bluuebunny/crossref_metadata_2025 huggingface dataset:
Mass spectrometry of homoadamantane derivatives
Authors: Yurchenko A. G. , Stepanov F. N. , Isaeva S. S. , Zolotarev B. M. , Kadentsev V. I. , Chizhov O. S.
Published: May 2005

Homoadamantane derivatives can be divided into two groups according to their mass spectra. To the first group belong compounds with electron attracting substituents (COOH, CI, COOCH3, Br); compounds with electron releasing substituents (OCH3, OH, NH3, NHCOCH3) constitute the second group.

The most characteristic feature of the first group compounds is the splitting off of the substituent. The hydrocarbon fragment [C11H17]+ thus formed then loses olefin molecules with the formation of corresponding ionic species C11−nH17−2n. The 3‐substituted compounds of this group undergo thermal Wagner‐Meerwein type rearrangements into adamantane derivatives, resulting in the [C10H15]+ (m/e 135) ion formation; this is the main difference between 1‐ and 3‐substituted homoadamantanes.

The series of [CnH2n−6X]+ ions (where X = OCH3, OH, NH2, NHCOCH3, n = 6 to 10) are characteristic of the mass spectra of the second group compounds, the ion [C6H6X]+, [M  C5H11]+ being the most abundant. The intensity ratio of [M  C5H11]+ to [M  C4H9]+ ions is 10:1 for 1‐substituted and 3:1 for 3‐substituted compounds of this group, allowing the location of the substituent. Some individual features of the spectra are also reported.
Mass spectrometry of onium salts—I. Studies on anilinium oxides
Authors: Undheim Kjell , Hvistendahl Georg
Published: May 2005

The mass spectra of the three isomeric trimethylanilinium oxides and their methyl‐d3 analogues show that the m‐ and p‐ isomers undergo intermolecular trans‐O‐alkylation before evaporation. In the o‐isomer, only 10% transalkylated product is observed and there is strong evidence that most of this isomer evaporates without undergoing structural changes. By indirect introduction, however, the o‐isomer showed only transalkylated product.

The most important fragmentation patterns on electron‐impact are α‐cleavage on the N‐methyl carbon or expulsion of the O‐substituent with formation of a quinoid structure. The latter dominates for the o‐ and p‐methyl ethers while the former is the most important pathway for the m‐isomer and for the corresponding phenols. Lower fragments are of modest intensity.
The electron‐impact‐induced fragmentation of some alkyl isocyanides and α‐branched alkyl cyanides
Authors: Heerma W. , De Ridder J. J.
Published: May 2005

The 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

The 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 indolizines
Authors: Jones Gurnos , Stanyer J.
Published: May 2005

The mass spectra of indolizine, the seven monomethylindolizines, the six 2,x‐di‐methylindolizines and a number of related simple indolizines are reported; the breakdown patterns are compared with those of the corresponding indoles.
The mass spectra of some 3,5‐diarylisoxazoles
Authors: Nonhebel D. C.
Published: May 2005

The 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

The 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

Characteristic 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

Specific 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

In 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

Studies 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

Two 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

The 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

The 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

The 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

The 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

Examination 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

The 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

Analysing 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

A 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

The 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

The 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

Negative 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

The 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

The 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

Dans 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

The 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

The 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

The 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

The 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

Le 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

High‐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

Elimination 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

A 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

The 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

The 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

Nous 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.
Fragmentation and rearrangement processes in the mass spectra of perhalogenoaromatic compounds—VI. Perfluoroaromatic heterocyclic derivatives of sulfur, selenium and tellurium
Authors: Cohen S. C. , Massey A. G. , Lanthier G. F. , Miller J. M.
Published: May 2005

The mass spectra of the compounds C12F8M2 (M = S, Se), (I), C12F8M (M = S, Se, Te), (II) and C12F8SX2 (X = Br, I), (III), have been measured. Results indicate that sulfur‐carbon bonds are more stable under electron bombardment than either selenium‐carbon or tellurium‐carbon bonds. Numerous metastable‐supported transitions are evident, which are incorporated into comprehensive fragmentation schemes for these compounds. Many metastable transitions, not previously reported, were observed for the fluorocarbon fragments and a fragmentation scheme is reported.

The bromine and iodine‐containing compounds behave remarkably like the heterocyclic systems, I and II, presumably due to initial loss of Br2 or I2 to form a ring system of type II.
The extent of electron‐impact‐induced ring contraction in the formation of [M − CH3] fragments from N‐acetylpiperidine
Authors: Richter W. J. , Liehr J. G. , Burlingame A. L.
Published: May 2005

In N‐acetylpiperidine, α‐carbon atoms (C‐2 or C‐6) of the ring have been recently identified as a source of loss of CH3 radicals from the molecular ion in addition to β‐carbon atoms (C‐3 or C‐5) and the acyl substituent (C‐8). Skeletal rearrangement by ring contraction to a five‐membered cyclic intermediate was invoked to be responsible for the expulsion of C‐2 or C‐6. Deuterium labelling suggested major and approximately equal contributions from the two losses of ring atoms as compared to an only minor contribution from loss of C‐8. 13C‐labelling of the latter now establishes the correctness of this inference, demonstrating that only 17% of the total loss of methyl arise from this position. Together with results of previous deuterium labelling this figure indicates that ring contraction contributes to the formation of [M − CH3] fragments to an extent of approximately 40%.
The mass spectra of some phenyl pyridyl ketones
Authors: Brown Ellis V. , Shambhu M. B.
Published: May 2005

The mass spectra of phenyl 2‐pyridyl, phenyl 3‐methoxy‐2‐pyridyl, phenyl 4‐methoxy‐2‐pyridyl, phenyl 5‐methoxy‐2‐pyridyl, phenyl 6‐methoxy‐2‐pyridyl ketones, phenyl 3‐pyridyl and phenyl 6‐methoxy‐3‐pyridyl ketones, and phenyl 4‐pyridyl ketone were studied. The major fragmentation pathway of all the ketones results in the formation of[C6H5CO]+ and [C5H4NCO]+ type ions. Another fragmentation path is the loss of carbon monoxide with formation of an [M  CO]+ ion after skeletal rearrangement.
Effets Isotopiques dans la Fragmentation par Impact Électronique de Méthanols Deutériés
Authors: Corval M. , Masclet P.
Published: May 2005

Les spectres de masse des méthanols CH3OH, CH2DOH, CHD2OH, CD3OH, CH3OD et CD3OD ont été enregistrés pour des énergies nominales des électrons allant de 11 à 35 eV. Les courbes qui représentent la variation, en fonction de l'negie des électrons, des effets d'isotopie relatifs à la stabilité des ions moléculaires et aux probabilités de coupure des liaisons sont comparées à celles déerminées par un calcul a priori. En adoptant une fonction simple de distribution de l'énergie d'excitation et un nombre d'oscillateurs moitié du nombre thérique, l'accord obtenu est dans l'ensemble satisfaisant, sauf en ce qui concerne la stabilité des ions moléculaires, pour laquelle la forme des courbes pourrait s'interpréter par l'intervention d'un état électronique de l'ion moléculaire autre que l'éat fondamental.
Mass spectrometry of 2‐arylaziridin‐2‐ylphosphonates
Authors: Nishiwaki Tarozaemon
Published: May 2005

The mass spectral fragmentations of 2‐arylaziridin‐2‐ylphosphonates having a carbonyl function at C(3) were studied. Cleavage of either a carbonyl group or PO(OR)2 from the molecular ion is the primary pathway.
Mass spectrometric characterization of pGlu‐peptides related to the thyrotropin releasing hormone
Authors: Bogentoft Conny , Chang Jaw‐Kang , Sievertsson Hans , Currie Bruce , Folkers Karl
Published: May 2005

Twelve synthetic di‐ and tripeptides which are related to the thyrotropin releasing hormone (TRH) have been subjected to electron‐impact without conversion to more volatile derivatives as background for structural elucidation of unknown peptides isolated on a microgram basis.
The doubly‐charged ion mass spectra of hydrocarbons
Authors: Ast T. , Beynon J. H. , Cooks R. G.
Published: May 2005

The doubly‐charged ion mass spectra of some hydrocarbons, including a variety of structural types, have been obtained by a new technique in which doubly‐charged ions are charge exchanged with neutral molecules and so separated from singly‐charged ions. The spectra show strong similarities, independent of hydrocarbon structure; characteristic ions include [CmH2]++ (m = 2 to 5), [CnH6]++(n > 6), [C10H8]++, [C12H8]++, [C11H10]++, [C7H7]++·, [C9H7]++· and [C13H11]++·. The fragmentation pattern of 2‐phenylnaphthalene has been reconstructed, based on observed reactions of metastable doubly‐charged ions to give fragment doubly‐charged ions. In addition, we examined metastable ion fragmentations leading to two singly‐charged ions for some of the characteristic ions, using several compounds. The value of doubly‐charged ion mass spectra of hydrocarbons appears to lie in the information they provide on ion structures; this information was sufficient to permit the proposal of structures for the major ions encountered in this study.
Comparative studies of electron‐impact (EI) and field ionization (FI) mass spectra of pentaerythritol derivatives
Authors: Tou James C.
Published: May 2005

The EI Mass spectra of the polyfunctional pentaerythritol derivatives show that the molecular ions [M]+· exhibit extensive ion fragmentation. No Information about [M]+·. can be obtained. In Contrast to this, the FI Mass spectra of these compounds show intense [M]+· and/or [M + 1]+, and a characteristic ion at m/e 31, which is assumed to be the oxonium ion \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_2 = \mathop {\rm O}\limits^ + {\rm H} $\end{document}. Because of surface adsorption and field attraction, FI mass spectrometry presents a serious problem in quantitative analysis of a mixture containing compounds with quite different degrees of polarization.
Valence‐change in the mass spectra of metal complexes
Authors: Lacey M. J. , Shannon J. S.
Published: May 2005

A review article is presented relating to the concept of valence‐change in the mass spectra of metal‐containing compounds. It is found that the modes of ion dissociation in these spectra are markedly dependent on the oxidation states normally assumed by the metal concerned and it is postulated that electron‐transfer may be possible between the complexed metal atom and its ligands in the ion, such that the odd‐ or even‐electron character of the ion is inter‐changeable. Ion reactions such as the consecutive loss of two radicals are normally of low probability in the mass spectra of organic compounds, but are often observed in the mass spectra of metal‐containing compounds and can be rationalized in terms of the valence‐change concept. Convincing evidence for valence‐change in some spectra is provided by the occurrence of reactions leading to the bare metal ion, or to the loss of neutral fragments containing the metal atom in a lower oxidation state than in the precursor molecule. Further applications of the concept may be found in the rationalization of the mass spectra of inorganic and organometallic compounds.
The mass spectra of the trimethylsilyl ethers of some hydroxylated di‐ and tetracarboxylic porphyrins
Authors: Chapman J. R. , Elder G. H.
Published: May 2005

The preparation and the mass spectra of the trimethylsilyl ethers of six hydroxyporphyrins are reported. In every case the side chain bearing the ether grouping is the most labile on electron‐impact and exhibits characteristic ‘benzylic’ cleavage. The presence of a metastable peak allows a definite identification of this cleavage to be made.
Electron‐impact induced fragmentation of dimethanonaphthalene‐type compounds
Authors: Malojčić R. , Stefanović D.
Published: May 2005

The mass spectra of endo,endo‐1,2,3,4,4a,5,8,8a‐octahydro‐1,4:5,8‐dimethanonaphthalen‐anti‐2‐01 (Ia) and its endo,exo‐2‐ol (IIa) and endo,exo‐10‐ol (IIIa) isomers have been examined. Fragmentation schemes have been constructed on the basis of metastable transition measurements, accurate mass determination and deuterium substitution. A presence of the double bond in the molecule and a favourable hydrogen atom orientation in the vicinity of the double bond play an important role in the ion degradation process.
Mass spectrometry of some butyrophenones
Authors: Frigerio A. , Rovere C.
Published: May 2005

The fragmentation patterns by electron‐impact of five butyrophenones (neuroleptic drugs) are presented and discussed, with particular emphasis being placed on the anomalous behaviour of azaperone.
Mass spectra of some azoles
Authors: Cotter J. L.
Published: May 2005

The principal electron‐impact fragmentation patterns of 3,4,5‐triphenyl‐1,2,4‐triazole, 2,5‐diphenyl‐1,3,4‐thiadiazole, their perfluorinated analogues and 2,5‐di(pentafluorophenyl)‐1,3,4‐oxadiazole have been established from metastable ion evidence and precise mass measurements. Although ions produced by expulsion of nitrogen from the molecular‐ions of these compounds are of low abundance, the simultaneous expulsion of nitrogen and a C7X5 radical (X = H or F) gives rise to abundant ions.
The mass spectra of five diacetyl[3]ferrocenophanes
Authors: Carroll Sammy R. , Pflug J. Lloyd , Winstead Jack A.
Published: May 2005

A mass spectrometric study of five diacetyl[3]ferrocenophanes has been made. The molecular ion was the base peak in these five compounds. Fragment ions with relative intensities greater than 10 percent occurred only in those compounds having an acetyl group in the alpha position to the trimethylene bridge.
Mass spectra of phosphoramidic acid esters
Authors: Jakobsen P. , Treppendahl S. , Wieczorkowski J.
Published: May 2005

The mass spectra of diphenyl, dibenzyl and six dialkyl phosphoramidates have been recorded and interpreted with the aid of high resolution measurements and the metastable defocusing technique.
On the nature of the transition state leading to elimination of ketene from acetanilide
Authors: Hammerum Steen , Tomer Kenneth B.
Published: May 2005

Examination of metastable peak abundance ratios for the elimination of HNC vs. DNC from the [M‐ketene]+· ion of various deuterium‐labeled acetanilides shows that the structure of this ion resembles aniline rather than cyclohexadieneimine. This is suggested to hold also for substituted acetanilides.
On the positional interchange of the phenyl‐ and hydroxyl groups in the [C9H11O]+‐ion, generated from 2‐methyl‐2‐phenylpropane‐1,3‐diol (C10H14O2) upon electron‐impact
Authors: Kerkhoff M. A. Th. , Nibbering N. M. M.
Published: May 2005

It is shown by deuterium‐labelling experiments, that a substantial part of the [M – CH2OH]+‐ions from 2‐methyl‐2‐phenyl‐propane‐1,3‐diol must have rearranged to carbonyl‐oxygen protonated phenylacetone by a positional interchange of the phenyl‐ and hydroxyl groups prior to decomposition.
Kinetic energy release in ionic fragmentations: Use as an ion structure probe
Authors: Jones E. G. , Bauman L. E. , Beynon J. H. , Cooks R. G.
Published: May 2005

The kinetic energy released in unimolecular reactions, as measured from the width of the corresponding metastable peak, shows only a small dependence on such parameters as source temperature, ion‐source residence time and ion acceleration voltage. Similarly, fragmenting ions generated from different members of an homologous series of molecular ions have been found to release the same kinetic energy and hence do not exhibit a degrees‐of‐freedom effect analogous to that for metastable abundances. In general, molecular ions formed by electron‐impact have been found to release slightly less kinetic energy on fragmentation than the corresponding ions formed via a fragmentation sequence. These observations suggest that kinetic energy release is a useful method of structural characterization of metastable ions; while increase in the average internal energies of the ions sample lead to larger energy releases, this effect is usually small. The use of a very narrow energy resolving (β) slit and a procedure in which the metastable peak width is extrapolated to zero slit width has been found to improve the accuracy of measurement of the kinetic energy release, particularly when the metastable and main beam peak widths are of comparable magnitude.
Spectres de masse des anomeres pyranniques et furanniques de la thymidine, de leurs acetates et des bromohydrines correspondantes
Authors: Ulrich J. , Cadet J. , Teoule R
Published: May 2005

L'étude du spectre de masse des anomères pyranniques et furanniques de la thymidine, de leurs acétates et des bromohyrines correspondantes apporte des informations, intéressantes pour l'analyse de al configuration anomérique de ce type de composés, décisives pour la dimension de l'hétérocycle oxygéné.

La stabilité des ions molécularies va de pair avec la stabilité chimique de ces molécules: les ions moléculaires des formes β sont plus ceux des formes α. L'instabilité des ions moléculaires des bromohydrines est telle qu'ils ne sont détectables que pour la forme β furannique.

L'elimination du radical CH2OH ou CH2OAc est caractéristique de la forme furannique. L'élimination de CH2O dans la forme β furannique est due à la proximité stérique de la base et de l'hydroxyle en 5′ du sucre. Les ions de rearrangement [BH  CHCH2]+ et dérivés proviennent d'und rupture du sucre favorisée dans la forme furannique.

Après cassure de la liaison glycosidique, les ions [B + H]+˙ et [B + 2H]+ formés sur la base, et [S]+ sont sensibles à la stéréochimie de la molécule. L'´elimination d'une molécule d'eau (ou d'acide ac´etique) est mormalement plus facile dans un cycle à 6 chaînons (pyrannique).

L'élimination simultance de 2 molécules d'eau ou d'acide acétique, prépondérante dans la forme furannique, nous a conduit à conduit à admettre und rupture du cycle pour former un ion à sttructure aliphatique conjuguée; la forme pyrannique donne un ion cyclique aromatique, en 2 étapes.
Mass spectrometry of onium compounds—XVII: Anilinium carboxylates. orthoeffect in anthranilic acid derivatives
Authors: Hvistendahl Georg , Undheim Kjell
Published: May 2005

The N,N,N‐trimethylanilinium carboxylates are transmethylated to the isomeric esters before evaporation in the mass spectrometer. Pyroltic reactions and electron‐impact fragmentations are elucidated by means of deuterio analogues. The orthoisomer behaves anomalously in that initial expulsion of a methyl radical is important. Deuteration has shown this reaction to take place along two distinct routes, either from the nitrogen or from the ester.
Mass spectrometry of onium compounds‐XVIII: Evaporation of N‐arylpyridinium‐3‐oxides
Authors: Undheim Kjell , Hansen Per Egil
Published: May 2005

Comparision of the fragmentation patterns and ionisation potentials for 3‐hydroxy‐2‐phenylpyridine and N‐arylpyridinium‐3‐oxides shows that the latter are evaporated as mesoins. The 2,4‐dinitrophenyl derivative constitutes an exception in that transarylation to the corresponding ether takes place before evaporation.
Metastable ion studies of various C3H6 radical cations
Authors: Gross Michael L. , Lin Ping‐Huang
Published: May 2005

Metastable abundance ratios have been measured involving four decomposition reactions of C3H6 radical cations formed from a variety of precursors. The ratios are quite similar in accord with extensive isomerization to a propene structure prior to fragmentation. Small, yet constant differences are observed for those C3H6 ions which have been shown to be formed as cyclic ions by ion cyclotron resonance studies. The differences are interpreted to reflect internal energy variations, which result because the initially formed ions have two different structures. The abundance ratios are shown to depend on ionizing energy, repeller voltage and accelerating voltage, but are independent of the degrees‐of‐freedom in the precursor as well as the number of steps necessary to produce the [C3H6]+· Despite small variations in metastable ratios, the classification of various [C3H6]+· ions can be achieved under a variety of conditions which affect the internal energy of the decomposing ions.
Schiff base derivatives of peptide esters: Relative abundance of N‐terminal, C‐terminal and ‘internal’ fragments as a function of the blocking group
Authors: Patil Gunvant V. , Hamilton Robert E. , Day Richard A.
Published: May 2005

Electron‐impact (EI) mass spectrometry of peptide derivatives is usually interpreted in terms of fragmentation where the charge resides on the N‐terminal fragments and to a lesser degree on the less common, charged C‐terminal fragments. Substituted and unsubstituted benzylidene, cinnamylidene, α‐ and β‐naphthylidene derivatives of a reference tripeptide, valileala, gave both N‐ and C‐terminal fragments as well as molecular ions. The order of increasing ion current (normalized) in C‐terminal fragments was: acetylacetonyl, 4‐dimethylaminonaphthylidene, p‐dimethyl‐aminobenzylidene, 3‐pyridylmethylidene, p‐diethylaminocinnamylidene, benzylidene, 2‐hydroxy‐naphthylidene, 4‐pyridylmethylidene, p‐nitrobenzylidene, p‐methoxybenzylidene, p‐cyanobenzylidene, cinnamylidene, p‐dimethylaminocinnamylidene, β‐indolylmethylidene, β‐naphthylidene, 2‐pyridylmethylidene and α‐naphthylidene. The order for this value among the N‐terminal fragments is significantly different, however (Day, Falter, Lehman and Hamilton, J. Org. Chem. in press). In addition to N‐ and C‐terminal fragments, many spectra contain internal fragments, arising from loss of fragments from both ends, which provide sequence information. These fragments are found in the mass spectra of Schiff bases formed from various aromatic aldehydes with peptide esters. The interpretation of the latter pattern is facilitate in some cases by deuterium labeling at the α‐carbon of the N‐terminal amino acid residue of peptides. Such a pattern provides sequence information supplemental to that available involving N‐ and C‐terminal fragmentations. In derivatives of hexaglycine, tetraphenylalanine and tryptophylmethionylaspartyl (β‐OEt) phenylalanine amide, for example, substantial sequence information was contained in the internal fragments; in some cases the sequence could be deduced only if the internal fragments were utilized. The 4‐dimethylamino‐naphthylidene derivatives have proven to be the most useful to date in terms of volatility, tendency to maximize cleavage into N‐terminal fragments, intensity of molecular ions and generation of useful mass spectra of certain peptide esters refractory to mass spectrometry in the form of any other derivative investigated.
Die Massenspektren der Nikotin‐N‐Oxide und der mit Ihnen Verwandten Tetrahydrooxazine
Authors: Schüller D. , Harke H.‐P.
Published: May 2005

Die massenspektren der drei Nikotin‐N‐oxide werden zusammen mit den Spektren von Tetrahydrooxazinen diskutiert. Die Verbindungen mit N‐Oxide‐Ffunktion im 5‐gliedrigen Ring lagern sich vor der Fragmentierung durch Elektronenstoß z.T. thermisch um.
Massenspeaktrometrische Untersuchungen zur Ketenabspaltung aus Zimtalkohol
Authors: Schwarz Helmut , Köppel Claus , Bohlmann Ferdinand
Published: May 2005

Die Ketenabspaltung aus dem Molekül‐Ion des Zimtalkohols kann nicht beschrieben werden durch den Mechanismus, der beim isomeren Dihydrozimtaldehyd die Bildung von C2H2O zeigt. Auch die elektronenstossinduzierte Isomerisierung von Allylakoholen zu Ketonen liefert keine plausiblen Erklärungen f¨︁r die experimentell bestimmte 2H‐Anteile im Ion [C7H8]+˙. Es wird gezeigt, dass bevorzugt, aber nicht ausschliesslich, die Wasserstoffe der Seitenkettten‐C‐Atome (1) und (2) an der Bildung des Neutralteiles teilnehmen.
Mass spectrometry of tropylium halides
Authors: Hvistendahl Georg , Undheim Kjell , Gyöösi Peter
Published: May 2005

The base peak and highest mass number in the spectra of tropylium iodide and bromide corresponds to the mass of the cation. Both appearance potential (AP) measurements and the fragmentation pattern strongly indicate that the gaseous species present is the tropylium radical. Rediction to the corresponding volatile free radical thus takes place prior to evaporation.
Single and double hydrogen rearrangements in the mass spectra of O‐ethyl, S‐alkyl methanephosphonothioates
Authors: Tashma Zeev , Katzhenler Jeoshua , Deutsch Joseph
Published: May 2005

Whereas the oxygen analogues of the title series gives rise to double hydrogen rearrangement on electron‐impact, alkylthiophosphonates show in addition a McLafferty rearrangement. The quantitative relationship between these two rearrangements in the thio series is dependent upon the chain length and branching on the alkyl group attached to sulphur. Comparison of the mass spectra of these compounds indicates that in the pathway of the double hydrogen rearrangement the hydrogen transferred to the sulphur atom originates primarily from the carbon δ to sulphur.
Permethylation of barbiturates. Separation and characterization of the reaction products by gas chromatography‐mass spectrometry
Authors: Thompson R. M. , Desiderio D. M.
Published: May 2005

A Series of barbiturates (I) has been permethylated with the methylsulfinylmethide carbanion and methyl iodide and the products (II to IV) separated, quantified and characterized by g.c.‐m.s. The ratios and fragmentation patterns of II to IV are highly dependent upon the nature of the R‐groups. All fragment ions have been confirmed by accurate mass measurements or perdeuteriomethylation.
Scrambling in ethane molecular ion: An INDO model for hydrogen exchange before mass spectral fragmentation
Authors: Parker Carol E. , Bursey Maurice M. , Pedersen Lee G.
Published: May 2005

INDO calculations for previously proposed activated complexes for scrambling in ethane molecular ion suggest that the structure equivalent to diborane is more stable than one in which hydrogens on the same side of the molecule exchange positions.