bluuebunny/crossref_metadata_2025_split huggingface dataset:
Triple quadrupole tandem mass spectrometric study of the 3‐picolinyl esters of fatty acids
Authors: Rubino Federico Maria , Zecca Luigi 
Published: May 2005

AbstractLow‐energy collision‐induced dissociation of some representative 3‐picolinyl esters of fatty acids were investigated. The daughter‐ion spectra of the precursor ions showed similar features to the electron impact mass spectra, but the low intensity of the parent‐ion signal did not allow reliable deductions. The parent‐ion spectra of some fragments that retain the pyridine derivatizing group contain structurally useful information, and are suitable for analytical application. These spectra also contain fragment ions which may account for an alternative pathway to that currently proposed for the generation of certain fragment ions within the ion source. Both pathways were investigated in this tandem mass spectrometric study. Isomerization and decomposition of distonic fragment ions through loss of alkenes yield species with a shorter alkyl chain, which are particularly stable when they contain allylic radicals.
Tandem mass spectrometry in the structural analysis of an oviposition‐deterring pheromone
Authors: Domon B. , Müller D. R. , Richter W. J. 
Published: May 2005

AbstractThe potential of tandem mass Spectrometry (MS/MS) as a stand‐alone technique in the structural analyses of an oviposition‐deterring pheromone (ODP, 1) is reviewed. Two facets of the salt‐like glycolipid structure of 1 were of major interest in this context: the substitution pattern of the lipid backbone (15‐glucosyioxy‐8‐hydroxypalmitate) and, more specifically, the configurational identity of the sugar portion (glucopyra nose). Throughout this study, trideuterioacetyl derivatives of ODP (1 → pentakis(trideuterioacetyl)‐ODP la) and the reference substrates were used. Probing of the sugar moiety by fast atom bombardment (FAB) and both low‐ and high‐energy collision‐induced dissociation (CID) of B2‐type sugar ions surprisingly failed as a single exception within a larger number of glycosidic substrates subjected to this approach. However, electrospray ionization (ESI) of la with the formation of the sugar ions in the gas phase by ‘first‐stage’ CID before mass selection circumvented this difficulty and provided an unambiguous and sensitive probe for sugar stereochemistry. When studying the ODP molecule as a whole, FAB‐generated M‐like ions such as [M − H]−, [M + Na]+ and [M − H + 2Na]+ were subjected to high‐energy CID using a four‐sector tandem mass spectrometer. Analyses of simple model substrates such as the 12‐trideuterioacetoxystearate anion facilitated the interpretation of the distinct charge‐remote fragmentation (CRF) behaviour of la. Whereas all M‐like species provided complete records of the lipid portion of la and its oxygenation pattern, only the sodiated cations allowed reliable location of the individual substituents. In these latter species complementary series of ‘sequence ions’ were observed that incorporated either the taurine or the sugar terminus and thus reflected CRF for both alternatives of terminal charge fixation.
Ortho effect in the mass spectrometric behaviour of N(pyrimidin‐4‐yl)aminobenzoic acids and their methyl esters
Authors: Plaziak Adam S. , Spychala Jaroslaw , Wójtowicz Hanna , Langer Jerzy J. , Thiel‐Pawlicka Halina , Golankiewicz Krzysztof 
Published: May 2005

AbstractOrtho‐. meta‐ and para‐isomers of N‐(pyrimidin‐4‐yl)aminobenzoic acid and their methyl esters were investigated by electron impact mass Spectrometry. Their fragmentation was found to be strongly dependent on the position of the substituent in the aminobenzoic moiety. Two different kinds of ortho effect were studied and confirmed with the aid of deuterium‐labelled derivatives.
Mass‐analysed ion kinetic energy and collisionally induced dissociation mass spectra of clusters of acetylated xylo‐oligosaecharides with protonated ammonia and methylannine
Authors: Kovàčcik V. , Hirsch J. , Kováč P. , Grützmacher H.‐Fr. 
Published: May 2005

AbstractPer‐O‐acetylated methyl glycosides of D‐xylan‐type di‐ and trisaccharides were studied by mass‐analysed ion kinetic energy (MIKE) and collisionally induced dissociation (CID) mass Spectrometry using protonated ammonia and methylamine, respectively, as reaction gases in chemical ionization (CI). The oligosaccharides form abundant cluster ions, [M + NH4]+ or [M + CH3NH3]+, and the main fragmentation of these ions in the MIKE and CID spectra is the cleavage of interglycosidic linkages. Thus, CI (NH3) or CI (CH3NH2) spectra in combination with the MIKE or CID spectra allow the molecular masses, the masses of monosaccharide units and the branching point in oligosaccharides to be established. In the case of disaccharides, it is possible to distinguish the (1 → 2) linkage from the other types of linkages.
Daughter ion mass spectra of 11‐pentafluorobenzyl ester derivatives of 11‐dehydiothromboxane B2 and B3
Authors: Ferretti Aldo , Flanagan Vincent P. 
Published: May 2005

AbstractCollisionally activated decomposition (CAD) mass spectra of the [M – C6F5CH2⋅]− ions of 1‐methyl cster‐11‐pentafluorobenzyl ester‐9,12,15‐tris(trimethylsilyl) and 9,12,15‐tris(ethyldimethylsilyl) ether derivatives of 11‐dehydrothromboxane B2 are presented and discussed. The spectra are interpreted with the aid of those of a corresponding 3,3,4,4‐tetradeutero compound and of an analogous derivative of 11‐dehydrothromboxane B3. Proposed fragmentation pathways are based on internal consistency of data from all four compounds. The migration of a trimethylsilyl or an ethyldimethylsilyl group is the salient feature of all the CAD spectra.
Collisional activation of metal cationized and deprotonated triterpenoids: Charge remote fragmentations
Authors: Madhusudanan K. P. , Singh Chandan 
Published: May 2005

AbstractThe collisional activation spectra of lithiated and bariated cations and deprotonated anions of the triterpenoic acids hederagenin and oleanoic acid and their acctyl derivatives were examined. On collisional activation these precursors undergo similar charge‐remote fragmentations including ring cleavage reactions and loss of substituents from the ring furthest from the site of charge. The presence of a double bond in ring C induces charge‐remote retro‐Diels–Alder reaction in these molecules.
Use of deuterium–hydrogen exchange to characterize the fragmentation pathways of arteether and its metabolites in a thermospray mass spectrometer
Authors: Chi Hsien Tao , Baker John K. 
Published: May 2005

AbstractWhereas the thermospray mass spectra of most compounds consist of only the pseudo‐molecular ion with little fragmentation, the thermospray mass spectra of arteether (a cyclic endoperoxide) and its metabolites are relatively complex. Assignments of structures to individual fragments from normal spectra was particularly ambiguous because of uncertainties as to which fragments arose from ammonium ion or methanol adducts. In this study, these assignments could be resolved through the comparison of the regular spectrum with the deuterium‐exchange spectrum (in an ND4O2CCH3–CD3OD–D2O mobile phase) achieved using ‘sandwiched slug’ injection technique. The mass spectra of arteether and four of its metabolites all showed [M + ND4]+ pseudo‐molecular ions with greater than 91% H/D exchange, indicating a high efficiency with a minimal use of deuterated mobile phase. Most fragments showed H/D exchange rates in the 70–90% range and the isotope shift of individual spectral lines (ΔM) was found to be extremely useful in determining the structure of the fragment.
Californium‐252 time‐of‐flight mass spectrometry of synthetic porphyrins
Authors: Tarnaud Eric , Robic Nadine , Gaudemer Alain , Bied‐Charreton Claude , Deprun Claude 
Published: May 2005

AbstractMass spectra of synthetic porphyrins were recorded using a 252Cf Time‐of‐flight mass spectrometer (TOF 21). They proved to be very useful for obtaining structure probes on porphyrins for which very little information was available owing to the presence of paramagnetic ions or to badly resolved NMR spectra.
Continuous‐flow fast atom bombardment mass spectrometry: A concept to improve the sensitivity
Authors: Hau J. , Schrader W. , Linscheid M. 
Published: May 2005

AbstractFor application of continuous‐flow fast atom bombardment (CFFAB), an ion source for a sector field mass spectrometer was designed which gives improved sensitivity and much better long‐term stability than a source with standard ion optics. The optics are based on two sets of static quadrupoles and a conical ion extraction device. It was shown that the gain in sensitivity has to be assigned mainly to the reduction of the chemical background in the CFFAB mass spectra. The reason for this reduction appears to be the exclusion of matrix fragment ions sputtered from the outer parts of the FAB target, whereas the center is continuously refreshed by the liquid emerging the capillary. The benefits of using this source were demonstrated in the course of the determination of the drug ifosfamide to a level of 1.5 ng cm−3 using selected ion recording and in the analysis of a Gramicidin S sample, where a minor component at a level of ∼1 pmol was detected.
Mechanism of electron impact ionization‐induced halogen elimination from 2‐methyl‐2‐bromosuccinates
Authors: Bornstein D. , Mandelbaum A. , Vidavsky I. , Domon B. , Mueller D. R. , Richter W. J. 
Published: May 2005

AbstractThe electron impact‐induced halogen elimination from 2‐methyl‐2‐bromosuccinates occurs only in the one of the two isomeric methyl ethyl esters in which the ethoxycarbonyl group is remote from the halogen, in analogy with the corresponding previously reported halosuccinates. However, the occurrence of debromination in dimethyl 2‐methyl‐2‐bromosuccinate contrasts with the behaviour of dimethyl bromosuccinate, indicating different mechanisms for this process in the two systems. Collision‐induced dissociation (CID) and deuterium labelling studies led to the conclusion that a hydrogen transfer from the 2‐methyl group to a carbonyl precedes the elimination of Br˙ from dimethyl 2‐methyl‐2‐bromosuccinate, resulting in a protonated dimethyl itaconate structure for the [M – Br]+ ion. An analogous process is the major route leading to [M – Br]+ ion from 1‐methyl‐4‐ethyl 2‐methyl‐2‐bromosuccinate. In this case deuterium labelling and CID measurements indicated a significant contribution of methyl ethyl citraconate and possibly mesaconate owing to partial operation of a mechanism similar to that reported for 1‐methyl‐4‐ethyl 2‐bromosuccinate.
Ion‐pair (X+ + Y−) formation from photodissociation of the interhalogen molecules BrCl, ICl and IBr
Authors: Kaur Devinder , Yencha Andrew J. , Donovan Robert J. , Kvaran Agust , Hopkirk Andrew 
Published: May 2005

AbstractExcitation functions for both positive and negative ions (X+ + Y−), formed by photodissociation in the vicinity of the onset of molecular ionization, for the jet‐cooled interhalogen systems BrCl, ICl and IBr are reported. The overall shape of the excitation functions indicates that a number of overlapping Rydberg systems are accessed leading to dissociation. From analyses of the ion‐pair excitation functions of the three molecules, by means of simulation calculations, the dominant Rydberg systems involved are found to be X(2Π3/2)cnsσ and X(2Π1/2)cnsσ: other weaker Rydberg systems, with configurations X(2Π3/2)cnpπ, A(2Π3/2)cnpπ, A(2Π1/2)npπ, A(2Π3/2)cnsσ and A(2Π1/2)cnsσ are also found to be present. It is concluded that the formation of ion pairs occurs by the same process in all three interhalogens, i.e. via predissociation of bound Rydberg states by ion‐pair states.
Electron affinities of naphthalene, anthracene and substituted naphthalenes and anthracenes
Authors: Heinis Thomas , Chowdhury Swapan , Kebarle Paul 
Published: May 2005

AbstractThe determination of electron transfer equilibria A− + B = A + B− in the gas phase, with a pulsed‐electron high‐pressure mass spectrometer, leads to ΔG1°, ΔH1°, and ΔS1° values. These can be converted into the free energy, enthalpy and entropy changes, ΔGa°(B), ΔHa°(B) and ΔSa°(B), for the reaction e + B = B−, since the corresponding values for the reference compounds A are known. Results were obtained for 18 substituted naphthalenes, anthracene and substituted anthracenes. The results are compared with some theoretical predictions and the corresponding reduction potentials in solution. Rate constants for 13 exoergic electron‐transfer reactions were also measured. These were found to be close to the ADO collision rates.
Reduced isotopic scrambling in neutralization–reionization mass spectra
Authors: Drinkwater Donald E. , McLafferty Fred W. 
Published: May 2005

AbstractFacile ion isomerization compromises isotopic position characterization by mass spectrometry, particularly for hydrocarbons. For example, hydrogen atom loss does not provide such characterization for [C6D5CH3]+˙ ions from electron impact ionization of toluene‐ar‐d5, as this loss is preceded by 89% H/D scrambling. Similarly, the corresponding low‐energy molecules formed from these ions by neutralization with Hg yield, on reionization, mass spectra that exhibit 78% scrambling. This is true for reionization to either positive or negative ions, collection of neutralized products scattered at larger angles and after collisional activation of the fast toluene neutral species. However, when these ions are neutralized with Cs vapor to form excited (∼5 eV) toluene molecules, half of the resulting losses occur before H/D scrambling. The resulting neutralization–reionization mass spectra are thus more useful for isomeric isotopic characterization. The method is not effective for ions such as [styrene]+˙ with an isomerization pathway(s) requiring far less energy than that for direct dissociation.
Metastable ion study of organosilicon compounds VI—triethoxymethylsilane and tetraethoxysilane
Authors: Tabei Eiichi , Mori Shigeru , Okada Fumio , Tajima Susumu , Ogino Kazuo , Tanabe Hirotaka , Tobita Seiji 
Published: May 2005

AbstractThe fragmentations of triethoxymethylsilane ((C2H5O)3SiCH3 (1)) and tetraethoxysilane ((C2H5O)4Si (3)) induced by electron impact were investigated by mass‐analysed ion kinetic energy (MIKE) spectrometry and a deuterium‐labelling study. These molecular ions begin to fragment by the loss of methyl, ethyl and/or ethoxy radicals. Almost complete scrambling of methylene hydrogen takes place in these resultant intermediate ions, prior to the elimination of acetaldehyde molecule. The fragmentations of [1]+˙ and [3]+˙ were compared with those of the corresponding carbon analogues, 1,1,1‐triethoxyethane ((C2H5O)3CCH3 (2)) and tetraethoxymethane ((C2H5O)4C (3)), respectively.
Conformational effect on gas‐phase protonation and NH4+ clustering of 1,2‐diols
Authors: Bouchoux Guy , Jezequel Sylvie , Penaud‐Berruyer Florence 
Published: May 2005

AbstractAb initio molecular orbital calculations at the MP2/6–31G*//3–21G level are reported on conformers of neutral ethane‐1,2‐diol (ethylene glycol; 1), its protonated from 1H+ and the ammonium adduct [1NH4]+ for an OCCO dihedral angle (θ) of 0–180°. The proton affinity (PA) of 1 was determined in ion cyclotron resonance bracketing experiments to be 820 ± 3 kJ mol−1. An adduct stabilization energy of 134 kJ mol−1 was calculated for [1NH4]+. Total optimization at the 3–21G level of cis‐ and trans‐cyclopentane‐1,2‐diol (2 and 3) and their protonated forms 2H+ and 3H+ showed distorted envelope structures with θ values of 47.2°, 73.4°, 33.0° and 58.0°, respectively. The calculation predicts PA(2) = 845 kJ mol−1 and PA(3) = 815 kJ mol−1.
Estimation of the polarizability of gaseous ions by ion trap mass measurements
Authors: Bortolini O. , Catinella S. , Traldi P. 
Published: May 2005

AbstractSignificant mass displacements from the expected instrumental value have been observed in ion‐trap experiments on several ionic species. This phenomenon has been extensively investigated and interpreted as the result of an interaction between the analyte and the radio‐frequency field present within the ion trap. Depending on the chemico‐physical characteristics of the analytes, deformation of the electron shell and forced alignment of the permanent dipoles may be induced. These two effects can be separated allowing an estimation of the polarizability related to the permanent dipoles for gaseous ions.
Mass spectrometry of transition metal π‐complexes. 40—(η4‐Norbornadiene)‐(η5‐cyclopentadienyl)rhodium derivatives
Authors: Zagorevskii D. V. , Chen Hongwen , Holmes J. L. , Nekrasov Yu. S. , Chizhevski I. T. , Rastova N. V. , Kolobova N. E. 
Published: May 2005

AbstractElectron impact mass spectra of substituted norbornadienecyclopentadienylrhodium complexes have been studied. The decompositions of molecular ions are (i) metal–ligand bond rupture, (ii) norbornadiene skeleton destruction, (iii) substituent or hydrogen atom elimination from the norbornadiene moiety and (iv) radical or neutral molecule elimination from the substituent(s) on the diene ligand. Norbornadiene ligand loss occurs more easily than loss of the cyclopentadienyl ring. Elimination of C2H2R and C2H3 from the diene ligand leads to the formation of rhodocenium or its corresponding substituted derivatives. It is proposed that bridging CC bond rupture followed by migration of the endo‐H atom around the six‐membered ring precedes the loss of the substituent. Some decomposition pathways of the norbornadiene ligand are explained in terms of specific interaction between the metal atom and substituent.
7H‐benz [kl]acridin‐7‐ylium closed‐shell ion produced from 1,8‐bis(phenylamino)naphthalenes under electron impact: Tandem mass spectrometric structure elucidation
Authors: Rentzea Marina , Rimmler Gösta , Neugebauer Franz A. 
Published: May 2005

AbstractNot only strongly basic aromatic amines such as ‘proton sponges’ show characteristic [M – Me2NH – H]+ peaks corresponding to cyclization to stable heterocyclic ions under electron impact. The fragmentation of the title compounds, which are weak bases, leads to [M – RNH2 – C6H5]+ heteroaromatic ions. These are the 7‐phenyl‐7H‐benz[kl]acridine radical cation and the delocalized stable 7H‐benz[kl]acridin‐7‐ylium ion as shown by unimolecular metastable ion spectra, collision‐induced decomposition (CID) tandem mass spectrometry (MS/MS) and accurate mass measurements. The high‐collision‐energy CID tandem mass spectra of these ions are perfectly superimposable on those of the ions produced by the reference substance, 7‐phenyl‐7H‐benz[kl]acridine obtained as a by‐product in the Ullmann phenylation of 1,8‐diaminonaphthalene. This combination of MS/MS experiments also provides strong support for the gas‐phase reaction mechanism leading to the benz[kl]acridine ions and for the structures of these ions.
Kinetic energy effects in an ion ensemble subjected to mass‐selective isolation and resonance excitation: A simulation study
Authors: March Raymond E. , Weir Mark R. , Tkaczyk Martin , Londry Frank A. , Alfred Roland L. , Franklin Anthony M. , Todd John F. J. 
Published: May 2005

AbstractA simulation study is described of the behaviour of ions confined in a quadrupole ion trap during each of two separate operations of a tandem mass spectrometric experiment. The two operations are those of mass‐selective ion isolation and mass‐selective resonance excitation to the point of ion ejection from the ion trap. The method of mass‐selective ion isolation simulated is that of consecutive ion isolation. Simulation data indicate that the collisional history of the ions prior to the isolation process can greatly influence the degree to which ions survive this process. Simulation data for mass‐selective resonance ejection are compared with experimental data obtained with a Finnigan‐MAT ion trap mass spectrometer. In each operation, the facility with which ions absorb energy from the field within the ion trap, whether this field is derived from the R.F. drive potential or a supplementary potential, can determine the extent to which ions are retained within the ion trap during the two mass‐selective operations described.
Tandem mass spectrometer for ion–molecule collision studies
Authors: Ardelean P. , Cuna C. , Ioanoviciu D. , Dunca F. , Malz L. , Petrut M. 
Published: May 2005

AbstractA variable‐angle tandem mass spectrometer designed and constructed in order to perform angle‐resolved energy distribution experiments required for the investigation of ion–molecule reaction mechanisms is described. The performance of the instrument was tested using the CH4+–CH4 system.
Electron impact mass spectra of polycyclic aromatic compounds with several types of pyridino‐ and benzobenzanthrone skeletons
Authors: Abliz Zeper , Aoki Junji , Ueda Toyotoshi , Kan Teruo , Takekawa Minoru , Iwashima Satoshi 
Published: May 2005

AbstractElectron impact mass spectra were measured for five isomers of pyridinobenzanthrones and three isomers of benzobenzanthrones. The fragmentation pattern and intensity of M2+, [M – H]+, [M – CO]i+, [M – CO – H(or 2H)]i+ and [M – CO – HCN]i+ (i = 1, 2) ions indicated remarkable differences and very interesting features according to the isomers with or without nitrogen and condensation positions of a pyridino or benzo ring to the benzanthrone skeleton. Further, the competition of decompositions through [M – H]+, [M – CO]+˙ or [M – HCN]+˙ ions was confirmed by the observation of metastable ions and the appearance energies of fragment ions. Interesting observations from these results were expulsion of an H atom in close proximity to the area around an OC group, a weak bonding interaction between sp2 CH and an OC group, inducing specific hydrogen rearrangement, and characteristic charge localization on heteroatoms.
Reactions within and between adjacent dimethylamino groups: Collision‐induced dissociation tandem mass spectrometric study of the 1,9‐bis(dimethylamino)phenalenium cation
Authors: Rentzea Marina , Hofmeister Jörg , Staab Heinz A. 
Published: May 2005

AbstractThe electron impact (EI) ionization‐induced fragmentation pathways of the new 1,9‐bis(dimethylamino) phenalenium cation [1]+ were investigated. The peri‐dimethylamino substituents of [1]+ are incorporated in a trimethine cyanine substructure and show strong steric interactions. A mechanism is proposed for the unusual elimination of CH3NCH2, HN(CH3)2 and (CH3)3N from [1]+ and for the accompanying cyclizations to heterocyclic ions: prior to fragmentation, the intact cation [1]+ rearranges, by reciprocal CH3 and H transfers, to new isomeric cations which decompose subsequently in a characteristic way. A wealth of consistent information on dissociation pathways and fragment structures is provided by collision‐induced dissociation tandem mass spectra, collision‐induced dissociation mass‐analysed ion kinetic energy spectra and exact mass measurements of the salt cation and of its primary fragment ions. The liquid secondary ion mass spectrum of [1]+ is very similar to its EI mass spectrum.
Electron impact mass spectrometry of some 6‐substituted tetrazolo[1,5‐c]pyrimidin‐5(6H)‐ones
Authors: Płaziak Adam S. , Celewicz Lech , Ciszewski Krzysztof , Golankiewicz Krzysztof 
Published: May 2005

AbstractThe electron impact mass spectra of 6‐methyltetrazolo[1,5‐c]pyrimidin‐5(6H)‐one, its 7‐ and 8‐methyl derivatives, three 8‐halo derivatives and two related nucleosides are reported. On the basis of the high‐resolution data and detected metastable ions, the fragmentation routes of their molecular ions are proposed. Coexistence of the tautomeric forms of the title compounds of cyclic (tetrazole) or linear (azide) structure can be suggested owing to the fragmentation pathways identified for the bases. Decomposition of the related nucleosides lies in the breaking of nucleoside bonds to produce the appropriate base and sugar fragments.