bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic studies in mass spectrometry—V: Evaluation of wide range electron energy kinetics and metastable ion relative abundance techniques, and the structures of [XC6H4CH2]+ ions generated from substituted benzyl phenyl ethers and toluenes
Authors: Brown Peter 
Published: May 2005

AbstractThe problem of ion structure and energy is discussed briefly and attention directed to the existence of two types of structural information. Studies of ion formation reactions bear on the initial structure of the ion, whereas decomposition reactions relate to the ion at a later time, after structural rearrangement has had chance to occur. The desirability of conducting both types of investigation concurrently is emphasized. Of the available experimental methods at this time, kinetic measurements for formation studies and metastablel ion relative abundances for decomposition studies have been utilized, although other techniques may eventually prove preferable in the future. The [M – Y] reaction of a series of substituted benzyl substrates XC6H4CH2Y, where Y = OC6H5 and H, has been examined, and the present results are compared with previous work on ion structure and energy in this area, with the aim of evaluating the potential of the newer techniques.
Mass spectrometric determination of the configuration of the 4‐substituted 1,2‐dimethyl‐4‐hydroxydecahydroquinolines
Authors: Zaikin V. G. , Wulfson N. S. , Zaretskii V. I. , Bakaev A. A. , Akhrem A. A. , Ukhova L. I. , Uskova N. F. 
Published: May 2005

AbstractThe mass spectra of a number of the epimeric 1,2‐dimethyl‐4‐alkyl‐4‐hydroxydecahydroquinolines (alkyl: CCH, CHCH2, C2H5 and COCH3) have been studied. The configuration at C‐2 and C‐4 in these molecules is proposed on the basis of the data obtained. Some aspects of the fragmentation pathways under electron‐impact are discussed.
Organic ions in the gas phase—XXIII: Loss of CH3 from polymethylbenzenes
Authors: Meyerson Seymour , Fields E. K. 
Published: May 2005

AbstractThe mass spectra of a series of deuteriated polymethylbenzenes confirm and extend the model derived from labeled p‐xylenes for the loss of a methyl radical under electron impact. A methyl group flanked by two methyls undergoes no exchange before being lost. But one adjacent to an unsubstituted position appears to exchange with the o‐hydrogen atom via a methyl‐methylene‐methyl cycle. At least in p‐xylene, reformation of the methyl group may well be concerted with its loss. A similarly concerted coupling of CH2 and H and loss of the resultant methyl group could account for an apparent inconsistency between the mass spectra of methyl alkyl and phenyl alkyl ketones.
Trimethylphosphine and trimethylamine: Rearrangements common to their mass spectra
Authors: Gillis R. G. , Long G. J. 
Published: May 2005

AbstractMetastable ions confirm the rearrangement of the [M  H]+ ion from trimethylphosphine and trimethylamine to give [C3H5]+. Two‐carbon fragments are seen but their origin is indeterminate. Extensive loss of H2 occurs, confirmed by metastable ions, but not of CH2.
Kinetic studies in mass spectrometry—VI: The [M  CH3] reaction in substituted ethylbenzenes
Authors: Brown Peter 
Published: May 2005

AbstractThe [M] → [M  CH3] reaction in a series of m‐ and p‐X substituted ethylbenzenes has been studied by wide range electron energy kinetics and metastable ion characteristics techniques. By this approach, qualitative measures of activation evergy differences between [XC6H4CH2]+ ions derived from m‐ and p‐X isomer substrates have been secured, for both their formation and further decomposition. These evergy differences are consistent with (but do not prove) ion structures that have been suggested by previous work in this area, involving the use of isotope labeling, and ionization and appearance potential methods.
The mass spectra of some chlorinated aromatic pesticidal compounds
Authors: Sphon J. A. , Damico J. N. 
Published: May 2005

AbstractMass spectral studies of some chlorinated aromatic pesticidal compounds are reported. The compounds studied include substituted diphenyl derivatives of methane, ethene and methanol.The diphenylmethanes are characterized by a relatively intense peak at m/e 165. Comparison of their low voltage spectra with 9‐dichloromethylfluorene indicates that this ion has a fluorenyl ion structure.The structure of the base peak (m/e 246) of the diphenylethenes was investigated by comparing competitive metastable transitions with 9‐dichloromethylenefluorene and utilizing defocusing metastables. Additional studies of model compounds suggest that the m/e 246 ion is very complex and is probably comprised of a number of structures.The mass spectra of the diphenylmethanols are significantly different from the other two groups. The hydroxyl group markedly affects the fragmentation process for these compounds; the characteristic peak is presumably the chlorobenzoyl ion and is probably precursor for other fragment ions.Mass spectral correlations of pesticidal compounds of similar structure are needed to obtain enough background to facilitate interpretation of the mass spectra of their metabolites. Furthermore, such studies make feasible the identification of characteristic product ions formed by rearrangement processes during ionization of organic molecules in the gas phase. This information can be a nucleus for correlating the other significant mass spectral data of an unknown compound. Intensive studies of carbamates,1 organophosphorus2 and bridged polycyclic chlorinated pesticidal3 compounds were invaluable in identifying metabolites of the aforementioned pesticides.4,5,6 The compounds in this
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Work are chlorinated aromatic pesticidal compounds which consist of a diphenylemthane, a diphenylethylene, or a diphenylmethanol structure. The compounds p,ṕ‐DDE were briefly discussed by Jorg, Houriet and Spiteller.7 The compounds examined are listed in Table 1.Treatment of data. The mass spectra of the pesticides are presented as bar graphs in Figs 1 to 12
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It a metastable peak is observed, the metastable transition is indicated by m* on the figures and also by (m*) when confirmed or identified using the defocusing technique.8 Since the relative abundances of the metastable peaks for these compounds are very small (<0.1%) on special effort was made to establish their presence unless they wre pertinent.
Mass spectrometry in cardenolide chemistry—I
Authors: Blessington B. , Morton I. M. 
Published: May 2005

AbstractThe mass spectrum of penta acetyl gitoxin is reported and discussed. This cardenolide derivative has recently been the subject of extensive metabolic study. Fragmentation processes are described which account for all of the major ions. High resolution measurements, metastable peaks and mass shifts, for the propionyl derivative, are reported to establish the validity of these proposals. A brief indication of the potential value of this technique, when combined with deuteroacetylation, to metabolic studies in this field is given, along with comments on the spectra of related compounds.
Some aspects of the mass spectra of triptycene and tri‐ and diphenylmethanes
Authors: Meyerson Seymour 
Published: May 2005

AbstractMass spectra of isotope‐labeled triptycenes, triphenylmethanes and diphenylmethanes rule out the bulk of postulated decomposition mechanisms and fragment‐ion structures. The formation of [M  H]+ and [M  2H]2+ from triptycene, of [M  H]+, [M  CH3]+ and [M  CH4]+ from triphenylmethane, and of [M  H]2+ and [M  2H]2+‐as well as the previously reported [M  H]+ and [M  CH3]+‐from diphenylmethane all seem to be preceded or accompanied by complete loss of position identity of the α and ring hydrogens in the original molecules. A statistical preference for loss of α hydrogens is found in the process leading to [M  2H]+ and [M  H]2+ from triptycene, as in the formation of [M  H]2+ from toluene.
The β‐cleavage reaction in ethers
Authors: Bernasek Steven L. , Cooks R. Graham 
Published: May 2005

Abstractβ‐Cleavage in n‐butyl ethyl ether occurs neither by simple bond fission with oxiranium ion formation nor by a mechanism analogous to the γ‐cleavage reaction in carbonyl compounds, but instead it involves skeletal rearrangement within the butyl chain.
Effects of halo substituents on electron‐impact induced fragmentation of cyclopropanes
Authors: Deem M. L. , Roboz J. 
Published: May 2005

AbstractBromine, fluorine and/or chlorine atoms on one cyclopropyl ring jointly influence the dominant primary modes of electron‐impact induced fragmentation. Decomposition ions include CBrX, C2HQ2X and C3HQ2X2, where × is an halogen atom and Q is from the group of an halogen atom, an hydrogen atom and a methyl group. For none of the compounds studied was formation of an ionic CBrX the dominant primary process. Gem‐dibromo‐gem‐dihalocyclopropanes preferentially eliminated dibromo divalent carbon and formed decomposition products of gem‐dihalogenated C2HQ2X′s. In cases where more stable allyl ions were formed, fragmentation was through C3HQ2X2.Upon electron‐impact, the ions CF, CHF2 and CF3 were produced in abundances directly related to the fluorine content of their cyclopropyl precursors.When fragmentation patterns for internally generated radical ions of the composition C2HQ2X were compared with patterns obtained by direct introduction of the same fluoroolefins into a mass spectrometer, incomplete correspondence was found. Variation in the mode of decomposition can be a consequence of differences in the energy levels of the olefin fragmented.Addition of two hydrogen atoms from water to quinones and to s‐tetrazines is well established in the literature. Reaction of an additional cyclic series, polyhalocyclopropanes, with water prior to electron‐impact is suggested.
A new mass spectrometric method for determining the degree of labeling with heavy isotopes: The study of deuterated toluenes
Authors: Beynon J. H. , Corn J. E. , Baitinger W. E. , Amy J. W. , Benkeser R. A. 
Published: May 2005

AbstractA new method of general applicability for determining the percentage deuterium labeling in organic compounds is described. It uses the heights of ‘metastable peaks’ in the mass spectrum to determine the relative amounts of deuterated and undeuterated species. The method is illustrated by describing the analysis of mixtures of toluene‐o‐d1 and toluene, of toluene α‐d1 and toluene, and of toluene‐2,6‐d2, toluene‐o‐d1 and toluene.
High resolution mass spectrometric studies of some bicyclic γ‐lactones
Authors: Chen Paul H. , Kuhn William F. , Will Fritz , Ikeda Robert M. 
Published: May 2005

AbstractThe mass spectra of three bicyclic γ‐lactones have been studied, and the fragmentation pathways have been proposed with the aid of accurate mass measurements and metastable transitions. An unusually low [M  CH3] ion and the presence of an abundant [M  C5H9] ion in the mass spectrum of dihydroactinidiolide were interpreted as a possible rearrangement involving a methyl migration. The eliminations of methyl radical, carbon monoxide and ketene are important processes in many cases.
Mass spectrometry of aralkyl compounds with a functional group—IX: Hydrogen scrambling in the molecular ion of hydrocinnamaldehyde
Authors: Venema A. , Nibbering N. M. M. , De Boer Th. J. 
Published: May 2005

AbstractThe molecular ion of hydrocinnamaldehyde (C6H5CH2CH2CHO) chiefly loses fragments C2H2O and C3H4O. Mass spectra of specifically deuterated analogues show that in the loss of C2H2O an α‐hydrogen atom (with respect to the aldehyde group) is transferred to the aromatic part. A shift of the aldehydic hydrogen to one of the ortho positions of the phenyl ring and loss of C2H2O by a McLafferty rearrangement is not observed.In the loss of C3H4O also an α‐hydrogen atom migrates to the aromatic part. Both reactions appear to occur with an extensive randomization of all hydrogen atoms in the molecular ion.
Four‐centred rearrangements in the mass spectra of aliphatic ethers
Authors: Tsang C. W. , Harrison A. G. 
Published: May 2005

AbstractThe [CH3OCHCH3]+ ions observed in the mass spectra of ethers of formula CH3OCH (CH3)R(R = H or alkyl) undergo two rearrangement fragmentation reactions to form [C2H5]+ and [CH2OH]+. The scope of the rearrangements has been investigated and it is shown that enlargement of the alkyl group on either side of the ether linkage leads to alternative fragmentation routes. From a study of metastable intensities it is concluded that the fragmentations probably occur directly from the [CH3OCHCH3]+ structure through four centred rearrangements rather than through the intermediacy of the [C2H5OCH2]+ ion.
The mass spectra of succinimides, hydantoins, oxazolidinediones and other medicinal anti‐epileptic agents
Authors: Locock R. A. , Coutts R. T. 
Published: May 2005

AbstractThe mass spectra of the following common anti‐epileptic agents; phensuximide, methsuximide, ethosuximide, ethotoin, mephenytoin, diphenylhydantoin, trimethadione, paramethadione, primidone and phenacemide, have been recorded and interpreted. In addition the mass spectra of succinimide, α‐phenylsuccinimide and the N‐deuterated derivative of ethotoin were studied. The investigated compounds fragment in an interesting manner and give rise to stable ions by which means they are readily identified. The most diagnostic fragmentation in the majority of the spectra was the expulsion of a (CO)2NR fragment from the molecular ion.
Alcaloïdes Steroïdiques—CII: La Fragmentation des Diamines Stéroïdiques et de Leurs Dérivés en Spectrométrie de Masse
Authors: Longevialle Pierre , Diatta Luc 
Published: May 2005

AbstractL'étude, en spectrométrie de massem des stéroïdes proteurs de deux groupements azotés dans des positions éloignées fait apparaítre un nouveau type de fragmentation débutant par une interaction de ces deux groupements. Le phénoméne est décrit dans le cas des diamines et de certains dérivés (imines, amides).
Rearrangement ions—I: Mass spectrum of thionylaniline‐1‐13C
Authors: Siegel Alan S. 
Published: May 2005

AbstractRecent publications1,2 concerning the mechanism for the electron‐impact induced loss of carbon monoxide from the molecular ion of thionylaniline have led to an examination of thionylaniline‐1‐13C. The results show that the C‐1 carbon atom is not lost in this process, but only suggest the loss of the C‐2 carbon atom.
Mass spectra of alkylferrocenes and biferrocenyls
Authors: Spilners Ilgvars J. , Larson John G. 
Published: May 2005

AbstractMass spectra of alkylferrocenes and biferrocenyls have molecular ion peaks which are also base peaks. The predominant fragment ions are formed by beta‐cleavage of the alkyl group. Gamma‐and alpha‐cleavages are the only other significant modes of alkyl side‐chain fragmentation. The cleavage of the alkyl group is often accompanied or followed by the cleavage of either one or both of the cyclopentadienyl‐iron bonds. Weak m/e 121 ([C5H5]+) mass peaks are found in the spectra of 1,1′‐dialkyl‐ and 1,1′‐disilyl‐ferrocenes. Therefore, the m/e 121 peak may not be used as a sensitive criterion to determine the presence of unsubstituted cyclopentadienyl rings. The relative intensity of the peak may, however, serve as an indicator.Expansion of the cyclopentadienyl ring to six‐ and seven‐carbon rings in the fragmentation of alkylferrocenes, diethylbiferrocenyl and deuterated ethylferrocenes is indicated. The spectra of benzylferrocene and benzylferrocene‐alpha‐d2 do not show a beta‐cleavage but suggest a pentalene ring formation. Methyl and phenyl groups in the beta‐position of substituted ferrocenes were found to migrate to the iron atom.
Electron‐impact studies—LIV: The formation of [C13H9]+ in the mass spectra of benzyl phenyl ketoxime and 2,3‐diphenyl‐2‐H‐azirine
Authors: Simons B. K. , Nussey B. , Bowie J. H. 
Published: May 2005

AbstractThe formation of m/e 165 in the spectrum of benzyl phenyl ketoxime involves the intermediacy of a rearranged 2,3‐diphenyl‐2‐H‐azirine radical ion. 2H and 13C labelling of the ketoxime together with 2H labelling of the azirine has allowed certain proposals to be made concerning the complex processes producing m/e 165 in both spectra. The mode of formation of m/e 167 in the spectrum of benzyl phenyl ketoxime has also been studied.
Electron‐impact studies—LV: Skeletal rearrangement and hydrogen scrambling processes in the positive and negative‐ion mass spectra of phenyl derivatives of elements of group IV and V
Authors: Bowie J. H. , Nussey B. 
Published: May 2005

AbstractThe mass spectra of many triphenyl/tetraphenyl derivatives of the Group IV and V elements exhibit the processes [M+˙  C12H10] and/or [M+˙  C6H5·  C12H10]. These fragmentations are not preceded by hydrogen scrambling between all the phenyl rings. Hydrogen scrambling does occur in certain fragment ions prior to fragmentation in both the positive and negative‐ion spectra. The process [M+˙  C12H10] occurs in the negative‐ion mass spectrum of tetraphenylsilane.
Metastable ion fragmentation processes in n‐alkanes
Authors: Goldberg P. , Hopkinson J. A. , Mathias A. , Williams A. E. 
Published: May 2005

AbstractThe n‐alkanes, propane to heptane, have been studied in a modified MS‐9 mass spectrometer under conditions that enabled the daughter ions, resulting from metastable fragmentation processes occurring in the first field free region, to be observed with high sensitivity. The precursor ions in these fragmentations have been identified unambiguously and a general fragmentation scheme for the n‐alkanes is proposed. The mass spectrometer incorporated a variable width monitor slit and narrow settings of this slit improved the energy resolution so that fine structure could be observed in some of the ‘metastable peaks’. The implications of this fine structure are discussed.
The mass spectra of N‐phenylphosphoramidate esters
Authors: McMurray W. J. , Lipsky S. R. , Zioudrou C. , Schmir G. L. 
Published: May 2005

AbstractThe mass spectra of diethyl and diphenyl N‐phenylphosphoramidate are reported. Their electron‐impact behavior is similiar to that observed for the corresponding phosphate esters. High resolution mass measurements are used to confirm the elemental composition of all the peaks in the spectra. Some interesting rearrangement fragments are observed in the spectrum of the diphenyl N‐phenylphosphoramidate ester.
The electron‐impact induced loss of water from meconine and related derivatives
Authors: King Bonnie M. , Evans D. A. , Biemann K. 
Published: May 2005

AbstractThe mass spectrum of meconine (I), a constituent of raw opium, exhibits several anomalous features (e.g. pronounced loss of H2O from the molecular ion) which are not readily explicable in terms of simple fragmentation processes. The study of the low resolution mass spectrum of meconine and its derivatives in conjunction with deuterium labeling experiments has indicated a highly specific fragmentation mechanism in which both hydrogen atoms eliminated as H2O originate from the methoxy function ortho to the lactone carbonyl group in meconine.
Mass spectrometric study of 1‐chloro‐2‐nitrosocycloalkanes, dimers in gaseous phase
Authors: Tou James C. , Chang Kuo Yuan 
Published: May 2005

AbstractThe electron‐impact mass spectra and the field ionization mass spectra of 1‐chloro‐2‐nitrosocyclohexane and 1‐chloro‐2‐nitrosocyclopetane are presented and discussed. The two compounds investigated exist in dimeric form in the gaseous phase.
Mass spectrometry in structural and stereochemical problems–CXCIII: On the combined hydroxyl and water loss in nitrophenylhydrazones
Authors: Liedtke Raymond J. , Duffield A. M. , Djerassi Carl 
Published: May 2005

AbstractThe mass spectrum of valeraldehyde o‐nitrophenylhydrazone displays only a low intensity peak (3% relative abundance) corresponding to the loss of 35 mass units from its molecular ion contrary to data previously published. Mention is also made of the fragmentation of 5‐nonanone 2,4‐dinitrophenylhydrazone in view of a recent challenge to a published rationalization for the electron impact promoted fragmentation for this compound.
Mass spectrometry of isomeric methyl phenylpentanoates and methyl phenylnonanoates
Authors: Ansell M. F. , Whitfield G. F. 
Published: May 2005

AbstractThe mass spectra of methyl 3‐, 4‐ and 5‐phenyl pentanoates, and all the straight‐chain methyl phenylnonanoates have been recorded. The major fragmentation patterns have been discussed; when the phenyl group is non‐terminal, cleavage was observed at the branching position. It is shown that a mixture of methyl 3‐, 4‐ and 5‐phenylpentanoates may be analysed both qualitatively and quantitatively by mass spectrometry; in a methyl phenylnonanoate mixture a similar analysis is possible with the exception of the 8‐ and 9‐phenyl isomers.
The expulsion of formic acid and methyl formate during the fragmentation of 3‐phenylpropionic acid derivatives under electron‐impact
Authors: Ballantine J. A. , Curtis R. F. 
Published: May 2005

AbstractExamination of the mass spectra of several 3‐arylpropionic acids and methyl esters showed that one of the major fragmentation processes corresponded to the expulsion of a molecule of formic acid or methyl formate directly from the molecular ion.
Loss of carbon dioxide in the mass spectra of some partially fluorinated β‐diketonato iron chelates
Authors: Clobes A. L. , Morris M. L. , Koob R. D. 
Published: May 2005

AbstractEvidence suggesting elimination of carbon dioxide as a decomposition path for tris(1‐phenyl‐4,4,4‐trifluoro‐1,3‐butandionato) iron (III) [Fe(btac)3] and tris (1‐thienyl‐4,4,4‐trifluoro‐1,3, butandionato) iron (III) [Fe(ttac)3] is presented and discussed. A mechanism is proposed for this reaction. Other examples of CO2 elimination are observed for substituted phenyl Fe(btac)3, tris(1‐cyclopropyl‐4,4,4‐trifluoro‐1,3‐butandionato) iron (III) and Co(III) (btac)3.
Studies of selenides of thiophene and furan series—V: Mass spectra of some thiophene, furan and selenophene derivatives
Authors: Chizhov O. S. , Zolotarev B. M. , Sukiasian A. N. , Litvinov V. P. , Gol'dfarb Ya. L. 
Published: May 2005

AbstractMass spectra of some selenides, sulphides and ethers of furan, thiophene and selenophene series are described. A new fragmentation reaction, consisting in splitting off alkyl, insertion of heteroatom in the cycle and loss of one of heteroatoms as CX, is discussed in detail.
Rearrangement ions—II: Mass spectra of the C‐13 labeled 2‐methyl‐2‐hydroxy‐propanes and 2‐methyl‐2‐aminopropanes
Authors: Siegel A. S. 
Published: May 2005

AbstractThe mass spectra of 2‐methyl‐2‐hydroxypropane (I) and 2‐methyl‐2‐aminopropane (II) exhibit fragment ions which suggest skeletal rearrangement processes. The C‐13 analogs of I and II, labeled in the 1‐ and 2‐positions, were prepared in order to determine the most probable mechanistic pathways for fragmentation. Label retentions in major fragment ions indicate that I and II decompose into common fragments through structurally similar intermediates.
The mass spectra of carboxylic acids–II: Fragmentation mechanisms in the homologous series HOOC(CH2)nCOOH
Authors: Holmes J. L. , St. Jean T. 
Published: May 2005

AbstractThe mass spectra of the homologous series of acids HOOC(CH2)nCOOH from n = 0 to 12 have been studied together with certain deuterium labeled members. The fragmentation mechanisms of the lower homologues are discussed in some detail. The loss of one or two molecules of water from the molecular ions was shown to proceed most favorably via a 6‐centred intermediate involving the methylene group β‐ to a carboxyl function. It was observed that the ease of carboxyl‐carboxyl interaction promoting CO2 elimination from the molecular ion could be simply correlated with n and thus serves as a structure‐identifying feature.