bluuebunny/crossref_metadata_2025_split huggingface dataset:
The electron‐impact‐induced fragmentation of some alkyl isocyanides and α‐branched alkyl cyanides
Authors: Heerma W. , De Ridder J. J. 
Published: May 2005

AbstractThe HRP mass spectra of some alkyl isocyanides (RNC in which R equals CH3, C2H5, n‐C3H7, n‐C4H9 and t‐C4H9) and two methyl branched alkyl cyanides (RCN in which R equals i‐C3H7 and t‐C4H9) have been studied. Using metastable ion transitions and appearance potentials, the fragmentation patterns and spectral characteristics of the isocyanides can be given. A comparison has been made with the mass spectral data of the corresponding cyanides.Although the mass spectra of alkyl cyanides and isocyanides show close relationship, evidence could be obtained that this resemblance is not caused by rearrangement of the isocyanide into cyanide molecules. The main difference between the spectra of both compounds is caused by the strength of the α‐bond, being weaker in the case of the isocyanides. The abundance of ions formed by α‐bond cleavage decreases with increasing size of the alkyl group.
Mass spectra of esters of α‐hydroxy and α‐methoxy acids
Authors: Goulden J. D. S. , Manning D. J. 
Published: May 2005

AbstractThe most abundant fragment produced by electron bombardment of esters of the type R1R2C(OR3)CO2R4 is the R1R2C = \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^{{\rm + } \cdot } $\end{document}R3 ion. Methyl glycollate (R1 = R2 = R3 = H, R4 = Me) eliminates the HCO˙ radical by a complex rearrangement involving the methylenic hydrogen atoms. The methyl and ethyl esters of methoxyacetic acid (R1 = R2 = H, R3 = Me, R4 = Me or Et) eliminate formaldehyde by the McLafferty rearrangement.
The mass spectra of some 3,5‐diarylisoxazoles
Authors: Nonhebel D. C. 
Published: May 2005

AbstractThe mass spectra of several 3,5‐diarylisoxazoles are reported. The fragmentation patterns of 3‐aryl‐5‐phenyl‐ and 5‐aryl‐3‐phenylisoxazoles are very significantly different.
The mass spectra of some pyrazole compounds
Authors: van Thuijl J. , Klebe K. J. , van Houte J. J. 
Published: May 2005

AbstractThe mass spectra of ten pyrazole compounds have been determined. Fragmentation schemes have been derived by means of the metastable defocusing method. The predominant process is cleavage of the nitrogen‐nitrogen bond resulting in expulsion of HCN. The process second in prominence is the loss of a nitrogen molecule after initial removal of a hydrogen radical or a substituent, giving the species [C3H2R]+, probably a cyclopropenyl ion. In general, the fragmentation pattern is strongly influenced by the substituent.
The mass spectra of some aliphatic and alicyclic sulphoxides and sulphones
Authors: Smakman R. , de Boer Th. J. 
Published: May 2005

AbstractCharacteristic fragmentation processes of aliphatic sulphoxides and sulphones such as loss of hydroxyl, ‘alkene’ and/or ‘alkenyl’ are associated with hydrogen migrations to oxygen. A study of the mass spectra of di‐n‐butyl sulphoxide and sulphone, the saturated five‐, six‐ and seven‐membered ring sulphoxides and sulphones and their site‐specifically deuterated analogues shows that these hydrogen migrations are nonspecific.Apparently steric factors play an important role in determining the relative contributions of initial hydrogen transfer from the various positions. The sites of abstraction probably determine the extent of competition between consecutive or concerted loss of hydroxyl, carbon‐sulphur fission or other processes (e.g. McLafferty rearrangement).Apart from the McLafferty rearrangement only the loss of hydroxyl from sulphones shows a strong dependence on the site of initial hydrogen abstraction: γ‐hydrogen is lost preferentially, yielding a cyclized [M  OH] ion.
Mass spectrometry of aralkyl compounds with a functional group–X A reinvestigation of the structure of the [C8H9]+‐ion from 1‐phenylethylbromide and of the molecular ion [C8H8]+˙ from styrene by use of 13C labelling
Authors: Venema A. , Nibbering N. M. M. , de Boer Th. J. 
Published: May 2005

AbstractSpecific 13C‐labelling in the side‐chain of 1‐phenylethylbromide and of styrene shows that it is not necessary to assume eight‐membered ring structures for the [C8H9]+‐ and [C8H8]++˙‐ions to explain the almost complete randomization of all hydrogen atoms, as might be concluded from D‐labelling data. It is now suggested that the eight‐membered ring is predominantly present in [C8H9]+ and [C8H8]+˙ ions of low internal energy. In particular this appears to apply to styrene, which generates a cyclooctatetraene molecular ion with the original side‐chain carbon atoms still linked together, as shown by 13C‐labelling.
Studies in mass spectrometry—XV: Retro‐diels‐alder fragmentation and double hydrogen migration in some polycyclic diketones
Authors: Deutsch Joseph , Mandelbaum Asher 
Published: May 2005

AbstractIn contrast to adducts I of bi‐1‐cycloalken‐1‐yls and p‐benzoquinone, their reduction products II do not exhibit a double hydrogen migration from δ positions accompanying a ‘retro‐Diels‐Alder’ type fragmentation. An ordinary retro‐Diels‐Alder fragmentation was found to take place, with charge retention in the diene portion of the molecule. A double hydrogen migration has been detected in II leading to m/e 112 ion c2, which differed, however, from that in I in charge retention and in the origin of the migrating hydrogen atoms. Adducts III of di‐1‐cycloalken‐1‐yls and naphthoquinone behave similarly to II. They exhibit relatively low abundance ions a, however, due to a double hydrogen migration from δ positions, similarly to I. The origin of the migrating hydrogen atoms have been determined by deuterium labelling. Mechanistic suggestions are presented to explain the observed facts.
The mass spectra of eleven derivatives of cyanocyclopropane
Authors: Lageot C. 
Published: May 2005

AbstractStudies of the mass spectrum of 1,2‐diphenyl 1‐cyclopropane show that a large number of fragmentations and rearrangements take place during the electron‐impact of this compound. The mechanisms involved were identical to those found in the studies previously made on the cyclopropanes. Other patterns of fragmentations and rearrangements will also be shown, resulting from the presence of the cyano and substituted diphenyl groups linked on the propanic ring. The nature of the para substituent is fundamental to the aspect of the mass spectra.
Mass spectrometry of isoxazole derivatives—III: Skeletal rearrangement ions in the mass spectra of isoxazoles having a heteroatom at C5
Authors: Nishiwaki Tarozaemon 
Published: May 2005

AbstractTwo skeletal rearrangements of the type[ABC]+.→[AC]+. + B previously found in the mass spectra of 5‐alkoxyisoxazoles are also seen for 5‐amino‐ and 5‐alkylmercapto‐isoxazoles. They are discussed in terms of formation of an azirine ion and its ring expansion to an odd electron ion having a five‐membered ring by means of bond formation involving nitrogen or sulphur. Fragmentation via an oxazole radical ion, which has a photochemical analogy, is also discussed.
Mass spectrometry of onium compounds—VI: Pyrimidinium oxides
Authors: Undheim Kjell , Hvistendahl Georg 
Published: May 2005

AbstractThe 5‐methyldihydrothiazolo (3,2‐c) pyrimidinium cation is evaporated as the corresponding anhydro base. In competition with anhydro base formation the 8‐ethoxy derivative eliminates ethyl bromide to give the corresponding betaine. The latter appears to be electronically rearranged and evaporated as a covalent valence isomer. The 3‐carboxy derivative investigated suffered decarboxylation and ring opening to a vinyl thione. In the absence of a pyrimidyl methyl group the thiazolo ring was attacked by the anion.The electronically induced fragmentations are discussed and used to deduce the structures of the pyrolytic products.
Cortisol and cortisone as test substances for the efficiency of an inlet system
Authors: Adley Thomas. J. , Granata Alessandro 
Published: May 2005

AbstractThe results of a recent report on the use of cortisol and cortisone as test substances for inlet systems have been contradicted. The ion appearing at [M ‐ 60]+ in the spectrum of each ofthese compounds has been shown to arise initially from an electron‐impact process rather than by pyrolysis and subsequent ionization of the molecular compound. Only at higher temperatures isa significant degree of pyrolysis observed.
Mass spectrometric behavior of trimethylsilyl derivatives of isomeric diamino‐, dihydroxy‐ and aminohydroxynaphthalenes
Authors: Smith J. L. , Beck J. L. , Vandenheuvel W. J. A. 
Published: May 2005

AbstractThe mass spectrometric behavior of the di‐TMSi derivatives of diamino‐,dihydroxy‐and aminohydroxynaphthalenes is described. The presence or lack of doubly‐charged ions in the mass spectra is correlated with substituent position. Comparison is made with the spectra of the disubstituted benzenes. Other fragmentations are discussed with supporting data from TMSi‐d9 derivatized compounds.
Acetylenic derivatives of metal carbonyls of the triad Fe, Ru, Os—XI Mass spectra of some binuclear complexes
Authors: Vaglio G. A. , Gambino O. , Ferrari R. P. , Cetini G. 
Published: May 2005

AbstractThe mass spectra of the following acetylenic derivatives of iron, ruthenium and osmium carbonyls are reported: the iron compounds Fe2(CO)6[C2(C6H5)s2]2, Fe2(CO)6[C2(CH3)2]2 and Fe2(CO)6[C2(C2H5)2]2, the ruthenium compounds Ru2(CO)6[C2(C6H5)2]2, and Ru2(CO)6[C2(CH3)2]2 and the osmium compounds Os2(CO)6[C2(C6H5)2]2, Os2(CO)6[C2HC6H5]2 and Os2(CO)6[C2(CH3)2]2. Iron compounds exhibit breakdown schemes where binuclear, mononuclear and hydrocarbon ions are present. On the other hand, ruthenium and osmium compounds fragment in a similar way and give rise to singly and doubly charged binuclear ions. Phenylic derivatives of ruthenium and osmium also give weak triply charged ions. The results are discussed in terms of relative strengths of the metal‐metal and metal‐carbon bonds.
The mass spectra of 2‐aryl‐4‐arylidene‐oxazol‐5‐ones, and the related thiazol‐5‐ones and imidazol‐5‐ones
Authors: Ballantine J. A. , Fenwick R. G. 
Published: May 2005

AbstractExamination of the mass spectra of a series of substituted oxazol‐5‐ones and other related heterocycles showed no evidence of electron‐impact induced isomerism. The electron‐impact fragmentations of these compounds were characterized by a single dominant fragmentation process.
Mass spectral rearrangements in benzylidene hippuric esters
Authors: McCamish M. , White J. D. 
Published: May 2005

AbstractThe mass spectra of a series of hippuric esters have been determined. A variety of novel rearrangements induced by the presence of a formed benzyl carbonium ion has been rationalized with the aid of high resolution measurements and isotopic and substituent labeling. An eight centered rearrangement is proposed for the observed transfer of oxygen from a nitro group to a double bond.
Evidence for one bromine participation in the expulsion of the other from 1,2‐dibrominated compounds
Authors: Pechine J. M. 
Published: May 2005

AbstractAnalysing the stereoisomeric effect on mass spectra for three pairs of geometric isomers (meso and racemic 2,3 dibromobutanes, cis and trans 1,2 dibromocyclohexanes and cis and trans dibromocyclopentanes) it is suggested that the [M—Br] ion formation is facilitated by participation of the other bromine, this participation being maximum when the two halogens are trans or diaxial. The particular bromine character and the analogy with solution chemistry are emphasized.
Some mass spectral and analytical aspects of deuterium labeling of straight‐chain olefins
Authors: Earnshaw D. G. , Doolittle F. G. , Decora A. W. 
Published: May 2005

AbstractA calculation method has been developed to enhance the effect of deuterium labeling in the mass spectra of linear vicinal dideuterioalkanes (LVDA). Individual LVDA can be identified from these enhanced spectra. Single carbon‐number mixtures of LVD nonanes and LVD decanes have been analyzed successfully using matrices derived from spectra of standards. In addition, enhanced mass spectra have been predicted for all of the LVD heptadecanes and LVD nonadecanes. Matrices have been constructed from the predicted spectra, and preliminary tests of these matrices have been conducted. All identifications and analytical results on the LVDA studied can be used to identify the precursor olefins.
Pyrolysis of some perfluoroalkylene‐linked aromatic imides
Authors: Cotter J. L. 
Published: May 2005

AbstractThe pyrolysis of perfluoroalkylene‐linked polyimides in an inert atmosphere has been studied using a pyrolysis‐gas chromatographic‐mass spectrometric method. The major primary gaseous degradation products were carbon monoxide and carbon dioxide. In addition large amounts of silicon tetrafluoride were produced by secondary reactions.Results obtained with 1,3‐di‐(3‐phthalimidophenyl)hexafluo0ropropane and bis[N‐phenyl‐1,3‐dioxo‐isoindolyl(5,5′)]hexafluoropropane suggest that the perfluoroalkylene groups have a greater influence on the electron‐impact induced fragmentation of the imide ring than on its thermal breakdown.
The fragmentation of aliphatic ketones in the mass spectrometer: A detailed study of nonan‐4‐one using ion kinetic energy spectroscopy
Authors: Eadon George , Djerassi Carl , Beynon J. H. , Caprioli R. M. 
Published: May 2005

AbstractThe ion kinetic energy (IKE) spectra of nonan‐4‐one, 7,7‐d2‐nonan‐4‐one and 1,1,1‐d3‐nonan‐4‐one have been recorded and interpreted. The various fragmentations observed in the IKE spectra have been confirmed and some new fragmentations found by carrying out high voltage scans with the magnetic field set successively to collect ions at each mass to charge ratio throughout the mass spectrum. Several new fragmentation modes have been discovered, and their significance is discussed.
Negative ion mass spectra of various fluorine containing molecules
Authors: Dudley Francis B. , Cady George H. , Crittenden Alden L. 
Published: May 2005

AbstractNegative ion mass spectra are reported for the compounds (CF3CO)2O, (C2F5CO)2O, (C3F7CO)2O, C3F7C(F)(CF3)2, n‐C6F14, CF3COCL, (CF3)2CO, BF3, N2F4 and SiF4.
Mass spectra of complexes of 8‐quinolinol with trivalent metals (AL, Ga, In, Sc, Cr and Fe)
Authors: Charalambous J. , Frazer M. J. , Lee R. K. , Qureshi A. H. , Taylor F. B. 
Published: May 2005

AbstractThe main fragmentation of the compounds MX3‐noxn (oxH=8‐quinolinol. n = 3; M=AL, Ga, In, Sc, Cr or Fe. n = 2; M=In or Fe; X=Cl or Br. InIox2. n = 1; M=AL, In or Fe; X= Cl or Br) involves loss of X and intact ox. radicals. The comparative abundances of the fragments are primarily related to the common oxidation states of the metals. For example, all the Mox3 compounds show the ions [Mox3]+ and [Mox2]+. The ions [Mox]+ and [M]+ are present when M=Ga, In, Cr or Fe but for the elements with only one oxidation state (Al or Sc) [M]+ is absent and [Mox]+ has only very low abundance. When M= Cr or Fe metal‐containing ions arising from loss of species such as CO, H2O, HX, C2H2, H and OH by fragmentation of the ox ligand are also present; this behaviour is rationalised in terms of the ability of these metals to undergo a unit change in oxidation state. When n=1 the ions [MXox2]+ and [Mox2]+ and when n= 2 the ions [MX2ox]+ and [Mox3]+ are present; these ions arise by ionization and fragmentation of species formed by redistribution reactions in the mass spectrometer.
Electron‐impact and molecular dissociation—XXI: Some studies on substituted indolosteranes
Authors: Harvey D. J. , Laurie W. A. , Reed R. I. 
Published: May 2005

AbstractThe mass spectra of a series of substituted indolosteroids have been obtained. With one or two exceptions these are some value in structural analysis; the N‐benzyl compounds are exceptional in this. One interesting observation is that substituents such as the oximino‐ or nitro‐groups only have a marginal effect upon the fragmentation‐pattern except on the masses of the various fragment ions.
Spectrographie de masse en série du bornane I: Bornanes monosubstitués
Authors: Daniel Alfred , Pavia André Armand 
Published: May 2005

AbstractDans le cadre d'une étude sur le mécanisme de fragmentation de bornanes 2 et 3 monosubstitués, les auteurs ont interprété les spectres de masse d'un certain nombre de cetones, oximes, alcools, amines et dérivés N‐methyles. Il est à noter que la fragmentation est différente selon la position des substituants, et que la rupture en α du substituant porteur de la charge est prépondérante. De plus, la rupture de cette liaison se fait du coté du carbone qui est le plus substitué. Enfin, les spectres de masse permettent de différencier sans ambiguité la position 2 de la position 3.
The influence of stereochemistry on the mass spectra of some trimethylsilylated pyranoses
Authors: Havlicek S. C. , Brennan Mary R. , Scheuer P. J. 
Published: May 2005

AbstractThe relative intensities of certain ions in the mass spectra of trimethylsilylated pyranoses have been observed to depend on the stereochemistry of the molecule. A system has been developed which is capable of explaining the differences between the anomeric forms of D‐glucose, D‐galactose, D‐mannose and D‐xylose.
Ring contraction upon electron‐impact as a function of ring size: The mass spectrometric fragmentation of acylated cyclic amines
Authors: Richter W. J. , Bursey J. M. , Burlingame A. L. 
Published: May 2005

AbstractThe structural prerequisites of skeletal rearrangement by ring contraction, previously observed in N‐acetylmorpholine, were explored by extending the study to N‐acetylpyrrolidine, ‐piperidine and ‐hexamethyleneimine. Fragmentation via ring contraction was found to be absent in the five‐membered ring, detectable in the six‐membered ring, and significant in the seven‐membered homologue. Ring contraction in these model compounds, i.e. in absence of oxygen as a second heteroatom in the cyclic moiety, is discussed in view of its implications and its support for an initially proposed radical‐induced rearrangement mechanism.
A feature of the fragmentation mechanism of exo‐2‐norbornyl chloride. Stereoselective hydrogen atom abstraction revealed by metastable ion studies
Authors: Holmes J. L. , McGillivray D. 
Published: May 2005

AbstractThe position of deuterium in the products of the addition of HCL and DCI to exo 5, 6‐d2 norbornene has been determined mass spectrometrically by measuring metastable ion abundances. The results show a stereo‐selective hydrogen atom abstraction when the molecular ion of exo‐2‐norbornyl chloride fragements by loss of a chloroethyl radical.
Studies in organic mass spectrometry—V: N‐arylsulphonyliminopyridinium betaines
Authors: Ikeda M. , Kato S. , Sumida Y. , Tamura Y. 
Published: May 2005

AbstractThe mass spectral fragmentation of N‐arylsulphonyliminopyridinium betaines has been rationalized using high resolution mass spectrometry as well as deuterium labelling. The most characteristic features are a very facile NS bond cleavage and skeletal rearrangements accompanied by the expulsion of SO2 from the molecular ion and the [M1] ion to the corresponding ionized N‐aryliminopyridinium betaines and azacarbazoles, respectively. The presence of methyl substituents at the α‐position of the pyridine ring has a significant effect on the mode of the fragmentation.
Spectrometrie de masse—VI. Fragmentation de dimethyl‐2,2 dioxolannes‐1,3 insatures
Authors: Kossanyi J. , Chuche J. , Duffield A. M. 
Published: May 2005

AbstractLe comportement d'une série de diméthyl‐2‐2 dioxolannes‐1,3 insaturés, sous l'effect du bombardement d'électrons, a été déterminé à l'aide des ions métastables et des measures de haute résolution sur les différents pics de fragmentation. La formation des ionsfragments principaux observés sur les spectres, tat à basse énergie qu'à haute énergie du faisceau d'électrons a pu être rationalisée.
High‐resolution mass spectra of anti‐ and syn‐isomers of acylferrocene oximes
Authors: Yamakawa Koji , Hisatome Masao 
Published: May 2005

AbstractHigh‐resolution mass spectra of anti‐ and syn‐acylferrocene oximes were examined at various ionizing voltages and fragmentation patterns of the oximes are presented. Significant differences between the anti‐ and syn‐isomers were found in the fragmentation behaviour of the low voltage (15 to 20 eV) spectrum of formylferrocene oxime.
Mechanistic information from deuterium isotope effects on mass spectral processes: The elimination of ketene from acetanilides and the subsequent loss of HNC
Authors: Uccella N. , Howe Ian , Williams Dudley H. 
Published: May 2005

AbstractElimination of ketene from the molecular ion of p‐chloroacetanilide takes place via a 4‐membered transition state, as evidenced by deuterium isotope effects on competing metastable transitions.
Anchimeric assistance in electron‐impact reactions: Homoallylic systems
Authors: Tomer Kenneth B. , Turk Jonathan , Shapiro Robert H. 
Published: May 2005

AbstractA combination of a kinetic approach, thermochemical approach and atomic labeling techniques has been employed to demonstrate that several series of allylic and homoallylic bromides undergo Br· expulsion with the aid of remote π‐electron density.
Ortho effects in mass spectrometric fragmentation processes
Authors: Cable J. , Kagal S. A. , MacLeod J. K. 
Published: May 2005

AbstractThe mass spectra of the phenylhydrazones and 2,4‐dinitrophenylhydrazones of ortho substituted benzaldehydes and acetophenones (X = I, Br, Cl, OCH3, OH) show characteristic [M − X]+ ions which allow the ortho derivatives to be distinguished from their meta and para isomers.
Mass spectra of methylsubstituted monosila‐ and monogermacyclobutanes, 1,2‐ disila‐ and 1,2‐digermacyclopentanes. Some correlations with thermal decomposition
Authors: Yu. Orlov V. , Gusel'nikov L. E. , Nametkin N. S. , Ushakova R. L. 
Published: May 2005

AbstractThe mass spectra of 1,1‐dimethyl‐1‐silacyclobutane (I—as reported by Cherniak et al.),6, 1,1‐dimethyl‐1‐germacyclobutane (II), 1,1,2,2‐tetramethyl‐1,2‐disilacyclopentane (III) and 1,1,2,2‐tetramethyl‐1,2‐digermacyclopentane (IV) are compared and some correlations between electron‐impact fragmentation and thermal decomposition are derived. The mass spectra of the germanium compounds with respect to the silicone compounds are enriched by light fragment ions and exhibit lower intensities of odd‐electron ions. The composition of some ions and apparently of neutral fragments coincides with that of the unstable intermediates which are suggested in the thermal decomposition mechanism of some related compounds. The loss of C2H4 is more characteristic under electron‐impact as well as in thermal decomposition of Si‐compounds, while C3H6 is preferable eliminated by the Ge‐compounds.
Etude comparative en spectrometrie de masse des series relatives aux perchlorofluorobenzenes et perchlorofluoropyridines
Authors: Hitzke J. , Peter F. , Guion J. 
Published: May 2005

AbstractNous présentons ici les résultats de l'analyse en spectrométrie de maasse des séries C6Cl6; C6Cl5F; 1,3‐F4C6Cl2; C6F5Cl; C6F6 obstenues par remplacvement successif des atomes de chlore par des atomes de flour, à partir de l'hexachlorobenzène. De měme, la série correspondante des perchloroflouropyridines est analysée. Les séquences de dégradations observées sont trés réguliéres dans les deux séries, et sont interprétables par des schémas simples, souvent confirmés par l'observation des pics métastables correspondents.