bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of molecular geometry on the fragmentation of methyl esters of cyclobut‐3‐ene‐1,2‐dicarboxylic acids
Authors: Weinstein S. , Gil‐Av E. , Leftin J. H. , Levy E. C. , Mandelbaum A. 
Published: May 2005

AbstractElimination of CH3OH from the molecular ions of the methyl esters of cyclobut‐3‐ene‐1, 2‐dicarboxylic acids under electron‐impact occurs to a much greater extent in stereoisomers having a trans configuration than in the cis analogues. Deuterium labelling shows that this process takes place via different mechanisms in the stereoisomeric esters. The abundance ratio [M  CH3OH]˙+/[M  CH3O]+ is suggested as the most sensitive criterion for the deduction of configuration in this system. Determination of the geometry of the cyclobutene esters by n.m.r. spectroscopy as well as by pyrolysis to corresponding isomeric muconates is also discussed.
The mass spectra of six fluorinated β‐diketones and their monothio analogues
Authors: Das M. , Livingstone S. E. 
Published: May 2005

AbstractThe mass spectra of the fluorinated β‐diketones RCOCH2COCF3 (R = Ph, p‐FC6H4, p‐ClC6H4, p‐BrC6H4, p‐MeC6H4 and 2‐thienyl) and their monothio analogues RC(SH)CHCOCF3 have been obtained. The replacement of one oxygen by sulphur in the β‐diketones brings about a greater complexity in the mass spectra. The β‐diketones fragment by first losing a ·CF3 radical and then successively lose CH2CO and CO to yield \documentclass{article}\pagestyle{empty}\begin{document}${\rm [R}\mathop {\rm C}\limits^{\rm + } {\rm = O]} $\end{document} and [R]+. The monothio‐β‐diketones also fragment by an analogous reaction pathway: viz. the initial loss of ·CF3 is followed by the successive loss of CH2CO and CS to yield \documentclass{article}\pagestyle{empty}\begin{document}${\rm [R}\mathop {\rm C}\limits^{\rm + } {\rm = S]} $\end{document} and [R]+. However, they also fragment by two other pathways involving the initial loss of ·H and ·X (X=F, Cl, Br, Me), the latter occurring only with those monothio‐β‐diketones having R=p‐XC6H4.
The mass spectra of the trimethylsilyl esters of acetyl, schiff base and isothiocyanate derivatives of some aminoalkylphosphonic acids
Authors: Harvey D. J. , Horning M. G. 
Published: May 2005

AbstractTrimethylsilyl esters of acetyl, Schiff base and isothiocyanate derivatives of a series of aminoalkylphosphonic acids were prepared for the purpose of characterizing these phosphorus compounds by combined gas chromatography and mass spectrometry. The mass spectra of these derivatives were investigated by means of high resolution mass measurments and deuterium labeling. Ions characteristic of the presence of the trimethylsilylphosnate group were observed at m/e 121, 195, 211 and 225 to 227 in the spectra of all the derivatives. Several ions produced by interaction between the trimethylsilyl group and the derivatized amino function were present, particularly in the spectra of the acetate derivatives ([M — 56]+, [M — R]+ and [M — 153]+, where R is the side chain attached to C‐1), and the isothiocynate derivatives (m/e 268, 253, 241, 190 and 116).
Mass spectrometric studies of alkyl‐, phenyl‐ and chloropyrimidines
Authors: Kato T. , Yamanaka H. , Abe H. , Sasaki S. , Ichikawa H. 
Published: May 2005

AbstractThe mass spectra of alkyl‐ and chloropyrimidines are recorded. A generalised fragmentation mechanism for the derivatives of pyrimidine is proposed. The principle of α‐cleavage for heterocyclic compounds as proposed in the previous paper is shown to be valid for pyrimidine derivatives. Electronic structures of some molecular and intermediate ions are calculated by the openshell CNDO/2 and INDO methods.
Massenspektrometrische Untersuchung Organischer Stickstoffverbindungen. XII—H‐übertragungen Durch Nachbargruppen‐Wechselwirkung bei αω′‐bis‐(N‐Piperidyl)‐Aromaten
Authors: Schwarz Helmut 
Published: May 2005

AbstractMit Hilfe von 2H‐markierten Modellverbindungen werden die durch Nachbargruppenwechselwirkung beeinflußten Fragmentierungen von verschiedenen Dipiperidinen aufgeklärt. Neben einer neuartigen McLaffery‐Umlagerung werden sowohl spezifische als auch selektive H‐übertragungen vor der Abspaltung von Peperidin nachgewiesen. Die Jeweils isomeren Diamine Können mit Hilfe der Massenspektrometrie eindeutig unterschieden und identifiziert werden.
Electron‐impact studies. LXXXVII—ortho effects in the negative ion mass spectra of salicylates and anthranilates
Authors: Bowie J. H. , Ho A. C. 
Published: May 2005

AbstractThe molecular anions of the methyl and phenyl esters of 4‐nitrosalicylic acid and 5‐nitroanthranilic acid eliminate ROH (R  Me or Ph) by an ortho rearrangement. The molecular anions of phenyl 3‐hydroxy‐5‐nitrobenzoate and phenyl 3‐amino‐5‐nitrobenzoate lose PhOH to a lesser extent, and a study of the pressure dependence of these eliminations indicates the operation of simultaneous two‐stage cleavage reactions. The competitive ortho effects observed when the nitro group is adjacent to either the ester or hydroxyl functions are described.
Mass spectral studies of some aryl and aroyl derivatives of glyoxime
Authors: Terent'ev P. B. , Kost A. N. , Lange Jerzy 
Published: May 2005

AbstractMass spectra of two diaroylglyoximes (Ia and Ib) are reported and compared with those of the corresponding dehydration products, 3,4‐diaroyl‐1,2,5‐oxadiazoles (IIIa and IIIb, respectively). In Ia and Ib, unlike in diarylglyoximes (Id and Ie), the largest ion is [M — 18]+, but this does not form in the ion source by a simple thermal dehydration. Similar spectra have been obtained for an alkyl aroyl derivative of glyoxime (Ic) and an isonitroso‐β‐diketone (II). A specific electron‐impact‐induced rearrangement leading to the formation of carboxylic acids has been observed in the mass spectra of all the acylated oximes under investigation.
Ein Computerverfahren für die Massenspektrometrische Untersuchung Organischer Proben bei Fraktionierter Direktverdampfung
Authors: Hillig H. , Riepe W. , Kwiatkowski J. 
Published: May 2005

AbstractEs wird ein Computerverfahren beschrieben, das es ermüglicht, die ‘Lebensgeschicht’ einer organischen Probe während der Totalverdampfung im Direkteinlaßsystem eines Massenspektrometers durch Zyklische Aufnahme von Massenspektren und Beobachtung der Verdampfungstemperatur zu verfolgen. Die Aufnahme der Spektren wird durch ein Datensystem gesteuert, das auch die Weiterverarbeitung übernimmt; es liefert darüber hinaus Beurteilungsmöglichkeiten fü die Entscheidung, ob die Probe einheitlich ist oder nicht. Liegt ein Gemisch vor, gibt der Rechner Hinweise, in wieviele Komponenten die probe durch die fraktionierte Verdampfung zerlegt wurde und welche aufeinanderfolgenden Spektren den einzelnen Fraktionen zugeordnet werden müssen.
Massenspektrometrische Untersuchungen von Isomeren Stickstoffverbindungen des Dibenzofurans
Authors: Riepe W. , Florea S. , Fǎrcǎşan V. , Cristea I. 
Published: May 2005

AbstractDie Massenspektren von isomeren Amino‐, Acetamino‐ und Nitrodibenzofuranen wurden aufgenommen und das Fragmentierungsverhalten untersucht. Es wurden zwischen einigen Isomeren deutliche Unterschiede gefunden, die zum Teil durch intramolekulare Wasserstoffbrücken, ortho‐Effekte oder durch Resonanzstabilisierung erklärt werden.
Electron‐impact‐induced fragmentation of morellin and related compounds
Authors: Yemul S. S. , Rao A. V. Rama 
Published: May 2005

AbstractThe mass spectra of morellin and other related natural products, isolated from the various Garcinia species, have been recorded and the data has been rationalised. The characteristic cleavage is the opening of the bicyclo(2.2.2) octenone ring system by a retro‐Diels‐Alder reaction. The γ‐pyrone ring also undergoes the retro‐Diels‐Alder fragmentation. These two modes of cleavage indicate the different substituents on the main skeleton of morellin. The hydrogenated derivatives show slight variations in their fragmentation modes. The mass spectral data assists considerably in the structural elucidation of similar complex molecules, if isolated in minute quantities.
Mass spectral studies of cycloheptatrienes. II—The monochlorocycloheptatrienes
Authors: Hoffman Michael K. , Friesen Marlin D. 
Published: May 2005

AbstractThe mass spectra of isomeric chlorocycloheptatrienes have been studied at high and low electron beam energies. Ion kinetic energy spectrometry was utilized to examine the major decomposition pathways. The extreme similarity found in the spectral characteristics of these compounds provides information about the structure of the decomposing molecular ion.
Massenspektroskopische Fragmentierungsreaktionen. VII.—Abbau der Polyenkette bei Carotinoiden
Authors: Johannes B. , Brzezinka H. , Budzikiewicz H. 
Published: May 2005

AbstractDer Ablauf der verschiedenen Zerfallsreaktionen der Polyenkette bei Carotinoiden wird and Hand von deuterierten Analogen diskutiert.
The electron‐impact‐induced fragmentations of some substituted 3‐aminopropionitriles
Authors: Gay M. L. , Molton P. , Ponnamperuma C. 
Published: May 2005

AbstractAs a part of our study of the chemistry of simulated Jovian atmospheres, we have synthesized a series of twelve alkyl aminopropionitriles to serve as model compounds. The spectra of these compounds have been obtained, and the transitions which are observed have been further investigated by scanning in the metastable mode and by obtaining the spectra of deuterium labeled 3‐(N‐ethylamino)propionitrile. The fragmentations which are observed are dominated by the amine group.
Mass spectrometry of 4‐amino‐4′‐nitroazobenzene compounds
Authors: Gilland J. C. , Lewis J. S. 
Published: May 2005

AbstractThe mass spectra of 32 substituted 4‐amino‐4′‐nitroazobenzene compounds have been recorded and the most intense peaks have been used to characterize these spectra. It was found that the spectra of 4‐amino‐4′‐nitroazobenzene compounds are characterized by peaks due to: (1) molecular ions, (2) fragment ions formed by cleavage of one of the carbon‐nitrogen bonds adjacent to the azo linkage with the positive charge remaining with the amine fragment, (3) ions formed by cleavage alpha to the amine nitrogen with the charge remaining with the amine substituent, (4) ions formed by cleavage beta to the amine nitrogen with the loss of the amine substituent fragment, (5) secondary ions formed by cleavage beta to the amine nitrogen with the loss of the amine substituent fragment from the primary amine fragment (2), and (6) ions formed by loss of NO from the molecular ion. This work shows that 4‐amino‐4′‐nitroazobenzene compounds exhibit fragmentation which is dependent in a consistent manner on the types of substituents. This work provides a basis for a systematic approach to the identification of 4‐amino‐4′‐nitroazobenzene compounds.
Analytical application of ion‐molecule reactions. Reactions of various substituted cyclopropane molecular ions with ammonia
Authors: Gross Michael L. , Lin Ping‐Huang 
Published: May 2005

AbstractBy ion cyclotron resonance it is found that various substituted cy clopropanes after ionization react with ammonia to give products which allow identification of the degree and kind ofsubstitution on the cyclopropl ring. For example, cyclopropyle reacts to give [CH2NH2]+ (m/e 30), methylcyclopropane gives [CH2NH2]+ (m/e 30) and the ethyl substituted [CH(C2H3)NH2]+ (m/e 44) and ethylopropane gives [CH2NH2]+ (m/e 30) and the ethyl substituted [CH(C2H5)NH2]+ (m/e 58). It is suggested that reactions of stable molecular ions with reagent neutrals may be a source of highly specific structural information for organic compounds.
Mass spectrometry of cycloheptatriene derivatives. III—skeletal rearrangements in the molecular ion of 7‐cyano‐7‐methylcycloheptatriene and in some of its fragment ions
Authors: Venema A. , Nibbering N. M. M. 
Published: May 2005

AbstractIt is shown by carbon and deuterium labelling experiments that a substantial part of the molecular ions of 7‐cyano‐7‐methylcycloheptatriene has rearranged to a tolylacetonitrile, both in the ion source and in the second field free region. The evidence follows from a comparative study of α‐methylbenzylcyanide, o‐ and p‐tolylacetonitriles and their labelled analogues. The decomposing [M — CH3]+ ion from 7‐cyano‐7‐methylcycloheptatriene presumably has a cyanomethylphenyl cation, instead of a cyanotropylium structure.
Mass spectrometry of onium compounds. XXX—Ionisation potentials in structure analysis of sydnones
Authors: Undheim Kjell , El‐Gendy Mahmoud A. F. , Hurum Torgeir 
Published: May 2005

AbstractComparative studies of the ionisation potentials of some sydnones indicate that these molecules are largely present in the gaseous phase as their valence isomeric N‐nitroso ketenes.
Field desorption mass spectra of phthalocyanines
Authors: Games D. E. , Jackson A. H. , Taylor K. T. 
Published: May 2005

AbstractMass spectr of phthalocyanines are readily obtainable by field desorption mass spectrometry. Molecular ions are normally the base peaks in the spectra and minimal fragmentation is observed. The technique provides a rapid method for the qualitative exmination of mixtures of phthalocyanines.
Mass spectra of some isopropyl benzene derivatives. A study of the ortho effect
Authors: Smith J. G. , Wilson G. L. , Miller J. M. 
Published: May 2005

AbstractThe mass spectra of a series of ortho, meta and para substituted isopropyl benzene derivatives have been determined where the second substituent is COOH, C(O)NH2, C(O)C6H5, C(Ph)(=NPh) or CH(Ph)(NHPh). Two bis‐isopropylbenzophenones have also been studied. The spectra are characterized by prominent ortho effects which distinguish the ortho derivatives from the meta and para.
The mass spectra of (trimethylstannyl)x methanes: Occurrence of tin‐carbon double bonds
Authors: Dimmel Donald R. , Wilkie Charles A. , Lamothe Paul J. 
Published: May 2005

AbstractThe mass spectra of (Me3Sn)nCH4−n, where n varies from 1 to 4, (Me3Sn)2CClX, where X equals H, Cl, Br or I, together with some tetraalkyltin compounds and Me3SnCCl3, are presented. Comparisons with mass spectra of the silicon analogs1 show a large number of similarities, including the appearance of allylic ions which require Group IV metal to carbon π‐bonding. Multiple rearrangements are observed with the halogenated tin compounds which bring the α‐halogen into direct bonding with the tin atom.
Mass spectral structure elucidation of substituted 4‐oxazolidones, the photocycloexpansion products of 2,4‐azetidindiones
Authors: Compernolle F. , Schutyser J. , De Schryver F. C. 
Published: May 2005

AbstractAbstract‐2‐Methoxy‐4‐oxazolidone structures are assigned to the photocycloexpansion products of the substituted 2,4‐azetidindiones on the basis of mass spectral evidence. A discussion is given of the mass spectra of 2‐methoxy‐4‐oxazolidones and of their hydrolysis products, the 2‐hydroxy‐4‐oxazolidones and the ring opened substituted 2‐hydroxy‐N‐formyl acetamides. Ring and chain forms, when both isolated, yield completely different mass spectra, indicating that no rapid tautomeric equilibrium is established in the gas phase.
Fragmentation d'azoles sous l'impact electronique VII –N‐ethylbenzimidazoles
Authors: Maquestiau A. , Van Haverbeke Y. , Flammang R. , Pardo M. C. , Elguero J. 
Published: May 2005

AbstractPar marquages isotopiques (13C et D), on montre que l'ion [M  CH3]+ observé dans le spectre de masse du l‐éthylbenzimidazole se réarrange quantitativement en une structure quinoxalinium avant l'élimination d'acide cyanhydrique.
Hydrogen cyanide elimination and rearrangement upon electron‐impact from schiff bases of benzaldehyde and aliphatic amines
Authors: Hanuš V. , Vereš K. , Cabák J. 
Published: May 2005

AbstractThe Schiff bases of benzaldehyde and aliphatic amines form immonium ions on electron‐impact, which rearrange and eliminate hydrogen cyanide in a different way than the corresponding derivatives of pyridine‐2‐aldehyde. The presence of at least one hydrogen on the α‐carbon atom in the amine moiety is a necessary condition for this rearrangement. A mechanism is suggested for this process.
Spectral properties of organometallic transition metal complexes I–Mass spectra of haloacteophenones haloacetylferroce, FcCO–CH2X, and related ferrocence complexes FcCOCI and FcCH2CI
Authors: Pannell K. H. , Bittman Linda J.(Russwinkle) 
Published: May 2005

AbstractThe mass spectral properties of the title compounds have been recorded and compared. For the haloacetyl systems ring expansions to tropylium ions and π‐benzene iron ions are observed. A major ion present in all haloacetyl spectra is that derived from the corresponding acetyl compound, CH3CO‐, formed via an instrument catalyzed reduction of the halo compounds by residual water. Some substituent effects are observed. Considerable halogen migration to iron is observed for the ferrocene complexes.
[C]+· and [CH]+ from doubly charged ions formed from malononitrile
Authors: Beynon J. H. , Caprioli R. M. , Cooks R. G. , Nibbering N. M. M. , Molenaar‐Langeveld T. A. 
Published: May 2005

AbstractThe metastable ions [M]2+, [M – H]2+· and [M – H2]2+ from malononitrile fragment by loss of [CH]+, [C]+· and [C]+·, respectively. The reaction of the molecular ion involves the methylene and nitrile carbon atoms in the statistical probability ratio, while that of [M – H]2+· involves exclusively the nitrile carbon and that of [M  H2]2+ involves an approximately equal contribution, from both sources. It is suggested that the metastable molecular ion fragments through a bipyrimidal intermediate.
Untersuchungen in der Thiazolreihe. III—massenspektrometrische Untersuchung von 2‐Amino‐3‐hydroxythiazoliumchloriden
Authors: Entenmann G. 
Published: May 2005

AbstractDer massenspektrometrische Zerfall von 2‐Aminothiazol‐3‐oxiden ist durch die Abspaltung von O und OH aus dem Molekülion charakterisiert. Deutliche Unterschiede zwischen 4‐Alkyl und 4‐Arylderivaten sowie die ausgeprägte Substituentenabhängigkeit des [M – OH]+·: [M – OH]+‐Verhältnisses lasses sich mit einer Stabilisierung des [M – O]+·‐Radikalkations durch aromatische Substituenten deuten. Die Temperaturabhängigkeit der Spektren weist auf ein Tautomeriegleichgewicht im Einlaßsystem hin.
Electron‐impact studies. XCIX—negative ion mass spectrometry of the o‐NO2C6H4XC6H5 systems. Aryl hydrogen scrambling and proximity effects
Authors: Wilson Joe C. , Bowie John H. 
Published: May 2005

AbstractWe report the first example of aryl hydrogen scrambling occurring in a molecular anion prior to or accompanying fragmentation, i.e. for the reaction [M]−· → [M  H2NO2.]− from o‐NO2C6H4XC6H5 (X = O or S). Proximity effects occur in these spectra when X = CO, NH, O, or S, and certain of these have been substantiated by 2H and 18O labelling.
The dissimilarity between the electron‐impact and photochemical or thermal behaviour of some methyl cyclobut‐3‐ene‐1,2‐dicarboxylates and muconates
Authors: Mandelbaum Asher , Weinstein S. , Gil‐Av E. , Leftin J. H. 
Published: May 2005

AbstractComparison of the mass spectral behaviour of the dimethyl esters of the epimeric (cis‐ and trans‐) cyclobut‐3‐ene‐1,2‐dicarboxylic acids and the isomeric muconates (cis, cis‐, cis, trans‐ and trans, trans‐) and some substituted analogues shows that no correlation exists between the electron‐impact‐induced fragmentation and the predicted photochemical or thermal transformations in these systems. The comparison involved fragmentation patterns (supported by deuterium labelling), metastable transitions, and also kinetic energy release in the field free region.
Mass spectra of 4‐substituted‐1,2,6‐trimethyl‐3,5‐diethoxycarbonyl‐1,4‐dihydropyridines
Authors: Esmans E. L. , Dommisse R. A. , Alderweireldt F. C. 
Published: May 2005

AbstractThe mass spectra of 4‐substituted‐1,2,6‐trimethyl‐3,5‐diethoxycarbonyl‐1,4‐dihydropyridines have been studied. The detailed fragmentation mechanisms, supported by high resolution measurements, the study of metastable ions and the use of deuterium labelling, are discussed.
Metastable ion studies. III—composite metastable peaks in fragmentations of some small hydrocarbon cations
Authors: Holmes John L. , Osborne Alexander D. , Weese Gwyneth M. 
Published: May 2005

AbstractComposite metastable peaks are generated in the unimolecular fragmentations (i) [C3H5]+ → [C3H3]+ + H2 (flat‐top upon flat‐top) and (ii) [C4H9]+ → [C3H5]+ + CH4 (flat‐top and gaussian). The measurement of appearance potentials and kinetic energy releases lead us to conclude, in agreement with earlier proposals, that in (i) the components can arise from the generation of the isomeric cyclopropenium and propargyl daughter cations. In (ii) the components are proposed to arise from the fragmentation of tert‐ and sec‐butyl cations yielding allyl as the common daughter ion.The composite peak observed in the fragmentation (iii) [C3H4]+· → [C3H3]+ + H· is shown to be present only if the decomposing molecular ion is large enough to also produce [C6H8]2+ ions. The second component in (iii) then arises from the reaction [C6H8]2+ → [C6H6]2+ + H2.
Isomerisation de l'ion moleculaire de derives substitues polycycliques du benzodioxinne‐1,4
Authors: Dagaut Jacques , Dizabo Pierre , Pompon Alain , Fillaux Joelle 
Published: May 2005

AbstractTrois dégradations (petre de phényle, d'hydrogé, d'un radical RCO) de dérivés benzocyclobuténiques du bemnzodioxinne‐1,4 diversement substitué ont été étudiés. Ces molécules deutériées en position spécifique ont permis, dans certains cas, de mettre en évidence l'existence de plusieurs isomères de l'ion moléculaire.
Application of mass spectrometry to the structural investigation of triterpenes. II—3,4‐A‐seco‐triterpenoids
Authors: Aplin R. T. , Cox I. R. 
Published: May 2005

AbstractThe mass spectral behaviour of a series of naturally occurring and synthetic 3,4‐A‐seco‐triterpenes has been examined and fragmentations characteristic of the 3,4‐A‐seco function observed. Deuterium labelling has been used to investigate the origins of their characteristic fragments.
Massenspektroskopische Fragmentierungsreaktionen. IX—Ringkontraktion bei 6‐ und 7‐ringen: eine überischt
Authors: Budzikiewicz H. , Lenz U. 
Published: May 2005

AbstractDie für mögliche Ringkontraktionen bei 6‐ und 7‐gliedrigen Perhydroheterocyclen in der Literatur vorhandenen Hinweise werden kritisch zusammengefaßt.
Substituent effects in the mass spectra of acetanilides
Authors: Gilbert J. R. , Stace A. J. 
Published: May 2005

AbstractThe kinetic shifts for an ion decomposition involving loss of CH2CO from a series of substituted acetanilide ions have been calculated using the Rice‐Ramsperger‐Kassel‐Marcus theory. The results indicate that in the main the observed changes in appearance potential‐ionisation potential for this reaction are due to a change in the number of degrees of freedom on introducing the substituent and not due to a substituent effect on the critical energy of reaction.
Analysis of carotenoids by field desorption mass spectrometry
Authors: Watts C. D. , Maxwell J. R. , Games D. E. , Rossiter M. 
Published: May 2005

AbstractThe mass spectra of a variety of authentic carotenoids covering a range of structural types have been studied using the field desorption technique. All the compounds examined show the molecular ion as the base peak, even where this ion is of very low intensity in the electron‐impact spectra. Little fragmentation is observed, but thermal decomposition can be induced in certain cases by using higher emitter currents. Application to a simple mixture of authentic compounds and a more complex mixture of sedimentary origin shows the potential of the method in the rapid qualitative screening of carotenoids in crude extracts.
Further investigation of the Ramberg‐Bäcklund process
Authors: Langler R. F. , Mantle W. S. , Newman M. J. 
Published: May 2005

AbstractA further examination of the Ramberg‐Bäcklund process in the mass spectra of β‐disulfones is reported. An alternative rationale is dismissed from consideration and additional evidence adduced for preferential abstraction of benzylic hydrogens by γ‐sulfonyl groups.