bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of method of ion preparation on low‐energy collision‐induced dissociation mass spectra
Authors: Nacson Sabatino , Harrison Alex. G. , Davidson William R. 
Published: May 2005

AbstractThe collision‐induced dissociation (CID) mass spectra of protonated cocaine and protonated heroin have been measured using a triple quadrupole mass spectrometer at 50 eV ion/neutral collision energy for protonated molecules prepared by different protonating agents. The CID mass spectra of protonated cocaine using H+(H2O)n, H+(NH3)n and H+((CH3)2NH)n as protonating agents are essentially identical and it is concluded that, regardless of the initial site of protonation, the fragmentation reactions occurring on collisional activation are identical. By contrast, protonated heorin prepared with H+(H2O)n and H+(NH3)n as protonating agents show substantial differences. That formed by reaction of H+(H2O)n shows a much more abundant peak corresponding to loss of CH3CO2H. From a comparison with model compounds, and from a consideration of the three‐dimensional structure of heroin, it is concluded that with H+(H2O)n as protonating agent significant protonation occurs at the acetate group attached to the alicyclic ring, leading to acetic acid loss on collisional activation, but that reaction of H+(NH3)n leads to protonation at the nitrogen function. The proton attached to nitrogen cannot interact with the acetate group and, consequently, the probability of loss of acetic acid on collislional activation is greatly reduced.
Ion chemistry of phthalamic acids. III. The origin of [M  1]+ ions under electron impact
Authors: Selva Antonio , Traldi Pietro , Ventura Paolo , Pellegata Renato 
Published: May 2005

AbstractElectron impact mass spectra and collisional activation/mass‐analysed ion kinetic energy spectra of some phthalamic acids and their deuterium labelled analogues suggested that the genesis of [M  1]+ ions is due to the loss of an aromatic hydrogen ortho to the amidic group, as for aromatic amides and thioamides.
Fast atom bombardment mass spectra of monosulphonated merocyanine dyestuffs
Authors: Haessner R. , Borsdorf R. , Dube G. , Lehmann A. , Ruotsalainen H. , Bach G. 
Published: May 2005

AbstractThe FAB mass spectra of four sulphonated merocyanine dyes are investigated. Negative ion spectra are superior to those in the positive ion mode. The special structure of merocyanines with an acidic group at one end of the molecule and a basic group at the other leads to significantly different fragmentation pathways for positive and negative ions.
Fast atom bombardment mass spectra of isobaric/isomeric phosphonium salts
Authors: Kroha Kyle J. , Busch Kenneth L. 
Published: May 2005

AbstractThe positive ion fast atom bombardment mass spectra of isobaric/isomeric aryl phosphonium salts typically contain abundant intact cations, which can be used to establish the cationic molecular weight, characteristic ions that can be used to delineate structural subgroups, and fragment ions corresponding to losses of small neutral molecules. Several of the fragmentation pathways were elucidated by parent ion and daughter ion tandem mass spectrometry experiments. Dependence of the fragmentation reactions on functional group substitution suggests that fast atom bombardment mass spectrometry is an excellent method for the differentiation of isobaric/isomeric phosphonium salts used in synthetic organic and industrial catalytic processes.
Electron impact induced fragmentation of dihydro‐1,4‐oxathiines. 1. 2,3‐substituted 5,6‐dihydro‐1,4‐oxathiines
Authors: Nevalainen Vesa , Vainiotalo Pirjo 
Published: May 2005

AbstractIn the electron impact induced fragmentation of 2,3‐disubstituted 5,6‐dihydro‐1,4‐oxathiines, the cleavage of the heterocyclic ring proceeds through the retro Diels‐Alder type of reaction. The further fragmentation of the resulting radical cation gives rise to substituted carbonyl or thiocarbonyl cations. This fragmentation favours the formation of an ion which, in the electron‐deficient carbon‐oxygen or carbon‐sulphur triple bond, is stabilized by an electron‐releasing group. The ring fragmentation was observed to be dependent on the nature of the 3‐substituent of the ring when a series of 3‐substituted 5,6‐dihydro‐2‐methyl‐1,4‐oxathiines was investigated.
Acute pressure dependence of the electron ionization mass spectrum of molybdenyl acetylacetonate
Authors: Didonato G. C. 
Published: May 2005

AbstractFormation of both fragment and polymeric ions observed in the electron impact mass spectrum of molybdenyl acetylacetonate exhibit a strong dependence on the instantaneous pressure in the ionization source. The indicated source pressure increases with increasing direct probe temperature. Utilizing a probe temperature increase of only 30°C min−1, the relative abundances of some ions can change by factors as high as 15 over a period of 60 s. Some ions are remarkably transient, appearing in only the few scans during which the source pressure corresponds to just that required for their formation. These rapid changes in the ion relative abundances are also exhibited in tandem mass spectra, and especially in parent ion scans.
Field ionization of high velocity neutral species. Rydberg states in noble gas atoms; the measurement of translational energy loss in neutralization‐reionization mass spectra
Authors: Bordas‐Nagy Jozsef , Holmes John L. , Mommers Alexander A. 
Published: May 2005

AbstractThe modification of a double‐focusing mass spectrometer of BE geometry (VG‐Analytical ZAB‐2F) to permit the field ionization of fast atoms in high Rydberg states is described. Field ionization was achieved by means of a pair of closely spaced, very fine metal meshes with a (kV) potential difference between them. High Rydberg noble gas atoms were generated from their ions by electron transfer from noble gas targets. Also described is a method, involving a field ionization observation, for measuring the net kinetic energy loss associated with the collision‐induced neutralization‐reionization of polyatomic ions.
Reactions of nucleophiles with triarylpropenones and triarylbutenones
Authors: Madhusudanan K. P. , Jain Raka , Mittal Shubhra , Durani Susheel , Kapil R. S. 
Published: May 2005

AbstractFrom a study of the reactions of nucleophiles with 1,2,3‐triaryl‐propenones and‐butenones in a chemical ionization source it has been found that stronger nucleophiles, such as, MeO−, EtO− and MeS−, attack the α,β‐unsaturated system at the β‐carbon (Michael addition) or the carbonyl carbon giving rise to tetrahedral adducts, while weaker nucleophiles, such as, Cl− form the adduct ion by H‐bonding with the β‐hydrogen. The effect of substituents and source temperature supports the operation of these processes. The triaryl butenone did not give the adduct ion with MeO− as deprotonation leads to a stable [M  H]− ion.
Electron impact induced cyclizations in 4‐chioro‐3‐(N‐aryliminomethyl) (2H) benzopyrans and benzothiopyrans
Authors: Ramana D. V. , Balasubramanian K. K. , Srinivas R. , Saiganesh R. , Swaminathan K. 
Published: May 2005

AbstractIntramolecular substitutions leading to cyclizations with the ejection of chlorine have been noticed during mass spectral fragmentation of 4‐chloro‐3‐(N‐aryliminomethyl) (2H) benzopyrans and benzothiopyrans. Very interesting ortho effects involving intramolecular substitutions have also been observed in 6‐methyl‐4‐diloro‐3‐[N‐(2‐methoxyphenyliminomethyl)] (2H) benzopyran and 6‐methyl‐4‐chloro‐3‐[N‐(2‐chlorophenyliminomethyl)]‐(2H) benzopyran. The proposed fragmentation mechanisms have been supported by the accurate mass measurements and linked scan studies.
Diethylhydrogensilyl cyclic diethylsilylene derivatives in gas chromatography/mass spectrometry of hydroxylated steroids. III‐Fragmentations of 5β‐pregnane‐17,20,21‐triol derivatives
Authors: Nakatat Hisao , Ishibashi Masataka , Itoh Masahiro , Miyazaki Hiroshi 
Published: May 2005

AbstractA reaction of N,O‐bis‐(diethylhydrogensilyl) trifluoroacetamide with 5β‐pregnane‐17,20,21‐triols afforded diethylhydrogensilyl (DEHS) cyclic diethylsilylene (DES) derivatives. 5β‐Pregnane‐3α,17α,20β,21‐tetraol yielded the 3α,21‐bis‐DEHS‐17α,20β‐DES compound, whereas the structure of the major product from its 20α isomer was assigned as the 3α,17α‐bis‐DEHS‐20α,21‐DES derivative, which would undergo facile isomerization to the unstable 3α,21‐bis‐DEHS‐17α,20α‐DES structure under electron ionization. Fragmentations of these DEHS‐DES compounds are discussed on the basis of isotope labelling experiments, linked scanning data, and accurate mass measurements.
Water loss from molecular protonated ions of benzyl 2‐phenylethyl ether and derivatives
Authors: Kingston Eric E. , Shannon James S. , Lacey Michael J. 
Published: May 2005

AbstractThe skeletal rearrangement for water loss is the dominant ion reaction in the chemical ionization mass spectrum of benzyl 2‐phenylethyl ether. Isotopic distributions obtained for this reaction with specifically labelled derivatives have been interpreted in terms of competing five‐ and six‐centred skeletal rearrangements. Chemical substitution of the alternative aromatic rings strongly influences the balance of the competition.
Analysis of polymer surfaces by SIMS: 7. Homopolymer and copolymer nylons
Authors: Briggs D. 
Published: May 2005

AbstractStatic secondary ion mass spectra (positive and negative) have been obtained from spin‐cast films of nylon−3, −4, −6, −7, −8, −11, −12, −46, −66 and −610 homopolymers, as well as nylon−6/66 copolymers covering the composition range. All spectra are highly characteristic and feature protonated multiple repeat unit fragments. Relative peak intensities from the nylon−6/66 copolymers correlate with composition. Overall, the fragmentation patterns bear a strong resemblance to high temperature pyrolysis mass spectra from these polymers.
SCN· loss by intramolecular substitution of electron impact ionized 3‐cyano‐5‐thiocyanatoalka‐2,4‐dienoic acid esters
Authors: Herzschuh R. , Schulze B. , Mühlstädt M. 
Published: May 2005

AbstractThe behaviour of some 5‐thiocyanatoalkadienoic acid esters under electron impact has been investigated by means of low‐resolution mass spectrometry. Some characteristic rearrangement processes have been observed under SCN· radical loss.
Silver sulfonates. A novel calibration material for field desorption mass spectrometry
Authors: Espinosa‐Leniz Rafael , White Edward 
Published: May 2005

AbstractAn equimolar mixture of silver methanesulfonate and silver trifluoromethanesulfonate has been investigated as a calibration material for exact mass determination in field desorption mass spectrometry. The mass scale was established using only field desorption by double exposure of the calibration material and the sample on a photographic plate. The precision and the accuracy of the method were tested by recording the mass spectra of a variety of peptides of known composition at a resolution of about 4000. The results indicate that the mass scale established is useful for the determination of the exact masses of field desorbed ions over the mass range examined: m/z 294–1147.
Mass spectrometry of substituted 1,3‐dihydro‐2H‐imidazole‐2‐thiones
Authors: Cert Arturo , Péerez‐Lanzac Mariana Trujillo 
Published: May 2005

AbstractThe electron impact mass spectra of the 4‐formyl‐1, 3‐dihydro‐2H‐imidazole‐2‐thione, its six 1‐methyl(n‐propyl, n‐hexyl)‐3‐methyl(phenyl)‐disubstptuted derivatives, and the 1,3‐dihydro‐1‐phenyl‐2H‐imidazole‐2‐thiome are discussed. The fragmentation pattern is strongly influenced by the alkyl or phenyl N‐substituents, as well as by the length of the alkyl chain. The odd‐electron ions containing an N‐phenyl substituent, but not a propyl or hexyl group, eject a hydrogen atom from the phenyl ring, while the presence of a long alkyl chain greatly enhances the loss of the sulphyhydryl radical and facilitates the expulsion of several alkenes, and alkyl and alkenyl radicals.
Fast atom bombardment mass spectra of some alkylammonium 4‐toluenesulfonate salts
Authors: Furton Kenneth G. , Poole Coliu F. 
Published: May 2005

AbstractThe fast atom bombardment positive ion mass spectra of low molecular weight alkylammonium 4‐toluenesulfonate salts are dominated by cluster ions of the type [(AB)nA]+ or [(AB)nH]+, where A is a cation, B an anion, n an integer from 0 to 4. With one exception the base peak is the cation A+.
Fast atom bombardment induced ring rupture of silatranes
Authors: Yan Lin , Chai Wengang , Wang Guanghui , Wu Guanli , Lu Kaijuan , Luo Yue 
Published: May 2005

AbstractDuring a comparison study of the fast atom bombardment (FAB) and electron impact mass spectra of 1‐organyl‐2,9,10‐trioxa‐6‐aza‐1‐silatricyclo[4.3.3.01,6]dodecanes, an unusual ion peak at m/z 164 was noticed in the FAB spectra. Accurate mass measurement indicated that m/z 164 corresponds to protonated 1‐[N,N‐bis(2‐hydroxyethyl)amino]‐1‐propanol (BHAP), which is produced by a ring‐rupture reaction. Further experiment showed that the intensity of the [BHAP + H]+ ion peak increased markedly as the 7keV Ar0 bombardment proceeded, suggesting a FAB‐induced reaction. The possible mechanism is also discussed.
Free radicals formed by ion beam neutralization of [DCO]+, [DOCO] +, [CD3OD2]+ and [(CD3)2COD] + on metal targets
Authors: Raksit Asit B. , Porter Richard F. 
Published: May 2005

AbstractA series of radicals formed when a fast beam of deuterated ions, [DCO] +, [DOCO] +, [CD3OD2]+ and [(CD) 2COD] +, is neutralized by electron transfer from K. Na and Zn atoms has been studied by a combination of charge stripping and beam scattering techniques For all systems studied, some fraction of The radicals from charge exchange are formed in excited dissociative states. Radical decomposition products have been identified and fragmentation energies have been measured. A metastable slate of CD3GD2 is observed with a lifetime greater than 0.5 μs. Stable radicals of DCO and (CD3)2 COD are formed by ion–Zn charge exchange. Indirect evidence indicates that [DCO] +–K charge exchang; leads to an excited radiative state of the radical.
Collision‐induced dissociations of substituted benzyl anions: Deprotonated 2‐Phenyl‐1,3‐dithiane
Authors: Bowie John H. , White Peter Y. , Blumenthal Thomas 
Published: May 2005

AbstractDeprotonated 2‐phenyl‐1,3‐dithiane undergoes competitive losses of H˙, C3H6 C2H4S, C3H4S, C7H6S, C10H10 and C10H10S upon collisional activation. The elimination of H occurs from the phenyl ring. The loss of C3H6 occurs by simple cleavage of the dithiane ring. All other processes involve specific proton transfer followed by either cleavage or internal nucleophilic displacement.
Electron impact induced fragmentation of dihydro‐1,4‐dithiines. 2,3‐Substituted 5,6‐dihydro‐l,4‐dithiines
Authors: Nevalainen Vesa , Vainiotalo Pirjo 
Published: May 2005

AbstractIn the electron impact induced fragmentation of 2,3‐disubstituted 5,6‐dihydro‐1,4‐dithiines, the most important cleavage of the heterocyclic ring occurs via the retro‐Diels‐Alder type of reaction. The further fragmentation of the resulting radical cation gives rise to substitutes thiocarbonyl cations. This fragmentation favours formations of ions in which the electron‐deficient carbon‐sulphur triple bond is stabilized by an electron‐releasing group. The ring fragmentation was observed to be dependent on the nature of the 3‐ and 2‐substituents of the ring when a series of 3‐ and 2‐substituted 5,6‐dihydro‐l,4‐dithiines was investigated. The fragmentation of dihydro‐l,4‐dithiines partly resembles the fragmentation of the corresponding dihydro‐l,4‐oxathiines. The presence of the two sulphur atoms in dihydro‐l,4‐dithiines give rise to more stable molecular ions than observed in the case of the dihydro‐1,4‐oxathiine analogues. Fragmentations of dihydro‐l,4‐dithiines can also involve extrusions of alkylradicals or HS‐radical from the heterocyclic rings of molecular ions.
A data acquisition system for mass‐analyzed ion kinetic energy spectra using a personal computer
Authors: Traeger John C. , Mommers Alexander A. 
Published: May 2005

AbstractAn inexpensive data acquisition system has been developed for mass‐analyzed kinetic energy experiments which involve scanning the electrostatic analyzer of a reversed geometry mass spectrometer. The various hardware and software design features are described. Results for data obtained with a commercially available VG ZAB‐2F mass spectrometer are presented and discussed.
Isobutane chemical ionization mass spectra of unsaturated alcohols
Authors: Munson Burnaby , Feng Ta‐Min , Ward Harry D. , Murray Roger K. 
Published: May 2005

AbstractAnalysis of the isobutane chemical ionization mass spectra of hexenols, cyclohexenols and various syn/anti pairs of bicyclic and tricyclic homoallylic alcohols shows that: (i) the spectra of the allylic alcohols are dominated by [M + H – H2O]+ and [M + C4H9–H2O]+ ions and contain traces of [M + H]+ ions; (ii) [M + H]+ ions are prominent in the spectra of acyclic and certain cyclic homoallylic alcohols; and (iii) [M + H]+ ions dominate the spectra of other acyclic unsaturated alcohols. The [M + H]+ ions may result from either: (a) protonation of the hydroxyl group, followed by a very rapid intramolecular proton transfer from the protonated hydroxyl group to the carbon–carbon double bond or internal solvation of the protonated hydroxyl group by the carbon–carbon double bond; and/or (b) direct protonation of the carbon–carbon double bond with significant internal solvation of the resulting carbocation by the hydroxyl group, which may lead to carbon–oxygen bond formation to give a protonated cyclic ether. The consequences of placing various geometric constraints on the possible intramolecular interactions between the hydroxyl group and the carbon–carbon double bond in unsaturated alcohols are explored.
Mass analysis of overlapping ion kinetic energy peaks arising from charge separation in dications
Authors: March R. E. , Harrison A. G. , Young A. B. 
Published: May 2005

AbstractA triple‐sector instrument of reversed geometry, BEQQ, has been employed to resolve overlapping ion kinetic energy peaks arising from charge separation of metastable dications. Separation was achieved through mass resolution of the dication in the magnetic sector and of the singly charged product ion of greater mass in the quadrupole mass filter accompanied by energy resolution with the electric sector; the electric sector was scanned to cover the complete range of each charge separation peak. Two overlapping ion kinetic energy peaks arising from charge separation of the diphenylenimine dication and up to four overlapping ion kinetic peaks arising from charge separations of dications arising from benzene‐1,3,5‐d3 have been resolved. The kinetic energy releases have been calculated in each case. Enhanced z‐discrimination is observed with the final stage of mass analysis.
Consecutive reactions in the vitamin D series. A New insight into the mechanism of vitamin D and provitamin D isomerizations in the mass spectrometer
Authors: Zaretskii Z. V. I. , Singh S. , Kingston E. E. , Harris F. M. , Beynon J. H. 
Published: May 2005

AbstractThe individual steps of the consecutive reactions
equation image
arising from metastable molecular ions, derived from vitamin D3, vitamin D2 and their respective provitamins (7‐dehydrocholesterol, ergosterol), were examined in different field‐free regions of a triple‐sector mass spectrometer of B/E/E geometry. The comparison of the translational energy release (T) and the metastable peak shapes corresponding to these reactions, as well as unimolecular and collision‐induced dissociation mass‐analysed ion kinetic energy spectra, showed that there are probably two structures of the [M – H2O]+˙ and [M – CH3˙]+ ions depending upon whether the respective ions are formed in the ion source through high‐energy reactions, or from the fragmentation of metastable molecular ions through slow, low‐energy processes which occur in the first field‐free region.
Effects of functional group interactions in the chemical ionization mass spectra of some substitutedcis‐1,3‐cyclopentane dicarboxylic acids and their derivatives
Authors: Vainiotal Pirjo , Mälkönen Pentti J. 
Published: May 2005

AbstractAmmonia, isobutane and methane chemical ionization mass spectra have been measured for some substitutedcis‐1,3‐cyclopentane dicarboxylic acids and their derivatives. The relative proton affinities of the different functional groups determine the protonation site in the molecule and thereby greatly affect the fragmentation. Intramolecular catalysis clearly facilitates the elimination of water in cases where functional groups can interact with each other.
Relative molecular mass information from aliphatic nitro compounds: A chemical ionization study
Authors: Ballantine James A. , Barton Jonathan D. , Carter James F. , Davies Jeremy P. , Smith Keith , Stedman Geoffrey , Kingston Eric E. 
Published: May 2005

AbstractThe mass spectra of a number of aliphatic nitro compounds have been studied using electron Ionization (EI) and a variety of chemical Ionization (CI) techniques in attempts to obtain relative molecular mass information. The use of positive ion ammonia chemical Ionization techniques gave very satisfactory results, providing abundant [M + NH4]+ ions, not only from both primary and secondary nitro compounds, but also from the much more labile tertiary nitro compounds. However, the use of methane and isobutane positive ion CI or EI conditions resulted in facile fragmentation with little relative molecular mass information being made available. Negative ion CI using methane, isobutane or ammonia as moderating gases all gave abundant [M − 1]− ions with primary and secondary nitro compounds but at much reduced sensitivity.
Bifunctional even‐electron ions. III. Fragmentation behaviour of aliphatic hydroxonium ions containing an additional carbomethoxy group
Authors: Záluorszky U. I. 
Published: May 2005

AbstractThe primary and subsequent fragmentations of the bifunctional oxonium ions \documentclass{article}\pagestyle{empty}\begin{document}${\rm R} \!-\! \mathop {\rm C}\limits^ + ({\rm OH})\! -\! ({\rm CH}_2)_n \! - \! {\rm COOCH}_3 $\end{document} (n = 0−5), a, are dominated by functional group interactions. Loss of CH3OH is the only appreciable primary fragmentation of the higher homoiogues, but for the lowest homologue (a0) this reaction is missing. Instead, CO loss is observed. The next homologue (a1) shov.s loss of CH2CO besides loss of CH3OH. The mode of the subsequent fragmentations is dependent on the chain length separating the functional group, and formation of cyclic ions is typical of the fragmentation behaviour of a2 and a3. Evidence for proton transfer from the carbonyl oxygen to the methoxy group of a protonated ester group is presented.
Unimolecular fragmentation reactions of protonated and methyl‐cationated n‐octanones and N‐nonanones. Sequential fragmentation reactions
Authors: Chowdhury Swapan , Harrison Alex G. 
Published: May 2005

AbstractProtonated and methyl‐cationated n‐octanonts and n‐nonanones have been prepared by chemical ionization methods and the unimolecular fragmentation reactions occurring on the metastable ion time‐scale have been exam ined. The [R1R2COR3]+ (R3 = H or CH3) species fragment by elimination of R3OH and by elimination of neutral alkenes. The elimination of (R1 — H), where R1 is the larger alkyl group of the original ketone, is particularly important. In addition, alkenyl ions are observed corresponding, nominally, to elimination of C3H7OR3 from the ionized octanones and to elimination of C3H7OR3 and C4H9OR3 from the nonanones. These ions are shown to arise largely, if not completely, by sequential elimination of R3OH plus an olefin (C3H6 or C4H8) from [R1R2COR3]+. A comparison is made of the unimolecular fragmentation reactions occurring in the second field‐free region and in the radio‐frequency‐only quadrupole of a hybrid BEQQ mass spectrometer.