bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass spectrometry in structural and stereochemical problems—CLXXXV Effect of phenyl group in the mass spectra of trans‐10‐phenyl‐2‐decalone and trans‐10‐phenyldecalin
Authors: Gray Robin T. , Djerassi Carl 
Published: May 2005

AbstractWith the use of deuterium labeling and metastable ion measurements, the major fragmentation pathways of trans‐10‐phenyl‐2‐decalone (II) have been deduced. A comparison with trans‐10‐phenyldecalin (IV) demonstrated the almost complete domination of the phenyl group in directing the electron‐impact promoted decomposition of II. In fact, in contrast to the spectra of the methylated analogs, only one fragmentation pathway is uniquely associated with the carbonyl function. The substitution of a phenyl group at the ring junction in IV has permitted the recognition of definitive fragmentation pathways for this compound also. Such definition has not previously been possible for unsubstituted alicyclic hydrocarbons. The formation of an abundant tropylium ion from both II and IV has been examined, but its genesis is too complicated to be accurately defined from the labeling data at hand.
The mass spectral behavior of β‐bromoethyl benzoate and some of its ring substituted derivatives: Evidence for oxygen participation in the formation of [M  Br]+
Authors: Shapiro Robert H. , Tomer Kenneth B. 
Published: May 2005

AbstractThe expulsion of a bromine atom from the molecular ion of β‐bromoethyl benzoate displays a kinetic behavior which resembles that of a rearrangement reaction. The two oxygen atoms in the resulting [M  Br]+ ion become equivalent before or during the secondary decomposition of this ion, as shown by oxygen labeling. In addition, the primary ions generated from benzophenone ethylene ketal and acetophenone ethylene ketal by phenyl and methyl expulsion, respectively, undergo subsequent fragmentation in the same way as the [M  Br]+ from β‐bromoethyl benzoate. These results strongly indicate that the carbonyl‐oxygen atom participates in the expulsion of bromine. The effect of ring substituents on the competing loss of bromine and McLafferty rearrangement is also discussed.
Mass spectrometry differentiation of isomeric alkyl porphyrins. Fragmentation analysis of meso‐tetraoxoporphyrinogens
Authors: Boylan David B. 
Published: May 2005

AbstractThe mass spectra of lead dioxide oxidation products of three etiotype porphyrins and one meso‐substituted etiotype porphyrin have been analyzed. The meso‐tetraoxo products formed, fragment upon electron‐impact to give mono‐, di‐, and tri‐pyrrole fragments with the pyrrole substituents still intact. From this fragment information it is possible to differentiate many isomeric alkyl porphyrins. Due to the inability to assign exact positions to the substituents on each pyrrole unit, however, definite isomeric identification is impossible without further information. High resolution gas chromatography retension data of volatile (trimethylsiloxy) SiIV derivatives may eventually provide the necessary additional information to make absolute structural assignment possible.The described method has been designed to prove detailed structural information about geoporphyrin materials. Geochemical conclusions from such data should help provide information about the origin of organic materials and thus help establish possible connections with early life processes.
Zur Massenspektrometrie von Nitrophenylverbindungen—II. Nitrophenylhydrazone Aliphatischer Aldehyde und Ketone
Authors: Seibl J. 
Published: May 2005

AbstractAls chemisch klassifizierende Derivate zur isolierung von Carbonylverbindungen aus Gemischen erlauben DNPH aliphatischer Aldehyde und Ketone wegen ihrer Molekülionenstabilität eine sichere massenspektrometrische Molekulargewichtsbestimmung und wegen ihrer unterschiedlichen Fragmentierungsmuster eine Gruppenzuordnung (Aldehyde, Ketone, minimale Kettenlänge). Reaktionsmechanistisch sind sie interessant als Beispiele für eine Reihe spezifischer Umlagerungsreaktionen beim monomolekularen Zerfall. Als Primärreaktion im Molekülion st eine Sauerstoffumlagerung aus der ortho‐nitrogruppe von wesentlicher bedutung, die die Fragmentierung zu einem guten Teil bestimmt.
The mass spectra of spiro‐alkanones with five‐ and six‐membered rings
Authors: Weringa W. D. 
Published: May 2005

AbstractThe mass spectral fragmentations of three spiro‐undecanones and four dispiro‐hexadecanones with six‐membered rings, and of two spiro‐nonanones with five‐membered rings are recorded and discussed. The fragmentation patterns for the spiro[4,4]nonanones and the spiro[5,5]undecanones have been determined by using specific deuterium labelling and in some cases the measurement of metastable transitions by the defocusing technique. The most important fragment ions in the spectra of four dispiro‐hexadecanones could be explained by assuming the same types of fragmentation as found for the monospiro‐ketones. The composition of the fragment ions has been checked by high resolution mass measurements.
The calculation of the 70 eV mass spectrum of thiacyclobutane
Authors: Gilbert J. R. , Stace A. J. 
Published: May 2005

AbstractThe mass spectrum of thiacyclobutane at 70 eV has been calculated using quasi‐equilibrium theory and an energy distribution given by f(E)= βE exp (‐ E2γ). The measured and calculated spectra are shown to be in reasonable agreement.
Metal‐metal chelate exchange reactions in the ion source of a mass spectrometer
Authors: Terlouw J. K. , De Ridder J. J. 
Published: May 2005

AbstractIn the mass spectra of several transition metal chelates with diethyldithiocarbamate as a ligand, intense peaks are present which could be assigned to extraneous metal (particularly nickel) containing ions. Using an Au‐Rh coated ion source, evidence was obtained for the occurrence of exchange reactions in the region of the filament assembly.
Mass spectrometry of benzylamines and benzylamine derivatives
Authors: Couch M. W. , Williams C. M. 
Published: May 2005

AbstractThe mass spectra of benzylamine, N‐ethylbenzylamine, N,N‐dimethylbenzylamine, p‐methoxybenzylamine and 4‐hydroxy‐3‐methoxybenzylamine, and their acetamide and trimethyl‐ silyl (TMS) derivatives have been recorded. Low and high resolution spectroscopy were employed in conjunction with ion kinetic energy (IKE) determinations to establish the empirical formulae of the fragment ions and their modes of fragmentation. In the case of the acetamide derivatives the acyl group is lost by acetoxy elimination giving rise to the [M — 1] ion of the parent amine which then undergoes fragmentation very similar to the original amine. The TMS derivatives present more complex fragmentation patterns which involve rearrangement of the TMS side chain during decomposition. Consequently the acetamide derivative of an unknown aromatic amine is preferred for diagnostic purposes.
Fragmentation and rearrangement processes in the mass spectra of perhalogeno‐aromatic compounds—VII. Pentafluorophenyl derivatives of nitrogen
Authors: Lanthier G. F. , Miller J. M. 
Published: May 2005

AbstractThe mass spectra of several perfluoroaromatic nitrogen compounds, including primary and secondary amines, diamines, nitriles, hydrazines, azines and azo compounds, are presented. Fragmentation patterns of these compounds are described and the data are discussed in terms of comparisons amongst perfluoroaromatic nitrogen compounds, and with reference to the hydrogen substituted analogs, or to oxygen and sulfur analogs of a particular compound.
Mass spectrometric fragmentations of hexafluoroacetone ketals derived from N‐alkenes
Authors: Johnson Bruce M. , Taylor James W. 
Published: May 2005

AbstractThe mass spectrometric fragmentation behavior of the cyclic hexafluoroacetone ketals derived from eighteen n‐alkenes is discussed with emphasis on locating the original olefinic bond. The major analytically useful fragments result from loss of CF3, loss of an alkyl side chain or loss of an aldehyde moiety from the ring. Influences of geometric isomerism on the spectra are examined by intensity ratios and ratios of competing fragmentations.
The mass spectra of carboxylic acids—VI: Metastable dissociations of isomeric ions in the mass spectra of oxalic and formic acids, and malonic and acetic acids
Authors: Holmes J. L. 
Published: May 2005

AbstractMetastable ion peak shapes and abundances have been studied for competing dissociations of the [H2CO2]+. ions produced in the mass spectra of formic and oxalic acids, and of [H4C2O2]+. ions produced from acetic and malonic acids. It is concluded that for each pair ions different with respect to structure and energy content are present; the difference is more apparent in the [H4C2O2]+. ions than in the smaller [H2CO2]+. species.
Spectrometrie de Masse—VIII: Elimination D'eau Induite par Impact Electronique Dans le Tetrahydro‐1,2,3,4 Naphtalenediol‐1,2
Authors: Perros P. , Morizur J. P. , Kossanyi J. , Duffield A. M. 
Published: May 2005

AbstractLa perte d'une molécule d'eau impact électronique est une voie de fragmentation importante du tétrahydro‐1,2,3,4 naphtalénediol‐1,2. A l'aide de composés marqués spécifiquement au deutérium, it a pu étre montré que les atomes d'hydrogéne hydroxyliques participent pour plus de 70% à cette élimination. Les autres d'hydrogéne impliques dans cette perte d'eau, sont principalement ceux de carbone C‐4. Une répartition statistique, à laquelle participeraient différents atomes d'hydrogéne a été envisagée sans pouvoir étre retenue définitivement.
High resolution mass spectrometry in molecular structure studies—VI: The fragmentation of amaryllis alkaloids in the crinine series. Compounds bearing a hydroxyl substituent at C‐11 (and some 11‐oxo derivatives)
Authors: Longevialle P. , Fales H. M. , Highet R. J. , Burlingame A. L. 
Published: May 2005

AbstractHigh resolution mass spectral fragmentation patterns of Amaryllidaceae alkaloids in the crinine series bearing a substituent at C‐11 have been investigated, as well as certain isotopically labeled derivatives. The substituent at C‐11 governs almost entirely the fragmentation pattern of these bases due to the ability of the hydroxylic hydrogen atom to rearrange. In contrast to the bases lacking this hydrozyl substituent, stereochemistry exerts a profound influence on the fragmentation.
The effect of 2,3‐substituents upon the mass spectrometric fragmentation of quinoxalines
Authors: Kováčik V. , Fedoroňko M. , Ježo I. 
Published: May 2005

AbstractThe mass spectrometric fragmentation of quinoxalines substituted with alkyl and aryl groups in the C‐2 and C‐3 positions and with groups containing heteroatoms have been studied. Fragmentation mechanisms for the compounds under investigation are proposed and discussed.
Ring contraction upon electron‐impact as a function of ring size: The mass spectrometric fragmentation of 2,3,4,5‐tetrahydrobenzoxepin and lower homologues
Authors: Richter W. J. , Liehr J. G. , Burlingame A. L. 
Published: May 2005

AbstractThe origin of a prominent [M – CH3] ion in the mass spectrum of 2,3,4,5‐tetrahydrobenzoxepin is investigated with the aid of extensive deuterium labelling of the saturated heterocyclic portion of the molecule, identifying the C‐2 methylene group as the chief source of the methyl radical expelled. Ring contraction of the seven‐membered cyclic molecular ion to a six‐membered intermediate is proposed in accordance with interpretations of similar findings on related acylated cyclic amines.
A study of negative ions from substituted benzils
Authors: Dillard John G. , O'Toole J. Herb. , Ogliaruso Michael A. 
Published: May 2005

AbstractThe mass spectra and the appearance potentials for the negative ions from a number of 4‐substituted and 4,4′‐disubstituted benzils, containing CH3, CH3O, CH3S, (CH3)2N and NO2 substituents have been measured. Molecular anions were observed for all benzils. The negative ion mass spectra of the CH3O‐ and CH3S‐substituted compounds also exhibited ions resulting from loss of CH3 from the parent; Cl− was observed too in the spectra of the chlorine substituted benzils. Only for the nitrobenzils is more than one fragment ion observed in the spectra. A comparison of the negative ion spectra with the positive ion spectra previously reported is also presented and discussed.
Surface dependent hydrogen rearrangement reactions in field ionisation mass spectrometry
Authors: Röllgen F. W. , Levsen K. , Beckey H. D. 
Published: May 2005

AbstractSurface dependent hydrogen rearrangement reactions under field ionisation conditions have been investigated. It was not possible to detect surface‐induced intramolecular hydrogen rearrangements in molecular ions, in accordance with theoretical expectations. The possibility of intramolecular hydrogen rearrangements exists only for radical ions chemically bound to the emitter surface, for example, the [M – H]+ ions of the alcohols. The great majority of surfacedependent hydrogen transfer reactions are intermolecular reactions between parts of different molecules or ions bound to the emitter surface. These reactions produce fragment ions, cluster ions and doubly charged ions.
Electron‐impact‐induced hydrogen migration in organic molecules. II—novel hydrogen migration in dihydro‐2‐stilbazole derivatives
Authors: Ramana D. V. , Sundaram N. 
Published: May 2005

AbstractThe mass spectra of 2′‐OH, 2′‐NH2 and 2′‐CH3‐dihydro‐2‐stilbazole derivatives show an interesting hydrogen migration. The hydrogen migration is shown to be taking place from the above mentioned substituents to the nitrogen of the pyridine ring followed by a β‐cleavage giving rise to a common ion e at m/e 93, perhaps through an 8‐membered transition state.
Metastable ion studies. IV—thermochemistry and ion structures among fragmenting [C3H6]+· ions
Authors: Holmes John. L. , Terlouw Johan. K. 
Published: May 2005

AbstractMetastable ion peak shapes, dimensions and relative abundances have been measured for the three fragmentations [C3H6]+· → [C3H4]+· + H2, [C3H6]+· → [C3H5]+ + H· and [C3H6]+· → [C3H3]+ + H2 + H·. [C3H6]+· ions were derived from propene, cyclopropane, tetrahydrofuran, cyclohexanone, 2‐methyl but‐1‐ene and cis‐pent‐2‐ene. Activation energies for these fragmentations have been evaluated. Three daughter ion dissociations ([C3H5]+ → [C3H3]+ + H2, [C3H5]+ → [C3H4]+· + H· and [C3H4]+· → [C3H3]+ + H·) have been similarly examined.Ion structures have been determined and the metastable energy releases have been correlated with the thermochemical data. It is concluded that the molecular ions of propene and cyclopropane become structurally indistinguishable prior to fragmentation and that differences in their metastable ion characteristics can be ascribed wholly to internal energy differences; the latter can be correlated with the photoelectron spectra of the isomers. The pathway for the consecutive fragmentation which generates the metastable ion peak (m/e 42 → m/e.39) has been shown to be

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It is likewise concluded that fragmentating [C3H6]+· ions generated from the various precursor molecules are also structurally indistinguishable and cannot be classified with either molecular ion of the isomeric C3H6 hydrocarbons.
The mass spectral fragmentation of 2,2′‐bis‐trimethylsilylbenzhydrylethers. An indication for transannular hydrogen/deuterium rearrangements and transannular elimination reactions
Authors: Akkerman O. S. , Evers E. A. I. M. , Kerkstra A. 
Published: May 2005

AbstractThe mass spectra of the methyl‐, trideuteromethyl‐, ethyl‐ and pentadeuteroethylethers of 2,2′‐bis‐trimethylsilylbenzhydrol are reported. The most significant ions arise from the [M – CH3]+ ion, formed by loss of a methyl radical from one of the trimethylsilyl groups. After ring formation by interaction of the siliconium ion centre with an aromatic nucleus, the ion loses (CH3)3SiOR (R = CH3, C2H5, CD3 and C2D5), giving ion m/e 223. The fragment (CH3)3SiOCH3 is also eliminated in the four ethers investigated from the ion [M – R]+. Attack of the siliconium ion. Indications are found for a transannular hydrogen/deuterium rearrangement and a transannular elimination reaction. The intensity of some peaks in the spectra are discussed in relation to group R.
Electron impact studies. CXII—The properties of positive ions produced by charge stripping from negative ions. [C6H5O]+, [C6H5S]+ and [C7H7S]+
Authors: Benbow John A. , Bowie John H. , Klass Gunter 
Published: May 2005

AbstractThe dissociative spectrum of the [C6H5S]+ ion derived by charge inversion from [C6H5S]−, shows a variety of fragmentations including the competitive losses of H⋅, C3H4 and the formation of [CHS]+. The spectrum of a deuteriated derivative shows that these three processes are preceded or accompanied by H/D scrambling. The corresponding [C6H5O]+ species also undergoes hydrogen scrambling prior to fragmentation. In marked contrast, the ion [p‐MeC6H4S]+ does not undergo hydrogen randomization between the methyl and aryl groups, and positional integrity is retained during fragmentation. These results are compared with the properties of the same ions produced by conventional ionization.
Electron impact studies. CXIV—The occurance of metastable ions for two‐ and multi‐ stage decomposition of negative ions derived from p‐nitrophenyl carboxylic acids
Authors: Bowie John H. , Stapleton B. Jane 
Published: May 2005

AbstractPronounced metastable peaks are observed for the two‐stage decomposition and the multi ‐ stage elimination from p‐NO2C6H4(CH2)nCO2H (n>1). 2H and 18O labelling shows that each process involves elimination of atoms from both the nitro and carboxyl groups. A consideration of the spectrum of p‐nitrophenylcyclohexane‐4‐carboxylic acid leads to the proposition that interaction between the two functional groups is not a necessary prerequisite for the elimination of HO⋅.
Importance Relative des Isomères de I'Ion Moléculaire de Dérivés Substitués Polycycliques du Benzodioxinne 1,4
Authors: Dagaut Jacques , Ricard Michele , Brun Jean Pierre , Leblanc Danielle 
Published: May 2005

AbstractDifférents isomères de I'ion moléculaire de dérivés benzocyclobuténiques du benzodioxinne 1,4 spécifiquement marqués au deutérium ont été mis en évidence. L'abondance de l'Blimination des radicaux benzoyles et formyles différement marqués ont permis de déterminer l'importance relative des isomères de l'ion moléculaire.
Enthalpy considerations applied to the relatively slow unimolecular reactions of a series of homologous CnH2n radical cations
Authors: Bowen Richard D. , Williams Dudley H. 
Published: May 2005

AbstractThe concept that the slow, unimolecular reactions of the homologous series of radical cations are largely determined by the relative energetics of the possible product combinations is discussed. The concept is shown to provide a reasonably consistent rationalization of the known metastable dissociations of and correctly predicts the reactions undergone by . The concept may be useful in discussing the unimolecular chemistry of isomers.
Influence de l'Insaturation Δ20(22) sur la Fragmentation du Cycle D des Stéroides
Authors: Schmit Jean P. , Charette Jean J. 
Published: May 2005

AbstractLes spectres de masse de deux séries de stéroides Δ20(22) insaturés ont été étudiés. L'analyse de la fragmentation du cycle D montre que la rupture da la liaison C‐15C‐16 est caractéristique de la présence d'une telle insaturation dans la chaîne latérale.
The Chemistry of C6H6O radical cations: A study of rearrangement reactions of halogen substituted ethyl phenyl ethers
Authors: Russell D. H. , Gross M. L. , Van Der Greef J. , Nibbering N. M. M. 
Published: May 2005

AbstractNew experimental data on the rearrangement reaction of various phenoxyethyl halides to give [C6H6O]+˙ are presented and compared with previous studies so that a coherent picture of this process can be developed. By examining the metastable kinetic energy release for low energy decomposing molecular ions of the phenoxyethyl halides, it has been concluded that formation of [C6H6O] occurs by competitive 1,2 and 1,3 hydrogen shifts from the alkyl carbons to oxygen followed by a rate determining CO bond cleavage. This is substantiated by the absence of a primary hydrogen isotope effect. For more highly activated molecular ions, a new mechanism comes into play as evidenced by the appearance of a small hydrogen isotope effect. It is postulated that this third mechanism involves transfer of the alkyl hydrogen to the ortho position of the ring by a rate determining 1,5 shift, followed by a 1,3 hydrogen shift from the ortho methylene group to oxygen and rapid CO bond cleavage. This 1,3 hydrogen shift to oxygen appears to be ‘catalysed’ by the halogen atoms yielding phenol ions. No indications have been found for the formation of tautomeric 2,4‐cyclohexadienone ions. Furthermore, highly activated molecular ions produce [C6H6O]+˙ which can undergo metastable decomposition to lose carbon monoxide. Kinetic energy release measurements for the latter reaction show that the majority of these [C6H6O]+˙ions have been formed as phenol ions as well. These arguments are supported by energetic measurements and by comparisons with previous ion cyclotron resonance and collisional activation studies.
Fragmentation de la Méthyl‐2 Indolizine sous Impact Electronique: perte de H˙ à partir de l'Ion Moléculaire; perte de HCN à partir de l'Ion [MH˙]+
Authors: Corval Madeleine , Brun Jean‐Pierre 
Published: May 2005

AbstractL'origine du radical H⋅ éliminé dans la source D'ions à partir de l'ion moléculaire de la méthyl‐2 indolizine est étudiée au moyen de quatre variétés marquées au deutérium. La perte de H⋅ intéresse préférentiellement le substituant méthyle, mais les hydrogènes (ou certains des hydrogènes) de chacun des deux cycles interviennent également, particulièrement ceux du cycle substitué. Les résults de l'étude par balayage combiné de l'élimination de HCN à partir des ions métastables [M‐H˙]+ sont compatibles avec l'équivalence de tous les hydrogènes de l'ion précurseur vis‐à‐vis de ce processus, impliquant une réorganisation extensive préalablement à la fragmentation.
Mass spectroscopic study of halocyanoacetylenes: Appearance energies and thermochemical data
Authors: Büchler Ulrich , Vogt Jürgen 
Published: May 2005

AbstractThe mass spectra of the cyanoacetylenes XCCCN, X  H, F, CI, Br, I, are reported, together with electron impact appearance energies as determined using a modified second derivative method. From these data the enthalpies of formation and the CX as well as the CC bond energies are deduced. These bond energies are discussed in comparison with values of corresponding saturated and acetylenic compounds.
Keto and enol forms of methyl acetate molecular ions, their stability and interconvertibility prior to fragmentation in the gas phase
Authors: Holmes John L. , Lossing F. P. 
Published: May 2005

AbstractThe heats of formation of the keto and enol forms of the molecular ion of methyl acetate are 577 ± 4kJ mol−1 and 477 ± 4KJ mol−1 respectively. Fragmentation by loss of CH3O˙ takes place at the thermochemical threshold for [CH3CO]+ formation for both isomers, which may therefore freely interconvert at internal energies corresponding to this decomposition threshold.
Mass spectrometry of the simple N‐ vinylpyridinium salts
Authors: Ellingsen Peter , Hvistendahl Georg 
Published: May 2005

AbstractN‐ Vinylpyridinium halides readily undergo a Hofmann type elimination, prior to evaporation in the mass spectrometer, with formation of pyridine, acetylene and hydrogen halide as volatile products. A second important reaction is thermally induced two electron reduction of the cation to the volatile N‐vinyldihydropyridine. Of minor importance is the formation of volatile compounds with the elemental composition of [cation + C2H] and [cation + C2H3]. The latter is suggested to have a divinyldihydropyridine structure. Its formation is explained as due to nucleophilic attack on the cation by the N‐vinyldihydropyridine present with displacement of pyridine.