bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isomeric characterization via ion neutralization and dissociation. Experimental variables
Authors: McLafferty Fred W. , Wesdemiotis Chrysostomos 
Published: May 2005

AbstractMajor 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

AbstractThe 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

AbstractA 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

AbstractFragment 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractN‐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

AbstractUnimolecular 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

AbstractLiquid 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

AbstractA 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

AbstractDouble 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

AbstractThe 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

AbstractPhotodissociation 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

AbstractThe 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

AbstractThe 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

AbstractUnder 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

AbstractThe 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

AbstractAngular 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

AbstractThe 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

AbstractExperimental 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

AbstractThe 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

AbstractThe 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

AbstractAn 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

AbstractPositive‐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

AbstractStructures 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°.