bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of charge‐exchange collision gas on ‘resolved’ E/2 mass spectra
Authors: Jonathan P. , Brenton A. G. , Beynon J. H.
Published: May 2005

A survey of the mass spectroscopic technique producing resolved E/2 mass spectra is undertaken, primarily to determine its dependence on the charge‐exchange collision gas used. The applicability of the resultant spectra to ion structure studies is discussed. Instrumental effects, influencing the spectral pattern, are explained and will aid those utilizing this technique for ion structure determination.
Mass spectra of some 1‐substituted‐4‐acetoacetyl‐3‐methylpyrazol‐5‐ols
Authors: Singh S. P. , Vaid R. K. , Dinakar P. , Singh Lukhvinder
Published: May 2005

The fragmentation of 1‐phenyl‐, l‐(2′‐pyridyl)‐ and 1‐(4′‐methyl‐2′‐quinolyl)‐4‐acetoacetyI‐3‐methyIpyrazol‐5‐ols (compounds 1, 2 and 3, respectively) on electron impact has been studied and the major processes interpreted. The common feature in the mass spectra of these compounds is the loss of ketene, acetonyl radical, acetone and two molecules of ketene from the molecular ion. Whereas the ion generated after the last process, which corresponds to 1‐substituted‐3‐methyIpyrazol‐5‐ols, loses methyl cyanide in the case of 1, similar ions in the case of 2 and 3 lose Ċ2HO moiety, necessitating an intramolecular hydrogen transfer followed by ring fission and subsequent loss of methyl cyanide. All these and other related processes have been substantiated with the help of accurate mass measurements of the fragment ions and B/E linked‐scan spectra.
Electron ionization and chemical ionization fragmentation of o/p isomers of bisphenol‐A with tandem mass spectrometry
Authors: Peltonen Kimmo , Kostiainen Risto
Published: May 2005

The fragmentation of o/p isomers of bisphenol‐A was examined by using collisionally activated decomposition and the tanden mass spectrometric techniques. Also chemical ionization was performed using methane, isobutane and ammonia. The o/p position of the hydroxy groups in the bisphenol‐A molecule directed the fragmentation both in electron and chemical ionization.
Ion–molecule reactions of fragment ions derived from protonated allyl methyl ether
Authors: Maquestian André , Beugnies Didier , Flammang Robert , Houriet Raymond , Rolli Eric , Bouchoux Guy
Published: May 2005

Unusual behaviour has been noted for allyl methyl ether (1) chemically ionized in a high‐pressure ion source. Tandem mass spectrometry indicates the formation of methylcyclopentadienyl and methoxy‐1‐propenylcarbenium ions (d, m/z 81 and e, m/z 85). The origin of these unexpected ions has been elucidated using conventional and Fourier transform ion cyclotron resonance experiments: primary fragment ions derived from protonated 1 (allyl ions a and methoxymethyl cations b) generate collision complexes with neutral 1, giving rise to the ions d and e, respectively, after methanol elimination.
Mass spectrometry in environmental organic analysis
Authors: Levsen K.
Published: May 2005

The use of mass spectrometry in environmental organic analysis is reviewed, with special emphasis on modern mass spectrometric methods.
Translational energy release and stereochemistry of steroids. IX‐The mechanism of the elimination of water from metastable ions in epimeric 3‐hydroxy steroids of the 5β‐series
Authors: Zaretskii Z. V. I. , Curtis J. M. , Brenton A. G. , Beynon J. H. , Djerassi Carl
Published: May 2005

The mechanism of water elimination from metastable molecular and [M − CH3˙]+ ions, as well as from ions deprived of ring D, in epimeric 3‐hydroxy steroids of the 5β‐series has been elucidated by deuterium labelling, by the measurements of the translational energy released during loss of water, and by collision‐induced decomposition mass‐analysed ion kinetic energy spectrometry. It was found that the dehydration of the metastable molecular ion in 3α‐hydroxy steroids of the 5β‐series occurs mostly regiospecifically as an elimination of the 3α‐hydroxyl together with the 9α‐hydrogen atom. The ring A in the molecular ion has to flip to the boat conformation to make this reaction possible. In the metastable molecular ion of 3β‐hydroxy steroids of the 5β‐series a different dehydration mechanism operates, with very little participation of the 9α‐hydrogen atom. The mechanisms of water loss from metastable [M − CH3˙]+ ions and from ions deprived of ring D differ from that of the molecular ion.
Pre‐ionization effects in the mass spectrometry of some azoxybenzenes
Authors: Waddell D. S. , Bunce N. J. , Boyd R. K.
Published: May 2005

The mass spectrometry of azoxybenzene, and of several of its substituted variants, has been investigated under both electron ionization (EI) and chemical ionization (CI) conditions. The EI spectra largely confirm earlier mechanistic conclusions of Bowie et al. (J. Chem. Soc. B, 621 (1967)), but extend this work to consideration of the mechanism of formation of the [M − O]+˙ ion. This unexpected ion has been shown, using techniques of tandem mass spectrometry, to arise from pre‐ionization reduction to the corresponding azobenzene probably at the ion source surfaces. These pre‐ionization effects cause the observed spectra to vary markedly with the conditions, including partial pressure of the sample, within the EI source. Under CI conditions (both methane and isobutane reagent gases) the pre‐ionization reduction process is even more marked, and can involve reductive cleavage to the appropriate substituted anilines. Addition of water vapour favours the latter process over formation of [M − O + H]+. Analogous processes have been reported previously for nitroaromatics, suggesting that mass spectra of aromatic compounds substituted with oxygenated nitrogen atoms may all prove to be susceptible to similar effects.
Electron impact mass spectrometry of some naphthoxypolymethylenethiopyrimidines
Authors: Stobiecki Maciej
Published: May 2005

The electron impact induced fragmentation of a large number of 2‐ and 4‐S‐(2‐naphthoxy)‐polymethyienethiouracils is discussed in detail, with the aid of exact mass measurements and observation of metastable decompositions. The 2‐ and 4‐thiopyrimidine structures can be easily distinguished by their mass spectra.
A fuzzy classification for identification of double bond position in dodecadienic compounds based on mass spectral data
Authors: Gu Yuan
Published: May 2005

A fuzzy classification and a computer pattern recognition program are presented for identifying double bond positional isomers of dodecadienic compounds by comprehensively analysing the mass spectra and calculating similarity coefficients of the compounds. Fifty‐four examples showed that this is an excellent classification method.
The [CH2 = CHOH/H2O]+˙ system: A theoretical study of distonic ions, hydrogen‐bridged ions and ion–dipole complexes
Authors: Postma R. , Van Helden S. P. , Van Lenthe J. H. , Ruttink P. J. A. , Terlouw J. K. , Holmes J. L.
Published: May 2005

Several isomeric forms of the vinyl alcohol/water radical cation have been investigated by high‐level ab initio molecular orbital theory calculations, including electron correlation effects. Of the ions considered here, the anti form of the O ⃛H ⃛O bridged complex is calculated to be the lowest in energy, having a stabilization energy of 100 kJ mol−1 with respect to the dissociation products [CH2CHOH]+˙ and H2O. Although the isomeric ions may formally be represented as distonic ions, hydrogen‐bridged ions and ion–dipole complexes, the only significant barrier separating the isomers appears to be the anti↔syn isomerization barrier. However, in the O ⃛H ⃛O bridged complex this barrier is found to be considerably lowered relative to the anti↔syn isomerization barrier for the free vinyl alcohol radical cation.
Gas‐phase ion–molecule reactions of thioic and dithioic acid derivatives. Condensation reactions with alkenes and alkynes
Authors: Paradisi Cristina , Kenttämaa Hilkka , Le Quang T. , Caserio Marjorie C.
Published: May 2005

A Fourier transform–ion cyclotron resonance study of thioacyl compounds as binary mixtures with unsaturated hydrocarbons has revealed that thioacetylium ions CH3CS+ generated by electron fragmentation fail to thioacyl‐ate even the most reactive aromatic hydrocarbons. Among the hydrocarbons studied, only 3‐hexyne and 2,4‐dimethyl‐2,5‐hexadiene were observed to react with CH3CS+. Apart from proton‐transfer reactions, the major ionic reaction of thioesters with arenes, alkynes and alkenes is condensation of the molecular ion of one component, usually the ester, with a neutral molecule of the other, resulting in the cleavage of the SCalkyl bond of the thioester. The nature of this reaction is discussed and a possible mechanism is suggested.
Awareness in mass speetrometry: An evaluation of services for retrieving and abstracting mass spectrometric literature
Authors: Lowes Stephen , Rose Malcolm E.
Published: May 2005

The commercially available methods for keeping mass spectrometrists aware of a vast literature are assessed. CA Selects: Mass Speetrometry was found convenient for browsing of current literature but disappointing in its coverage. The lack of an index makes it impracticable for retrospective searching. On the other hand, the Mass Speetrometry Bulletin contains over three times more references, is sectionalized for casual browsing, and its individual issue and annual indices make it very suitable for current and retrospective searching of specific topics. Chemical Abstracts itself contains many more mass spectrometric references than its CA Selects: Mass Speetrometry derivative but that information is difficult to extract comprehensively using the volume indices provided. Both Mass Speetrometry Bulletin and Chemical Abstracts can be accessed by on‐line systems. Use of computer searches proved to be excellent for current awareness and retrospective searching of selected topics within mass spectrometry. The mass spectrometrist can readily generate a tailor‐made set of terms to extract just the information of personal interest from Mass Speetrometry Bulletin and/or Chemical Abstracts. A detailed search requires use of both databases. On‐line searching provided faster and more comprehensive extraction of information than manual searching. On‐line systems would, however, be too expensive for browsing in general mass Speetrometry. Some problems and improvements in the various services are described and the role of some publications reviewing mass Speetrometry is briefly discussed.
Triazolopyridine, a new derivative for the structural determination of fatty acids by gas chromatography/mass spectrometry
Authors: Vetter Walter , Meister Walter , Oesterhelt Gottfried
Published: May 2005

Triazolopyridine is proposed as a new derivative for the location of branches and double bonds in fatty acids. It is compared with previously used derivatives and found to be clearly superior to the pyrrolidide and slightly superior to the β‐picolinyl ester with regard to the structure‐specific fragmentation pattern. It is prepared by reacting the activated acid with 2‐hydrazinopyridine followed by cyclization.
Electron impact mass spectra of isobenzofurans, isonaphthofurans and some of their Diels–Alder adducts
Authors: Dibble Peter W. , Rodrigo Russell
Published: May 2005

The mass spectra of a wide variety of substituted isobenzofurans (IBF) have been studied by the direct examination of stable IBFs and IBF ions formed in the retro‐Diels–Alder cleavage of oxabicyclo adducts. In general, the fragmentation patterns observed are very dependent upon the nature and position of substitution. The dimethyl acetylenedkarboxylate adducts also show additional interesting and novel fragmentation pathways that are not IBF related.
A mass spectrometric study of halogenated beryllium μ4‐oxohexa‐μ‐acetates
Authors: Sipachev Viktor A. , Nekrasov Yurii S.
Published: May 2005

The electron impact mass spectra of Be4O(CHal3CO2)6 (Hal = F, Cl) are reported. The compounds give two series of fragment ions, [Be4OLx]+ and [Be4OL+]+, where L is an intact ligand or its fragmentation product. The major ligand dissociation path is the elimination of CHal2CO2 with halogen transfer to the metal. Other processes of importance are the loss of acid anhydride fragments, CF2 with fluorine shift to the carboxyl group carbon atom, and halogens. Trinuclear ions also undergo decarboxylation, e.g. to give [Be2O(CHal3CO2)2(CHal3)]+. Both spectra contain comparatively intense peaks of double‐charged ions. The fragmentation patterns are rationalized by stereochemical considerations.
A mass spectral study of the acid‐catalysed oxygen exchange in laevulinic acid
Authors: Srzić D. , Horvat J. , Šunjić V. , Kralj B.
Published: May 2005

The sequence, i.e. site selectivity of the acid‐catalysed 16O/18O exchange in laevulinic acid (1) is studied by mass spectrometry, ion kinetic energy spectroscopy and accurate mass measurements on 1 and its 13C(1)‐labelled congener. In the fragmentation pathways all ions of interest in the spectrum of 1 originate from the molecular ion, which may exist in six tautomeric or isomeric forms (1a–1d). The mechanism of gas‐phase cyclization of 1a is rationalized in terms of three different pathways. Formation of the most prominent fragment ions and the sequence of 16O/18O exchange at the carbonyl and carboxy group are discussed. The results indicate the ions of m/z 56, m/z 61 and m/z 98 to be the only three which have incorporated oxygen atoms originating from the carboxy group in 1 and could thus be used in further elucidadon of the rearrangement mechanism of 5‐hydroxymethylfuran (2) or 5‐hydroxymethylfuran‐2‐carbaldehyde (3) into laevulinic acid (1).
The effects of emitter heating on field ionization mass spectra of nitrogen‐containing organic molecules
Authors: Nelson P. R. , Abbey L. E. , Moran T. F.
Published: May 2005

Field ionization mass spectra of nitrogen‐containing organic compounds were examined as a function of carbon dendrite emitter heating current. The intensities of singly charged molecular, quasimolecular and dimer ions decreased with increasing emitter heating current; whereas, the opposite trend was observed for singly charged fragment ions. The abundance of doubly charged ions originating from aromatic compounds increased with heating current.
Comparison of [C6H6]2+ ion structures: Application of electron capture induced decomposition to the study of isomers
Authors: Vékey Kàroly , Gareth Brenton A. , Beynon John H.
Published: May 2005

Structures of [C6H6]2+ ions formed by electron impact from benzene, 2,4‐hexadiyne and 1,5‐hexadiyne have been investigated by the recently developed electron capture induced decomposition method, by charge‐separation reactions and by ion abundances in electron impact mass spectra. Significant differences were found among the isomers indicating the structural integrity of these [C6H6]2+ ions. The observed differences indicate that the most likely atomic configuration of [C6H6]2+ ions produced from benzene and 2,4‐hexadiyne is the same as in the corresponding neutral species. A new method is suggested by which the structure (atomic configuration) of doubly charged ions may be determined.
Ortho effects in organic molecules on electron impact. Part 16. Novel oxygen transfers from the nitro group to acetylenic carbons in 2‐nitrodiphenylacetylenes
Authors: Ramana D. V. , Krishna N. V. S. Rama
Published: May 2005

Oxygen transfers to both acetylene carbons are noticed in parallel fragmentation pathways during the electron impact induced decompositions of 2‐nitrodiphenylacetylene. The oxygen transfer to β‐acetylenic carbon leads to the most abundant ion corresponding to benzoyl cation while transfer to the α‐acetylenic carbon affords less intense fragments corresponding to [MOH]+, [MCO]+ ˙ and [MCO2]+ ˙. The proposed fragmentation pathways and ion structures are supported by high‐resolution data, linked‐scan spectra and chemical substitution.
Electron impact fragmentation of some cyclohexyl thiophosphororganic amides
Authors: Moldovan Zaharie , Palibroda Nicolae , Culea Monica , FeneşAn Ioan , Hantz Andrei
Published: May 2005

This paper presents the mass spectra, fragmentation pathways and structures of ions obtained by electron impact from methyl cyclohexyl phosphinomorpholinylamidothioate (1), cyclohexyl phosphonomorpholinylamidochloridothioate (2), cyclohexyl morpholinylamidophosphonothioic acid (3) and O‐methyl cyclohexyl phosphonomorpholinylamidothioate (4). The fragmentation pathways and ion structures were established by exact mass determinations on compound 1 and by metastable transitions of all the compounds.
Secondary processes in mass spectrometry of alkylmercury halides
Authors: Zagorevskii D. V. , Mikeladze M. Sh. , Nekrasov Yu. S. , Lependina O. L.
Published: May 2005

The sensitivity of the mass spectrometer towards RHgX alkylmercury halides in the electron impact technique was found to decrease in the order X = Cl > Br > I. The intense peaks corresponding to the more heavy halides registered in the mass spectra of RHgX were shown to arise owing to the secondary processes of halogen exchange occurring in the mass spectrometer. The non‐volatile bromine and iodine compounds adsorbed in some form on metallic surfaces of the ionization chamber (so‐called ‘memory effect’) could be the source of heavy halogens. These reactions are hampered in chemical ionization mass spectrometry under the sufficiently high pressure of the reagent gas (NH3).
Calibration in positive and negative ion fast atom bombardment using salt mixtures
Authors: Vékey Károly
Published: May 2005

Two salt mixtures are described far mass calibration in fast atom bombardment: CsI and NaI for positive ion mode, and CsI and CsF for negative ion mode. The mixtures give many more peaks than CsI and therefore better mass accuracy can be obtained both in scanning and in peak‐matching mode. Their use is especially advantageous for computerized data acquisition. The mass range of 23–3500 for positive ion mode, and 19–3000 for negative ion mode, has been tested and gave good results.
Chemical ionization with aggressive gases—a simple glow discharge source for sector field instruments
Authors: Schneider B. , Breuer M. , Hartmann H. , Budzikiewicz H.
Published: May 2005

A simple glow discharge source has been developed for chemical ionization with aggressive gases. Test results with NO as a reagent gas will be reported.
Hydrogen rearrangements in alkyl‐, styryl‐ and alkyl propenyl sulfoxides
Authors: Liu Lilian Kao , Su C. Y. , Li Wen‐Shan
Published: May 2005

The McLafferty‐type rearrangements, which are the most facile fragmentation for the styryl‐ and the alkyl propenyl sulfoxides, have been proven to involve at least a β‐hydrogen by deuterium labelling studies. γ‐Hydrogen also rearranges, yet a cyclopropane instead of an alkene is eliminated. Furthermore, alkyl propenyl sulfoxides undergo hydrogen migration only to the surfinyl oxygen.
Structures and stabilities of [C3H2]+ ˙ and [C3H2]2+ ions
Authors: Wong Ming Wah , Radom Leo
Published: May 2005

Ab initio molecular orbital theory using basis sets up to 6‐311G* *, with electron correlation incorporated via configuration interaction calculations with single and double substitutions, has been used to study the structures and energies of the C3H2 monocation and dication. In agreement with recent experimental observations, we find evidence for stable cyclic and linear isomers of [C3H2]+ ˙. The cyclic structure (, a) represents the global minimum on the [C3H2]+ ˙ potential energy surface. The linear isomer (, b) lies somewhat higher in energy, 53 kJ mol−1 above a. The calculated heat of formation for [HCCCH]+ ˙ (1369 kJ mol−1) is in good agreement with a recent experimental value (1377 kJ mol−1). For the [C3H2]2+ dication, the lowest energy isomer corresponds to the linear [HCCCH]2+ singlet (h). Other singlet and triplet isomers are found not to be competitive in energy. The [HCCCH]2+ dication (h) is calculated to be thermodynamically stable with respect to deprotonation and with respect to CC cleavage into CCH+ + CH+. The predicted stability is consistent with the frequent observation of [C3H2]2+ in mass spectrometric experiments. Comparison of our calculated ionization energies for the process [C3H2]+ ˙ → [C3H2]2+ with the Qmin values derived from charge‐stripping experiments suggests that the ionization is accompanied by a significant change in structure.
Scatter profiling: A potentially useful technique for isomeric ion distinction and stability determination
Authors: Ballantine J. A. , Reid C. J.
Published: May 2005

A method to determine the extent of angular scattering of fragment‐ion products of keV‐collision‐activated decomposition (CAD) reactions and, in particular, the collisional scatter incurred by the parent ions prior to their dissociation, is outlined. Since the half‐widths of the collisional scatter profiles correlate approximately with the mean reaction endothermicities for some ‘test’ reactions, the method may, in principle, be used to estimate the stabilities of isomeric ion structures relative to a common fragmentation threshold level. For single‐proton‐loss CAD reactions of some [H3, C, X]+ ions (X = F, Cl, OH) with either [H3CX]+ or ylidion, [H2CXH]+ structure, collisional scatter is found in each case to be greater for the isomeric ion with the more stable structure. The estimated magnitudes of the mean energy depositions occurring in the keV‐collision‐activation processes are generally much larger than the calculated minimum energy requirements, suggesting that survivable [M  H]+ products can be formed with up to several eV of internal energy.
The cycloaddition of the 1,3‐butadiene radical cation with acrolein and methyl vinyl ketone
Authors: Castle Lyle W. , Gross M. L.
Published: May 2005

The 1,3‐butadiene radical cation reacts with acrolein and methyl vinyl ketone to produce ‘stable’ adducts. The nature of the reaction and the structures of the adducts were investigated by collisional activation decomposition (CAD) combined with tandem mass spectrometry (MS/MS), and also by Fourier transform mass spectrometry. The CAD spectra of gas‐phase adducts were compared with those of suitable model compounds. On that basis, it was determined that the 1,3‐butadiene radical cation undergoes a cycloaddition with these α,β‐unsaturated carbonyl compounds. The butadiene radical cation serves as the ‘ene’, and the acrolein and methyl vinyl ketone react as dienes, forming cycloadducts having 2‐ethenyl‐2,3‐dihydropyran radical cation structures.
Formation of [C18H36]+ ˙ and [C7H7O2]+ in the mass spectrum of n‐octadecyl benzoate
Authors: Meyerson Seymour
Published: May 2005

A series of deuterium‐labeled n‐octadecyl benzoates serves to extend the literature using lower homologues for study of the mass‐spectral reactions characteristic of alkyl esters. The benzoic acid radical cation (a) arises largely via hydrogen migration from C(2), as expected for the conventional mechanism passing through a six‐membered quasicyclic intermediate; the presence of contributions from other processes is simply noted in passing. The octadecene radical cation (b) and protonated benzoic acid (c) arise by paths seemingly closely related to each other but differing from the path dominant for a. The data are rationalized in terms of a reaction sequence passing through two ion‐neutral complex intermediates. The first, (d), consists of octadecyl carbenium ion and benzoyloxy radical; the second, (e), consists of octadecene radical cation and benzoic acid. The ionized partner in d appears to undergo none to several hydride migrations, but most prominently one; that in e may dissociate promptly to yield b or may persist, undergoing multiple hydride migrations to effect essentially complete scrambling of hydrogens, before dissociating to yield c. The argument for this mechanistic sequence to form b and c rests basically on its ability to account plausibly for the experimental data, and literature precedents cited for specific aspects of it furnish additional support. The low critical energies and small kinetic energy releases observed in this work are in accord with the characteristics listed by McAdoo for decompositions mediated by ion‐neutral complexes, and the selection of an octadecyl, as opposed to a smaller alkyl, ester predisposes the molecule to favor such low‐energy processes.
Isomeric characterization via ion neutralization and dissociation. Experimental variables
Authors: McLafferty Fred W. , Wesdemiotis Chrysostomos
Published: May 2005

Major deficiencies of mass spectrometry for characterizing isomeric molecules, and of collisionally activated dissociation for characterizing isomeric ions, can be alleviated by complementary information from new techniques of neutraiization‐reionization (NR) mass spectrometry. Mass data can be obtained from most fragments of the original species, irrespective of their ability to retain the charge; dissociation of fast neutrals prepared from isomeric ions can involve novel reaction pathways and can minimize competing isomerization reactions; isomeric neutrals undergoing similar dissociations can be differentiated by forming them with different internal energies; reionization of the neutral products to negative as well as positive ions can provide increased selectivity; and structural information on the resulting ions can be derived using MS/MS/MS, Dissociation by novel non‐isomerization pathways can also be effected by a second addition (or subtraction) of an electron to produce an unstable ion of opposite charge. Special techniques can yield neutralized products in favorable dissociative states by collisional activation, by using neutralization targets of selected ionization energy, or through Franck‐Condon factors. Optimum excitation of the neutral is important, as this should be high enough to minimize rearrangement, to maximize the differences in the dissociation pathways of isomers, and to minimize the further dissociation of the characteristic primary products of the neutral. NR experiments can, thus, also provide information on the energy surfaces for unimolecular dissociations of neutrals that are difficult to study by conventional techniques. Dissociations of the neutrals can be differentiated from those occurring after reionization by separate collisional activation of the neutrals, by changing the ionization energy of the neutralization agent, or by reionization to ions of opposite charge.
Fragmentation processes of methylbutyl trifluoroacetates studied by tandem quadrupole mass spectrometry and isotope labeling
Authors: Hsu Chang S. , Fǎrcaşiu Dan
Published: May 2005

The fragmentation patterns of 3‐methyl‐2‐butyl trifluoroacetate and 2‐methyl‐2‐butyl trifluoroacetate were investigated by GC/MS/MS, with electron impact and collision‐induced dissociation, on regular and isotope‐labeled (deuterium and 18O) esters. The atoms found in various fragments could be traced back to specific positions in the parent molecules. In this way, molecular rearrangements potentially occurring during the formation of esters by trifluoroacetolysis of 3‐methyl‐2‐butyl p‐toluenesulfonate or trifluoroacetic acid addition to various 2‐methylbutenes could be shown. Rearrangements also occurred during the fragmentation, particularly during the expulsion of the small fragments CO, C2H4 and F2CO. For the decompositions of oxygen‐containing ions these rearrangements were highly specific. By contrast, alkyl cations lead to fragments that are fully scrambled (statistical label distribution). Alkene radical cations ([CnH2n]+ ˙) fragment to daughter ions that are extensively, but less than statistically scrambled. Hydrogen scrambling may also occur in fluoroalkyl cation fragments.
Mass spectrometry of basic aluminum sucrose octasulfate using fast atom bombardment with a saturated tetramethylammonium ion sample matrix
Authors: Baker Randall J.
Published: May 2005

A fast atom bombardment method to produce stable molecular cations of sucrose octasulfate8− is described. The technique centers on ion exchange of the nonvolatile inorganic aluminum hydroxide cations for more volatile organic tetramethylammonium ions.
Ortho effects in organic molecules on electron impact: 21—Oxygen transfers from the ortho nitro group to sulphur in N‐aryl‐2‐nitrobenzenesulphenamides and phenyl‐2‐nitrophenyl disulphide
Authors: Ramana D. V. , Sundaram N. , George M.
Published: May 2005

Fragment ions arising as a result of oxygen transfers from the nitro group to sulphur have been noticed in N‐aryl‐2‐nitrobenzenesulpbenamides and phenyl‐2‐nitrophenyl disulphide. In the case of the former a double oxygen transfer to the sulphur has been noticed in the molecular ion whilst a single oxygen transfer to the β‐sulphur atom and a double oxygen transfer to the α‐sulphur atom have been observed in the latter. The proposed fragmentations are confirmed by high‐resolution data, B/E linked‐scan spectra and chemical substitution.
Fragmentation of acylium ions from methyl levulinate. Isomerization processes involving carbon and oxygen atoms of both carbonyl groups
Authors: Corval M. , Harrata A. , Morizur J‐P.
Published: May 2005

The fragmentations of the acylium ions OC+CH2CH2CO2CH3 and OC+CH2CH2COCH3 generated from methyl levulinate are governed extensively by the interaction of the two carbonyl groups. Both species eliminate a molecule of CO unimolecularly and under CID conditions. The results derived from measurements of 13C and 18O labelled precursors, together with kinetic energy release values, have been used to study the mechanisms. In the first of these acylium ions, both carbonyl groups are equivalent; this phenomenon can be the result of a 1,4 methoxy shift. In the second acylium ion, only the oxygen atoms change their positions; this isomerization occurs via the [MH]+ of γ‐valerolactone. Some other fragmentation processes also discussed in relation to 2H labelling are the formation of the [M  COOCH3] + ion and the loss of HCOOCH3 in the collision‐induced dissociation mass spectra of the first acylium ion, and the formation of the [CH3CO]+ ion and the loss of H2O for the second one.
Mass spectral fragmentation pathways in nitramines. A collision‐induced dissociation study
Authors: Yinon Jehuda , Brumley William C. , Brilis George M. , Bulusu Suryanarayana
Published: May 2005

A collision‐induced dissociation (CID) study of five synthesized nitramines was carried out using a hybrid EBQQ mass spectrometer. CID spectra were obtained in two modes: B/E linked‐scan mode and MS/MS mode using the EB sector combination as the first mass spectrometer and the QQ as collision cell and second mass spectrometer, respectively. Fragmentation pathways of the compounds were determined in the electron‐impact mode. It was found that dominant fragmentation pathways included the loss of OH, NO2 and HNO2 in addition to the loss of CH2NNO and CH2NNO2.
Comparative study of the behaviour of 2‐amidoketophenones and 1‐aza(3,4: 5,6: 8,9)tribenzocyclonona‐2,7‐diones under electron impact
Authors: Erra‐Balsells R.
Published: May 2005

The electron‐impact mass spectra of several 2‐amidoketophenones and l‐aza(3,4:5,6:8,9)tribenzocyclonona‐2,7‐diones have been examined.
Negative‐ion liquid secondary ion mass spectrometry of antiparallel N‐carbamoylmorpholine‐linked nucleic acid oligomers: Evidence for fragmentation from molecular radical ion precursors
Authors: Laramée James A. , Arbogast Brian , Deinzerf Max L. , Stirchak Eugene P. , Weller Dwight D.
Published: May 2005

N‐Carbamoylmorpholine‐linked nucleic acid oiigomers were analyzed by negative‐ion liquid secondary ion mass spectrometry. Cleavage of the carbamate backbone in repeating fashion on both sides of the carbonyl groups gives two sequence ion series. The main fragment arises from cleavage of the base‐morpholine bond. Important fragment ions are postulated to arise from cleavage of an M−· radical ion precursor.
Metastable ion study of organosilicon compounds part II—hexamethyldisiloxane
Authors: Tobita Seiji , Tajima Susumu , Okada Fumio , Mori Shigeru , Tabei Eiichi , Umemura Mitsuo
Published: May 2005

Unimolecular reactions of the metastable silicenium ion (CH3)3SiOSi(CH3)2 + generated by dissociative ionization of bexamethyldisiloxane were investigated by mass‐analysed ion kinetic energy (PUKE) Spectrometry. The characteristic fragmentations observed were losses of CH4 and (CH3)2SiO molecules. Complete scrambling of all methyl groups prior to these reactions was found by investigating the MIKE spectra of deuterium labelled analogues (CD3)3SiOSi(CH3)2+ and (CH3)3SiOSi(CD3)3+. The loss of methane was accompanied by a large kinetic energy release (T0.5 = 482 meV). The MIKE spectra of silicenium ions were compared with those of their carbon analogues. The most predominant reaction of metastable (CH3)3COC(CH3)3+ ion was the loss of CH2C(C H3)2 leading to protonated acetone. Significant differences between the ion fragmention characteristics of silicon and carbon compounds were found.
Cluster ions in the secondary ion mass spectrometry of choline and acetylcholine halides
Authors: Ohashi Mamoru , Lino Takashi , Takahashi Tomoyuki , Yoneda Michiaki , Kyushin Soichiro , Tsujimoto Kazuo
Published: May 2005

Liquid secondary ion mass spectra of choline and acetylcholine halides exhibit several series of cluster ions whose origins were investigated using B/E and B2/E linked‐scan techniques. In the case of choline halides three series of cluster ions were identified as (Me3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2OH + nM), (Me3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2OMe + nM) and (Me3N\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2OH · Me3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2O− + nM), while (CH3COOCH2CH2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}Me3 + nM), (Me3\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}CH2CH2OH + nM) and (CH2 = CH\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^ + $\end{document}Me3 + nM) were observed in the spectra of acetylcholine halides. For these cluster ions, bimolecular reactions induced on ion bombardment under secondary ion mass spectrometric conditions are discussed.
Tautomerism and electron impact mass spectra of pyrimidin‐4(3H)‐ and ‐4(1H)‐ones
Authors: Pihlaja Kalevi , Oksman Pentti , Stájer Géza , Bernáth Gábor
Published: May 2005

A mass spectrometric identification and differentiation of pyrimidin‐4(3H)‐ and ‐4(1H)‐ones was carried out. N‐Substitution at position 1 or 3 made the distinction of the two sets of compounds very easy because of their characteristic fragmentation pathways. Most interesting were the spectra of the N‐unsubstituted derivatives, which illustrated a predominance of the two possible NH tautomers in relation to the 4‐hydroxy structure.
Ortho effects in organic molecules on electron impact part 22. Competing oxygen transfers from the nitro group to sulphur and the olefinic double bond in 2‐nitrophenyl styryl sulphides
Authors: Ramana D. V. , Sundaram N. , George M.
Published: May 2005

Double oxygen migration to sulphur from the ortho‐nitro group leading to eliminations of SO2 and ·SO2H from the molecular ions and single oxygen transfer to the olefinic double bond in the side‐chain giving rise to the most abundant ion at m/z 138 have been observed in 2‐nitrophenyl styryl sulphides on electron impact. The proposed fragmentation mechanisms and the product ion structures were confirmed with the aid of high‐resolution data, B/E linked scan and CID spectra.
Azinyl sulphides. Part X. Mass spectrometry of some 3‐ and 4‐quinolinyl sulphides and 3,4‐quinolinediyl bis‐sulphides
Authors: Pluta Krystian , Maślankiewicz Andrzej
Published: May 2005

The mass spectral fragmentations of ten of the title compounds are discussed. All the 3,4‐quinolinediyl bis‐sulphides give characteristic ions at m/z 159 and 132 while 3‐ and 4‐quinolinyl sulphides form ions at m/z 160 and 133. The most characteristic distinction between 3‐ and 4‐quinolinyl sulphides is the intensity of the [M ‐ 1]+ ion. The elimination of ·SH and ·CH3 radicals is also different.
Structures of [C3H6O]+· ions from propylene oxide and methyl‐substituted 1,3‐dioxolanes by photodissociation and ion/molecule reactions
Authors: van de Guchte W. J. , van der Hart W. J.
Published: May 2005

Photodissociation experiments and ion/molecule reactions with pyridine and hex‐1‐ene show that [C3H6O]+· ions from propylene oxide isomerize to the vinyl metbyl ether structure. [C3H6O]+· fragment ions from methyl‐substituted 1,3‐dioxolanes have lower internal energies. In these cases a mixture of photodissociating ring‐opened propylene oxide ions and vinyl methyl ether ions is observed.
Laser‐induced molecular ion formation and gas‐phase ion formation from polycyclic aromatic hydrocarbons, coals and coal products detected by Fourier transform mass spectrometry
Authors: Greenwood Paul F. , Strachan Michael G. , Willett Gary D. , Wilson Michael A.
Published: May 2005

The results from the laser‐ablation Fourier transform mass spectrometric examination of a variety of polyaromatic hydrocarbons (PAHs), coals and other geochemically related materials are presented. Both molecular and quasi‐molecular ions have been detected from different ring‐sized PAHs. A relationship between the ease of sodium‐adduct ion formation and the size of the aromatic array is observed. Nevertheless, suppression of [M + Na]+ ion formation in PAHs can be achieved by the addition of coal. In addition, distributions of low‐mass positive‐ and negative‐ion carbon clusters (Cn +, 14 ⩽ n ⩽ 27 and Cn, −, 4 ⩽ n ⩽ 30), high‐mass positive‐ion carbon clusters (Cn+, 60 ⩽ n ⩽ 260) and low relative molecular mass organic compounds (< 600 daltons) have been observed from the coals. It appears that the ease of C formation may be used as an indicator of coal rank. Irradiance conditions also influence the observed distribution of high‐mass positive‐ion carbon clusters. Furthermore, distributions of the high‐mass positive‐ion carbon clusters at different irradiances supports an earlier proposal that their formation is kinetically controlled.
Static secondary ion mass spectrometry of poly(butylmethacrylates) fragmentation reactions of four isomeric butanolate anions
Authors: Lub J. , van der Wel H.
Published: May 2005

The negative secondary ion mass spectra of the four isomeric poly(butylmethacrylates) are presented. The four isoineric butanolate anions which are formed fragment in a way which is specific for each isomer. In all cases, α,β‐elimination (relative to the oxygen atom) of suhstituents from the parent anions plays an important role. The mechanism of elimination of alkanes and molecular hydrogen from the butanolate anions is explained by the formation of hydride or alkyl anions from the α‐position of the butanolate anions. These newly generated ions abstract a proton or, with less probability, an aikyl subsrituent from the β‐position.
Mass spectrometric investigation of para‐substituted benzenesulphinamide derivatives
Authors: Fujiki Kiyoko
Published: May 2005

Under electron impact conditions the mass spectrometric behaviour of secondary and tertiary para‐substituted benzenesulphinamide derivatives has been studied. The fragmentation modes of these compounds, including a characteristic H2O loss from the molecular ions of N‐benzylamides, deduced with the aid of high‐resolution techniques, are described.
Comparative study of the behaviour of 1H‐indazoles and 1‐(p‐aminophenyl)indazoles under electron impact
Authors: Erra‐Balsells R.
Published: May 2005

The electron impact mass spectrometric fragmentation pathways for several 1H‐indazoles and 1‐(p‐amino‐phenyl)indazoles were investigated. An interesting relationship between the substitution pattern in the framework of the indazole derivatives and the fragmentation patterns was observed.
Breakdown diagrams for low‐mass cations from angle‐resolved mass spectrometric measurements
Authors: Reid C. J.
Published: May 2005

Angular scatter distributions, P(θ), of 4 keV collisionally activated ions of propan‐1‐ol, ethanol, dimethyl ether, propyne and nitromethane undergoing specific dissociation reactions were obtained by measuring the ‘scatter profiles’ of fragment ions. The most probable (and root mean square) angles associated with these distributions were found to be proportional to the root mean internal energy depositions, but there was not a one‐to‐one relationship between individual angles and energies. However, by using as a basis set the angular distributions found for some non‐dissociative reactions involving ‘single‐valued’ distributions of internal energy gain, it was possible to modify the P(θ) functions to give approximate energy deposition functions which could be presented in breakdown‐diagram form. Such data were generally found to be in agreement with those observed previously.
Routine liquid charomatography/fast atom bombardment mass spectrometry of peptides and enzymatically digested proteins
Authors: Bell David J. , Brightwell Malcolm D. , Haran Margaret , Neville William A. , West Andrew
Published: May 2005

The development of a high‐performance liquid chromatography (HPLC)/fast atom bombardment (FAB) interface and the subsequent commercial availability of such systems has facilitated the routine application of the technique to problems in pharmaceutical research and development. Although many products are amenable to FAB analysis and hence LC/FAB, the greatest benefit of the interface has been in the field of peptide and protein analysis. It has been found that, even with post‐column matrix addition, chromatographic resolution is maintained and, by plotting mass chromatograms, the resolution may be greater than that achieved by the less specific UV detector. As only 1% matrix is required in the final eluent, the system is stable for extended periods and has been used for 3 h LC/FAB experiments or used continuously for multiple analyses over 8 h periods. In addition to the acquisition of relative molecular mass information, the constant background can be completely subtracted to yield structurally significant fragment ions which may allow sequencing of components from the single LC/FAB experiment. Applications of LC/FAB to date include the characterization of Iys(78)‐plasminogen by the on‐line analysis of complex mixtures of peptides resulting from the various enzymatic digests.
Mechanism of formation of alkali metal cation adducts in plasma desorption mass spectrometry of biomolecules
Authors: Demirev P. , Fenyö D. , Håkansson P. , Sundqvist B. U. R.
Published: May 2005

Experimental data on correlations between the directions of the incident primary ion and the ejected protonated [M + H]+ and alkali metal adduct [M + Cs]+ molecules for three peptide samples with an incident beam of 72.3 MeV 127I14+ ions are reported. Measurements were carried out in a linear time‐of‐flight mass spectrometer by monitoring the secondary ion yield as a function of electrostatic deflection in a direction perpendicular to the spectrometer axis. No difference was observed in the direction in which [M + H]+ and [M + Cs]+ ionic species are preferentially desorbed. The results obtained suggest that alkali metal cation attachment to biomolecules in plasma desorption mass spectrometry is realized in a close spatial location and time interval with protonation. Formation of ion‐molecule complexes occurs at an early stage of the desorption event and precedes their ejection into the gas phase.
Mass spectrometric study of some cycloalkane/ene‐condensed 2‐thioxo‐2935556‐pyrimidin‐4(1H)‐ones and cycloalkane/ene‐condensed [l,3] thwzino [3,2‐a]‐pyrimidinones under electron impact
Authors: Himottu Marja , Pihlaja Kalevi , Stájer Géza , Bernáth Gábor , Vainiotalo Pirjo
Published: May 2005

The mass spectra of four cycloalkane/ene cis‐ and trans‐condensed 2‐thioxo‐2,3,5,6‐tetrahydropyrimidin‐4(1H)‐ones and the corresponding cycloalkane/ene cis‐ and trans‐condensed [l,3]thiazino[3,2‐a]pyrimidinones were measured. Fragmentation pathways were confirmed by metastable ion analyses and exact mass measurements. The bicyclic isomers were easy to distinguish from each other, whereas the corresponding tricyclic isomeric adducts gave fairly similar mass spectra, owing to their favoured reiro‐Diels‐ Alder fragmentations accompanied by the migration of one or two hydrogen atoms.
Rearrangements in the mass spectra of α‐phenylcinnamic acid and its derivatives
Authors: Madhusudanan K. P. , Murthy V. S. , Fraisse D. , Becchi M.
Published: May 2005

The electron impact ionization and collisional activation mass spectra of α‐phenylcinnamic acid and its derivatives have been studied. The loss of a phenylic hydrogen is not an important process in these molecules, unlike the unsubstituted cinnamic acids. However, in o‐chloro‐α‐phenylcinnamic acid and its methyl and trimethylsilyl derivatives loss of Cl resulting in the formation of 2‐substituted‐3‐phenylbenzopyrilium ion is an important fragmentation pathway. The rearrangement ions observed at m/z 118 and 107 in the Spectrum of α‐phenylcinnamic acid have been found to have the structures of the M+˙ of benzofuran and PhCH\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^{\rm +} $\end{document}H, respectively. The ion at m/z 121 in the spectrum of the methyl ester of α‐phenylcinnamic acid has been found to have the structure PhCH\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm O}\limits^{\rm +} $\end{document}Me.
A personal computer‐based data control interface for neutralization‐reionization and tandem mass spectrometry
Authors: Drinkwater Donald E. , Turecek Frantisek , McLafferty Fred W.
Published: May 2005

An improved data‐acquisition and management system interfaces an IBM‐compatible personal computer to a tandem mass spectrometer. In addition to increased spectral resolution and storage, the control system measures the absolute abundance (peak areas) of product ions, and also that of the precursor; these are capabilities critical for collisional activation, metastable ion decomposition and neutralization‐reionization mass spectra. Improved experimental control features include multiple mass range and repetitive scan selection, spurious transient rejection and comparative spectral display.
Formation and fragmentation of the [M + Na]+ ion of glycosides in fast atom bombardment mass spectrometry
Authors: Takayama Mitsuo , Fukai Toshio , Nomura Taro , Yamauchi Tatsuo
Published: May 2005

Positive‐ion fast atom bombardment (FAB) mass spectra of flavonol and steroid glycosides with sodium chloride added showed well known characteristic features; of the appearance of [M + Na]+ peaks, disappearance of [M + H]+ peaks and a significant decrease in the peak heights of fragment ions. Compared with the features in the FAB mass spectra of crown ethers with addition of salt, and above features suggest a complexation between Na+ and the glycosides in matrix solution. The B/E‐constant linked scanning technique was used to obtain structural information of the [M + Na]+ ion of the glycosides. The B/E spectra gave the daughter‐ion peaks, suggesting that coordination of Na+ with the biosides and triosides occurs at the sugar moiety, whereas the coordination with the monoglycosides occurs at the aglycone moiety, except for monoglycosides in which the aglycone moiety does not contain significant oxygen functional groups such as OH and CO.
Structure of ions [ZnNCR]+ and [Zn(NCR)2]+ (R = H, CH3) in the gas phase
Authors: Palii Sergiu P. , Raevskii Nikolai I. , Zagorevskii Dmitrii V. , Indrichan Konstantin M. , Borisov Yurii A. , Gerbeleu Nikolai V. , Nekrasov Yurii S. , Zagorevskii D. V. , Nekrasov Yu. S. , Timofeev O‐ S. , Gren' A. I.
Published: May 2005

Structures of [ZnNCR]+ and [Zn(NCR)2]+ ions (R = H, Me), which are abundant in the mass spectra of many types of coordination compounds, were studied by the MNDO method. In all cases the most stable isomers correspond to the zinc ion coordinated with the nitrogen(s) of the nitrile ligand. For [Zn(NCR)2]+, the N‐Zn‐N angles are ∼108°.