules by ion kinetic energy spectrometry
Authors: Franchetti V. , Freiser B. S. , Cooks R. G. 
Published: May 2005

AbstractCollision induced dissociation of protonated aromatic ions formed in a chemical ionization source has been studied using the technique of mass analyzed ion kinetic energy spectrometry. The observed fragmentations are concordant with those seen in the photodissociation spectra of the same ions with one significant exception. Loss of H is always a major collision induced dissociation process but is not observed in photodissociation spectra. This differences is not due to differences in the total amount of energy transferred in ionic excitation but to differences in the form in which the energy is supplied. Collision induced dissociation can lead to processes forbidden in photoexcitation, particularly those associated with electron unpairing in violation of the even→even+even rule for fragmentations.
Reference standards for negative ion mass spectrometry
Authors: Hirata Yukio , Matsumoto Kozo , Takeuchi Tsugio 
Published: May 2005

AbstractThe negative ion mass spectra of phosphonitrile chlorides (PNCl2)n (n≥3) are studied. Since this series of compounds give very intense negative [M]− and [MCl]− ions, they can be used as good reference standards for negative ion mass spectrometry.
Isomerisation du Thiazole et de l'Isothiazole avant Fragmentation
Authors: Salmona Gérard , Vincent Emile‐Jean 
Published: May 2005

AbstractLes ions moléculaires du thiazole et de l'isothiazole s'isomérisent en une structure commune prépondérante avant de se fragmenter. Ceci est mis en évidence par l'analyse de l'intensité des ions métastables et des libérations d'énergie cinétique.
Etude par Spectrométrie de Masse de la Fragmentation d'une Série de Diols Aliphatiques
Authors: Blanc Pierre‐Alain , Gülaçar Fazil O. , Buchs Armand 
Published: May 2005

AbstractLa fragmentation d'une série de diols aliphatiques de formule générale HO(CH2)nOH avec n = 2‐11 a été étudiée à l'aide de molécules marquées avec du deutérium. Les marquages du n‐butanediol‐1,4 et du n‐hexanediol‐1,6 ont notamment permis de mettre en évidence des réactions d'échange intramoléculaire d'hydrogène; ces échanges deviennent plus importants avec l'allongement de la chaîne.
Chemical ionization mass spectra of some 2‐norbornyl derivatives
Authors: Jelus Barbara L. , Dalrymple David L. , Michnowicz John , Munson Burnaby 
Published: May 2005

AbstractChemical ionization mass spectra of exo‐ and endo‐2‐norbornanols and their phenylurethane derivatives have been obtained with several reactant ions. Small differences are noted in the abundances of norbornyl and [M+H]+ ions for the phenylurethane derivatives: more norbornyl ions with the exo compounds. Relative rate constants for decomposition of [M+H]+ ions, kexo/kendo ≅ 1‐2. No evidence was found for s̀‐participation in the decomposition of these ions. The i‐C4H10 chemical ionization spectrum of endo‐2‐norbornanol contains a much greater abundance of [M‐H]+ ions than the i‐C4H10 chemical ionization spectrum of exo‐2‐norbornanol. This difference presumably results from steric hindrance toward attack of the endo hydrogen.
Stereochemisch kontrollierte Cope‐analoge Zerfallsprozesse von Sulfinylverbindungen im Massenspektrometer
Authors: Lüdersdorf Reinhard , Praefcke Klaus , Schwarz Helmut 
Published: May 2005

AbstractDas Ausmaß der Eliminierung von HX (X = SOCH3, SCH3) aus [MSTol]+‐bzw. [MHHSTol]+‐Ionen (Tol = CH3C6H4), die sowohl durch Elektronenstoßionisation als auch durch chemische Ionisation aus 2‐sulfinylsubstituierten Cyclopentanthiocarbonsäure‐S‐arylestern erzeugt werden, wird in entscheidender Weise durch die Stereochemie der vicinalen Substituenten bestimmt.
Field ionization mass spectrometry of higher n‐alkenes
Authors: Rang S. A. , Müürisepp A.‐M. A. , Liitmaa M. M. , Eisen O. G. 
Published: May 2005

AbstractIn a strong electric field the molecular ions of n‐alkenes ≤C‐12 decompose via cleavage of the CC bond β to the double bond to form the characteristic alkenyl ions that may be used for the identification of positional isomers. For 3‐alkenes (>C‐10), 4‐, 5‐ and 6‐alkenes the formation of the ions with m/e 54 via double β‐cleavage is typical. The field ionization mass spectra of the cis and trans isomers are indistinguishable.
Three‐dimensional representation of metastable peaks at high mass resolution
Authors: Lacey Michael J. , Macdonald Colin G. 
Published: May 2005

AbstractIsobaric daughter ions formed from a common metastable ion have been analysed at high mass resolution. A three‐dimensional representation is used to summarize the data for competitive CO and C2H4 losses and competitive CHO˙ and C2H5˙ losses from metastable molecular ions of cyclohexanone.
Intensitätsverhalten von Molekülanionen organischer Substanzen unter verschiedenen Versuchsbedingungen
Authors: Albers Georg , Knof Hans 
Published: May 2005

AbstractQuantitative Messungen negativer Ionen werden von einigen ausgewählten organischen Verbindungen mit einem umgebauten kommerziellen Massenspektrometer bei 10−4 Torr Quellendruck durchgeführt. Aus der gemessenen Druckabhängigkeit der Molekülionenintensität von Einzelverbindungen und von binären Mischungen kann auf zwei verschiedene Quellen langsamer Sekundärelektronen geschlossen werden. Die Ionenintensität hängt bei niedrigen Gesamtdrücken in der Ionenquelle linear von der Probenmenge in einem doppeltlogarithmischen Maßstab ab, und die langsamen Elektronen werden hauptsächlich durch Wandeffekt erzeugt, während bei hohen Drücken Plasmaeffekte mit einer nichtlinearen Druckabhängigkeit auftreten.
Studies directed toward synthesis of quassinoids. VI—mass spectral fragmentation of D‐ring seco esters and δ‐lactone derivatives of cholic acid
Authors: Dias Jerry Ray , Ramachandra R. , Nassim Bahman 
Published: May 2005

AbstractAnalogy and deuterium labeling demonstrate that considerable remote group interaction occurs between functional groups at positions 7 and 16 in 16, 17‐secosteroids. It is proposed that ion‐dipole interact̂ions separations of distances of 10 to 2 Å will involve energies of 1–30 kcal mol−1 and can play a significant role in fragmentation processes. Successive loss of one, two and three HOAc molecules from a milecular or daughter ion increase progressively in relative intensity; irregularity in this pattern indicates the operation of special factors or multiple genesis of daughter ions having the same m/e. Evidence is presented which suggests that facile ketene ejection from the acetate functional group only occurs from a radical ion and must be preceded by transfer of a hydrogen radical from the acetate group to the site of charge localization.
Mécanismes de fragmentation en spectrométrie de masse par ionisation chimique. III—ions formés par cyclisation
Authors: Audier H. E. , Milliet A. , Perret C. , Tabet J. C. , Varenne P. 
Published: May 2005

AbstractLa fragmentation en spectrométrie de masse par ionisation chimique de composés bifonctionnels peut conduire à la formation d'ions cycliques.
Fragmentation sous l'impact electronique d'imidazo[1,5‐b]triazepinones‐1,2,4 et d'imidazo[4,5‐b]pyridinones
Authors: Bernardini Antoine , Viallefont Philippe , Zniber Rachid 
Published: May 2005

AbstractLes spectres de masse des deux séries d'imidazo[1,5‐b]triazépinones‐1,2,4 et d'imidazo[4,5‐b]pyridinones, obtenues par condensation de diamino‐1,5 imidazoles avec un dérivé β‐dicarbonylé, sont décrits et analysés. Les principales fragmentations sont données et leur utilité à la détermination de structures des composés isomères est montrée.
Energetics of the loss of H2 from [C3H7]+
Authors: Mead Phillip T. , Traeger John C. , Christie John R. , Derrick Peter. J. 
Published: May 2005

AbstractThe internal energies of [C3H7]+ ions contributing to the metastable peak [C3H7]+ → [C3H5]+ + H2 are higher (by perhaps > 100 kJ mol−1) than those of the ion contributing to the threshold current in appearance energy measurements on [C3H5]+. The measured appearance energy may lead to an underestimation of the activation energy, i.e. negative ‘kinetic shift’, due to quantum, mechanical tunnelling. The distribution of energy released in the decomposition can be explained on the basis that much of the reverse activation energy and a statistical proportion of the excess energy is released as translation.
Mass spectra of bile acid methyl ester acetate derivatives
Authors: Dias Jerry Ray , Nassim Bahman 
Published: May 2005

AbstractDeuterium labeling in the acetate derivatives of cholic acid demonstrates that electron impact induced consecutive loss of HOAc from the molecular ion occurs in the following order of decreasing preference: 12α‐OAc > 7α‐OAc > 3α‐OAc. Numerous examples are presented showing that consecutive loss of HOAc from a common ion generally increases progressively with relative intensity. In the acetate pregnan‐20‐one derivatives of cholic acid, loss of 43 mass units from the molecular ion comes from the 12α‐OAc and not the 17β‐acetyl sidechain. Ketene is ejected from an acetoxy group located in an α position to a carbonyl on which an ion‐radical charge is localized.
Field desorption mass spectrometry of 1‐methylpyridinium salts
Authors: Larsen Elfinn , Egsgaard Helge , Holmen Hans 
Published: May 2005

AbstractQuaternary pyridinium salts were investigated by field desorption, field ionization and electron impact mass spectrometry. Thermal decomposition of the salts under field desorption conditions was found to give very abundant volatile products, identified as the dihydro analogues and the ‘methides’ of the cations. The formation of the volatile compounds, especially those with molecular weights corresponding to those of the (cation −1), (cation +1) and (cation +13) was studied in detail by deuterium and 13C labelling experiments.