bluuebunny/crossref_metadata_2025_split huggingface dataset:
The high resolution mass spectrum of 2‐acetamido‐1,3,4,6‐tetra‐O‐acetyl‐2‐deoxy‐α‐D‐glucopyranose
Authors: Dougherty Ralph C. , Horton Derek , Philips Kerstin D. , Wander Joseph D. 
Published: May 2005

Abstract2‐Acetamido‐1,3,4,6‐tetra‐O‐acetyl‐2‐deoxy‐α‐D‐glucopyranose (I), and its analogs specifically mono (trideuterioacetylated) at O‐1 (III), at N‐2 (II), at O‐4 (IV) and at O‐6 (V), have been examined by high‐resolution mass spectrometry. From the elemental compositions of the fragment ions, the mass‐number shifts resulting from deuterium incorporation and analysis of metastable transitions, it has been possible to specify in detail the fragmentation pathways undergone by this molecule. The principal degradations of I proceed by initial rapid decomposition of the molecular ion (whose intensity is insignificant) by three routes: (i) by loss of the C‐1 acetoxyl group as a radical to give the glycosyl cation (a), (ii) by loss of the 1‐acetyl group as a radical to give an acyclic ion m/e 346 (b) and (iii) by loss of a C‐6 fragment and acetic acid derived from the 3‐acetate group to give m/e 241 (c).
The negative ion mass spectra of methanol and deuterated methanol
Authors: Thynne J. C. J. 
Published: May 2005

AbstractThe negative ion mass spectra of methanol, methanol‐d and trideuteromethanol have been measured at 70 eV. Use of deuterated methanols has enabled the ion at m/e 31 to be identified as CH3O− and not CH2OH−. Isotope effects have been determined for H− and D− formation, and for OH− and OD− formation. It has been shown that OH− formation occurs as a rearrangement reaction as well as by simple CO bond fission.
Preferred electron‐impact elimination of two CHO groups from A triapentafulvalenequinone. Formation of a triafulvalene radical cation?
Authors: Agranat Israel 
Published: May 2005

AbstractThe mass spectral fragmentations of 1,2‐diphenyl‐ and 1,2‐di (phenyl‐d5)‐4,5‐benzotriapentafulvalene‐3,6‐quinone indicate the preferred elimination of two CHO groups with the formation of triafulvalene radical cations.
Ionisation and appearance potentials in the evaluation of nonbonded interactions—IV: Conformational effects in methyl‐substituted 1,3‐oxathianes
Authors: Jalonen Jorma , Pasanen Paavo , Pihlaja Kalevi 
Published: May 2005

AbstractThe ionization and appearance potentials for the molecular and [M  Me]+ ions of several stereoisomeric methyl‐1,3‐oxathianes were measured. The differences between the ionisation and/or appearance potentials are shown to correlate well with the conformational energy differences in question.
Negative ion mass spectrometry—I: The spectra of some stabilised alkylidenetriphenyl‐phosphoranes
Authors: Alexander R. G. , Bigley D. B. , Todd J. F. J. 
Published: May 2005

AbstractThe 70 eV negative ion mass spectra of a series of phosphoranes exhibit significant peaks for ions resulting from skeletal rearrangements. The primary fragmentation reactions of the molecular anions, which involve reduction of the phosphorus from the penta‐ to the ter‐valent state, have been rationalised in terms of the relative stabilities of the products formed. The processes occurring are in some cases analogous to and in other cases complementary to, those previously observed in the positive ion spectra of similar compounds.
Elektronenstossinduzierte fragmentierung von polymethylbenzaldehyden—III: Bildung und Zerfall des Formyltropylium‐ions aus Dimethylbenzaldehyd
Authors: Schwarz Helmut , Bohlmann Ferdinand , Vorlaender Wolfgang 
Published: May 2005

AbstractDie elektronenstossinduzierte Bildung des sehr instabilen ‘formyltropylium‐Ions’ aus Dimethylbenzaldehyd kann durch den Mechanismus einer vinylogen α‐Spaltung erklärt werden.
Electron‐impact‐induced rearrangements of organic ions–II:1 Unimolecular decompositions of some isomeric [C9H10H]+ metastable ions
Authors: d'Alcontres Guglielmo Stagno , Cum Giampietro , Uccella Nicola 
Published: May 2005

Abstract[C9H10N]+ cations (m/e 132) are generated by electron‐impact from structurally distinct compounds within a mass spectrometer. They undergo three metastable fragmentation processes, preceded by isomerisation reactions of the precursor ions. The kinetics and energetics of the unimolecular reactions involved are discussed.
Massenspektrometrische Untersuchung von Amiden–I: Energetische Betrachtungen zur el Ektronenstosin‐Duzierten Fragmentierung von Piperidin‐ und Piperidein‐ Amiden
Authors: Schwarz Helmut , Bohlmann Ferdinand 
Published: May 2005

AbstractDie Aktivierungsenergie für die Bildung von [RCO]+‐Ionen aus verschiedenen Piperidin und Piperidein‐Amiden wird ermittelt und ein Zusammenhang mit der CN‐Bindungsenergie der A‐midfunktion diskutiert. Ausserdem wird ein cyclischer Fragmentierungs‐mechanismus mit Hilfe energetischer Gesichtspunkte begründet.
Mechanismus der elektronenstossinduzierten Äathylenabspaltung aus dem Ion [C9H11]+ aus 2,5‐Dimethylbenzylbromid
Authors: Schwarz Helmut , Köoppel Claus , Bohlmann Ferdinand 
Published: May 2005

AbstractDie Untersuchung von 13C‐markiertem Dimethylbenzylbromid zeigt, dass dem [M – Br]+‐Ion die Struktur eines Dimethyltropylium‐Kations zukommt.
The mass spectra of some N‐substituted barbitals and their trimethylsilyl derivatives
Authors: Watson J. Throck , Falkner Fred C. 
Published: May 2005

AbstractThe mass spectra of N‐propyl and N‐butyl barbitals show the loss of olefin radical (CnH2n‐1) in analogy to structurally similar molecules such as N‐alkyl succinimides and 3‐alkyl uracils. Trimethylsilylation of the N‐substituted barbitals suppresses this fragmentation and loss of olefin via apparent McLafferty rearrangement from the even‐electron ion, [M – 15]+, becomes significant. The trimethylsilyl derivatives of N‐allyl barbital and N‐phenyl barbital show an unusually facile elimination of the appropriate isocyanate from the molecular ion.
The effect of stereochemical peculiarities on the electron‐impact‐induced fragmentation of matridine and its stereoisomers
Authors: Wulfson N. S. , Ziyavidinova Z. S. , Zaikin V. G. 
Published: May 2005

AbstractWith the aid of the mass spectra of 14,14‐d2 analogues the majority of the m/e 98 ions in the spectrum of allomatridine were shown to contain ring D, whereas in the case of matridine and isosophoridan the m/e 98 ions mainly include rings A or B. The m/e 84 ion results mostly from a charge localisation on ring D for allomatridine and isosophoridan, while in the case of matridine it may arise due to charge localisation on ring D accompanied by migration of the 14‐H atom from the charged fragment, as well as on rings A or B with a hydrogen atom migrating to the charged species.
Substituent and H/D randomization in the mass spectra of substituted diphenylacetylenic compounds
Authors: Safe S. 
Published: May 2005

AbstractThe mass spectra of several substituted diphenylacetylenes are reported and the [metastable ion]/[daughter ion] ratios for the isomeric chloro‐ and bromodiphenylacetylenes suggested substituent scrambling in their respective molecular ions. The metastable ion data also indicated equilibration of the chloro substituents in a series of isomeric dichlorodiphenylacetylenes. In addition, the fragmentation patterns for the amino‐ and nitrodiphenylacetylenes differed somewhat from most other aromatic amino and nitro compounds. The aminodiphenylacetylenes fragment with expulsion of H2CN from the molecular ion and the expulsion of HCN from the [M – 1]+ ion was only a relatively minor reaction. 4‐Nitrodiphenylacetylene loses NO from the molecular ion and OH from the [M – NO]+˙, whereas the more familiar loss of OH from the molecular ion was not observed. The mass spectra of several deuterated substituted diphenylacetylenes clearly showed extensive (but not complete) H/D equilibration in the molecular ion or some subsequent decomposition ion. Comparative studies between 4‐chloro and 4‐bromo substituted biphenyl, diphenylacetylene and diphenyldiacetylene indicated similar degrees of H/D randomization, and the results showed that the CC group did not inhibit the proton equilibration between the two phenyl groups.
Electron‐impact spectra of ms‐tetra‐phenylchlorins and the stability of chlorins
Authors: Meot‐Ner M. , Adler A. D. , Green J. H. 
Published: May 2005

AbstractThe mass spectrum of ms‐tetraphenylchlorin was observed to contain a significant porphyrin peak. Attempts to obtain metallochlorin spectra yeilded mainly metalloporphyrin spectra. Sublimation experiments established that the chlorin to porphyrin conversion resulted from electron‐impact excitation and did not arise from thermolysis on the probe or from impurities. In conjunction with previous literature data, this is interpreted as showing that the apparent stability of chlorins with respect to porphyrins is mainly a matter of the activation energies required under specific constraints.
Studies in chemical ionization mass spectrometry:Steroidal ketones
Authors: Michnowicz John , Munson Burnaby 
Published: May 2005

AbstractThe CH4 chemical ionization (CI) spectra of several keto‐steroids are reported as well as the H2 and C3H8CI spectra of a few keto‐steroids. [M + H  H2O]+ is an abundant ion in the CH4CI spectrum of 5α‐androstane‐17‐one and the water loss from the [M + H]+ ions does not involve the hydrogens on C‐18 and only involves the C‐16 hydrogens to about 10%. The major loss process has not been determined.3‐Keto and 17‐Keto steroids are readily distinguished by their CH4CI spectra. The effectiveness of substituents for directing attack by [CH5]+ and [C2H5]+ can be estimated:carboxyl > methoxy ≃ carbonyl > bromo ≃ chloro > hydroxy. Significant differences are observed in the H2CI spectra of two 5α‐vs. 5β‐steroids. Propane CI Spectra are similar to methane CI spectra, but show generally less fragmentation.
Positive ion fragmentation mechanisms of some simple aldehydes and epoxides and trimethylene oxide
Authors: Pritchard J. G. 
Published: May 2005

AbstractThe metastable ion spectra of ethylene oxide, acetaldehyde, acetaldehyde‐d4, propylene oxide, propionaldehyde and trimethylene oxide are presented. They reveal no reason to suppose that electron‐impact‐induced isomerisation of oxide to aldehyde structure occurs, although many spectral features are common to various members of this set. The spectra of phenylacetaldehyde and styrene oxide are compared, and the more plausible possibility of partial isomerisation in this case is discussed.
Mass spectral fragmentation studies in usnic acid and related compounds
Authors: Kutney James P. , Sanchez Ignacio H. , Yee Trevor H. 
Published: May 2005

AbstractA study of the fragmentation patterns of the naturally occurring lichen substance, usnic acid (I) and various other chemically and biochemically derived compounds is reported and discussed. From these results it is demonstrated that the characteristic fragmentation patterns observed are of considerable utility in determining not only the substitution patterns on these highly oxygenated molecules, but also the structural elucidation of new compounds within the series.
Steric strain and electron‐impact. The behaviour of some n,n'‐dimethyl‐1,1‐binaphthyls, some n,n'‐dimethylbiphenyls and model compounds
Authors: Loudon A. G. , Mazengo R. Z. 
Published: May 2005

AbstractFor the title compounds I(M), A[M  H]+ and A[M  Me]+ have been determined. In the biaryl compounds, unlike the xylene and the two dimethylnaphthalenes studied, A[M  Me]+ is noticeably dependent on the position of the methyl group. Deuterium labelling of the methyl groups in the biaryl compounds reveals that more than one process is involved in the formation of the [M  Me]+ ion. In contrast, only in the case of 2,2′‐dimethylbiphenyl is the appearance potential of the [M  H]+ ion position dependent. The labelling results suggest complete scrambling of the hydrogen atoms before formation of the [M  H]+ ions. Some comments are made on the problem of trying to relate differences in strain energies and ionisation and appearance potentials in alkyl substituted aromatics.
Spectrometrie de Masse des Epoxydes Phenyles—II
Authors: Fetizon Marcel , Henry Yannik , Aranda Gérard , Audier Henri‐Edouard , De Luzes Hugues 
Published: May 2005

AbstractLes époxydes aromatiques se fragmentent soit directement par élimination d'une molécule d'aldéhyde ou de cétone pour donner un ion symétrique soit aprés réarrangements de l'ion moléculaire en composés carbonylés. Les substituants du noyau ont une trés grande influence sur les fragmenta‐tions.
Thermal decompositions of N‐methylpyridinium, quinolinium, isoquinolinium and phenanthridinium salts in a mass spectrometer. Evidence for a specific HI elimination and for an oxidation to amides
Authors: Salsmans R. , Van Binst G. 
Published: May 2005

AbstractThe mass spectra of some N‐methylpyridinium, quinolinium, isoquinolinium and phenanthridinium salts (R+X−)The salt will be represented by R+X− or RX, R+ being the organic moiety, with its associated mass and X‐ the inorganic anion.
are analyzed (X− = I− or ClO4−). For X− = I−, thermal decomposition gives rise mainly to the superimposed spectra of CH3I and the free base. Hence, iodide salts cannot be determined specifically by their mass spectra. When an α‐methyl group is present, e.g. 2‐methylpyridinium methiodide, elimination of HI becomes an important thermal process. For X− = ClO4−, the same pattern is observed, but in addition a generally important peak at [R + 15] is present. This peak is due to the oxidation, mainly α to the nitrogen of the organic moiety by the ClO4− ion, giving rise to the corresponding amide. In some cases, chlorination of the organic moiety has been observed as well as double oxidation. The thermal processes for the perchlorate salts are characteristic and are useful in the elucidation of the quaternary structure.
Mass spectra of benzenesulfonylhydrazides
Authors: Balza Felipe , Duran Nelson 
Published: May 2005

AbstractThe mass spectrometry of substituted benzenesulfonylhydrazides (X.C6H4.SO2NHNH2) has been studied, with X = p‐CH3, H, p‐CH3O and p‐Br. The intensities of [XC6H4SO2]+ and [XC6H4]+ follow the Hammett relationship [In(Z/Z0) =ρδp+] with ρ of 0.375 and 2.37, respectively.
Mass spectrometry of organic compounds. VIII—Remote group interaction in hydroxyorganotins
Authors: Kingston David G. I. , Tannenbaum H. P. , Kuivila H. G. 
Published: May 2005

AbstractHydroxyorganotins of the general formula R3Sn(CH2)nOH undergo rearrangement on electron‐impact to yield ions in which oxygen has become directly bonded to the tin atom. The scope of this rearrangement is discussed, and it is shown that steric and structural factors play a significant but not decisive effect in its occurrence.
Phosphates D'énols: XI—Étude en Spectrométrie de Masse des Dérivés Diméthyliques
Authors: Gaydou Emile M. , Peiffer Gilbert , Etienne Marc 
Published: May 2005

AbstractL'étude d'une série de phosphates énoliques du type A an spectrométrie de masse conduit à des schémas de rupture influencés par la nature des substituants R, R′ et R″, On observe généralement à côte de la perte du groupement énolique, des phénomènes des phénomènes de double ou simple réarrangement d'hydrogène. Lorsque R et R′ sont des groupements alcoyles, ce sont les atomes d'hydrogène magnified image du groupement fixé en 1 qui migrent. En l'absence de groupement alcoyle en 1, ce sont les atomes d'hydrogène du groupment en 2 qui provoquent le réarrangement. Enfin si R, R′ et R″ sont des atomes d'hydrogène, on a essentiellement perte de l'enchaînement éolique sans réarrangement.
Structure and mechanism of fragmentation of [C2H5O]+
Authors: Keyes B. G. , Harrison A. G. 
Published: May 2005

AbstractThe decomposition reactions of [C2H5O]+ ions produced by dissociative electron‐impact ionization of 2‐propanol have been studied, using 13C and deuterium labeling coupled with metastable intensity studies. In addition, the fragmentation reactions following protonation of appropriately labeled acetaldehydes and ethylene oxides with [H3]+ or [D3]+ have been investigated. In both studies particular attention has been paid to the reactions leading to [CHO]+, [C2H3]+ and [H3O]+.In both the electron‐impact‐induced reactions and the chemical ionization systems the fragmentation of [C2H5O]+ to both [H3O]+ and [C2H3]+ proceeds by a single mechanism. For each case the reaction involves a mechanism in which the hydrogen originally bonded to oxygen is retained in the oxygen containing fragment while the four hydrogens originally bonded to carbon become indistinguishable.The fragmentation of [C2H5O]+ to produce [CHO]+ proceeds by a number of mechanisms. The lowest energy route involves complete retention of the α carbon and hydrogen while a higher energy route proceeds by a mechanism in which the carbons and the attached hydrogens become indistinguishable. A third distinct mechanism, observed in the electron‐impact spectra only, proceeds with retention of the hydroxylic hydrogen in the product ion.Detailed fragmentation mechanisms are proposed to explain the results. It is suggested that the [C2H5O]+ ions formed by protonation of acetaldehyde or ionization of 2‐propanol are produced initially with the structure [CH3CH\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^ + $\end{document}H] (a), but isomerize to [CH2CH\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^ + $\end{document}H2] (e) prior to decomposition to [C2H3]+ or [H3O]+. The results indicate that the isomerization a → e does not proceed directly, possibly because it is symmetry forbidden, but by two consecutive [1,2] hydrogen shifts.A more general study of the electron‐impact mass spectrum of 2‐propanol has been made and the fragmentation reactions proceeding from the molecular ion have been identified.
Massenspektrometrische Untersuchung von Amiden. VI—Mechanismus der Methyl‐Abspaltung aus Crotonsä;urepiperidid
Authors: Bohlmann Ferdinand , Mathar Wolfgang , Schwarz Helmut 
Published: May 2005

AbstractDurch die Untersuchung 2H‐markierter Verbindungen wird belegt, daß im Falle von Crotonsäurepiperidid nur die Wasserstoffe der Methylgruppe an der CH3·‐Abspaltung teilnehmen.
Electron‐impact studies. LXXXIV—Substituent effects in the negative ion mass spectra of aryl esters
Authors: Bowie J. H. , Nussey B. 
Published: May 2005

AbstractLinear plots may be obtained for the fragmentations of aryl p‐cyanobenzoates using the McLafferty approach, but the correlations are not as satisfactory as those observed1 for aryl nitrobenzoates. Some satisfactory correlations of substituent effects are noted in the negative ion spectra of substituted benzyl‐p‐nitrobenzoates and substituted phenyl‐(p‐nitrophenyl)acetates. Pronounced rearrangement peaks are observed in the spectra of substituted phenyl‐(p‐nitrophenyl)acetates. Appearance potential studies suggest that the similarities in ρ values obtained1 for the fragmentations of aryl m‐ and p‐nitrobenzoate molecular anions are probably due to the correspondence between Hammett σ values and appearance potentials in the two series.
Analyse en Spectrometrie de Masse de Derives Fluores en Serie Pyrimidine et Triazine
Authors: Hitzke J. , Cambon A. , Guion J. 
Published: May 2005

AbstractNous avons synthétisé tous les dérivés fluorés de la perchloropynmidme, de la 2,4,6 trichloropyrimidine et de la perchloro s‐triazine. La r.m.n. du fluor associée au couplage chromatographie en phase vapeur‐spectrométrie de masse, nous ont permis de séparer et d'identifier les produits obtenus. Nous presentons et discutons le comportement de ces composes sous l'impact électronique.
Mass spectrum of nitromethane
Authors: Meyerson Seymour , Fields Ellis K. 
Published: May 2005

AbstractThe mass spectrum of nitromethane points to rupture of the CH3NO2 bond as the dominant primary reaction, as also observed in pyrolysis, photolysis and radiolysis. Isomerization of the molecular ion to the nitrite configuration seems to contribute little in the mass spectrum of nitromethane, in contrast to those of nitrobenzene and other nitroarenes. The nitrite ion is probably the immediate precursor of [NO]+ at its appearance potential, but most of the [NO]+ yield seems to stem from secondary decomposition of excited [NO2]+.
Phosphates d'enols. XII—Etude en Spectrometrie de Masse de Derives Diethyliques et di‐n‐Butyliques
Authors: Gaydou Emile M. , Peiffer Gilbert 
Published: May 2005

AbstractL'étude des fragmentation en spectrométrie de masse de phosphates diéthyliques (1) et di‐n‐butyliques (2) est grandement influencée par la nature des substituants R, R′, R″ fixés sur la double liaison
magnified image
Lorsque R = H on observe une perte prépondérante d'éthylène ou de butène‐1. Dans le cas où R = CH3 le procesus de double réarrangement se produit avec participation des groupements alcoyles de l'enchaînement énolique.
The internal energy of product ions formed in mass spectral reactions
Authors: McAdoo D. J. , Bente P. F. , Gross M. L. , McLafferty F. W. 
Published: May 2005

AbstractMajor factors which determine the distribution of internal energy of a primary product ion A+, P(E)A+, at formation are delineated in terms of the quasi‐equilibrium theory and a variety of experimental evidence is offered to support these conclusions. These major factors include: the P(E) of the molecular ion, the rate constants as a function of energy, κ(E), for M+·→A+ + N0 and for competing reactions of M+·, and the partitioning of excess internal energy between A+ and N0. The ‘fluctuation effect’ on this partitioning makes P(E)A+ relatively insensitive to many structural and energy changes.
Mass spectrometry in structural and stereochemical problems: CCXXXVI—corrected electron‐impact‐induced migratory aptitudes in aryl phenyl carbonates
Authors: Jaeger David A. , Tomer Kenneth B. , Woodgate Paul D. , Gebreyesus Tarekegn , Djerassi Carl , Shapiro Robert H. 
Published: May 2005

AbstractCorrected relative migratory aptitudes for aryl groups in the electron‐impact‐induced rearrangement of aryl phenyl carbonates have been determined.
Studies in organic mass spectrometry. XVI—A combined approach to the structures of ions generated from the molecular ions of acyclic β‐diketones through loss of small neutral molecules
Authors: Conrath K. , Van Sande C. De , Vandewalle M. 
Published: May 2005

AbstractThe structures of ions produced from acyclic 1,3‐diketones by loss of carbon monoxide, ketene or olefins are investigated. Structural inference is made by comparison of the heats of formation of these ions with data for ions of known structure generated from other precursors. All assignments are confirmed by a study of metastable transitions. Loss of carbon monoxide yields ions in the keto form. Expulsion of a ketene or olefin moiety results in enol type ions.
Thermochemistry and metastable energy release for the dissociation [C3H7]+ → [C3H5]+ + H2
Authors: Holmes J. L. , Weese G. M. 
Published: May 2005

AbstractThe reverse activation energy, Erev, for the dissociation [C3H7]+ → [C3H5]+ + H2 has been determined as 0.24 ± 0.06 eV from measurements of the AP of [C3H5]+ produced by electron‐impact from thermally generated sec‐C3H7 radicals. The energy release observed in the corresponding metastable dissociation is 0.21 ± 0.01 eV, indicating that virtually all of Erev is partitioned as translational Kinetic energy of the fragmentation products. The metastable ion peak shape is also discussed with respect to the evaluation of the energy release.
Differentiation of tautomers by ion cyclotron resonance spectrometry: \documentclass{article}\pagestyle{empty}\begin{document}${\rm (CH}_{\rm 3} {\rm)}_{\rm 2} \mathop {\rm N}\limits^{\rm + } {\rm = CH}_{\rm 2} {\rm vs H}_{\rm 3} {\rm C}\mathop {\rm N}\limits^{\rm + } {\rm H = CHCH}_{\rm 3}$\end{document}
Authors: Tomer Kenneth B. 
Published: May 2005

AbstractIon cyclotron resonance spectrometry and deuterium labeling have been used to determine that nondecomposing \documentclass{article}\pagestyle{empty}\begin{document}${\rm (CH}_{\rm 3} {\rm)}_{\rm 2} \mathop {\rm N}\limits^{\rm + } {\rm = CH}_{\rm 2}$\end{document} ions do not isomerize to \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} {\rm CH = }\mathop {\rm N}\limits^{\rm + } {\rm HCH}_{\rm 3}$\end{document}.