bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mass spectrometry of kaurene derivatives—II: Kaurenolides and related systems
Authors: Kalinovsky A. I. , Serebryakov E. P. , Simolin A. V. , Kucherov V. F. , Chizhov O. S. 
Published: May 2005

AbstractThe mass spectra of a number of natural (II, IV, XII) and modified kaurenolides (I, III, V to XI) are reported. The major fragmentations of these compounds occur by rupture of the ring B to give fragments B and C, both of which contain the ring A. In the case of the 7‐hydroxycompounds (II and III) their mass spectra are markedly different due to the difference in configuration at C7.
Negative ion mass spectrometry of the new riboflavin metabolite: 7,8‐dimethyl‐10‐formylmethyl‐isoalloxazine ethyl‐hemi‐alcoholate (flavin‐10‐acetaldehyde ethyl‐hemi‐alcoholate)
Authors: Tümmler R. , Steinfelder K. , Owen E. C. , West D. W. 
Published: May 2005

AbstractFlavin‐10‐acetaldehyde ethyl hemi‐alcoholate obtained at the Hannah Dairy Research Institute by bacterial degradation of riboflavin was examined in the Electron Attachment (EA) apparatus at the Forschungsinstitut Manfred von Ardenne. At low temperatures pyrolysis was negligible and the peak of greatest mass was only four units less than the molecular weight. The fragmentation patterns at greater field strengths indicated metastable peaks of masses in accord with the fragmentation pattern at lower fields. The patterns at the lower temperatures used resembled in important respects the EA pattern from riboflavin in an earlier study. In explanation of the fragmentation pattern obtained, structures have been assigned to the ions recorded.
The mass spectra of N‐acyliminopyridinium and isoquinolinium betaines
Authors: Ikeda M. , Tsujimoto N. , Tamura Y. 
Published: May 2005

AbstractThe mass spectral fragmentation behaviour of N‐acyliminopyridinium and isoquinolinium betaines has been investigated. Major fragmentations of the pyridinium betaines can be rationalized in terms of charge localization on the pyridinium nitrogen. The most prominent process is α‐cleavage followed by loss of NCO to furnish a pyridine ion. The electron‐impact induced fragmentation of N‐benzoyliminopyridinium betaine (I) was compared with that of thermolysis. The completely analogous behaviour has been observed in the corresponding isoquinolinium betaines.
The mass spectrum of tropylium fluoroborate
Authors: Gardner R. J. 
Published: May 2005

AbstractThe mass spectrum of tropylium fluoroborate (C7H7+BF4−) shows a base peak corresponding to the cationic portion of the salt (m/e91) and intense peaks occur at m/e 109 (C7H6F+) and m/e 110 (C7H7F+.). The latter peaks are probably of thermal origin. A similar rearrangement is observed in trityl fluoroborate (C19H15+BF4−) and may be a general feature of the mass spectra of aromatic fluoroborates.
Alcaloïdes stëroïdiques—cxi Influence D'un Groupement Hydroxyle sur la Fragmentation D'amines, Amides et Imines Stéroïdiques en Spectrométrie de Masse
Authors: Longevialle P. , Einhorn J. , Alazard J. P. , Diatta L. , Milliet P. , Monneret C. , Khuong‐Huu Q. , Lusinchi X. 
Published: May 2005

AbstractLa prtsénce d'un groupement hydroxyle dans les molécules de certaines amines, amides et imines stéroídiques joue un grand rôe dans la fragmentation de celles‐ci en spectrométrie de masse. Cette fragmentation est initiée par le transfert, parfois à longue distance, de l'hydrogéne hydroxylique sur les groupements azotés et donne naissance à des ions caractéristiques de la place de l'hydroxyle.
Correlation of structure and fragmentation modes of costunolide and its derivatives
Authors: Sathe R. N. , Deshpande S. N. R. , Kulkarni G. H. , Kelkar G. R. , Das K. G. 
Published: May 2005

AbstractMass spectral studies on costunolide and lactones derived therefrom, have revealed some general fragmentation modes involving the losses of 44, 55, 57, 59, 71, 73 and 83 mass units from the molecular ion. The probable genesis of these ions is established by high resolution, metastable transitions and deuterium labelling studies. Comparison has been made with the mass spectra of some C6‐ desoxy esters.
The elucidation of the primary structure of the hypothalamic thyroid stimulating hormone releasing factor of ovine origin by means of mass spectrometry
Authors: Desiderio Dominic M. , Burgus Roger , Dunn Thomas F. , Vale Wylie , Guillemin Roger , Ward Darrell N. 
Published: May 2005

AbstractThis paper illustrates the role that mass spectrometry played in the first elucidation of the primary structure of a hypothalamic releasing factor. It has been demonstrated that ovine TRF has the structure 2‐pyrrolidone‐5‐carboxylyl‐histidyl‐proline amide.
Electron‐impact induced fragmentation of partially fluorinated β‐diketones
Authors: Rubesch M. , Clobes A. L. , Morris M. L. , Koob R. D. 
Published: May 2005

AbstractThe ionic fragmentation of twelve partially fluorinated β‐diketones, RCOCH2COCF3 was studied with a medium resolution mass spectrometer. In addition to the anticipated fragmentation by β‐cleavage, a number of interesting rearrangements are observed. [CF3COCH2CO]+., an ion common to all of the compounds investigated, decomposes predominantly by elimination of HF. When R is an alkyl group containing hydrogen γ to the adgacent carbonyl, the McLafferty rearrangement occurs. The [RCOCH2CO]+.ion eliminates neutral RH when R is phenyl, thienyl, or cyclopropyl. An intense metastable peak, absent when R is an alkyl substituent, accompanies the rearrangement in these three compounds. A number of fragments characteristic of the R substituent are also observed in many cases. This is interpreted as indicating a considerable degree of charge localization on the R moiety.
The behaviour of perchloro‐3,4‐dimethylenecyclobutene,‐pentafulvene and‐ pentafulv‐alene under electron‐impact
Authors: Agranat Israel , Loewenstein Ruth M. J. , Bergmann Ernst D. 
Published: May 2005

AbstractThe mass spectra of 1,2‐dichloro‐3,4‐bis(dichloromethylene)cyclobutene (IV) and of hexachloropentafulvene (II) have been studied. Compound IV cannot be an intermediate in the formation of II from octachloro‐1,2‐dimethylenecyclobutane (III) under electron‐impact, as previously suggested. In the mass spectra of II and IV the species [C6]+ and [C5]+ occur, obviously through cleavage of the semicyclic C‐C bond.The mass spectrum of pentachlorofulvalene (VI) shows strikingly that successive elimination of an even number of CI atoms is preferred over that of an odd number of CI atoms; probably corresponding C‐CI bonds in the two rings are broken simultaneously. Amongst the fragments, the species [C10]+ and [C7]+ and possibly also [C8]+ and [C9]+ have been observed.
Gas chromatographic and mass spectrometric characteristics of some bicyclic thioketones
Authors: Campbell M. M. , Anthony G. M. , Brooks C. J. W. 
Published: May 2005

AbstractThree bicyclic thioketones were examined by combined gas chromatography‐mass spectrometry. Deuterium labelling was employed in the interpretation of the fragmentation processes in thiocamphor. Compared with the oxygen analogues, the thiones yielded on electron‐impact a higher proportion of characteristic fragment ions containing the hetero‐atom.
Rearrangements in the electron‐impact induced fragmentation reactions of 5‐alkylthio‐1,3,4‐thiadiazolyl‐2‐amines
Authors: Barnes C. S. , Goldsack R. J. , Rao Ravindra Pratap 
Published: May 2005

AbstractThe low resolution mass spectra of a number of homologous 5‐alkylthio‐1,3,4‐thiadiazolyl‐2‐amines have been determined. With the methylthio compound the only significant loss from the molecular ion is the sulphydryl radical. As the homologous series is ascended this reaction becomes less important and is insignificant with the butylthio isomers. The ethylthio compound suffers extensive loss of ethylene and when the alkyl group contains three or more carbon atoms the main reaction is always loss of the olefin coresponding to the alkyl group.All of the n‐alkylthio compounds showed in addition loss of methylthio radical from the molecular ion. A mechanism is proposed and comparisons made with alkyl phenyl thioethers and alkylthio substituted heterocycles.
Electron‐impact induced hydrogen scrambling in cyclohexanol and methylcyclohexanols
Authors: Shapiro Robert H. , Levine Steven P. , Duffield A. M. 
Published: May 2005

AbstractExact mass measurements and the mass spectral behavior of O‐deuterated cyclohexanols, coupled with a re‐evaluation of previously published data1,2, show that the hydrogen attached to oxygen undergoes partial scrambling with the 2, 3, 5 and 6 position ring hydrogens prior to or during the formation of the major primary fragment ions.
Fluorinated carbohydrates—IX The mass spectra of deoxyfluorohexopyranose derivatives
Authors: Chizhov O. S. , Kadentsev V. I. , Zolotarev B. M. , Foster A. B. , Jarman M. , Westwood J. H. 
Published: May 2005

AbstractThe mass spectra of some deoxyfluorohexopyranose acetates bearing the fluorine substituent at positions 2,3,4, or 6 were determind. The fragmentation pathways were analogous with those for hexopyranose acetates, except that the cleavage of bonds between carbon atoms was hindered by the attachment of a fluorine substituent to one of the carbon atoms.
Heterocyclic studies—XXII. Mass spectra of some 3‐hydroxypteridin‐4‐ones
Authors: Clark Jim , Smith C. 
Published: May 2005

AbstractMass spectra of 3‐hydroxypteridin‐4‐one and five of its mono‐and di‐methyl derivatives are recorded. Fragmentation of the non‐methyl compound (I; R1  R2  R3  H) occurred mainly by successive losses of NO, CO, HCN and HCN. Changes in m/e values of the major peaks with methyl‐substitution pattern in the derivatives were consistent with the proposed fragmentation pattern. Several minor fragmentation pathways were also observed but all involved an initial loss from the oxygen containing ring.
Application of mass spectrometry to oligosaccharide sequencing
Authors: Kochetkov N. K. , Chizhov O. S. , Malysheva N. N. , Shiyonok A. I. 
Published: May 2005

AbstractA recent publication by Johnson et al1. Prompted us to record our earlier findings from mass spectral studies of oligosaccharide (see ref.2). This investigation has shown the possibility of oligosaccharide sequencing by means of the mass spectra of their phenylozotriazoles and N‐arylglycosylamines.
Mass spectra of chloro‐substituted benzophenones
Authors: George W. O. , Hassid D. V. , Phillips J. 
Published: May 2005

AbstractThe mass spectra of all three monochloro‐, seven of the dichloro‐ and two of the trichloro‐substituted benzophenones are reported. The major fragments in the spectra are due to α‐fission to oxonium ions followed by the well‐known subsequent fragmentations. The ring bearing the greater number of chlorine atoms appears to cleave more readily, with 2‐chloro substituents enhancing this tendency. There is evidence for the formation of the biphenylene ion in all monochloro and all dichloro compounds studied and for the formation of the chloro biphenylene ion in both trichloro compounds studied. In the case of 2,2′‐, 2,4‐ and 3,4‐dichlorobenzophenones evidence exists for hydrogen transfer between rings.
Mass spectral evidence for the conversion of benzenephosphonic acid to its cyclic, trimeric anhydride and of benzenephosphonous acid to phenylphosphine
Authors: Wiley Richard H. 
Published: May 2005

AbstractThe mass spectra of benzenephosphonic and benzenephosphonous acids are readily observable under normal operating conditions and, at low sample temperatures (50 to 85°C), the 70 eV electron‐impact degradations are characteristic. The phosphonic acid shows peaks for the molecular ion at 158 amu and for characteristic degradation fragments at 141 (C6H5PO2H), 94 (C6H6O), 78 to 7 (C6H6, C6H5), 65 (H3PO2, C5H5), 51 (C4H3), 47 (PO) and 39 (C3H3) amu. Above 120°, however, and after a pressure surge indicative of a thermal dehydration in the sample, a peak at 420 amu associated with the cyclic, trimeric anhydride, (C6H5PO2)3, is observed along with a characteristic set of fragment peaks at 373, 357, 343, 327, 280, 262, 233, 216 and 199 amu, whose interrelations are summarized in Scheme 1. The phosphonous acid, at 75°C and at 70 eV, shows peaks for the molecular ion at 142 amu and for characteristic degradation fragments at 124 (C6H5PO), 111 to 107 (C6H5PH ± 2H), 94 (C6H6O), 78 to 7 (C6H6, C6H5), 65 (H3PO2, C5H5), 51 (C4H3), 47 (PO) and 39 (C3H3) amu. The phenylphosphine is apparently formed by rearrangement in the excited state after electron‐impact rather than by thermal disproportionation in the sample as the latter requires the formation of relatively more of the phosphonic acid than is observed. At higher sample temperatures (120°C) somewhat increased amounts of the phosphonic acid, presumably formed by partial disproportionation in the sample, are observed. Accurate mass assignments and broad metastables confirm the postulated fragmentation processes.
Etude de steroides fluores par spectrometrie de masse—III: Spectres de masse de quelques cetones fluorees
Authors: Chavis C. , Fonzes L. , Guida A. 
Published: May 2005

AbstractUne série de 24 cétones stéroïdes fluorées a été étudiée enspectrométrie de masse. Les différentes positions de la fonction cétone et de l'atome de fluor ont permis de mettre en évidence des fragmentations intéressantes.
Mass spectrometry of aralkyl compounds with a functional group—XII: Unorthodox elimination of hydrogen cyanide from hydrogen randomized molecular ions of benzylcyanide and of o‐, m‐ and p‐cyanobenzylcyanides, revealed by D‐, 13C‐ acid 15N‐labelling
Authors: Molenaar‐Langeveld T. A. , Nibbering N. M. M. , De Boer Th. J. 
Published: May 2005

AbstractSpecific D‐labelling in the side‐chain and in the phenyl ring, 13C‐labelling in the benzylic position and in the cyano group and 15N‐labelling in the cyano group of benzylcyanide show, that the molecular ion, decomposing in the second field free region, i.e. having a low internal energy, loses hydrogen cyanide with participation of both side‐chain carbon atoms (22% benzylic carbon and 78% cyano carbon) after a complete randomization of all hydrogens. This sharply contrasts with the loss of hydrogen cyanide from the hydrogen randomized molecular ion, decomposing in the ion source, where the original cyano group is involved exclusively.The molecular ions of (o, m, p)‐cyanobenzylcyanides, decomposing in the ion source as well as in the second field free region, also lose hydrogen cyanide, involving to some extent (6 to 15%) a carbon atom, different from that of the side‐chain cyano group, after an extensive randomization of hydrogens as shown by specific D‐labelling in several positions and by 13C‐ and 15N‐labelling in the side‐chain cyano group. Furthermore, the molecule of hydrogen cyanide, eliminated in the ion source and in the second field free region, appears to contain predominantly the side‐chain cyano group (±70%), thus suggesting that few or none of the molecular ions have rearranged to a seven membered ring.
Mass spectrometry of pyridine compounds—II: Hydrogen exchange in the molecular ions of isonicotinic—and nicotinic acid as a function of internal energy
Authors: Neeter R. , Nibbering N. M. M. 
Published: May 2005

AbstractFrom the mass spectra of site‐specifically deuterated analogues of isonicotinic acid it appears that the molecular ion eliminates hydroxyl and water after an exchange between the hydroxylic and β‐hydrogens. The percentage of exchange in these reactions depends on the internal energy of the molecular ion and is shown to be 53 to 57% in the ion source, 92 to 97% in the first and ∽ 100% in the second field free regions.Furthermore, the isotope effect i, operative in the loss of water, increases with decreasing internal energy of the molecular ion, being 1.6, 2.0 and 2.3 in the ion source, first‐ and second field free regions, respectively.In the molecular ions, losing successively hydroxyl and carbon monoxide as deduced from diffuse peaks in the first‐and second field free regions, a substantially lower percentage of exchange (ca. 20%) is found, which is due to the higher internal energy of these molecular ions.In the molecular ion of nicotinic acid only one of the ortho hydrogens (α) is involved in the exchange of hydrogen. The percentage of exchange for loss of hydroxyl in the ion source is 66%. Molecular ions, which successively eliminate hydroxyl and carbon monoxide, show a 45% exchange of hydrogen as calculated from diffuse peaks in the first‐ and second field free regions.
A mass spectrometric study of 4‐hydroxy‐6‐methyl‐2‐pyridone and its derivatives
Authors: Wulfson N. S. , Zaikin V. G. , Ziyavidinova Z. S. , Burikov V. M. , Mukerjee S. K. 
Published: May 2005

AbstractThe mass spectra of 4‐hydroxy‐6‐methyl‐2‐pyridone, its N‐methyl and N‐phenyl derivatives, and also their 4‐O‐acetyl and 3‐C‐acyl derivatives have been studied. The proposed fragmentation pathways were supported by comparison of the mass spectra and in some cases by the spectra of deutero analogues. A strong N‐phenyl group effect has been found, which in the case of N‐phenyl‐4‐hydroxy‐ and N‐phenyl‐4‐acetoxy‐6‐methyl‐2‐pyridones promotes the formation of the stable [M—H]+ and [M—CH3CO]+ ions respectively. These ions are not characteristic of the N—H and N—Me analogues.
2‐(1‐Azulyl)ethyl tosylate methylene scrambling in the gas phase. Similarities to solution chemistry
Authors: Graham Cooks R. , McDonald Richard N. , Curtis James R. , Petty Herbert E. 
Published: May 2005

AbstractThe methylene groups in 2‐(1‐azulyl)ethyl tosylate are largely scrambled prior to formation of fragment ions in the mass spectrometer. This process also occurs in the 3‐nitro analog, where it is dependent on sample residence time in the source and independent of electron energy. It could not be observed with the isomeric 6‐substituted tosylates, the 1‐substituted acetates or alcohols, or with 2‐(p‐anisyl)ethyl tosylate. Scrambling occurs in the neutral molecule prior to ionization and a mechanism involving absorption onto the metal surface and formation of a complexed ethylenazulonium ion is suggested.
Potentiel d'ionisation, potentiel d'apparition et courbes d'ionisation differentielle pour les 1‐2 dimethylcyclohexanes CIS et Trans
Authors: Lageot C. 
Published: May 2005

AbstractLes potentiels d'ionisation et d'apparition de différents ions ont été mesurés pour les deux composés cis et trans 1‐2 diméthylcyclohexanes par la méthode EDD. Les différences notées dans les courbes d'ionisation différentielle des ions [M—CH3]+. et [M—2CH3]+. nous conduisent à admettre une réorganisation donnant naissance à des ions cyclobuteniques.
Potentiel d'ionisation, courbes d'efficacite d'ionisation differentielle, localisation de la charge de 9 cyclopropanes
Authors: Lageot C. 
Published: May 2005

AbstractRües potentiels d'ionisation, les courbes d'efficacité d'ionisation différentielle ont été déterminées par la méthode EDDEDD: Energy Difference Distribution (voir R. E. Winters).6
pour 9 cyano‐1 diphényl‐l,2 cyclopropanes. II est montrk que les composés comprenant le groupement diméthylamino possedent les potentiels d'ionisation les plus bas. Pour ces cornposés, on peut établir une corrélation qualitative entre le potentiel d'ionisation, la première cassure dans la courbe d'efficacité d'ionisation différentielle et la constante de Hammett. Pour les composés comprenant le groupement nitro, la valeur constante de la première cassure au dessus du potentiel d'ionisation nous permet de penser que ce substituant a un rǒe primordial dans l'état excité des ions moléculaires.
Aromatic perchlorocarbons and perchlorocarbon radicals as mass spectral reference standards
Authors: Freeburger Michael E. , Mason Hughes B. , Spialter Neonard , Tiernan Thomas O. 
Published: May 2005

AbstractThe mass spectral cracking patterns of several aromatic perchlorocarbons and perchlorocarbon radicals are reported. These include the first examples of mass spectra of stable carbon free‐radical substrates, and they do not differ significantly from those of structurally similar neutral substrates. All the compounds show successive loss of chlorine atoms with very little fragmentation of the carbon skeleton. This class of compounds has potential value to mass spectroscopists as reference standards in the range m/e 300 to 700.
Studies in organic mass spectrometry—IV: N‐iminopyridinium betaines
Authors: Ikeda M. , Tsujimoto N. , Tamura Y. 
Published: May 2005

AbstractThe mass spectra of N‐iminopyridinium betaines, which have been generated within the ion source by pyrolysis of the corresponding hydrochlorides, have been compared with those of pyridine N‐oxides.
Electron‐impact induced skeletal re‐arrangement of 2‐methoxy‐3‐methylpyrazine and 2‐methylthio‐3‐methylpyrazine
Authors: Kolor Michael G. , Rizzo Donald J. 
Published: May 2005

AbstractThe mass spectra of 2‐methoxy‐3‐methylpyrazine (I), 2‐methoxy‐6‐methylpyrazine (II), 2‐methylthio‐3‐methylpyrazine (III) and 2‐methylthio‐6‐methylpyrazine (IV), are given and the major fragmentation pathways discussed. The novel loss of H2O from the molecular ion of I and the corresponding loss of H2S from the molecular ion of III indicate that a skeletal rearrangement takes place in the molecular ion preceding the expulsion of H2O and H2S. Proposed mechanisms for this behavior are discussed with evidence being drawn from accurate mass measurement, metastable ions, and deuterium and carbon‐13 labeling of the methoxy group. The absence of ions in the spectra of II and IV corresponding to the loss of H2O and H2S from these molecular ions clearly indicates that the position of the methyl group with respect to the methoxy group, or the methylthio group is in‐timately involved in this mechanism.
Heterocyclic studies—XXIV: Mass spectra of some pteridin‐4(3H)‐ones and 3‐methoxypteridin‐4(3H)‐ones
Authors: Clark Jim , Maynard Ruth , Smith C. 
Published: May 2005

AbstractMass spectra of pteridin‐4(3H)‐one and all its mono‐, di‐ and tri‐C‐methyl derivatives are recorded. Spectra of 3‐methoxypteridin‐4(3H)‐one and four of its mono‐ and dimethyl derivatives are also recorded.Pteridin‐4(3H)‐one fragments mainly by loss of CO and HCN in either order. Methyl substitution in the pyrazine ring leads to that ring fragmenting in preference to the oxygen bearing pyrimidine ring. Elucidation of fragmentation pathways was facilitated by changes in peak positions with changing methyl substitution patterns.3‐Methoxypteridin‐4(3H)‐ones fragment mainly through initial loss of CH2O, but the ions so produced break down differently from isomeric molecular ions of pteridin‐4(3H)‐ones. Several fragmentation pathways are discussed.
Rearrangement and cyclization reactions in the mass spectra of a series of isatin carbonyl derivatives of medicinal interest: 2‐Oxo‐3‐indolinylidene anils (n‐arylketimines), 2‐oxo‐3‐indolinylidene phenylhydrazones, 2‐oxo‐3,3‐bis‐(o‐diaminoaryl) indolyl deriv‐atives and their 2,3‐quinoxaline heterocyclic analogues
Authors: Ballantine J. A. , Fenwick R. G. , Popp Frank D. 
Published: May 2005

AbstractThe mass spectra of several types of carbonyl derivatives of isatin have been examined and the fragmentation pathways have been studied. There are many differences from previously reported data on similar derivatives of less complex carbonyl compounds and several rearrangement processes have been shown to be involved in the cleavage reactions. Some interesting examples of ‘ortho‐effects’ have also come to light as a result of this investigation.
Spectrometrie de masse de biphenyles 0,0'–pontes—II
Authors: Maquestiau A. , Van Haverbeke Y. , Delalieu F. 
Published: May 2005

AbstractL'étude par spectrométrie de masse de trois types de biphényles montre que ces produits se dégradent de façon similaire. Néanmoins, des variations d'intensité suggèrent que la nature du pont influence les cinétiques de plusieurs mécanismes en cascade.
Über eine einfache methode zur formierung von Rhenium‐Kathoden
Authors: Müller J. 
Published: May 2005

AbstractDurch Einwirkung flüchtiger metallorganischer Thorium‐Verbindungen, z.B. Th(C5H5)4, auf Rhenium‐Kathoden werden deren Emissionseigenschaften wesentlich verbessert. Es kann bei reduziertem Kathodenheizstrom und dadurch bei tieferen Ionenquellentemperaturen gearbeitet werden. Der Effekt hält über mehrere Wochen oder Monate an.