bluuebunny/crossref_metadata_2025 huggingface dataset:
Fragmentation sous impact electronique de l'acetate de tertiobutyle
Authors: Corval Madeleine
Published: May 2005

L'examen des spectres de masse à resolution moyenne de l'acétate de tertiobutyle et de trois variétés marquées asu deutérium permet de déterminer les modes defragmentation à 70 e V, confirmés pour la présence de transitions métastables. Oute le réarrangement de McLafferty deux types de réarrangement moins classiques des ions oxygénés sont observés, et quelques effets d'isotopie sont mis en évidence.
Massenspektrometrische Untersuchung ungesättigter Carbonylverbindungen: Radikal‐eliminierung durch α‐Spaltung oder Cyclisierung?
Authors: Schwarz Helmut , Richter Bernd , Bohlmann Ferdinand
Published: May 2005

Die Mechanismen der Alkyleliminierung aus verschieden Carbonylverbindungen werden diskutiert. Sowohl das Fragmentierungsverhalten als auch die Isomerisierungstendenz der Molek%uUl‐Ionen werden stark durch die Anzahl der Doppelbindungen, die Natur der Ketofunktion und die Position des eliminierten Radicals beeinfluust.
Ionisation potentials in structure analysis of isomeric nitrones, oxaziranes, O‐ether oximes and acid amides
Authors: Thorstad Olav , Undheim Kjell , El‐Gendy Mahmoud A. F.
Published: May 2005

Comparative studies of the ionisation potentials and the mass spectra of some isomeric nitrones, oxaziranes, O‐ether oximes and acid amides gave no evidence for hermally‐induced isomerisation in the mass spectrometer. Characteristic differences in the electron‐impact‐induced fragmentation patterns are discussed.
Effects of bifunctional interactions in the chemical ionization mass spectrometry of carboxylic acids and methyl esters
Authors: Weinkam Robert J. , Gal Joseph
Published: May 2005

The methane chemical ionization mass spectra of dodecan‐1, 10‐dioic acid and the methyl ester show enhanced water and methanol elimination relative to monofunctional analogs. Elimination of acetic acid from 1,10‐diacetoxydecane, however, was reduced relative to 1‐acetoxydecane. This appears to be the result of bifunctional interactions. The steric requirement of this interaction is shown in an homologous series of dicarboxyl compounds. The change in interfunctional separation is shown to affect the proton and ammonium ion affinities in the ammonia chemical ionization spectra of the dicarboxyl compounds in a manner explained in terms of proton and ammonium ion complex formation. The observation is extended to various other functional groups.
Differentiation of isomeric cyclic diamides by electron impact mass spectra
Authors: Foti S. , Montaudo G. , Lüderwald I. , Przybylski M. , Ringsdorf H.
Published: May 2005

The behaviour under electron impact of two series of isomeric cyclopentane‐ and cyclohexane‐1, 2‐ and ‐1, 3‐dicarboxylic acid dipiperidides was studied. Diagnostic fragmentation pathways were found to differentiate the isomeric diamides. Additional evidence was obtained from the metastable transitions.
Field desorption mass spectrometry of quaternary ammonium salts: Cluster ion formation
Authors: Veith H. J.
Published: May 2005

The field desorption mass spectra of salts such as quaternary ammonium and carbenium salts with organic cations in addition to high cation intensities show signals for cluster ions composed of the salt cation + salt molecule, i.e. [C + nM]+, n = 1–5, thus allowing determination of the molecular weights of salts. In some cases cluster ions of the type [nM – 1]+ are detected. Conditions for the formation of cluster ions are discussed.
On the formation of the [M  OH]+ ion in m‐nitrobenzaldoxime. evidence for a cyclohexadiene‐type intermediate ion
Authors: Vijfhuizen Peter C. , Verboom Wim , Heerma Wigger
Published: May 2005

In m‐nitrobenzaldoxime a strongly enhanced loss of OH⋅ is observed as compared with the p‐nitro compound. Evidence is presented for a fragmentation mechanism involving the formation of a cyclohexadiene‐type intermediate ion formed by a rearrangement of the hydroxyl hydrogen to the phenyl ring.
Massenspektrometrische Untersuchungen zu Dyotropen Umlagerungen
Authors: Schwarz Helmut , Kliment Miroslav , Reetz Manfred T. , Holzmann Gerhard
Published: May 2005

Die elektronenstoßinduzierte spaltung der Sauerstoff‐Kohlenstoff‐(bzw. silicium)‐Bindung wird durch eine gleichzeitige Wanderung der Silylfunktion zum Sauerstoff ermöglicht. Der mechanistische Verlauf entspricht teilweise dem von dyotropen Umlagerungen.
Mass spectrometric studies of 6‐chloro‐6H‐dibenz[c,e] [1,2]oxaphosphorine‐6‐sulphide and its derivatives
Authors: Bhatia M. S. , Pawanjit
Published: May 2005

The electron‐impact induced fragmentation of 6‐chloro‐6H‐dibenz[c,e] [1,2]oxaphosphorine‐6‐sulphide and its 6‐ethoxy and 6‐hydroxy derivatives has been studied and it has been found that formation of the dibenz[c,e] [1,2]oxaphosphorin system and elimination of HCP are common features. β‐Hydrogen rearrangement, in the case of the ethoxy derivative, is comparable to ethers with a POCH2CH3 linkage.
Effect of substituent group interaction in the fragmentation of some pyrrolidin‐3‐ones
Authors: Cum Giampietro , Sindona Giovanni , Uccella Nicola
Published: May 2005

The decomposition after electron impact of someN‐alkyl andN‐aryl pyrrolidin‐3‐ones has been examined and fragmentation mechanisms influenced by the substituents on the nitrogen have been observed. Accurate mass measurement, deuterium labelling, kinetic energy release measurements and metastable (DADI) ion abundances, permit the elucidation of the probable mechanism of formation of the most intense fragment ions. The available experimental evidence indicates the occurrence of rearrangement processes leading to important product ions in the mass spectra of theN‐aryl derivatives. This type of fragmentation has been interpreted as the result of the combined action of two groups on the nitrogen atom of the heterocyclic nucleus.
Computer‐aided interpretation of mass spectra. STIRS prediction of rings‐plus‐double‐bonds values
Authors: Dayringer Henry E. , McLafferty F. W.
Published: May 2005

The number of rings‐plus‐double‐bonds (R + DB) in an unknown molecule can be predicted from its mass spectrum using the ‘Self‐Training Interpretive and Retrieval System’.2 The average R + DB value of the 15 compounds selected by the overall match‐factor (highest MF11.0 values) predicts the R + DB value of the unknown within ±1 of the correct value for predictions between 0 and 4 in 87% of the cases, and within ±2 for predictions between 5 and 11 for 77% of the cases.
Mass spectra of some perfluoroalkyl and perfluoroalkylether substituted 1,2,4‐oxadiazoles
Authors: Paciorek Kazimiera J. L. , Nakahara James H. , Kratzer Reinhold H. , Rosser Robert W.
Published: May 2005

Electron impact fragmentation patterns were obtained for 1,4‐bis[(5‐perfluoro‐n‐heptyl)‐1,2,4‐oxadiazolyl]‐benzene, its perfluoroalkylether substituted analogue, 3,5‐bis(perfluoroalkyl)‐, 3,5‐bis(perfluoroalkylether)‐ and 3‐perfluoroalkylether‐5‐perfluoroalkyl‐1,2,4‐oxadiazoles. In the compounds containing the phenylene group the molecular ion constituted the base peak; the main process was the breakdown of the oxadiazole ring with concurrent liberation of the perfluoroalkyl or perfluoroalkylether nitrile molecule; cleavage of the fluorinated chain α to the oxadiazole ring was found to take place to a considerable degree. In the perfluorinated 1,2,4‐oxadiazoles cleavage β to the oxadiazole ring occurred preferentially; fragmentation of the ring itself took place to a limited degree only. The 3‐perfluoroalkylether‐5‐perfluoroalkyl‐1,2,4‐oxadiazole appeared to undergo the primary β‐cleavage exclusively at the perfluoroalkylether sidechain.
Hydrogen migrations in mass spectrometry. III–Energetics of formation of [R′CO2H2]+ in the mass spectra of R′CO2R
Authors: Benoit F. M. , Harrison A. G. , Lossing F. P.
Published: May 2005

The appearance potentials for the [R'CO2H2]+ ion produced in the fragmentation process \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm R}^{\rm '} {\rm CO}_{\rm 2} {\rm R}} \right]_{}^{_.^ + } $\end{document} → [R'CO2H2]++[R2H] have been measured using mono‐energetic electron impact techniques for ethyl, n‐propyl, and i‐propyl formates and acetates. The results indicate that at the threshold the product ion has the protonated acid structure with the hydrogen on the carbonyl and not the hydroxyl group, and that the neutral product for the propyl esters is the allyl radical and not the cyclopropyl radical. For the propyl formates and acetates the appearance potential of the [R'CO2H2]+ ion is identical with the adiabatic ionization potential of the parent ester (measured by photoelectron spectroscopy) indicating that fragmentation occurs for ground state molecular ions. A two‐step mechanism is proposed to rationalize the results.
A study of deuterium exchange in adamantane carboxylic acids and alcohols under electron impact
Authors: Yurchenko A. G. , Dovgan N. L. , Chizhov O. S. , Karpenko N. F. , Ya. Podel'ko A.
Published: May 2005

The mass spectra of 1‐adamantyl substituted carboxylic acids and alcohols with and without deuterated hydroxyl groups were studied. Deuterium exchange between functional group and adamantane nucleus was observed and a possible explantation of the phenomenon is given.
Mass spectrometry of transition‐metal π‐complexes. III—a study of an iron‐coordinated tautomer of phenol
Authors: Calleja J. , Davis R. , Ojo I. A. O.
Published: May 2005

A study of the fragmentation of the \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{\left({{\rm C}_{\rm 6} {\rm H}_{\rm 6} {\rm O}} \right){\rm Fe}} \right]_{}^{_.^ + } $\end{document} ion formed from two different precursors suggests that the ions adopt different structures over that part of the energy distribution giving rise to decomposition in the ion source.
Equivalency of the carbon atoms in the molecular ion of cyclopropabenzene
Authors: Wentrup‐Byrne E. , Gülaçar F. O. , Müller P. , Buchs A.
Published: May 2005

The carbon atoms of the molecular and [MH]+ ions of cyclopropabenzene which are formed upon electron impact at 70 and at 12 eV lose their positional identity completely before C2H2 is expelled.
Mass spectra of substituted Δ2‐1,2,4‐oxadiazolines—I
Authors: Srivastava R. M.
Published: May 2005

The electron impact fragmentation of four Δ2‐1,2,4‐oxadiazolines with substituents at positions 3 and 5 has been examined. The direct analysis of daughter ions and high resolution mass measurements provided valuable information regarding certain ions. The present study clearly demonstrates that the substitution of phenyl or a substituted phenyl group for alkyl at C‐3 and alkyl in place of a phenyl substituent at C‐5 in the oxadiazoline system alters the fragmentation modes considerably.
Der massenspektrometrische Verlust eines N‐Substituenten aus monoacylierten 1.3‐Diaminopropanen
Authors: Eckhardt Gert , Gessi Ennio
Published: May 2005

N‐Acyl‐N′,N′‐dialkyl‐1.3‐diaminopropane spalten beim elektronenstoßinduzierten Zerfall einen N‐Substituenten aus den Molekülionen ab. Die Natur aller N‐Substituenten bestimmt, ob vorzugsweise die Acyl‐ oder eine Alkylgruppe eliminiert wird.
Electron impact spectra of 2‐diazoacetophenones
Authors: Thomas C. W. , Leveson L. L.
Published: May 2005

The mass spectra of nine 2‐diazoacetophenones are reported. Rearrangements are examined by means of low electron voltage measurements, deuterium labelling and high resolution studies.
Transfert d'Hétéroatomes (Cl, Br, OH) lors de la Fragmentation d'Acétyléniques δ‐Fonctionnalisés
Authors: Arseniyadis S. , Gore J. , Roumestant M. L.
Published: May 2005

Les spectres de masse de trois alcynes δ‐fonctionnalisés montrent qu'il y a migration de chlore, de brome et. d'hydroxyle vers l'insaturation. La similitude existant entre ces spectres et ceux des composés alléniques isomères suggère qu'il y a transformation acétylène→allène après l'impact électronique.
Zum massenspektrometrischen Verhalten von Diarylaminen
Authors: Riepe W. , Zander M.
Published: May 2005

Zur Deutung des Fragmentierungsverhaltens von Diarylaminen im Massenspektrometer ist die Annahme von Carbazol‐Ringschlüssen am plausibelsten. Dabei kann zunachst eine Cyclisierung unter Abspaltung eines Wasserstoffatoms angenommen werden, wonach es in einem zweiten Schritt unter Abspaltung eines weiteren Wasserstoffs zur Ausbildung der Carbazolstruktur kommt. Wie durch die Untersuchung von 10 Diarylaminen gezeigt wird, hangt die Bereitschaft zum postulierten Ringschluß von der Größe des π‐Elektronensystems ab.
On the chemical ionization reactions of alkyl substituted cyclopropanes
Authors: Andrist A. Harry , Gemperline Paul J. , Chen Hsiao‐Chiung
Published: May 2005

As predicted by semi‐empirical molecular orbital calculations, the methane chemical ionization mass spectra of alkylcyclopropanes exhibit both proton addition and hydride abstraction processes; both the calculations and the observed substituent effects suggest the common intermediacy of gas phase cyclopropylcarbinyl cations. In agreement with this hypothesis are the results of an isotopic labeling experiment which identifies the reactive site as the cyclopropylcarbinyl carbon.
Mass spectral skeletal and hydrogen rearrangements in some bicyclic ketones
Authors: Henion J. D. , Kingston D. G. I.
Published: May 2005

The mass spectra of bicyclic ketones bicyclo[4.2.1]nonan‐9‐one, bicyclo[5.2.1]decan‐10‐one, bicyclo[4.3.1]decan‐10‐one and bicyclo[5.3.1]undecan‐11‐one specifically deuterated in positions both adjacent and nonadjacent to the carbonyl carbon have been investigated. The fragmentation and rearrangement processes predominating appear to be dictated by the inherent strain in the molecules. An unusual tendency for fragment ions to recyclize is supported by deuterium labeling results, high resolution mass measurements, metastable studies and comparison with model compounds. The mass spectra of the bicyclic ketones under investigation are considerably more complex than those of acyclic ketones.
Utilisation du 13C en Spectrométrie de Masse: Etude de la Fragmentation de Disaccharides
Authors: Bosso Claude , Taravel François , Ulrich Jacques , Vignon Michel
Published: May 2005

Un ensemble de 29 dérivés disaccharidiques dans la série du D‐glucose et présentant des liaisons glycosidiques α‐ et β‐ (1 → 3), α‐ et β‐ (1 → 4) et β‐ (1 → 6) a été analysé par spectrométrie de masse en impact électronique. Outre les mécanismes déjà connus le marquage au 13C de quelques composés conduit à proposer un mécanisme de formation pour un ion c formé de l'unité réductrice B avec rétention de C‐1′ de l'unité non réductrice A d'où part la fragmentation et le réarrangement.
Hydrogen rearrangement in the mass spectra of (E)‐1‐alkylsulfonyl‐2‐phenylethenes
Authors: Liu Lilian Kao , Hong C. T.
Published: May 2005

A novel McLafferty‐type rearrangement has been found to be the most facile fragmentation of (E)‐1‐alkylsulfonyl‐2‐phenylethenes and the migratory aptitudes for different kinds of hydrogen involved has been qualitatively estimated as benzylic ∼tertiary>secondary>primary.
Evidence for a [2+4] cycloaddition in the ion‐molecule reaction of ionized 1,3‐butadiene with vinyl ethyl (methyl) ether in the gas phase
Authors: Van Doorn R. , Nibbering N. M. M. , Ferrer‐Correia A. J. V. , Jennings K. R.
Published: May 2005

By use of deuterium labelling it is shown that the radical cation of 1,3‐butadiene reacts with vinyl methyl (or ethyl) ether in the gas phase through a [2+4] cycloaddition reaction. This leads to an excited collision complex of ionized 4‐methoxy‐ (or ethoxy) cyclohexene, which expels mthanol (or ethanol) through a 1,3 elimination, as does 4‐methoxycyclohexene itself upon electron impact. The spectrum of daughter ions produced by collision induced decomposition of the resulting ion with m/e 80 has been compared with spectra produced by the collision induced decompositions of the m/e 80 ions given by 1,3‐cyclohexadiene, 1,4‐cyclohexadiene, 1,3,5‐hexatriene and the [M–MeOH]\documentclass{article}\pagestyle{empty}\begin{document}$\mathop +\limits_\cdot$\end{document} ion from 4‐methoxycyclohexene.
Field desorption ‘without fields’?
Authors: Beckey H. D. , Röllgen F. W.
Published: May 2005

A field independent thermal desorption of ions has been suggested to occur under conditions of field desorption mass spectrometry by several authors. It is shown that these speculations are incorrect for theoretical reasons and inconsistent with experimental facts.
Cyclization reactions in the chemical ionization spectra of bifunctional alkyl phenyl ethers
Authors: Van de sande C. C. , Van Gaever F. , Dhaenens L. , Myngheer R.
Published: May 2005

Evidence is presented for the formation of cyclic onium ions from bifunctional alkyl phenyl ethers under chemical ionization conditions.
Negative ion chemical ionization mass spectrometric studies of tetradentate schiff base coordination compounds. Fluorinecontaining reagent gases
Authors: Baumgartner Erwin , Dillard John G.
Published: May 2005

Negative ion mass spectra using chemical ionization conditions have been measured for a series of tetradentate Schiff base corrdination compounds of Co(II), Ni(II) and Cu(II). Fluorine‐containing reagent gases CF4, SO2F2 and SF6 have been used. The formation of molecular negative ions for the complexes is dependent on the reagent gas used. The secondary ions detected are produced by incorporation of CF3, F and F2 species into the coordination compounds.
Ionen‐Cyclotron‐Resonanz‐Messungen von Ion/Molekül‐Reaktionen bei Chinonen
Authors: Suhr Harald , Szabo Andras , Miller Lary L.
Published: May 2005

Die ICR‐Spektren von p‐Benzochinon, Methyl‐p‐benzochinon, Durochinon und Tetrafluor‐p‐benzochinon stimmen bei 10−6 Torr weitgehend mit den normalen Massenspektren überein, zeigen jedoch oberhalb von 10−5 Torr zahlreiche Signale für Produktionen. Doppelresonanzmessungen ergaben, daß alle Produktionen durch Analagerung des Molekularions bzw. eines Fragmentions an ein neutrales Chinonmolekül gebildet werden und zwar meistens unter Abspaltung von Kohlenmonoxyd.
Spectrométrie de Masse d'Hétérocycles Azotés. X–Contribution à l'Etude du Comportement de ll'Ion Aniline et des Ions Aminopyridines avant Fragmentation par Perte de HCN
Authors: Aubagnac Jean‐Louis , Campion Philippe
Published: May 2005

L'examen des spectres MIKE de dérivés marqués au deutérium de l'aniline, des aminopyridines et de la chloro‐2 amino‐5 pyridine montre qu'avant fragmentation par perte de HCN, le mixage, absent dans le cas des aminopyridines, est limité mais notable dans le cas de l'aniline. Pour ce dernier composé, le mixage est modifié fortement par de faibles variations de l'énergie des ions étudiés, variations situés à l'intérieur de la région d'énergies correspondant aux ions métastables. De plus, l'examen des spectres MIKE des dérivés monodeutériés des aminopyridines permet d'infirmer pour ces composés le mécanisme de perte de HCN généralement admis.
The formation of [C9H10]+˙ ions by loss of a molecule of water from molecular ions of 3‐phenylpropanol with lifetimes of 10−11 to 10−5 s
Authors: van der Greef J. , Nibbering N. M. M.
Published: May 2005

Field ionization kinetic experiments in conjunction with deuterium labelling have been shown that the molecular ions of 3‐phenylpropanol with lifetimes as short as 10−11s lose a molecule of water via a specific 1,3 elimination. At times > 10−11s two distinct hydrogen interchange processes in the molecular ions appear to complete with this reaction. One of the intechange processes involves the benzylic and hydroxylic hydrogen atoms and starts to complete with the elimination of water at shorter molecular ion lifetimes than the other interchange process in which the ortho hydrogen atoms also participate. Decomposing [C9H10]+˙ ions generated by elimination of water from the molecular ions of 3‐phenylpropanol or by direct ionization of various isomeric C9H10 compounds could not be distinguished adequately, illustrating isomerization either to a common ion structure or to a set of ions with rapidly interconverting structures. A consideration of the energetics of the elimination of water from 3‐phenylpropanol suggests that at threshold energies 1‐phenylpropene or indane type structures can be formed. Arguments for the latter have been obtained from the observation that a labile fluorine atom is present in the [M – H2O]+˙ ions generated from 3‐pentafluoro‐phenylpropanol.
Loss of hydroxyl radical from cis‐ and trans‐1‐cyclohexyl 2‐phenyl‐3‐benzoylaziridines: A unique eight‐centered rearrangement elimination
Authors: Tarburton Philip , Sun Tung , Cromwell Norman H. , Gross Michael L.
Published: May 2005

Following electron impact ionization of the title compounds, a rapid electrocyclic ring opening of the [M]+˙ of both isomers occurs. A subsequent fragmentation of each is loss of hydroxyl which occurs by rearrangement to the carbonyl function. Properties of [MOH]+ are in accord with a stable structure for this ion and therefore it is assigned as the 4‐phenylisoquinium ion. The proposed mechanism and ion structures are supported by deuterium labeling and defocused metastable ion studies.
Mass spectra of 1,1‐bis(acylamido)‐1‐deoxyalditol acetates
Authors: Matulewicz María Cristina , Cerezo Alberto Saúl
Published: May 2005

The mass spectra of fourteen 1,1‐bis(acylamido)‐1‐deoxyalditol acetates and of two model compounds have been recorded. The most important feature of the fragmentation of these derivatives is the cleavage of the C–1–C–2 bond which produces fragment
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None of the alditol derivatives yields the molecular ion.
Oxygen rearrangement of molecular ions of 3‐phenylpropionates
Authors: Liehr Joachim G. , Caprioli Richard M. , Beynon John H. , Morgan Roger P. , Richter Wilhelm J.
Published: May 2005

The oxygen rearrangement in molecular ions of 3‐phenylpropionates has been investigated with the aid of mass analyzed ion kinetic energy spectra. Elimination of an allyl radical followed by expulsion of ketene from the molecular ion of allyl 3‐phenylpropionate is shown to result in formation of protonated benzaldehyde. The oxygen rearrangement has been found to be inoperative in ionized methyl 3‐methyl‐3‐phenylbutyrate. [M  CH3  CH2CO]+ ions in the spectrum of the latter compound are formed by elimination of the 3‐methyl substituent and subsequent methoxy migration.
Potential energy profiles for the unimolecular reactions of [C3H7S]+ Ions
Authors: Broer W. J. , Weringa W. D.
Published: May 2005

Appearance energies were measured for several types of [C3H7S]+ ions. From these appearance energy values the heats of formation of the ions were calculated. For the isomeric ions that could not be generated in the mass spectrometer, the heats of formation were estimated by means of the isodesmic substitution method. Transition state energies for the decomposition to C2H4 and [CH3S]+ along two pathways were determined from the appearance energies of these ions. Using the energy values, potential energy diagrams were constructed for the rearrangements and decompositions of the [C3H7S]+ ions. A supplementary 13C Clabelling experiment is described for the determination of the rearrangement pathway of [CH3CH2CHSH]+ ions prior to decomposition.
Comparative study of pulsed laser and fission fragment induced desorption with nucleotic compounds
Authors: Schueler B. , Krueger F. R.
Published: May 2005

Mass spectra obtained under pulsed laser induced and fission fragment induced desorption of nucleosides and their nucleobases are reported and compared. No striking differences are observed. The nature of the excitation process for both methods is discussed. Fission fragment induced desorption is known to be due mainly to a sudden non‐resonant electric perturbation, which in conjunction with thermal activation also plays a major role in laser induced desorption.
Mass spectra of pyridine monoamidoximes and their O‐trimethylsilyl ether derivatives
Authors: Pearse George A. , Jacobsson Sven
Published: May 2005

The mass spectra of pyridine‐2‐, ‐3‐, and ‐4‐amidoxime and their O‐trimethylsilyl derivatives have been investigated. Also included in this study were the deuterated derivates. Main pathways of fragmentation of these compounds have been proposed. A comparison with the mass spectra of the corresponding pyridine aldoximes has been made.
Mass spectrometry of organic compounds of the group V elements: V‐Cyanamides, cyanphosphines, cyanarsines and vinylogues
Authors: Kostyanovsky R. G. , Pleshkova A. P. , Voznesensky V. N. , El'natanov Yu. I.
Published: May 2005

New data have been obtained confirming distinct differences in fragmentation of compounds of trivalent nitrogen and other group V elements under electron impact. These data have been obtained for the fragmentation of the cyanamides, cyanphosphines and cyanarsines, as well as of their vinylogues.
The fragmentation behaviour of some spirobenzthiazoles under electron impact
Authors: Herzig Ulrike , Krenmayr Peter , Varmuza Kurt
Published: May 2005

The electron impact induced fragmentations of ten spiro‐benzthiazoles have been studied. The principal decomposition reactions have been elucidated by metastable studies, exact mass measurements, and by deuterium exchange of the imino hydrogen. The primary fragmentation step is an α‐cleavage reaction, which leads to ring opening of the ring fused to the benzthiazole moiety of the molecule. The subsequent decompositions resemble those of cyclohexylamines. They follow a general pattern, the details of which are discussed with respect to the nature and position of the heteroatom in the saturated ring.
Application of a secondary ion mass spectrometer as a detector in liquid chromatography
Authors: Benninghoven A. , Eicke A. , Junack M. , Sichtermann W. , Krizek J. , Peters H.
Published: May 2005

Recently developed new techniques of ion formation from organic solids may become very useful in the application of mass spectrometers as detector units in liquid chromatography. Details of a liquid chromatograph mass spectrometer coupling device are presented. Some features of this device, combined with a quadrupole secondary ion mass spectrometer, are demonstrated experimentally by the analysis of aqueous solutions of leucine and cytosine. It is demonstrated that the sensitivity of the liquid chromatography secondary ion mass spectrometry combination covers the concentration range occurring in liquid chromatography.
Fragmentation of alkylbenzoates by electron impact: Transposition and rearrangement of the alkyl chain
Authors: Audier Henri E. , Milliet Arielle
Published: May 2005

The electron impact induced fragmentation of alkylbenzoates produces an ethylenic ion in a stepwise reaction. The first step is exothermic and involves the transfer of one hydrogen radical from the chain to the oxygen atom on the carboxyl; several intermediate ions having a large energy excess can be formed. The orientation of the reaction is directed by the relative breaking rates of these different intermediate ions. At low energy the transferred H is the one which leads to the most stable ion and consequently to the most substituted ethylenic fragment. In several cases chain rearrangements take place during the reaction. This phenomenon is the result of both the exothermic character of the first step and the large difference between the ΔH of the monosubstituted, disubstituted or trisubstituted ethylenic ion which is the final state of this fragmentation.
Electron impact mass spectra of some substituted aromatic boronate derivatives of bifunctional compounds
Authors: Singhawangcha Sureerat , Pooie Colin F. , Zlatkis Albert
Published: May 2005

The electron impact mass spectra of the 3,5‐bis(trifluoromethyl)benzeneboronate, 2,4‐dichlorobenzene‐boronate and 4‐bromobenzeneboronate derivatives of some bifunctional diols and aminoalcohols are characterized by prominent molecular ions with diagnostically useful modes of fragmentation. Many of the principal ions in the mass spectra retain boron in their structure.
Mass spectrometry of nitrogen heterocycles:XI—Loss of HCN from indazole studied by 15N labelling
Authors: Atmani Aziz , Aubagnac Jean‐Louis , Pellegrin Valdo
Published: May 2005

A small preference for the N‐1 nitrogen atom is observed in the loss of HCN from the molecular ion of 15N labelled indazole. In addition there is a small isotope effect.
A novel mass marker for metastable ion scans in a double focusing mass spectrometer
Authors: Porter C. J. , Brenton A. G. , Beynon J. H. , Popplestone A.
Published: May 2005

Characterization and assignment of the products of metastable decompositions which are transmitted by a double focusing mass spectrometer, is often complicated by the inability to measure precisely the parent/daughter ion mass values directly from the spectra which appear on chart paper. This is often because there are considerably fewer peaks in these types of spectra compared with a normal mass spectrum obtained from high energy reactions in the ion source. Electronic circuits are described which permit accurate parent/daughter ion mass values to be obtained when the products of metastable decompositions are transmitted through the ZAB‐2F double focusing mass spectrometer. Digital logic circuitry is also described which is used to mark mass values during a scan by driving either a solenoid pen drive unit for a chart recorder or a galvanometer on a multi‐range ultraviolet oscillograph recorder.
Mass spectrometry: XI—Electron impact induced fragmentation of some amides of F‐acids and their deuterated homologues
Authors: Greiner Jacques , Pastor Raphael , Cambon Aimé
Published: May 2005

The mass spectrometry of perfluoro compounds (F‐alkyl compounds) has seldom been the subject of systematic studies. Fluorocarbons excepted, only a few mass spectra of such compounds have been analysed and corresponding fragmentations correlated. In this paper we report the mass spectra of 19 amides of perfluoro acids (RFCONHR) with R=benzyl, 2‐phenylethyl, 2‐phenylpropyl, 3‐phenylpropyl, 2‐(N‐phenylamino)ethyl, and RF=F‐methyl, n‐perfluoropropyl, n‐perfluoropentyl and n‐perfluoroheptyl. These compounds exhibit quite different behaviour from their hydrocarbon homologues under electron impact (for instance no [RFCO]+ fragment was found). Specific deuterium labelling and high resolution measurements have been used to show typical rearrangements and to establish the fragmentation routes.
Rearrangement reactions of 2‐nitrothiobenzamides upon electron impact
Authors: Clausen K. , Scheibye S. , Lawesson S.‐O. , Bowie J. H. , Blumenthal T.
Published: May 2005

The decomposing molecular cations derived from (substituted) 2‐nitrothiobenzamides fragment by complex rearrangement reactions. When the alkyl substituents (R) attached to N are methyl, the major fragmentations are [M]+˙ → [MSO]+˙ and [MSO]+˙ → [(MSO)+˙–R˙]+. This remains a basic pathway when R ⩾ Et, but other rearrangements are also observed. For example, when R=Et, additional competitive processes are [M]+˙ → [MHO˙]+ and [M]+˙ → [MC2H4O]+˙.
Fragmentation of dihydro‐ and tetrahydro‐1,5‐benzothiazepines under electron impact
Authors: Wen‐Gang Chai , Guang‐Hui Wang , Sheng Jin , Heng‐Liang Jin
Published: May 2005

The fragmentation mechanisms of dihydro‐ and tetrahydro‐1,5‐benzothiazepines under electron impact have been studied in detail using high resolution mass spectrometry, metastable decompositions and deuterium labelling techniques. Both kinds of the benzothiazepines possess high stability. The [MSH]+ and the cyclic benzothiazole ions derived from the fragmentation and severe skeletal rearrangement of the molecular ion comprised the main features of the spectra. Some doubly charged ions were noticed in the low resolution electron impact mass spectra.
Water loss from [C5H10O]+˙ isomers: A reassessment
Authors: Holmes John L. , Dakubu Mumuni , Rye Robin T. B.
Published: May 2005

From a detailed analysis of metastable peak shapes it is proposed, contrary to earlier conclusions, that the loss of H2O from the molecular ions of the C5H10O isomers cyclopentanol, pentanal and pent‐1‐en‐3‐ol yields only [penta‐1,3‐diene]+˙ in the metastable time frame. Therefore the composite metastable peak for this process arises from two competing reaction channels yielding a common daughter ion. The observation that the first two isomers also produce [penta‐1,4‐diene]+˙ as a daughter ion is attributed to a high energy (ion source) reaction which contributes negligibly to first field free region fragmentations.
Chemical ionization desorption mass spectrometry of some quaternary ammonium salts
Authors: Hasiak Bruno , Ricart Guy , Barbry Didier , Couturier Daniel , Hardy Michel
Published: May 2005

The ammonia chemical ionization desorption spectra of N,N‐dimethyl quaternary ammonium iodides in addition to high protonated molecular ion [M + H]+ intensity, show signals for an ion radical composed of N‐methyl abstracted salt cation and ammonia [C + NH3CH3]+˙. These ions corresponding to the cation +2 show increased importance in the chemical ionization mode, using the same reagent gas. The technique of chemical ionization desorption appears suitable for the analysis of salts, and thus for the determination of the molecular weight of both anion and cation.
The computer processing and interpretation of mass spectral information. V—generation of a table of isotopic spectra of structural fragments
Authors: Sukharev Yu. N. , Molgachova N. S. , Nekrasov Yu. S.
Published: May 2005

A package of dialogue programs intended for generation of isotopic spectra from specified elemental compositions containing any number of elements is described. Structural fragments (super‐elements), once in the table, acquire the status of a separate chemical element. All operations with super‐elements are analogous to those with polyisotopic elements of the periodic table. The user can modify the table at his discretion to suit his purpose. The table increases the flexibility of interactive data processing programs and thus the dialogue is made to approach the natural chemist's language. The programs written in FORTRAN IV are intended for a minicomputer with a core memory of about 24 K words.
Mass spectrometry of thio analogues of pyrimidine bases: Benzylthiouracils and p‐nitrobenzylthiouracils
Authors: Wyrzykiewicz E. , Stobiecki M. , Golankiewicz K.
Published: May 2005

The mass fragmentation of twelve new 2‐ and 4‐benzylthio substituted derivatives of uracils is discussed and fragmentation pathways, elucidation of which was assisted by accurate mass measurements and metastable transitions, are proposed. It has been found that the position of uracil ring thiation may be deduced on the basis of mass spectral fragmentation patterns.
Secondary ion mass spectra of oligosaccharides
Authors: Kambara Hideki , Hishida Shinzaburo
Published: May 2005

The mass spectra of oligosaccharides such as glucose, sucrose, lactose and raffinose obtained by static secondary ion mass spectrometry operated at 10−6 Torr are presented. Cationized molecular ions are observed in high intensity. Fragment ions are compared with daughter ions produced by collision induced dissociation of field desorbed cationized molecular ions.
Site of protonation and bifunctional group interactions in α,ω‐hydroxyalkylamines
Authors: Davis D. V. , Cooks R. G.
Published: May 2005

Chemical ionization mass spectrometry and mass analyzed ion kinetic energy spectrometry in conjunction with collision induced dissociation are used to study the fragmentation behavior of a series of α,ω‐hydroxyalkylamines. The difference between the ionic population present at equilibrium in the source, and that which is sampled under nonequilibrium conditions, is revealed in the striking differences observed in product distributions in the chemical ionization mass spectra and the mass analyzed ion kinetic energy spectra. The major fragmentations in the mass analyzed ion kinetic energy spectra, loss of NH3 and H2O, show large variations in intensity as a function of the chain length between the hydroxy and amino functionalities. These results are rationalized through analysis of the relevant thermochemical data.
Mechanisms of water elimination and other degradations of 2‐hydroxy‐5‐ketobornane cations in the gas phase
Authors: Fraefel A. , Mändli M. , Seibl J.
Published: May 2005

The mechanisms of water elimination in 2‐hydroxy‐5‐ketobornanes have been investigated and compared with those in borneol and isoborneol in order to ascertain whether and how such processes are affected by incorporation of a remote second functional group of lower ionization energy. Analysis of metastable ion peak shapes and specific labelling with 2H and 18O are employed as methods for differentiating between individual reaction paths. In addition, those degradation reactions which give rise to the most prominent fragments and pattern differences in the mass spectra of the epimeric keto alcohols were scrutinized. The elimination of water is shown to exhibit entirely different features due to the presence of the carbonyl group. The other most important degradation reactions all proceed by hydrogen transfer from the hydroxyl group onto the charged product and concomitant loss of the hydroxyl oxygen in a neutral entity. The results are interpreted in terms of initial charge radical localization on the carbonyl group initiating the relevant chemical reactions. Peak shape analysis proves a very valuable, and at times the only useful way to distinguish individual reactions.
Novel cluster ions from magnesium and zinc acetates in filament heated in‐beam electron impact mass spectrometry
Authors: Matsumoto Kozo , Kosugi Yoshio
Published: May 2005

Mass spectral peaks of cluster ions believed to be due to penta‐μ‐acetato‐μ4‐oxo‐tetramagnesium and tri‐μ‐acetato‐μ3‐oxo‐trimagnesium, or the corresponding zinc compounds, were detected when magnesium acetate or zinc acetate was heated on a tungsten filament and impacted at the same time by an electron beam. Structures of these non‐transition metal complexes are analogues of the so‐called ‘electron‐sponge’ complexes, [Ru3O(OAc)6L3]. Previously reported new cluster ions from lithium acetate are formulated by similar structures.
Fast atom bombardment mass spectrometry of two isomeric tripeptides
Authors: Barber Michael , Bordoli Robert S. , Sedgwick R. Donald , Tetler Lee W.
Published: May 2005

Fast atom bombardment of solids is presented as the basis of a new ion source for mass spectrometry. This novel technique is particularly useful for obtaining mass spectra from involatile and thermally labile materials. The ion source produces both positive and negative ions with equal facility, and examples of both are presented for two underivatized tripeptides. The normal second field free region metastables are observed in a double focusing mass spectrometer and comprehensive metastable pathways have been traced using Barber‐Elliott (V‐scan) techniques.
Electron impact induced migrations of aryl groups in substituted 4(3H)‐quinazolinones
Authors: Tureček František , Světlík Jan
Published: May 2005

Electron impact mass spectra of 2‐diphenylmethyl‐3‐aryl‐4(3H)‐quinazolinones display ions arising from migrations of different aryl groups in the molecular and [MH]+ ions. The most abundant ion due to rearrangement, [C13H9NO]+˙, is formed by migration of a phenyl from the benzhydryl group onto N‐1 and subsequent cleavage of the heterocyclic ring. Other rearrangements involve initial migration of the N‐3 aryl group to the benzylic carbon. The mechanisms of migrations were elucidated by means of deuterium and 15N labelling and are supported by metastable spectra.
Mass spectral behaviour of some m‐dimethoxybenzene and sym‐trimethoxybenzene sulphur derivatives
Authors: Bottino Francesco , Fradullo Rosa , Pappalardo Sebastiano
Published: May 2005

The mass spectra of fifteen m‐dimethoxybenzene and sym‐trimethoxybenzene sulphur derivatives (including thiols, sulphides, disulphides and trisulphides) have been investigated. Main fragmentation pathways have been proposed for each class of sulphur compound. Primary skeletal rearrangements of the molecular ions occurring in (poly)sulphur‐bridged derivatives can provide a sensitive diagnostic tool both in structure elucidation and in the problem of locating methoxy substituents.
The formation of [CH3CH2C(OH)CH2]+˙ from 1‐hepten‐3‐ol
Authors: McAdoo David J. , Hudson Charles E.
Published: May 2005

The [C4H8O]+˙ ion in the mass spectrum of 1‐hepten‐3‐ol is shown to be \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} {\rm{CH}}_{\rm{2}} {\rm{C(= }}\mathop {\rm{O}}\limits^{\rm{ + }} {\rm{H}})\mathop {\rm{C}}\limits^{\rm{.}} {\rm{H}}_{\rm{2}} $\end{document} by collisional activation spectra, appearance energies and comparison of the ratios of the intensities of metastable decompositions. [C4H8O]+˙ appears to be formed by rearrangement of ionized 1‐hepten‐3‐ol to \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm{CH}}_{\rm{3}} \mathop {\rm{C}}\limits^{\rm{.}} {\rm{HC(= }}\mathop {\rm{O}}\limits^{\rm{ + }} {\rm{H)CH}}_{\rm{2}} {\rm{CH}}_{\rm{2}} {\rm{CH}}_{\rm{2}} {\rm{CH}}_{\rm{3}} $\end{document} followed by γ‐hydrogen rearrangement‐β‐cleavage.
A revised mechanism for the structure‐specific gas phase enol cation‐cyclobutanol reaction
Authors: Bouma Willem J. , MacLeod John K. , Radom Leo
Published: May 2005

Ion cyclotron resonance studies using deuterium labelled substrates have revealed a more complex mechanism than previously proposed for the structure‐specific ion/molecule reaction of the [C2H4O]+˙ and [C3H6O]+˙ enol ions with neutral cyclobutanol. This requires the intermediacy of a species in which all of the methylene groups present in both the reactant ion and neutral can become equivalent.
Stable adduct formation during the gas phase reactions between the trimethylgermanium cation and organic nucleophiles. An ion cyclotron resonance study
Authors: Trenerry V. Craige , Bowie John H.
Published: May 2005

The trimethylgermanium cation (Me3Ge+) reacts with aliphatic organic neutrals (M) which contain N, O or S, to form adducts [M + Me3Ge+] in the gas phase. These adducts are more stable than their analogues formed from the trimethylsilyl cation, and thus Me3Ge+ is a useful analytical reagent for chemical ionization mass spectrometry.
Factors affecting reactivity in ammonia chemical ionization mass spectrometry
Authors: Keough T. , Destefano A. J.
Published: May 2005

Several factors affecting reactivity in ammonia chemical ionization mass spectrometry (NH3 CI) have been examined. These include the sample proton affinity, the preferred site of protonation and [NH4]+ attachment, and substituent effects. In general, compounds having proton affinities ≲787 kJ mol−1 do not yield analytically useful intensities of the [M·NH4]+ adduct ion. Substituted aromatic compounds in which the ring is the most basic site yield little (if any) [M·NH4]+ ion even if the proton affinity of the compound is greater than 787 kJ mol−1. On the other hand, some aromatic compounds in which the substituent is the most basic site yield relatively abundant adduct ions. The spectra of compounds possessing a good leaving group (X) exhibit only weak [M·NH4]+ ions, but intense [M·NH4 − HX]+ and [M − X]+ ions formed by substitution and elimination reactions. Electronic effects strongly influence these processes. Several examples are presented in which isomers are readily differentiated because of different reactivities under ammonia chemical ionization conditions.
The use of triple quadrupoles for sequential mass spectrometry: 2—A detailed case study
Authors: Dawson P. H. , French J. B. , Buckley J. A. , Douglas D. J. , Simmons D.
Published: May 2005

A detailed exploration of the application of triple quadrupoles in sequential mass spectrometry has been carried out using dimethylmorpholinophosphoramidate as a case study of an ion of relatively high mass and complex structure. Both metastable ion decomposition and dissociation by low energy collision were examined. Variation of the basic instrument parameters allowed the investigation of the cross‐section for dissociation as a function of collision energy, the change in fragmentation patterns with collision energy, the kinetic energy distributions of daughter ions and the overall kinetics of dissociation in a succession of ion decomposition sequences giving daughter and granddaughter ions. The daughter ions could also be produced in the source region and examined separately so that a genealogical tree could be established.
Mass spectral fragmentation of ethene and propene dithioketals of cyclobutanone
Authors: Mohammadi Mohammad , Willett James D.
Published: May 2005

A detailed analysis of the electron impact induced fragmentation of ethene and propene dithioketals of cyclobutanone is presented. The tetradeuterio analog of the cyclic dithioketals was prepared as an aid in analyzing the fragmentation patterns. Cleavage of the 1,3‐dithiolane ring system is favored at 15 eV, whereas cyclobutane ring cleavage is favored at 70 eV. Thus, the primary fragmentation pathway seems to be dependent upon the ionization energy.
The chemical ionization mass spectra of 2,4‐adamantanediol diacetates and dimethyl ethers
Authors: D'Haenens L. , Van de Sande C. C. , Schelfaut M.
Published: May 2005

The chemical ionization mass spectra of the isomeric 2,4‐adamantanediol diacetates and dimethyl ethers have been determined using methane and isobutane as reagent gases. The significant differences in the spectra of the diacetates allow an unambiguous identification of the isomers. The spectra of the trideuteroacetates reveal the occurrence of protolysis in the ionizing plasma.
Gaseous [C7H8]+˙ ions: [Methylene cyclohexadiene]+˙, a stable species in the gas phase
Authors: Burgers Peter C. , Terlouw Johan K. , Levsen Karsten
Published: May 2005

Using collisional activation and collisional ionization spectra in conjunction with isotopic labelling and energetic data it is demonstrated that the metastable decomposition of ionized n‐butylbenzene and 2‐phenylethanol leads to [C7H8]+˙ ions which have the methylene cyclohexadiene structure. From appearance energies of metastable peaks a value of 960±10 kJ mol−1 was obtained for its heat of formation.
Mass spectrometry of nitroazoles: 3—ortho effects: The loss of OH˙ and H2O from methyl substituted nitrodiazoles
Authors: Luijten W. C. M. M. , van Thuijl J.
Published: May 2005

Methyl substituted nitrodiazoles which have the substituents at adjacent positions in the ring are subject to several ortho effects. Deuterium labelling of the methyl group and the mobile N‐bonded hydrogen show that the loss of OH˙ originates from the substituents. In some cases the N‐bonded hydrogen atom participates also in the loss of OH˙ and of H2O.
Concerning the Beckmann rearrangement of aryl heteryl ketoxime ions
Authors: Grützmacher Hans‐fr. , Römer Christian
Published: May 2005

The possible Beckmann rearrangement of aryl heteryl ketoxime ions has been investigated by studies on the 70 eV mass spectra, metastable ion spectra and collision induced dissociation spectra of pairs of isomeric ketoximes and corresponding amides. Aryl cycloalkyl ketoximes were also studied, and the molecular ions of these and the corresponding amides showed no evidence of interconversion. The introduction of the heterocyclic moieties made little change to this situation although some novel rearrangements were observed.
2‐substituted‐2,3‐dihydro‐4H‐pyrans: Competition between ‘retro Diels‐Alder’ fragmentation and substituent loss
Authors: Morizur J‐P. , Mercier J. , Sarraf M.
Published: May 2005

The mass spectra of two series of 2‐substituted‐2,3‐dihydro‐4H‐pyrans (six ethers and six carbonyl derivatives) showed a marked dependence upon the nature of the substituent. α‐Cleavage (substituent loss) was the only primary decomposition observed in the carbonyl series, while ‘retro Diels‐Alder’ reactions competed with α‐cleavage in the ether series. An unambiguous interpretation of this difference in behaviour, based on the consequence of charge localization and thermochemical data, is proposed.