bluuebunny/crossref_metadata_2025_split huggingface dataset:
A cyclization reaction in the electron‐impact induced fragmentation of some N‐propargylic oxoquinazolines and anilines
Authors: Bogentoft Conny 
Published: May 2005

AbstractEvidence for an acetylenic rearrangement, involving the ring‐closure of ions containing the N‐propargylaniline substructure to the corresponding quinoline ions, has been obtained in a study of the electron‐impact induced fragmentation of 1,4‐dihydro‐4‐oxo‐2‐phenyl‐1‐propargylquinazoline (I) and 1,2,3,4‐tetrahydro‐2‐oxo‐3‐phenyl‐1‐propargylquinazoline (II). The N‐propargylaniline moiety is formed from compounds I and II through the RDA process. N‐Methyl‐N‐propargylaniline (III), which was examined as a model compound, was also found to undergo this rearrangement but N‐methyl‐N‐propargyl‐2,6‐xylidine (IV), on the other hand, exhibits a quite different fragmentation pattern due to its blocking methyl groups, which prevent the rearrangement. Exact mass measurement and specific deuterium labelling were used to establish the fragmentation routes.
Mass spectrometry in structural and stereochemical problems—CC A study of the fragmentation processes of some pyrilium salts
Authors: Duffield A. M. , Djerassi Carl , Balaban Alexandru T. 
Published: May 2005

AbstractThe principal mode of fragmentation, at both 70 and 15 eV, of pyrilium iodides (I to V) which are substituted by at least one methyl group is the elimination of hydrogen iodide from the non‐detectable molecular ion. In contrast the mass spectrum (Fig. 6) of 2,4,6‐triphenyl pyrilium iodide (VI) shows its dominant fragmentation to be due to the loss of an iodine atom from the molecular ion. The mass spectra (for example Figs. 6 and 7) of 2,4,6‐triphenyl pyrilium iodide, bromide and tetrafluoroborate (VI, VII and VIII) are virtually identical except for the peaks corresponding to a molecule of iodine (m/e 254), hydrogen iodide (m/e 128) and iodine (m/e 127) in the mass spectrum (Fig. 6) of the iodide. Other fragmentation routes common to these pyrilium salts are described.
Studies on the syntheses of azole derivatives—V: The mass spectra of 1,2,4‐triazoles and oxadiazoles (studies on the syntheses of heterocyclic compounds—CCCLXXIV)
Authors: Kametani Tetsuji , Hirata Shoji , Shibuya Shiroshi , Shio Masahisa 
Published: May 2005

AbstractThe electron‐impact induced fragmentation of twenty 3‐alkyl‐1‐phenyl‐Δ2‐1,2,4‐triazolin‐5‐ones, three 1‐phenyl‐1,2,4‐triazolin‐3,5‐diones and ten 2‐alkyl‐4‐phenyloxadiazolin‐5‐ones has been studied by conventional mass spectrometry. The major cleavages take place in the 1‐phenyl‐Δ2‐1,2,4‐triazolin‐5‐one nucleus, producing three major fragment ions. 4‐Phenyloxadiazolin‐5‐ones exhibit a similar fragmentation pattern to 1‐phenyl‐Δ2‐1,2,4‐triazolin‐5‐ones. Furthermore, several additional fragmentation processes are observed in the case of specific 1,2,4‐triasolines.
Ion kinetic energy spectroscopy
Authors: Chait E. M. , Askew W. B. 
Published: May 2005

AbstractPreliminary results indicate the value of ion kinetic energy (1KE) spectra in adding a new dimension to structural information obtained by mass spectrometry. These spectra are especially useful in the distinction of some isomer pairs. Energy spectra provide a summary of gaseous ion chemistry occurring as metastable transitions in the first‐field free‐drift region of the double‐focusing (Mattauch‐Herzog geometry) mass spectrometer and are produced by scanning the electrostatic sector voltage while recording the ions transmitted by the sector with the beam monitor electrometer.
Negative and positive mass spectra of some substituted trinitromethanes
Authors: Larkins John T. , Nicholson Jesse M. , Saalfeld Fred E. 
Published: May 2005

AbstractThe negative and positive ion mass spectra of a series of substituted trinitroalkanes (nitroform, tetranitro methane, methyl, fluoro, chloro, bromo and iodo‐trinitro methane) have been measured with an Aatlas CH‐4 Mass Spectrometer, under varying electron energies from 70 over the total range at which ions are produced. The modes of decomposition of the compounds are presented. A few metastable transitions are observable in the negative ion spectra, but only at high electron energies (ion pair region) and are very low in intensity. the negative and positive ion clastograms of these polynitro compounds showed little parent‐daughter ion correlation. Finally, the negative ions formed appear to contain excess amounts of kinetic energy even at low electron energies; as a retult there is a great deal of overlap in the various mechanisms for the formation of negative ions.
Mass spectra of bis‐π‐allylic‐palladium halides
Authors: Lammens H. , Sartori G. 
Published: May 2005

AbstractThe mass spectral fragmentation of (π‐allyl‐PdCl)2, (π‐methallyl‐PdCl)2, (π‐crotyl‐PdCl)2 and (π‐allyl‐PdBr)2, (π‐methallyl‐PdBr)2, (π‐crotyl‐PdBr)2 are described and discussed.It is shown that the breakdown of these complexes after ionization depends on the nature of the groups attached to the metal.
Studies in organic mass spectrometry—II
Authors: Ikeda M. , Tsujimoto N. , Tamura Y. 
Published: May 2005

AbstractThe mass spectra of various N‐aryliminopyridinium and isoquinolinium betaines have been recorded. The most prominent fragmentation process of these compounds is N‐N bond cleavage with the charge retention on both the pyridine and aryl fragments. An ortho‐effect has been observed in the mass spectrum of N‐o‐nitrophenyliminopyridinium betaine (IXa).
Energy and substituent effects on the mass spectra of substituted benzophenones
Authors: Einolf Noel , Munson Burnaby 
Published: May 2005

AbstractFor two competing decompositions of the same molecular ion to give products [A1+] and [A2+], the ratio [A1+]/[A2+], is equal to the ratio of rate constants for the formation of the stable ions. Thr ratios, [Y C7H4O+]/[C7H5O+], were determined for several benzophenones for electron energies from 15 to 70 eV. Plots of log [Y C7H4O+]/[C7H5O+] vs.[ω+] gave good straight lines at all energies. Similar correlations have been reported for log [Y C7H6+]/[C7H7+] from substituted diphenyl ethanes and are also true for substituted acetophenones, log [YøCO+]/[CH3CO+]. A few charge exchange data were obtained which showed the same general trend as the electron‐impact data and emphasize the contribution of low energy ions in the 70 eV mass spectra. Relatively poor correlations were obtained for the [Y C6H4+] and [C6H5+] ions that are formed by both one‐step and two‐step decompositions.
Oberflächenreaktionen bei der Feldionisierung von Aldehyden und Nitrilen
Authors: Migahed M. D. , Beckey H. D. 
Published: May 2005

AbstractOberflächenreaktionen von Aldehyden und Nitrilen bei hoher elektrischer Feldstärke wurden rnassenspektrometrisch untersucht. Einige allgemeine Erscheinungen werden für den Fall von Oberflächenreaktionen von Crotonaldehyd aufgezeigt. Die Feldionisations Massenspektren (FI) polarer Substanzen hängen stark davon ab, ob die organischen Mikronadeln auf dem FI‐Emitter eine dichte oder eine poröse Struktur hahen. Protonentransfer‐Reaktionen werden mit den meisten polaren Substanzen beobachtet. Sie können reduziert werden, wenn die Emitteroberfläche mit einer stark adsorbierten Substanz bedeckt wird, die nicht mit der polaren Substanz reagiert. Die ursprünglich dichte Struktur der Mikronadel kann sich zu einer porösen Struktur wandeln. Die FI‐Massenspektren polarer Substanzen können sich dann im Laufe der Zeit wegen Kapillarkondensation oder der Bildung von Multischichten drastisch verändern.Die Erhöhung der Emittertemperatur verringert die Intensität der Fragment‐ und dimeren Ionen der polaren Substanzen, die Multischichten auf der Emitteroberfläche bilden. Thermische Desorption der Multischichten verringert die Anzahl der in ihnen vorkommenden Reaktionen. Selbst bei hohen Temperaturen (750° C) ist die Reduzierung von Fragmentintensitäten infolge des Abbaus der Multischichten ausgeprägter als diezunahmevon Fragmentintensitäten infolge thermischer Bindungsbrüche, vorausgesetzt daß das C, N, O‐Gerüst der Moleküle entweder aus starken Bindungen, wie konjugierten Doppelbindungen zusammengesetzt ist, oder da13 es eine zyklische Striktur hat.Es wird gezeigt, daß die FI‐Massenspektren der Benzonitrile wesentlich einfacher sind als die einiger aliphatischer Nitrile, und daß die Mechanismen der Feldpolyrnerisation in beiden Fällen verschieden sind.
Carbon‐nitrogen bond cleavage provoked by hydrogen rearrangement: The fragmentation of N‐acetylpyrrolidine and homologues
Authors: Richter W. J. , Tesarek J. M. , Burlingame A. L. 
Published: May 2005

AbstractCarbon‐nitrogen bond cleavage provoked by hydrogen rearrangement in molecular ions is reflected in several prominent features of the fragmentation of acylated cyclic amines, notably N‐acetylpyrrolidine. Contrary to the behavior of the free amine, the positional origin of the atoms involved in the ejection of ethylene from the molecular ion of the acetyl derivative reveals participation of an α‐carbon atom, i.e. a carbon atom directly attached to nitrogen. Abstraction of hydrogen from the α‐position of the ring moiety by the acyl substituent is proposed as initiating the over‐all process. The analogous behavior of systems incorporating larger rings or extended acyl substituents (N‐acetylpiperidine, N‐acetylhexamethyleneimine, N‐propionylpyrrolidine and N‐n‐butyrylpyrrolidine) lends support to the general applicability of this mechanistic rationale.
Mass fragmentation and structure of siphonaxanthin, siphonein and derivatives
Authors: Strain H. H. , Svec W. A. , Aitzetmüller K. , Cope B. T. , Harkness A. L. , Katz J. J. 
Published: May 2005

AbstractHigh resolution mass spectrometry has been employed to establish the structural formulae of the unique carotenoid pigment siphonaxanthin, its natural ester, siphonein and several derivatives. Siphonaxanthin exhibits a fragmentation reaction that is unusual among carotenoid pigments, namely, the elimination of carbon dioxide, observed as [M ‐ CO2] and [M ‐ (CO2 + H2O)]. This reaction involves the migration of an oxygen atom. Siphonaxanthol, a partially hydrogenated siphonaxanthin, exhibits a similar reaction involving the elimination of carbon monoxide and formaldehyde. From the fragmentation of derivatives of siphonaxanthin, such as the triacetate, the dimethyl ether and siphonaxanthol, and also from the fragmentation of related pigments, such as loroxanthin and fucoxanthin, the unique structural units responsible for the elimination of the carbon dioxide and carbon monoxide have been identified.
Vapor phase bimolecular reactions of alkyl siliconium and other metal ions in mass spectrometry
Authors: Harvey D. J. , Horning M. G. , Vouros Paul 
Published: May 2005

AbstractThe vapor phase reactions of various metal alkyl and alkoxy ions are discussed. Ions produced from suitable precursors can react with neutral molecules which contain an electronegative site. It appears that ions containing a positively charged silicon, tin, germanium or mercury center are more reactive than corresponding carbonium ions.
The mass spectrum of 1:12, 2:3, 4:5, 6:7, 8:9, 10:11‐hexabenzocoronene
Authors: Reed R. I. , Tennent A. 
Published: May 2005

AbstractThe mass‐spectra of 1:12, 2:3, 4:5, 6:7, 8:9, 10:11‐hexabenzocoronene and the isomer 1:2, 3:4, 5:6, 7:8, 9:10, 11:12‐hexabenzocoronene have been examined. The former is typically that of an aromatic conjugated hydrocarbon and is sparse, the latter is more intense. It is conjectured that the former may be found in interstellar space.
Mass spectra of partially fluorinated β‐diketonato complexes of Al(III), Cr(III), Fe(III) and Co(III)
Authors: Clobes A. L. , Morris M. L. , Koob R. D. 
Published: May 2005

AbstractThe mass spectra of the Al(III), Cr(III), Fe(III) and Co(III) complexes of the anions of hexafluoroacetylacetone (hfac) trifluoroacetylacetone (ttac), benzoyltrifluoroacetone (btac) and thenoyltrifluoroacetone (ttac) have been determined and are discussed here. Emphasis is placed on discerning which of the observed reactions may properly be attributed to the influence of the metal in the complex and those which may be thought of as arising from the nature of the ligand. The most important influence of the coordinated metal is related to its ability to be reduced2; however, the presence of the metal serves to prohibit or facilitate certain rearrangement reactions relative to the free protonated ligand. Since essentially all fragmentation occurs within or by loss of a ligand, the nature of the ligand determines the nature of the observed fragments. Where intramolecular com‐petition of fragment types is possible (tfac, btac and ttac complexes), the most probable fragment of a given class, odd electron or even electron, is easily determined. The most commonly eliminated fragments are CF3and CF2. Certain metastable peaks are associated with consecutive decomposition in the field free region. Such a phenomenon appears to be common for molecules of the type studied here.
A study of the fragmentation of caprolactam and its methyl derivatives under electron‐impact
Authors: Mitera J. , Kubelka V. 
Published: May 2005

AbstractA study of the low and high‐resolution mass spectra of caprolactam (I), 1‐methylcaprolactam (II), 3‐methylcaprolactam (III), 4‐methylcaprolactam (IV), 5‐methylcaprolactam (V), 6‐methylcaprolactam (VI), 7‐methylcaprolactam (VII) and deuterium labelled compounds has facilitated the proposal of some principal fragmentation mechanisms of ionized molecules of these compounds.The base peaks in the spectra of all compounds studied (except 3‐methylcaprolactam) are the ions m/e 30 and m/e 44 respectively formed through the cleavage of the C6–C7 bond and the C2–N bond with simultaneous transfer of a hydrogen atom.It has been proved that the fragmentation of molecular ions leading to ions with the structure of cyclopentanone 2‐methylcyclopentanone and 3‐methylcyclopentanone respectively (according to the position of methyl group) is the general feature of the fragmentation of caprolactam and its methyl derivatives.
The characteristics of oxime ethers upon electron‐impact
Authors: Graham Cooks R. , Varvoglis A. G. 
Published: May 2005

AbstractThe O‐methyl ethers of aromatic and aliphatic aldoximes and ketoximes are characterized by hydrogen and skeletal rearrangements involving four‐membered cyclic transition states. In the aliphatic compounds, four‐centered rearrangement sometimes yields the species with the higher ionization potential, in contradiction of Audier's rule. The n‐propyl oxime ethers show a novel skeletal rearrangement involving CH2O elimination. The [M—H]+ process in the aromatic aldoxime ethers and an [M—Cl]+ process in an o‐chloro derivative involve atom elimination by intramolecular aromatic substitution. Aromatic aldoxime ethers and the isomeric nitrones behave completely differently upon electron‐impact.
Rearrangement in the mass spectrometer via a 3,3,1‐bicyclic reaction path
Authors: Breuer S. W. , Gladstone W. A. F. , Hirst P. A. 
Published: May 2005

AbstractThe fragmentation of some azoacylals showed a 3,3,1 bicyclic rearrangement which could be demonstrated by a deuterium labelling study.
The loss of CO and HCN in the fragmentation of isatin and the methyl isatins
Authors: Butcher M. 
Published: May 2005

Abstract3‐13C‐Isatin has been shown to eliminate the 2‐carbonyl group as the initial fragment, followed predominantly by loss of HCN. In 4‐, 5‐and 6‐methyl‐isatin the loss of the second carbonyl group competes evenly with HCN loss, whilst the 7‐methyl isomer fragments almost exclusively by successive loss of two molecules of CO from the molecular ion.
Properties and reactions of 1,3‐oxathianes—II: Mass spectra of 1,3‐oxathiane and its alkyl derivatives
Authors: Pihlaja Kalevi , Pasanen Paavo 
Published: May 2005

AbstractThe mass spectral fragmentation patterns of 1,3‐oxathiane and several of its alkyl derivatives have been recorded. Of the nine possible modes of ring cleavage yielding fragments containing two to four atoms, only six modes were actually observed and, moreover, two of them clearly predominated. The modes of fragmentation of 1,3‐oxathianes differ from those of 1,3‐dioxanes, but resemble closely those observed for 1,3‐oxathiolanes when the different ring sizes are taken into account.
Electron‐impact studies—LXIV: Negative‐ion mass spectrometry of functional groups. Nitroaniline derivatives
Authors: Bowie J. H. , Blumenthal T. , Walsh I. 
Published: May 2005

AbstractThe various fragmentations of the o‐nitrobenzanilide molecular anion have been studied by labelling procedures and substituent effects. The loss of HO· from the molecular anion is a specific proximity effect, involving the oxygen of the nitro group and the hydrogen of the amide moiety. The losses of NO· from variously substituted nitrobenzenes are considered in depth and it is suggested that the nitro→ nitrite rearrangement is a radical reaction. Negative‐ion mass spectrometry may be used for the structure determination of sulphonamides and nitrophenylhydrazones.
Massenspektrometrie und ihre anwendun auf strukturelle und stereochemische Probleme—CCVI: Beobachtungen bei der Fragmentierung Olefinischer Kohlenwasserstoffe
Authors: Mayer Klaus K. , Djerassi Carl 
Published: May 2005

AbstractBei Olefinen der allgemeinen Struktur I, II und III erleidet das unter Elektronenbeschuss erzeugte Molekülion neben der als Hauptreaktion ablaufenden McLafferty‐Umlagerung auch bei milden Anregungsbedingungen eine vor der Fragmentierung eintretende Isomerisierung.Es wurde versucht, Herkunft und Entstehungsweg eines sowohl beim Abbau des Molekülions als auch des McLafferty‐Ions gebildeten gemeinsamen Bruchstückes mit Hilfe von 13C‐ und D‐Markierung zu klären.Der Einfluss einer Verzweigungstelle in γ‐, ω‐ oder ϵ‐Position zur Doppelbindung bei Olefinen vom Typ I auf deren Verhalten im Massenspektrometer wurde untersucht.
General aspects of the mass spectra of some benzyloxyalkyl substituted purine and pyrimidine nucleoside analogues; A demonstration of the concept of charge localization
Authors: Grose W. F. A. , Eggelte T. A. , Nibbering N. M. M. 
Published: May 2005

AbstractThe molecular ions of the title compounds appear to lose a molecule of benzaldehyde or a benzyl radical. The first reaction is followed by the elimination of a second molecule of benzaldehyde, the second reaction by either the expulsion of a molecule of benzaldehyde or a molecule of benzylalcohol. These degradations can be readily explained by assuming charge localization in the purine or pyrimidine part of the molecular ions. For the successive loss of a benzyl radical and of a molecule of benzaldehyde from the molecular ions, however, charge localization at one of the ether oxygen atoms may also be responsible to some extent, as demonstrated by the mass spectrum of 1,3‐dibenzyloxy‐2‐ethylpropane.
Fluorinated carbohydrates—X: The mass spectra of acetylated deoxyfluoro‐D‐glucitols
Authors: Adamson J. , Barford A. D. , Bessell E. M. , Foster A. B. , Jarman M. , Westwood J. H. 
Published: May 2005

AbstractThe deoxyfluoro‐D‐glucopyranoses with the fluorine substituent severally at positions 6, 4, 3 and 2 were converted into the corresponding deoxyfluoro‐D‐glucitol pentaacetates (I to IV) and their 1‐deuterated analogues (V to VIII). The mass spectra of these derivatives were rationalised in terms of the position of the fluorine substituent on the carbon chain.
Spectrometrie de masse, problemes de structure et de stereochimie—CCVII Fragmentations des Ethers Insatures
Authors: Morizur Jean‐Pierre , Djerassi Carl 
Published: May 2005

AbstractEn liaison avec I'accumulation de données pour I'interprétation automatique des spectres de masse des composés organiques le comportement des éthers insaturés est examiné. Trois groupes ont été étudiés: allylique, allylique substitué et éthers possédant 2 ou 3 groupes méthylènes entre la double liaison et I'atome d'oxygène. Un total de 36 composés dont 11 dérivés deutériés ont été préparés et leurs principales voies de dégradation rationalisées. I1 est montré que les éthers allyliques s'isomérisent aprés l'ionisation en éthers vinyliques, alors qu'aucune migration de la double liaison soit avant soit après l'impact électronique n'est observée entre les éthers allyliques, homoallyliques et ceux ayant 3 groupes méthylènes entre la double liaison et I'atome d'oxygène. Quand la chaîne saturée a au moins sept atomes de carbone les éthers allyliques expulsent une molécule d'alcool saturé [R' + C3H6OH] faisant intervenir un quadruple transfert d'hydrogène avant la fragmentation.
Feldionen‐Massenspektren von Kohlenhydraten
Authors: Krone H. , Beckey H. D. 
Published: May 2005

AbstractMit Hilfe der Feldionisation wurde die Massenanalyse von Mono‐ und Oligosacchariden durchgeführt. Die FI‐SpektrenFI wird als Abkürzung für Feldionisation und ES für Elektronenstoß‐Ionisation benutzt.
unsubstituierter Monosaccharide zeigtren zwar alle einen intensiven Peak auf der MZ [M + 1], eignen sich aber wegen der thermischen Labilität nur schlecht für Strukturanalysen. Im Hinblick auf Oligosaccharide ist eine Permethylierung für die Aufnahme von FI‐Massenspektren vorteilhaft. Permethylierte Disaccharide, die über C‐1—C‐4 bzw. über C‐1—C‐6 verknüpft sind, zeigten charakteristische Unterschiede in den Fragment‐Ionenintensitäten. Dagegen lassen sich aus dem FI‐Spektrum der permethylierten Raffinose nicht alle Verknüpfungsarten entnehmen. Für zukünftige Untersuchungen thermisch labiler Substanzen eignet sich die Felddesorptionsmethode besser als die Methode der Probenverdampfung aus einem Ofen mit anschließender Feldionisation.
Modification of a double focusing mass spectrometer for the observation of metastable ions decaying in two field‐free regions
Authors: Hills L. P. , Futrell J. H. 
Published: May 2005

AbstractThe occurrence of ‘metastable’ ions formed in the ion source as one species decays to a lower mass ion prior to mass analysis provides direct evidence for dissociation mechanisms in organic mass spectra. Both unimolecular and collision‐induced decay processes provide useful information on available dissociation pathways, ion structures, and energetics. In double‐focusing mass spectrom‐eters the existence of two field‐free regions presents a convenient vehicle for studying these processes and for obtaining kinetic information on consecutive metastables through simple modification in circuitry and operating conditions. These modifications are described and the method is used to demonstrate consecutive metastable decay processes in acetyl acetone, 1‐butene, toluene and alumin‐um hexafluoroacetylacetonate. Drift tube pressure studies showed that, within experimental error, consecutive metastables observed in acetyl acetone and 1‐butene were collision‐induced, while toluene and the aluminum chelate both exhibit two‐step unimolecular decays.
Oligosaccharide sequencing by means of mass spectrometry—I: N‐phenylosotriazole acetates
Authors: Chizhov O. S. , Kochetkov N. K. , Malysheva N. N. , Shiyonok A. I. , Chashchin V. L. 
Published: May 2005

AbstractFragmentation of the acetates of the N‐phenylosotriazoles of some mono‐, di, tri‐, tetra‐ and pentasaccharides under electron‐impact (EI) has been studied. The mass spectra of these derivatives can be used for determination of the sequence of monosaccharide units in oligosaccharides (oligosaccharide sequencing), of molecular weight, of the location of the position of the interglycosidic bond in disaccharides and of the position of the methyl group in partially methylated monosaccharides.
Electron‐impact and molecular dissociation—XX: Some studies on the indolosteranes
Authors: Harvey D. J. , Laurie W. A. , Reed R. I. 
Published: May 2005

AbstractThe mass spectra of a series of indolosteranes have been obtained in order to investigate whether or not such a method may prove a diagnostic tool in determining structure. While differences are revealed they are sometimes too slight for this purpose. An interesting observation made here is that in the fragmentation pattern those ions which contain the indole grouping usually predominate.