bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical ionization mass spectrometry of some crown ethers
Authors: Van Gaever F. , Van de Sande C. C. , Bucquoye M. , Goethals E. J. 
Published: May 2005

AbstractMethane and isobutane chemical ionization mass spectrometry is superior to the classical electron impact technique for the analysis of aliphatic macrocyclic polyethers of the 4n‐crown‐n type. The latter reagent gas is particularly suited for molecular weight determinations.
Etude Structurale de Cations‐Radicaux
Authors: Maquestiau A. , Van Haverbeke Y. , Flammang R. , Menu A. , Wentrup C. 
Published: May 2005

AbstractLes spectres d'énergie cinétique de cations‐radicaux issus de 26 précurseurs sont décrits. L'étude des caractéristiques d'ions métastables telles que les libérations d'énergie cinétique, les rapports d'abondances ioniques ou encore les distributions isotopiques pour des composés marqués, montre que tous les ions métastables sont isomérisés en une structure commune ou des mélanges semblables de structures avant fragmentation. Les dissociations induites par collisions et l'ionisation collisionnelle ont été utilisées pour l'étude des ions stables dont la durée de vie est supérieure au temps de vol entre la source et le collecteur. Les résultats sont interprétés sur la base de mélanges de structures initiales et isomérisées.
Spectrographie de Masse de Diazastéroïdes Possédant le Motif Tétrahydroisoquinoléique
Authors: Verchère Catherine , Hocquaux Michel , Viel Claude 
Published: May 2005

AbstractNous avons recherché les fragmentations caractéristiques dans la série de la dihydro‐3,4 isoquinoléine et de la diaza‐8,13 oestrone. La recherche des pics métastables, ľétude des spectres ‘simili’ MIKE et ľétude de dérivés deutériés ont été utilisées. En série diazastéroïdique, nous avons mis en évidence trois grands types de fragmentation, ainsi qu'un départ préférentiel de ľhydrogène porté par le carbone 14.
Spectrométrie de Masse d'Hétérocycles Azotés. VII—Phenyl‐1 Triazole‐1,2,3
Authors: Aubagnac J.‐L. , Campion P. , Guenot P. 
Published: May 2005

AbstractLa comparaison des spectres normaux et MIKE du phényl‐1 triazole‐1,2,3 et de ses dérivés deutériés et marqués au 13C indique que les ions peuvent se décomposer selon deux voies compétitives: une rupture simple sans réarrangement est préférentielle pour les ions de haute énergie (spectre normal). Au contraire, la perte de HCN domine pour les ions de basse énergie (métastables) et a lieu après mixage complet des atomes d'hydrogène.
The gas enhanced negative ion mass spectra of polychloroanisoles
Authors: Busch Kenneth L. , Hass J. Ronald , Bursey Maurice M. 
Published: May 2005

AbstractMethane or a methane–oxygen mixture was used as an enhancement gas to obtain negative ion mass spectra of polychloroanisoles. Dichloroanisoles did not react with oxygen but the more highly chlorinated anisoles did. Compounds with hydrogen ortho to the methoxy group had [M1]− ions, while others gave . The fragment arose through loss of an ortho chlorine and amethyl hydrogen. The loss of HCl followed by oxygen displacement of a remaining ortho or para chlorine produced [M55]− ions; the para position was the preferred site of displacement. Another ion‐molecule reaction with oxygen leads to [MCH2Cl]−. The fragmentations resemble those of chlorinated aromatics such as the polychlorodibenzodioxins.
Electron impact mass spectra of some enols and their alkyl ethers
Authors: Nagraba Krzysztof , Moskal Janusz , Moskal Aleksandra 
Published: May 2005

AbstractThe mass spectra of α‐arylamino‐β‐hydroxycrotonic acid anilides and their O‐methyl and O‐ethyl ethers have been determined and the characteristic fragmentation pathways are discussed. The proposed fragmentation patterns are supported by the appropriate metastables and deuterium labelling.
EA‐Massenspektren Cyansubstituierter Heterocyclen
Authors: Holzmann G. , Rothkopf H. W. 
Published: May 2005

AbstractDie EA‐Spektren cyansubstituierter Heterocyclen zeigen spezifische Fragmentierungen, die eine massenspektrometrische Unterscheidung isomerer Systeme gestatten. Die Strukturen der aus den Molekülanionen bzw. [(M – H)]− ‐Ionen direkt gebildeten ‐Ionen werden durch Vergleich der MI‐ bzw. CA‐spektren verschiedener Vorläuferionen untersucht. Das Fragmentierungsverhalten von Tetracyan‐substituierten Heterocyclen setzt Umlagerungen der Molekülanionen voraus.
In‐beam electron impact mass spectrometry of aliphatic alcohols
Authors: Ohashi Mamoru , Nakayama Noboru 
Published: May 2005

AbstractThe characteristics of the in‐beam electron impact mass spectra of six isomers of undecanol as well as several 1‐alkanols have been examined. In addition to the characteristic ions observed in the conventional electron impact spectra, the [2M+1]+, [2M+1‐H2O]+, [2M+1‐2H2O]+, [2M‐R or R′]+, [2M‐H2OR or R′]+, [2M2H2OR or R′]+ and [M+1H2O]+ peaks are common in the in‐beam electron impact mass spectra of the undecanol isomers of structure RCH(OH)R′. Deuterium labelling experiments have shown that the extra proton in the protonated dimer ions, [2M+1]+, originates from the hydroxy group. The processes which produce the important peaks in the high m/e regions are discussed.
Flophemesyl derivatives of alcohols, phenols, amines and carboxylic acids: Derivatives for mass spectrometric ion monitoring and structure determination
Authors: Francis Ainsley J. , Morgan E. D. , Poole C. F. 
Published: May 2005

AbstractThe flophemesyl (or pentafluorophenyldimethylsilyl) derivatives of representative alcohols, phenols, carboxylic acids and amines show rather simple spectra with a few abundant ions at high mass, characteristic of the parent compound and a few ions at low mass characteristic of the flophemesyl group. These derivatives are useful in the structure determination of simple compounds, and for the determination by single or multiple ion monitoring of known compounds at low levels.
N′,O,O′‐triacetyl‐N‐caffeoylputrescine: A new synthesis and mass spectrometry
Authors: Eagles John , Self Ron , Synge Richard L. M. 
Published: May 2005

AbstractSome puzzling features of a published mass spectrum of the title compound have been clarified by mass spectrometric study of a specimen prepared by a new route, by coupling O,O′‐diacetylcaffeoyl chloride with N‐monoacetylputrescine.
The consecutive loss of two H2O molecules from protonated 1,2‐ and 1,3‐ cyclohexanediols in the gas phase: An example for the incidence of skeletal rearrangement in chemical ionization mass spectrometry
Authors: Wolfschütz Roland , Schwarz Helmut , Blum Wolfgang , Richter Wilhelm J. 
Published: May 2005

AbstractThe consecutive dehydration of protonated molecules [MH]+ of 1,2‐ and 1,3‐cyclohexanediols (cis and trans isomers) by loss of two H2O molecules has been investigated. Analysis of 2H labelled compounds showed that loss of the first H2O molecule represents a simple heterolysis, i.e. a dissociation without exchange of hydrogens between O—H and C—H bonds. Subsequent elimination of the second H2O molecule in the process [MH–H2O]+→[MH–2H2O]+ followed several competing paths. The two major ones corresponded formally (with reference to an intact 6‐ring skeleton) to 1,3‐ and 1,4‐eliminations; in comparison, the alternative 1,2‐elimination is only a minor route at most. At least for the 1,3‐elimination, water loss from the [MH–H2O]+ ions is not direct, but is associated with skeletal rearrangement, most probably of the Wagner‐Meerwein‐type, effecting contraction of the 6‐ to a 5‐membered ring.
The origin of the [M – 1]+ ion in the mass spectra of N,N‐dialkylbenzamides. A reinvestigation of the mechanism
Authors: Fong C. W. , Hameister C. R. 
Published: May 2005

AbstractA reinvestigation of the mechanism of formation of the [M – 1]+ ion in a series of N,N‐dialkylbenzamides suggests that previous mechanisms put forward to account for the formation of the [M – 1]+ ion are deficient. A new mechanism is proposed which accounts for the data observed previously, as well as our results for a series of N,N‐dialkyl‐2‐chlorobenzamides, 4‐substituted N,N‐dimethylbenzamides and some related compounds. For the N,N‐dialkyl‐2‐chlorobenzamides, comparison of the abundances of the [M – 1]+ ion with the [M – 35]+ ion suggests that a concurrent reaction is occurring, besides loss of the ortho aromatic hydrogen atom. A study of substituent effects on the intensity ratio [M – 1]+/[M]+ shows an upward concave plot of this against σ+, suggesting that two competing mechanisms occur for the formation of the [M – 1]+ ion.
Structure and formation of gaseous [C4H5O]+ ions. I—isomeric ions of the type C3H5\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O
Authors: Hommes Henk , Terlouw Johan K. 
Published: May 2005

AbstractCharacterization of [C4H5O]+ ions in the gas phase using their collisional activation spectra shows that the four C3H5\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O isomers CH2C(CH3)\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O, CH2CHCH2\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O, CH3CHCH\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O and ▹\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O are stable for ≥ 10−5 s. It is concluded further from the characteristic shapes for the unimolecular loss of CO from C3H5\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O ions generated from a series of precursor molecules that the CH2CH(CH3)\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O‐ and CH2CHCH2\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O‐type ions dissociate over different potential surfaces to yield [allyl]+ and [2‐propenyl]+ [C3H5]+ product ions respectively. Cyclopropyl carbonyl‐type ions lose CO with a large kinetic energy release, which points to ring opening in the transition state, whereas this loss from CH3CHCH\documentclass{article}\pagestyle{empty}\begin{document} $\mathop {\rm C}\limits^ + =\!= $\end{document}O‐type ions is proposed to occur via a rate determining 1,2‐H shift to yield 2‐propenyl cations.
The fragmentation of 5‐phenyl‐1,4‐benzodiazepin‐2‐ones. Mechanism for the formation of [M  H]+
Authors: Benz Wolfgang , Vane Floie M. , Rapp Uwe 
Published: May 2005

AbstractThe fragmentations under electron impact of 5‐phenyl‐1,4‐benzodiazepin‐2‐ones are investigated with the aid of high resolution, metastable decompositions and deuterium labeling. Based on our data a mechanism for the formation of the [M – H]+ ion is proposed. It is shown that the [M – CHO]+ ion is probably formed by two different pathways. Data on two minor fragment ions give support to the structure proposed for the [M – CHO]+ ion.
Elimination sous Impact Electronique de HCN et H· a partir de l'Indole. Comparaison avec l'Indolizine
Authors: Corval Madeleine 
Published: May 2005

AbstractLes deux fragmentations primaries de l'indole sous l'impact d'électrons, perte de HCN et perte de H⋅, sont étudiées au moyen de onze variétées marquées au deutérium. Tous les hydrogènes sont impliqués dans le processus de perte de HCN, avec une prédominance des hydrogènes du cycle pentagonal, plus marquée dans le spectre à 70 eV que dans la gamme d'éenergie des ions métastables, où les trois sommets du cycle pentagonal sont équivalents. Les résultats d'ordre qualitatif relatifs à la perte de H⋅ mettent en évidence l'existence d'un effet d'isotopie et sont également compatibles avec une prédominance des hydrogènes du cycle pentagonal, qui d'une élimination très préférentielle de l'hydrogène lié à l'azote. Ce comportement est comparé à celui de l'indolizine, et les niveaux d'énergie des états de transition menant à la perte de HCN sont discutés pour les deux composeés.
Isomerisierung von Methoxy‐ und Carbomethoxysubstituierten Cycloalkyl‐ und Alken‐radikalkationen
Authors: Schwarz H. , Wesdemiotis C. , Levsen K. , Heimbach H. , Wagner W. 
Published: May 2005

AbstractUnter Benutzung mehrerer Techniken, wie Stoßaktivierung, Charakteristik metastabiler Ionen und Feldionisationskinetik, wird das äußerst komplexe Isomerisierungsverhalten von methoxy‐ und caarbomethoxysubstituierten Cycloalkanen (drei‐bis siebengliedrege Ringe) analysiert. Das Ausmaß der Isomerisierung hängt sowohl von der Ringgröße als auch vom Substituenten ab, während die Ringöffnung unabhängig von den elektronischen Eigenschaften der Substituenten immer die C‐1C‐2‐Bindung betrifft. Hierbei werden ausschließlich lineare Alken‐Radikalkationen erzeugt. Bei OCH3‐ und COOCH3‐Substituenten wird die Lage der resultierenden Doppelbindung terminal oder α,β‐ungesättigt hauptsächlich durch die Ringgröße des Cycloalkan‐Molekülions und weniger durch den Substituenten beeinfluß. Alkylsubstituierte Cycloalkane (drei‐ bis fünfgliedrige Ringe) lagern sich allerdings nur zu terminalen Alken‐Radikalkationen um. Die Barriere der Doppelbindungswanderung scheint vom Substituenten abhängig zsu sein.
Fragmentation of even electron ions. Protonated ketones and ethers
Authors: Sigsby M. L. , Day R. J. , Cooks R. G. 
Published: May 2005

AbstractA systematic study of the types of fragmentation undergone by internally excited protonated molecules is presented. Two representative functional groups, ethers and ketones, are selected, and both aliphatic and aromatic substituents are examined. The ions are formed by protonation or alkylation in a chemical ionization source, and caused to fragment by collision at high relative kinetic energy. The prevalence of 1,3‐rearrangements and the breakdown of the even electron fragmentation rule highlight the ion chemistry uncovered here. Specific findings include: (i) electron unpairing reactions associated with alkyl radical loss are common. These are probably energetically less favorable simple bond cleavages and are observed in competition with entropically less favorable elimination reactions. (ii) Alkane elimination is a characteristic reaction, which often occurs by a four‐centered mechanism. Several variations on this reaction type are encountered. (iii) Alkene elimination is another ubiquitous reaction which occurs by a four‐centered mechanism in the systems studied here. Competition between alkene and alkane loss is extremely sensitive to the particular system in hand.
Mass spectra of flavonoids. Electron impact mass spectra of flavan‐4‐ols
Authors: Radford Terence , Sweeny James G. , Iacobucci Guillermo A. , Hribar Jeremy D. , Weibel Leo A. 
Published: May 2005

AbstractThe electron impact mass spectra of seven flavan‐4‐ols are reported. Fragmentation pathways were investigated using deuterium labeling and high resolution measurements. The results are consistent with previously proposed ion structures for these compounds, but indicate that the mechanisms suggested for certain hydrogen rearrangements should be revised.
Structural correlations with kinetic energy release during loss of chlorine from nineteen selected chlorinated biphenyls
Authors: Hass J. Ronald , Bursey Maurice M. , Levy Louis A. , Harvan Donald J. 
Published: May 2005

AbstractUnimolecular and collision induced decompositions of the major ions of selected polychlorinated biphenyls in the field free region between the magnetic and electric sectors of a reversed Nier‐Johnson instrument were studied. Loss of a single chlorine atom is associated with a wide range of kinetic energy releases but still can be correlated by a single reaction mechanism. Loss of two chlorines is interpreted as a rapid sequential loss from isomerized molecular ions for all but one compound. The decompositions which metastable ions undergo are not always the same as those of high energy ions in the source. Correlations between substituent positions and kinetic energy release can be made for the [M]+·→[MCl]+ and [MCl2]+· processes.
Kinetic energy release in unimolecular decompositions of ions. hydrogen rearrangements
Authors: Cole Neil W. , Rickard Gregory J. , Christie John R. , Derrick Peter J. 
Published: May 2005

AbstractThe partition of reverse activation energy in hydrogen rearrangements is considered in terms of atomic motions composing the transition state reaction coordinate. It is shown how this approach predicts that, in general, elimination of H2 from any small ion (as defined in the paper) is likely to be characterized by partition of significant proportions of any reverse activation energy as translational energy of the products. Hydrogen rearrangements in large ions leading to fragments of comparable mass are much less likely to partition reverse activation energy into product translation.
The mass spectral fragmentation of phenyl ω‐dialkoxyethyl tellurides
Authors: Knapp Furn F. 
Published: May 2005

AbstractThe 70 eV mass spectrum of phenyl ω‐dimethoxyethyl telluride [C6H5TeCH2CH(OR)2, RCH3]contains an intense peak at m/z 238 which corresponds to a rearrangement ion [C6H5TeOR]+. The formation of this species is further illustrated by the presence of a peak at m/z 241 in the spectrum of the hexadeuterated analog (RCD3) and a peak at m/z 252 in the spectrum of the ethyl analog (RCH2CH3). These combined results illustrate the presence of only one of the alkoxyl groups in the rearrangement ion. Several other abundant ions that contain oxygen but not tellurium are present in the spectra of these compounds. High resolution analyses have aided in the determination of the origin and composition of several of the characteristic ions formed upon electron impact fragmentation of phenyl ω‐dimethoxyethyl telluride.
Fragmentation sous l'Impact Electronique d'Amino‐4 triazole‐1,2,4 ones‐5
Authors: Bernardini Antoine , Viallefont Philippe , Milcent René 
Published: May 2005

AbstractLes spectres de masse d'un certain nombre d'amino‐4 triazole‐1,2,4 ones‐5 différemment substituées en position 1 sont rapportés; ils mettent en évidence de nouveaux réarrangements et des migrations d'hydrogène. La comparaison des spectres normaux et des spectres d'énergie cinétique obtenus selon la technique simili MIKE a permis de déterminerla structure des ions moléculaires et des ions fragments et de décrirela formation de ces derniers. Ces résultats montrent que ľion moléculaire des amino‐4 triazolones‐5 non substituées en position 1 existe probablement en phase gazeuse sous deux formes tautomères (N‐1‐H et OH).
Mass spectrometry of transition metal π‐complexes. XV—The effect of substituents on the fragmentation of benchrotrenyls under electron impact
Authors: Nekrasov Yu. S. , Vasyukova N. I. 
Published: May 2005

AbstractMass spectra of substituted benchrotrenyls RC6H5Cr(CO)3 where RH, F, CI, I, CH3, OCH3, COOCH3, C2H5, N(CH3)2, NH2, C6H5, C(CH3)3, p‐C6H4NH2, CH2C6H5, CH2CH2C6H5), 1,3,5‐(CH3)3C6H3Cr(CO)3 and 1,2,3,5‐(CH3)4C6H2Cr(CO)3 have been studied. It has been found that for monosubstituted benchrotrenyls there is a linear dependence of the parameter log [Cr]+/[RC6H5Cr]+) on the number of degrees of freedom of the [RC6H5Cr]+ ion. Decarbonylation of the molecular ions is not affected by the nature of the substituent R. The results are interpreted in terms of the quasi‐equilibrium theory of mass spectra.
A Photoionization study of some benzoyl compounds—Thermochemistry of [C7H5O]+ formation
Authors: McLoughlin R. G. , Traeger J. C. 
Published: May 2005

AbstractAppearance energies for [C7H5O]+ fragment ions, formed from a variety of benzoyl compounds, have been measured by photon impact. The mean heat of formation calculated for [C7H5O]+ is 705 ± 6 kJ mol−1, which can be correlated with either a single threshold structure or a mixture of structures with similar heats of formation. Previously observed variations of ΔHf([C7H5O]+) with precursor molecule are shown to be consistent with a structure dependent kinetic shift, rather than the presence of isolated electronic states.
Loss of hydrogen cyanide from monocyanopyridines upon electron impact: Dewar pyridine structures and ring opening—Ring closure reactions revealed by 13C and 15N Labelling
Authors: Molenaar‐Langeveld T. A. , Vermeulen N. P. E. , Nibbering N. M. M. , Morgan R. P. , Brenton A. G. , Beynon J. H. , Sharma D. K. Sen , Jennings K. R. 
Published: May 2005

AbstractExtensive 13C and 15N labelling has shown that the molecular ions of 2‐, 3‐ and 4‐cyanopyridine with lifetimes up to 10−6 s eliminate hydrogen cyanide originating predominantly from the ring (˜65%). Moreover, this hydrogen cyanide loss occurs after an equilibrated positional interchange of the ring carbon atoms at positions interchange of the ring carbon atoms at positions 2, 4 and 6 via Dewar pyridine structures. In molecular ions with lifetimes of 10−6–10−5 s skeletal rearrangements have taken place in such a way that both nitrogen atoms have become equivalent prior to the loss of hydrogen cyanide. Arguments are put forward that this equivalence of nitrogen atoms is caused by the intermediacy of ions with a 1,4‐dicyanobuta‐1,3‐diene structure. About 60% of these intermediate ions eliminate hydrogen cyanide in a fast process. The remaining 40% of these ions undergo ring closure again to a pyridine ring in which the carbon atoms of positions 2, 4 and 6 are positionally interchanged rapidly via Dewar pyridine structures followed by ring opening again and eventual loss of hydrogen cyanide. This interpretation of the 13C and 15N labelling results is further corroborated by a study of the loss of hydrogen cyanide from molecular ions of 1,4‐dicyanobuta‐1,3‐diene labelled with 13C in both cyano groups.
Identification of some isomeric [C8H6O]+˙ ions generated from phenyl substituted cyclic ketones using collisional activation
Authors: Van Den Heuvel C. G. , Nibbering N. M. M. , Heimbach H. , Levsen K. 
Published: May 2005

Abstract[C8H6O]+˙ ions with o‐quinonoid ketene, benzocyclobutenone, phenyl ketene and benzofuran structures have been generated from various precursors. Their collisionally induced decompositions in both field free regions of a double focusing mass spectrometer with so‐called reversed geometry have been studied using mass analysed ion kinetic energy scans and B/E linked scans. In both cases the abovementioned [C8H6O]+˙ structures can be distinguished–except the benzocyclobutenone ion which gives very similar spectra to the o‐quinonoid ion–on the basis of the intensity ratios [m/z 77]/[m/z 76] and [m/z 104]/[m/z 102]. The stable [C8H6O]+˙ ions generated from the molecular ions of 7 ‐phenylbicyclo[3.1.1]heptan‐6‐one appear to have the phenyl ketene structure, as was suspected from previous kinetic energy release measurements.
Structure and formation of gaseous [C4H5O]+ Ions. II–Ions of the type HCC\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}(OH)(CH3)
Authors: Burgers Peter C. , Hommes Henk , Terlouw Johan K. 
Published: May 2005

AbstractLoss of an alkyl group X⋅ from acetylenic alcohols HCCCX(OH)(CH3) and gas phase protonation of HCCCOCH3 are both shown to yield stable HCC\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}(OH)(CH3) ions. Ions of this structure are unique among all other [C4H5O]+ isomers by having m/z 43 [C2H3O]+ as base peak in both the metastable ion and collisional activation spectra. It is concluded that the composite metastable peak for formation of m/z 43 corresponds to two distinct reaction profiles which lead to the same product ion, CH3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}O, and neutral, HCCH. It is further shown that the [C4H5O]+ ions from related alcohols (like HCCCH(OH)(CH3)) which have an α‐H atom available for isomerization into energy rich allenyl type molecular ions, consist of a second stable structure, H2C\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm C}\limits^{\rm + } $\end{document}C(OH)CH2.