bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass spectra of perfluoroalkyl and perfluoroalkylether nitriles and acyl halides
Authors: Paciorek Kazimiera J. L. , Nakahara James H. , Rratzer Reinhold H. 
Published: May 2005

AbstractElectron impact fragmentation patterns were obtained for perfluoroalkylether nitriles, C,F,O[CF(CF3)CFIO]ICF(CF3)CN (x = 1 and 2), perfluoroalkylether acyl halides, CSF,OCF(CF,)‐CF2OCF(CF3)COX (X = F and Cl), n‐perfluorooctanonitrile and n‐perfiuorooctanoyl chloride. The perfluoroalkyl and perfluoroalkylether nitriles afforded ions characteristic of the nitrile function. The major fragment from the acyl chlorides was the [COClJ]+ ion; the presence of chlorine was evidenced also by rearrangement ions of the general form [RfCl] t. The perfluoroalkylether compounds appeared to undergo a typical fragmentation governed by the cleavage of the carbon‐oxygen bond.
Mass spectra of heterocyclic compounds. II‐Hexahydro‐1,3,5,‐triazines
Authors: Corral Renée A. , Orazi Orfeo O. 
Published: May 2005

AbstractThe twelve tri‐N‐sulphonylhexahydro‐1,3,5‐triazines (R = alkyl or aryl) exhibit a common fragmentation pattern; most of the fragments are directly or indirectly generated from the [M  RSO2]+ ion. Tri‐N‐Benzylsulphonylhexahydro‐1,3,5‐triazine (R = PhCH2) departs from the others mainly because the key ion [M  RSO2]+ suffers a skeletal rearrangement with loss of SO2. The rationalizations presented are supported by metastable evidence, accurate mass measurements and deuterium labelling.
The mass spectra of [17‐13C]phyllocladene and [3‐13C]methylenecholestane—III
Authors: Cruz R. A. , Castillo R. C. , Garcia F. J. , Reed R. I. 
Published: May 2005

AbstractThe mass spectra of [17‐13C]phyllocladene and [3‐13C]methylenecholestane have been examined. It is shown that there are some rearrangements at 70 e V as in the case of [17‐13C]kaurene. However, no extensive randomization is evident at the molecular ion level. The results are interesting because very little is known about 13C randomization in polycyclic aliphatic hydrocarbons. The percentage retention of label was calculated for each ion.
Regiospecificity for water elimination. A mass spectral study of 1‐tetralol and 2‐tetralol
Authors: Gross M. L. , Chiu E. , Pokorny D. , Deroos F. L. 
Published: May 2005

AbstractIn order to provide a comparison with the extensive research on the mechanism for elimination of water from various cyclohexanols, the mass spectra of 1‐tetralol(1,2,3,4,‐tetrahydro‐1‐naphthalenol) and 2‐tetralol(1,2,3,4‐tetrahydro‐2‐naphthalenol) have been investigated. Deuterium labeling experiments show that the 1‐tetralol molecular ion expels water by a highly specific 1,4 elimination, whereas 2‐tetralol undergoes a 1,3 elimination. Both of these processes are competitive with cycloreversion reactions. The ionization potentials and appearance potentials for the major fragments \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm M - H}_{\rm 2} {\rm O}} \right]_{}^{_.^ + } $\end{document} and the cycloreversion products hae been measured using the Electron Distribution Difference method. In addition, the kinetic energy release in the metastable decompositions to lose water have been measured. It has been found that the 1,4 elimination for 1‐tetralol releases over 50% of the available energy in the transition state, which is unexpected in view of the 6‐membering ring transition state involved. This research also includes an investigation of the nature of the various \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 10}} } \right]_{}^{_.^ + } $\end{document} ions formed in the rearrangement reaction to lose water.
Spectrométrie de Masse D'Hétérocycles Azotés. VI—Tautomérie en Phase Gazeuse d'Isoxazolones‐5
Authors: Aubagnac Jean‐Louis , Bourgeon Dominique 
Published: May 2005

AbstractLa comparaison de la fragmentation sous l'impact électronique d'isoxazolones‐5 avec celles des dérivés méthylés: méthoxy‐5 isoxazoles, méthyl‐2 isoxazolones‐5 et diméthyl‐4,4 isoxazolones‐5 conduit à la conclusion qu'à l'état gazeux et avant fragmentation, les isoxazolones‐5 existent sous la forme du tautomère CH. En outre, il a été établi dans le cas des méthoxy‐5 isoxazoles que le réarrangement isoxazole→azirine→oxazole qui se produit par voie thermique entraǐne pour ces composés une modification des intensités de certains ions en fonction des conditions opératoires.
Zur wecheslwirkung der amidfunktion mit dem β‐C‐atom bei zerfällen α,β‐ungesättigter amid: Sauerstoff‐ odder stickstoff‐attacke?
Authors: Levsen K. , Berendsen G. E. , Nibbering N. M. M. , Schwarz H. 
Published: May 2005

AbstractDurch die Untersuchung 13C‐markierter Crotonsäureamide und die Analyse von ‘collisional activation’ (CA)‐Spektren geeigneter Referenzverbindungen wird belegt, daß die durch eine Nachbargruppenwechsel‐wirkung zwischen β‐C‐Atom und Amidfunktion verursachte Radikal‐Eliminierung vom β‐C‐Atom im wesentlichen durch eine Stickstoff‐Attacke und nur untergeordnet durch einen Angriff des Carbonylsauerstoffs eingeleitet wird. Die resultierenden Ionenstrukturen werden diskutiert.
The structure of the ion: An ion kinetic energy spectrometry study
Authors: Hoffman Michael K. , Friesen Marlin D. , Richmond Geraldine 
Published: May 2005

AbstractThe kinetic energy release (T) values for the loss of CO from ions from five compounds have been obtained and are consistent with at least two different structures for the ion. This result is supported by the T value obtained for the decomposition of the molecular ions.
The formation and structure of radical cations
Authors: van Thuijl J. , van Houte J. J. , Maquestiau A. , Flammang R. , de Meyer C. 
Published: May 2005

Abstract ions generated from a number of different presursors have been studied by high kinetie energy ion—molecule reations. It has been shown that at least four distinct stable species oeeur, of which acetonitrile and methyl isoeyanide retain their original structure. With imidazole or pyrazole as precursors, a mixture of open thain radical cations, not identical to the above species and probably interconvertible via the 1H‐azirine radocal cation, is formed. From butrynitrile, pyrrole, crotonitrile, allyl interconvertible via the and cyanocyopropane a fourth species, probably the vinylidenimine ion, is formed.
Reversible cyclomerization and long range hydrogen abstraction by electron impact of 7‐coumarinyl diesters ROOC(CH2)nCOOR
Authors: Compernolle F. , Schouteden E. , De Schryver F. C. 
Published: May 2005

AbstractThe mass spectra of 4‐methyl‐7‐coumarinyl and 7‐coumarinyl diestes ROOC(CH2)nCOOR (n = 2‐12) have ben studied by appearance potential measurements, deuterium labelling and by comparison with suitable reference compounds such as the mised diestes ROOC(CH2)nCOOR′ (R=4‐methyl‐7‐coumarinyl and R′ = methyl and phenyl) and 3.4‐dihydro‐4‐methyl‐coumarinyl diestes. Observations on the fragment ions of m/e 324, produced from the 7‐coumrinyl diestes and their photocyclomers, by elimination of the central bridge as OCCH(CH2)n–2CHCO, demonstrate the existence and reversible formation of cyclomeric molecular ions. A stable bound system between the coumrin end groups is formed only at high internal energies by expulsion of a hydrogen atom, followed by elimination of the central bridge from the [MH]+ ion. It is also shown that the lifetime of the open form molecular ions decreases remarkably for chain lengths with n larger than 6.
Mass spectral aspects of 7‐phenacylxanthopterins
Authors: Iwanami Yasuo , Inagaki Takeshi , Sakata Hisanori 
Published: May 2005

Abstract7‐Phenacylxanthopterin and its para‐substituted derivatives, which exist in the chelate rign form initially lose CO from pyrazine rings followed by a hydrogen atom. This ion can also be formed in the reverse order, but not for the 4‐amino analogues. Fragmentation of the intramolecularly hydrogen bonded sidechain also occurs involving loss of a benzoyl or phenyl radical. Linear plots at 40 eV for the loss of the benzoyl radical were obtained for log (Z/Z0) against the Hammet σ constants not only for the fragmentation of the xanthopterins but also for that of the amino analogues.
Electron impact studies on some aryl heteryl ketoximes
Authors: Kallury R. Krishna Mohan Rao , Rao P. L. K. Marutatmaja 
Published: May 2005

AbstractThe mass spectra of nine aryl heteryl ketoximes indicated that a gaseous phase Beckmann rearrangement occurs to a significant extent, as confirmed by the exact mass measurements of the resulting aroyl cation peaks. Loss of oxygen, hydroxyl radical and migration of the oxime hydrogen to the heterocycle is observed to take place in varying proportions.
Mass spectrometry of heterocyclic compounds. I—the behaviour of some quaternary heterocyclic iodides under electron impact
Authors: Bologa Margareta , Palibroda N. , Moldovan Z. , Ciurdaru Gh. 
Published: May 2005

AbstractThe mass spectra of five quaternary heterocyclic iodides have been investigated. The main thermal process is the anhydro base formation by HI elimination. The influence of the second heteroatom, X, on the fragmentation mode of the thermally produced anhydro bases is analysed.
On the characterization of dihydro‐oxazin‐6‐ones and N‐acetylazetidin‐2‐ones by mass spectrometry
Authors: Bexon J. J. , Todd J. F. J. , Drey C. N. C. , Ridge R. J. 
Published: May 2005

AbstractMass spectrometry has been used in an attempt to resolve the ambiguity in the structures of the isomeric dihydro‐oxazin‐6‐ones and N‐acyl‐azetidin‐2‐ones.
Secondary ion mass spectrometery: A new analytical technique for biologically important compounds
Authors: Benninghoven A. , Sichtermann W. 
Published: May 2005

AbstractThe secondary ion emission of about 40 biologically important compounds including amino acids, peptides, drugs, vitamins, pharmaceuticals, etc. has been determined by static secondary ion mass spectrometry. Unexpected ‘parent‐like’ secondary ions such as [M + H]+ and [M − H]−, as well as fragment ions, correlated with functional groups, are emitted with relatively high absolute yields. The secondary ion mass spectra allow an unambiguous identification of all samples with detection limits in the 10−12 g range.
The loss of CH3⋅ from some unsaturated dithioesters
Authors: Burgers Peter C. , Terlouw Johan K. , Meijer John , Dijkstra Geo 
Published: May 2005

AbstractThe mechanism for the loss of CH3⋅ (and C2H5⋅) from the molecular ions of some unsaturated dithioesters of the type magnified image with n=0, 1, 2, has been studied. Based on first field free region metastable ion characteristics it is proposed that 1,3‐dithiolium type product ions are generated. Deuterium labelling experiments indicated that the molecular ions of the 2‐alkenyl alkanedithioates magnified image undergo a rearrangement prior to fragmentation which resembles the [3,3]sigmatropic rearrangement in solution chemistry.
Electron impact induced fragmentations and rearrangements of some phenyl substituted phosphine oxides
Authors: Koch Charles W. , Eargle Dolan H. , Kenyon George L. 
Published: May 2005

AbstractElectron impact induced fragmentations and rearrangements of 1‐phenyl‐2,2,3‐trimethylphosphetane 1‐oxide, 1‐phenylphospholane 1‐oxide and 1‐phenylphosphorinane 1‐oxide were investigated. A process common to all of these phosphine oxides was electron impact induced formation of new carbon‐carbon bonds involving the phenyl rings. Evidence for such rearrangements included observation of hydrocarbon fragment ions containing seven or more carbons.
Electron impact and chemical ionization mass spectrometry of cyclic boronate derivatives of sphingosines and related compounds
Authors: Simon J. Gaskell , Charles J. W. Brooks 
Published: May 2005

AbstractElectron impact and isobutane chemical ionization mass spectrometric data are reported for cyclic boronate esters of sphinganine and 4‐sphingenine and of the related N‐ethyl, N‐dimethylaminomethylene and acetone Schiff base compounds. Fragmentation of the 6‐membered boronate ring is promoted by the presence of the 2‐amino or 2‐imino substituent and by Δ4 unsaturation. Evidence is presented for a transannular interaction stabilizing the ion formed by loss of the alkyl or aryl group, attached to the boron atom, in the case of the N‐dimethylaminomethylene derivatives. An NH2 migration is postulated to occur in 4‐sphingenine boronates under electron impact. Mass spectrometric data are also reported for 4D‐hydroxysphinganine bis‐boronates.
A study of the decomposition of field ionized doubly charged molecular ions
Authors: Migahed M. D. , Allam S. H. 
Published: May 2005

AbstractThe dissociation of field ionized doubly charged organic molecular ions into doubly charged fragment ions and neutral fragments is discussed. The kinetic energy released during the dissociation of the singly and doubly charged molecular ions rules out the possibility of a direct correlation between their mechanisms of formation. Further, the pressure as well as the temperature dependence revealed that the singly charged molecular ions are formed by direct ionization of the neutral molecules, while the doubly charged molecular ions are formed through a second ionization process of the adsorbed molecular ions on the field anode surface.
Einfluß der chemischen Struktur auf die EA‐Massenspektren von aromatischen Kohlenwasserstoffen sowie von N‐ und S‐Heteroanaloge
Authors: Albers Georg , Knof Hans 
Published: May 2005

AbstractDer Einfluß der chemischen Struktur von aromatischen Kohlenwasserstoffen mit Molekulargewichten über 100 und ihren N‐ und S‐Heteroanalogen auf die Bruchstückbildung und die Ionenintensitäten bei der Elektronenanlagerungsmassenspektrometrie wird untersucht. Die Ausbeute negativer Ionen hängt haupsächlich von der chemischen Struktur und nicht so sehr von den Heteroatomen ab. Eine Ausnahme zu dieser Regel ist die Bildung von Sulfidanionen, die mit einer sehr hohen Ausbeute an Molekularionen abläuft.
Fragmentation de Quelques Hydrazines, Tétrahydrocinnolines et Pyrazolidines sous I'Impact Electronique
Authors: Cauquis G. , Chabaud B. , Ulrich J. 
Published: May 2005

AbstractLes spectres de masse de diverses hydrazines, tétrahydrocinnolines et pyrazolidines, issues de la condensation d'une cation diazénium ou de sa base conjguée sur des oléfines sont discutés. Le mode de fragmentation principal des hydrazines trisubstituées correspond à un processus de rétroaddition libérant le cation diazénium et l'oléfine. On Observe aussi une rupture de la liaison NN qui peut s'expliquer par une délocalisation de la charge de l'ion moléculaire sur les noyaux phényles que toutes les hydrazines considérées protent sur l'un de leurs atomes d'azote. Cette rupture de la liaison NN est la fragmentation dominante dans le cas des tétrahydrocinnolines. Par contre, elle n'est pas observable chez les pyrazolidines. Ces dernières subissent principalement une fragmentation voisine d'une rétroaddition de type dipolaire‐1,3. Celle‐ci libère le cation diazénium dont la base conjuguée qui est une imine d'azométhine a été utilisée dans la synthèse.
A collisional activation study of ions generated from the molecular ions of 2‐phenoxyethyl halides
Authors: Borchers F. , Levsen K. , Theissling C. B. , Nibbering N. M. M. 
Published: May 2005

AbstractCollisional activation spectra of ions generated from phenol, [2,2,2]oct‐2‐en‐5,7‐dione and site specifically deuterium labelled 2‐phenoxyethyl halides, , have shown that 2,4‐cyclohexadienone and phenol ions are distinct stable species in the gas phase for ≥ 10−5 s.
Fragmentation in chemical ionization mass spectrometry and the proton affinity of the departing neutral
Authors: Harrison Alex. G. , Onuska Francis I. 
Published: May 2005

AbstractChemical ionization mass spectra of six 5,6‐dihydro‐2‐methyl‐1,4‐oxathiins, and some of the sulfoxides and sulfones derived therefrom, have been determined employing hydrogen, methane and isobutane as reagent gases. The major fragmentation reaction of the protonated molecule, [R′COX·H]+, involves loss of the neutral HX molecule. For the sulfides and sulfones, with X ranging from OH to N(CH3)C6H5, it is observed that the importance of this fragmentation is inversely correlated with the proton affinity of the departing HX molecule in both the H2 and CH4 chemical ionization. For the sulfoxides no consistent correlation is observed and this is attributed to the interference of competing and/or consecutive fragmentation reactions. In the isobutane chemical ionization mass spectra only the protonated molecule is observed for most of the compounds studied.
Thiosugars. VI—mass spectrometry of 2,3‐epithio‐D‐allose derivatives
Authors: Yamaguchi Tadatoshi , Kojima Masaharu 
Published: May 2005

AbstractThe behaviour under electron impact of methyl 2,3‐dideoxy‐2,3‐epithio‐α‐D‐allopyranoside, methyl 2,3‐dideoxy‐2,3‐epithio‐β‐D‐allofuranoside, 1,6‐anhydro‐2,3‐dideoxy‐2,3‐epithio‐β‐D‐allopyranose, 1,6‐anhydro‐2,3‐dideoxy‐2,3‐epithio‐β‐D‐allofuranose and 2,3‐dideoxy‐2,3‐epithio‐β‐D‐allofuranose has been examined. The fragmentation pathways have been deduced by determination of the fragment ions elemental compositions, assignment of the metastable ions fröm the mass number shifts resulting from deuterium replacement, and by the comparison with an epoxide analogue.
Ionisation et Fragmentation en Spectrométrie de Masse. VII—Structure de l'Ion [C6H6O]+ Issu de la Décomposition du Phényléthyléther Sous Impact Electronique
Authors: Bouchoux Guy 
Published: May 2005

AbstractL'energie d'activation de la fragmentation [C6H5OC2H5]+ → [C6H6O]+ +C2H4 est calculée. Après évaluation de la variation d'enthalpie correspondante, une structure de type phénol est déterminée pour l'ion [C6H6O]+. L'énergie d'activation de la réaction inverse est comparée à l'énergie moyenne de translation des fragments [C6H6O]+ et C2H4. L'aspect concerté ou non concerté du mécanisme de cette fragmentation est discuté.
Pyrones. II—the mass spectra and fragmentation mechanisms of methyl maltol (3‐methoxy‐2‐methyl‐4H‐pyran‐4‐one) and methyl allomaltol (5‐methoxy‐2‐methyl‐4H‐pyran‐4‐one)
Authors: McGillivray David L. , Poulton Gerald A. 
Published: May 2005

AbstractThe mass spectra of methyl maltol (3‐methoxy‐2‐methyl‐4H‐pyran‐4‐one) and methylallomaltol (5‐methoxy‐2‐methyl‐4H‐pyran‐4‐one) and a number of deuterium labelled analogues have been studied in detail. The two pyrones have common fragmentation pathways, all of which can be traced back to a primary rearrangement of the molecular ion. The loss of water from the molecular ion occurs by two processes, both involving the methoxymethyl protons. The loss of methyl from the molecular ion also occurs by two routes, only one of which involves the methoxy methyl protons directly.
Recherches en série diazépine‐1,4 et triazépine‐1,2,4. XI—etude en spectrométrie de masse des fragmentations de triazépines‐1,2,4
Authors: Hasnaoui A. , Lavergne J.‐P. , Viallefont Ph. 
Published: May 2005

AbstractLes spectres de masse de onze triazépines‐1,2,4 présentant cinq types de structure et possédant les groupes oxo, thioxo, méthoxy ou méthylmercapto dans les positions 3 et 5 sont déorits. Chaque structure est caractérisée par un ensemble original de ruptures. Pour certains composés la participation à ľéquilibre, à ľétat vapeur, de certaines formes tautomères a été discutée.
The dependence of the extent of C2H6 elimination on the orientation of the C2H5 group in ethylbicyclo [4.4.0]decanes
Authors: Zaikin V. G. , Smetanin V. I. , Musaev I. A. , Kurashova E. Kh. 
Published: May 2005

AbstractThe elimination of C2H6 from the molecular ions of trans‐fused 2‐ and 3‐ethylbicyclo [4.4.0] decanes with the axial C2H5 group takes place to a greater extent than in the corresponding equatorial epimers.
Mass spectral studies on steroidal compounds. VIII—a comparative study of 6‐ and 7‐oxalactones
Authors: Ahmad M. S. , Moinuddin G. , Khan I. A. 
Published: May 2005

AbstractThe mass spectra of three steroidal ring B 7‐oxalactones and one 6‐oxalactone have been examined and comparison made with previously studied spectra of 6‐oxa isomers. Whereas the mass spectra of 6‐oxalactones are conspicuous by an intense peak at m/e 318, no such peak was found for 7‐oxalactones. On the contrary, the 7‐oxalactones showed characteristic [M  CH2O]+ ions. Thus, mass spectrometry offers an excellent means of differentiating between isomeric 6‐ and 7‐oxa ϵ‐lactones in the cholestane and β‐sitostane series. The fragmentation pathways suggested are supported by accurate mass measurement of some of the salient fragment ions.
Hydrogen migrations in mass spectrometry. VI—the chemical ionization mass spectra of substituted benzoic acids and benzyl alcohols
Authors: Ichikawa Hiroshi , Harrison Alex. G. 
Published: May 2005

AbstractThe H2 and CH4 chemical ionization mass spectra of a series of series of substituted benzoic acids and substituted benzyl alcohols have been determined. For the benzoic acids the major fragmentation reactions of the protonated molecule involve elimination of H2O or elimination of CO2, the latter reaction involving migration of the carboxylic hydrogen to the aromatic ring. For the benzyl alcohols the major fragmentation reactions of [MH]+ involve loss of H2O or CH2O, analogous to the CO2 elimination reaction for the benzoic acids. It is shown that the CO2 and CH2O elimination reactions occur only when a conjugated aromatic ring system is present, and that for the carboxylic acid systems, methyl groups and, to a lesser extent, phenyl groups are capable of migrating. The only discernible effect of substituents on the fragmentation of [MH]+ is an enhancement of the H2O loss reaction in the benzoic acid system when an amino, hydroxyl, or halogen substituent is ortho to the carboxyl function. This ‘ortho’ effect, which differs in scope from that observed in electron impact mass spectra, is attributed to an intramolecular catalysis by the ortho substituent of the 1,3 hydrogen migration in the carbonyl protonated acid followed by H2O elimination. Apparently, this route is favoured over the direct elimination of H2O from the carbonyl protonated acid, since the latter has a high activation energy barrier because of unfavourable orbital symmetry restrictions.
The mass spectrometric fragmentation of n‐heptane
Authors: Lavanchy André , Houriet Raymond , Gäumann Tino 
Published: May 2005

AbstractThe electron impact fragmentation of n‐heptane has been investigated using 13C labelled derivatives. A mechanism is proposed for the loss of alkyl radicals where the cleavage of a CC bond is coupled with the rearrangement of a hydrogen atom, thus yielding a secondary alkyl ion that eventually fragments further by a subsequent loss of olefin. For alkyl ions with less than six carbon atoms this consecutive pathway is in competition with formation directly from the molecular ion. The consecutive pathway contributes about 15% to the intensity of the alkyl ions with four and five carbon atoms and 80% for smaller ions. The electron energy dependence was studied.
Collisional activation spectra at improved resolving power obtained by the use of a collision chamber and a linked scan of the electric and magnetic sector field strengths
Authors: Stradling R. S. , Jennings K. R. , Evans S. 
Published: May 2005

AbstractA method for obtaining collisional activation spectra at much higher resolving power than before by use of a collision chamber and a B/E linked scan, is described.
Redox processes in the evaporation of N‐phenylpyridinium salts in the mass spectrometer
Authors: Ellingsen P. , Hvistendahl G. , Undheim K. 
Published: May 2005

AbstractN‐Phenylpyridinium and 1,4‐diphenylpyridinium halides undergo both one and two electron reductions to the N‐phenyl‐ and 1,4‐diphenylpyridine free radicals and the corresponding 1,2‐ and 1,4‐dihydro derivatives respectively, prior to evaporation in the mass spectrometer. In addition, a third component is found in the gas phase, possibly due to dimerization of the free radical followed by dehydration.