bluuebunny/crossref_metadata_2025_split huggingface dataset:
INDO calculations on the [Be3O(HCO2)3]+ ion configuration
Authors: Sipachev Viktor A. , Gloriozov Igor' P. 
Published: May 2005

AbstractSCF–MO–LCAO–INDO calculations show that the total energy of the [Be3O(HCO2)3]+ ion, which is the base peak in the mass spectra of the beryllium μ4‐oxoformato complex, depends on the deviation of the ion configuration from planarity. The planar form is shown to have the lowest energy. The results obtained confirm the suggestion that steric interactions are the major factor governing fragmentations of beryllium μ4‐oxocarboxylato complexes under electron impact.
Wasserstoffumlagerungen bei der elektronenstoßinduzierten Fragmentierung von Aminoäthern
Authors: Eckhardt Gert 
Published: May 2005

AbstractAuf Grund von Wechselwirkungen der funktionellen Gruppen ist das massenspektrometrische Verhalten vieler Aminoäther des Typs RO(CH2)nNR1R2 deutlich verschieden von dem einfacher äther und Amine. Zusätzlich zu α‐Spaltungen werden häufig zwei weitere Primärfragmentierungen beobachtet, eine, die zu [M–Aldehyd]+. bzw. [M–Keton]+.‐Ionen, eine andere (bei n≥3), die zu [M–R]+‐Ionen führt. Beide Prozesse sind mit Wasserstoffumlagerungen verbunden, die mit Hilfe deuterierter Verbindungen untersucht wurden, und ihre Bedeutung ist stark abhängig von den Substituenten R, R1, R2 und der Länge der Kohlenstoffkette n zwischen den Heteroatomen. Diese Abhängigkeit kann durch die zugrundeliegenden Zerfallsmechanismen gut erklärt werden.
Spectrométrie de Masse d'Hétérocycles Azotés. IX—Structure des Ions [MCH2CO]+⋅ Formés à Partir des Ions Moléculaires d'Acétamido‐2 Benzazoles et mixage d'Hydrogěnes avant leur Fragmentation
Authors: Aubagnac Jean‐Louis , Campion Philippe 
Published: May 2005

AbstractII est établi que le départ de cétěne à partir des ions molécularies de l'acétamido‐2 benzothiazole et de l'acétamido‐2 benzimidazole s'effectue suivant un mécanisme γ quatre centres pour donner l'ion amino‐2 benzazole correspondant. Pour les ions métastables γ faible énergie et é longue durée de vie, un mixage des hydrogěnes intervient avant fragmentation par départ de HNC au niveau de l'ion amino‐2 benzazole. Un mécanisme est proposé pour ce mixage.
Über quantitative Beziehungen zwischen Fragmenten und ihren relativen Intensitäten im Massenspektrometer. V—Untersuchungen an N‐t‐Alkylaminen und ‐acetamiden
Authors: Záhorszky U. I. 
Published: May 2005

AbstractDie Ionenintensitätsverhältnisse aus α‐Spaltungen von N‐t‐Alkyl‐ethylaminen sind oberhalb 18 eV unabhängig von der Elektronenenergie und gehorchen in diesem Bereich dem ‘Ionenmasseneffekt’. Der Verlauf der Intensitätsverhältnisse über den gesamten Energiebereich kann durch Zusammenwirken von Auftritts‐energie‐Differenzen und Ionenmasseneffekt erklärt werden. Anhand der N‐t‐Alkyl‐acetamide wird gezeight, daß der übliche Anstieg der Intensitätsverhältnisse I(MRgroß): I(MRklein) mit zunehmender Elektronenenergie im oberen Energiebereich hauptsächlich durch den Weiterzerfall der Ionen verursacht wird. Für die Bildungstendenz der Sekundärionen wird ein Zusammenhang mit den Massen sowie offenbar mit der inneren Energie der Primärionen festgestellt. Der ‘Ionenmasseneffekt’ ist kein direkter Effekt der Ionenmassen.
Ionisation Chimique de Composés Aromatiques Nitrés
Authors: Maquestiau A. , Van Haverbeke Y. , Flammang R. , Mispreuve H. , Elguero J. 
Published: May 2005

AbstractLes dissociation induites par collisions d'ions [MH‐30]+ observés lors de l'ionization chimique (méthane) de composés aromatiques nitrés indiquent que ces ions sont formés par réduction suivie de protonation et non par perte de NO⋅ des ions moléculaires protonés.
Metastable peaks of exponential shape
Authors: Hijazi Nasrat H. , Holmes John L. , Terlouw Johan K. 
Published: May 2005

AbstractIt is shown that a monotonically decreasing translational kinetic energy distribution predicted from the quasi‐equilibrium theory for the unimolecular fragmentation ([CH2CO]+˙→[CH2]+˙ +CO) is reflected in an exponential shape for the metastable peak in contrast to the commonly observed Gaussian type profile.
Réactions de Transposition Ionique et de Rétrocycloaddition de Dihydro‐3a, 8a Pyrazolo (3,4‐b) Indoles Sous l'Impact Electronique
Authors: Daunis Jacques , Soufiaoui Mohamed , Laude Bernard 
Published: May 2005

AbstractTrois composés isomères de structures dihydro‐3a, 8a pyrazolo (3,4‐b) indole, hydrazone D'aryl indolyl cétone et triaryl‐1,3,4 pyrazole possèdent le měme spectre de masse; il est montré que celui‐ci résulte de la superposition des spectres des deux premiers composés en équilibre après ionisation. Les dihydro‐3a, 8a pyrazolo (4,3‐b) indoles résultant de la deuxième possibilité de cycloaddition, ont aussi les měmes fragmentations. Ces résultats rendent impossible le détermination par spectrométrie de masse, de la structure des produits formés lors de la réaction de cycloaddition.
The application of a new sampling technique using an atomizer for chemical ionization mass spectrometry to free amino acids, drug components, higher phthalates and oligomers of styrene and ethyleneglycol
Authors: Hirata Yukio , Takeuchi Tsugio , Tsuge Shin , Yoshida Yu 
Published: May 2005

AbstractA new vacuum atomizing sample introduction device was developed and applied to take stable and reproducible chemical ionization mass spectra of various involatile compounds. As examples, chemical ionization spectra of some free amino acids, drug components in a cold medicine, higher phthalates, oligomers of styrene and ethyleneglycol, etc., are presented.
Mass spectra of some naturally occurring stictane triterpenoids and their trimethylsilyl derivatives
Authors: Holland Patrick T. , Wilkins Alistair L. 
Published: May 2005

AbstractThe mass spectra of ten di‐ and tri‐oxygenated stictane triterpenoids and their trimethylsilyl derivatives have been studied in detail. Gas chromatography mass spectrometry of the TMS derivatives on OV‐17 and OV‐101 columns provided useful separations and identifications of mixtures of stictanes triterpenoids in lichen extracts. The major fragmentations involve ring C, but specific cleavages in rings A, B and E are also observed which allow the substitution pattern of the skeleton to be readily determined. The formation of an intense [M – C5H11⋅]+ ion for 22α‐OTMS stictanes appears specific to their ring E configuration.
α‐Silyl ketones: A high resolution mass spectrometric study
Authors: Ho Benedict Y. K. , Dexheimer Edward M. , Spialter Leonard , Smithson Lee D. 
Published: May 2005

AbstractThe mass spectrometric fragmentation modes of a series of α‐silyl phenyl ketones are reported. For comparison, the fragmentation modes of the analogous silanol and α,β‐epoxysilane are also reported. Migration of phenyl moieties to silicon is common throughout the ketone series.
Metastable ion studies. XII—Molecular and fragment ion structures for isomeric C4H6O2 acids
Authors: Holmes John L. , Terlouw John K. , Vijfhuizen Peter C. , A'Campo Cor 
Published: May 2005

AbstractMetastable peak characteristics, ionization and appearance energy data and isotopic labelling experiments have been applied to a study of the fragmentation behaviour of the molecular ions of the isomeric C4H6O2C acids, cis and trans‐crotonic acids, methacrylic acid, butenoic acid and cyclopropane carboxylic acid. Prior to the losses of H2O and CH3, all the metastable molecular ions rearrange to [cis‐crotonic acid]+⋅ ions. Loss of H2O, which generates a composite metastable peak, is proposed to yield vinylketene and/or cyclobutenone molecular ions. Detailed mechanisms are presented for the isomerizations of the various molecular ions and for the above fragmentations. Ionized 3‐butenoic and cyclopropane carboxylic acids display a major loss of CO from their metastable ions, a minor process in the other isomers. The metastable peaks consist of two components and these are ascribed to the formation of propen‐1‐ol and allyl alcohol as daughter ions. Some comparative data are presented for the isomeric C5H8O2 acids, tiglic acid, angelic acid and senecioic acid.
Studies in chemical ionization mass spectrometry. 2–i‐C4H10 and NO spectra of alkynes
Authors: Busker E. , Budzikiewicz H. 
Published: May 2005

AbstractThe position of the triple bond of n‐alkynes can be determined by the analysis of the relative abundance of the CnH2n−1 ions in the chemical ionization (i‐butane) spectra. However, chemical ionization (NO) spectra where both hydrocarbon and NO‐containing ions are formed in a characteristic manner are more reliable for this purpose. The limitations of the fragmentation rules established earlier for electron impact spectra of alkynes were investigated by examination of additional examples.
Electron impact fragmentation of 2‐arylhydrazonopropandioic acid derivatives
Authors: Kallury R. Krishna Mohan Rao , Loudon Alexander G. 
Published: May 2005

AbstractExamination of the mass spectra of eleven 2‐arylhydrazonopropandioic acid derivatives reveals that a radical ion which is tentatively formulated as a 1H‐diazirine species is produced in each case (except for the diphenyl este) by more than one process. Formation of what is formally the aryl amine radical ion occurs by a novel hydrogen rearrangement. Simple cleavage of the bonds β to either the aromatic ring or the CN moiety also produces abundant ions. The diphenyl ester behaves anomalously yielding the phenol ion instead of the amine. The proposed mechanisms were confirmed by metastable studies, deuterium labelling and exact mass measurements.
The origins of the base peak in the electron impact spectrum of limonene
Authors: Harris Debi , McKinnon Stewart , Boyd Robert K. 
Published: May 2005

AbstractThe origins and nature of the [C5H8]+⋅ ions which form the base peak in the electron impact spectrum of limonene, at nominal electron energies greater than 11 eV, have been investigated. Linked scan techniques were used to study unimolecular and collision induced fragmentation reactions. No fragmentation pathway leading to [C5H8]+⋅ could be found. Measurement of ionization efficiency curves indicated that the threshold for formation of C5H8[+⋅] lies above the range of internal energies deposited in incident ions by collisional activation. By a combination of comparisons of collisionally activated spectra and energetic considerations, the [C5H8]+⋅ ions formed from limonene were shown to resemble those of the molecular ion of isoprene, while the neutral fragment is most likely isoprene also. Deuterium labelling experiments yielded evidence of extensive scrambling prior to fragmentation. The most probable mechanism of formation of [C5H8]+⋅ appears to involve a retro Diels–Alder reaction of a structurally intact molecular ion of limonene.
The determination of steric purity of amines and amino acids by gas chromatography and mass spectrometry
Authors: Wiecek C. , Halpern B. , Sargeson A. M. , Duffield A. M. 
Published: May 2005

AbstractAmines and amino acids have been condensed with a mixture of N‐TFA‐R‐prolyl chloride and n‐TFA‐S‐[1‐2H]‐prolyl chloride and the resulting four diastereoisomers have been separated by gas chromatography into two peaks. The amount of each diastereoisomer formed was then determined by chemical ionization mass spectrometry. The steric purity of the enantiomeric mixture can be calculated from these values. The method is not dependent on the diastereoisomer formation going to completion.
Molecular ion rearrangements of benzenesulfonylhydrazides
Authors: Kascheres Concetta , Bravo Ruiess Van Fossen 
Published: May 2005

AbstractThe mass spectra of a series of substituted benzenesulfonylhydrazides are discussed. The main fragmentation mode of these compounds corresponds to rearrangement of the molecular ion with subsequent loss of N2H˙ and/or N2H2. These fragmentations are confirmed by mass analysed ion kinetic energy spectra. Simple cleavage of the SN bond with retention of the charge on nitrogen is observed for all the hydrazides studied but is favoured by electron withdrawing substituents. This latter fragmentation could not be confirmed by mass analysed ion kinetic energy spectra as it is probably very rapid and occurs mainly in the source.
Hydrogen transfer in the retro diels–alder fragmentation of oxygen‐containing heterocyclic compounds. II—Chromones
Authors: Eguchi Shizuko 
Published: May 2005

AbstractMass Spectra of unsubstituted, 2‐methyl‐, 3‐methyl and 2,3‐dimethylchromones were examined. These compounds showed [RDA]+˙ and [RDA + H]+ ions as characteristc ions, together with [MH]+,[MCO]+˙,[MCHO]+ and [RDACO]+˙ ions. Based on deuterium labelling experiments and measurement of metastable peaks by the ion kinetic energy defocusing technique, the origin of transferred hydrogen in the [RDA + H]+ ion was clarified. The mechanism of the [RDA + H]+ ion formation is discussed.
Metastable [C4H8O]+˙ ions: Additional decompositions via the [2‐butanone]+˙ ion
Authors: McAdoo David J. , Hudson Charles E. , Witiak Dennis N. 
Published: May 2005

AbstractThe losses of methyl and ethyl through the intermediacy of the [2‐butanone]+˙ ion are shown to be the dominant metastable decomposition of 14 of 19 [C4H8O]+˙ ions examined. The ions that decompose via the [2‐butanone]+˙ structure include ionized aldehydes, unsaturated and cyclic alcohols and enolic ions. [Cyclic ether]+˙ [cyclopropylmethanol]+˙ and [2‐methyl‐1‐propen‐1‐ol]+˙ ions do not decompose through ionized 2‐butanone. The rearrangements of various [C4H8O]+˙ ions the the 2‐butanone ion were investigated by means of deuterium labeling. Those pathways involve up to eight steps. Ions with the oxygen on the end carbon rearrange to a common structure or mixture of structures. Those ions which ultimately rearrange to the [2‐butanone]+˙ ion then undergo oxygen shifts from the terminal to the second and third carbons at about equal rates. However, this oxygen shift does not precede the losses of water and ethylene. Losses of water and ethylene were unimportant for ions with the oxygen initially on the second carbon. Ionized n‐butanal and cyclobutanol, but not other [C4H8O]+˙ ions, undergo reversible hydrogen exchange between the oxygen and the terminal carbon. Rearrangement of ionized n‐butanal to the [cyclobutanol]+˙ ion is postulated.
A mass spectral study of 1‐(aryldimethylsilyl)‐2‐propanones and their isomeric 2‐(aryldimethylsiloxy)‐1‐propenes
Authors: Tsai Robert S.‐C. , Larson Gerald L. , Oliva Alfonso 
Published: May 2005

AbstractThe mass spectra of a series of β‐ketosilanes, p‐YC6H4Me2SiCH2C(O)Me and their isomeric silyl enol ethers, p‐YC6H4Me2SiOC(CH3)CH2, where Y = H, Me, MeO, Cl, F and CF3, have been recorded. The fragmentation patterns for the β‐ketosilanes are very similar to those of their silyl enol ether counterparts. The seven major primary fragment ions are [MMe·]+, [MC6H4Y·]+, [MMe2SiO]+˙, [MC3H4]+˙, [MHCCCF3]+˙, [Me2SiOH]+˙ and [C3H6O]+˙ Apparently, upon electron bombardment the β‐ketosilanes must undergo rearrangement to an ion structure very similar to that of the ionized silyl enol ethers followed by unimolecular ion decompositions. Substitutions on the benzene ring show a significant effect on the formation of the ions [MMe2SiO]+˙ and [Me2SiOH]+˙, electron donating groups favoring the former and electron withdrawing groups favoring the latter. The mass spectral fragmentation pathways were identified by observing metastable peaks, metastable ion mass spectra and ion kinetic energy spectra.
Effects of annulation on the mass spectral behaviour of bicyclo[4.3.0]‐3‐nonene derivatives: Alkoxy esters
Authors: Tureček F. , Hanuš V. 
Published: May 2005

AbstractFragmentation of ethyl(18‐alkoxybicyclo[4.3.0]‐3‐nonene‐7‐carboxylates) was found to depend on the annulation of the rings. Following ionization, the cis‐annulated isomers lose alcohol and benzene, while the trans‐isomers fragment by other reaction paths. The regiospecificity of alcohol elimination from both the ester and the ether groups was determined by using deuterium‐labelled analogues. A mechanism is discussed which rationalizes the differences observed in the spectra of the annulation isomers.
The mass spectral fragmentation of some substituted 3‐Amino‐2‐salicylideneamino‐benzofurans
Authors: Blythin D. J. , Kyriakidis N. , Waight E. S. 
Published: May 2005

AbstractElectron impact mass spectra of eight of the title compounds are discussed. The important fragment ions are shown by high resolution and deuterium labelling to contain the benzofuran nucleus and to involve extensive rearrangement processes. Fragmentation pathways have been confirmed by measurement of daughter ion spectra (B/E linked scans).
Gas chromatography mass spectrometry of some steroidal spirolactones
Authors: Boreham D. R. , Vose C. W. , Balasubramanian V. , Brooks C. J. W. 
Published: May 2005

AbstractGas chromatography mass spectrometry of a number of steroidal spirolactones and their TMS ethers is reported. Open tubular column gas chromatography provides useful structural information for these compounds as shown by shifts in retention index values. The electron impact fragmentation pathways have been established for a number of the compounds. The results of the study indicate that open tubular column gas chromatography mass spectrometry will be of value in studies of the metabolism of this class of steroids in animals and man.
The Loss of a hydroxyl group from the molecular ions of alkylnitrobenzenes
Authors: Butcher A. R. , Thomas C. B. 
Published: May 2005

AbstractIt is confirmed that the loss of HO˙ from the molecular ion of o‐nitrotoluene involves exclusively a hydrogen from the methyl group. However, in higher homologues hydrogen atoms from non‐benzylic sites are also implicated. With such compounds this fragmentation mode is shown not only by the ortho but, to a lesser extent, by the meta and para isomers as well. The proportion of the total ion current borne by the [M – 17]+ ion follows the order ortho > meta > para, which is attributed to substituent migration around the ring with a hydroxyl radical only being lost when the groups are on adjacent ring atoms. Other ions present in the spectra point to interaction between substituents to form a new heterocyclic ring.
Zum massenspektrometrischen Fragmentierungsverhalten von Thiophen‐Benzologen
Authors: Riepe W. , Zander M. 
Published: May 2005

AbstractDas Fragmentierungsverhalten bei den untersuchten Thiophen‐Benzologen ist sehr ähnlich. Unterschiede treten nur in der Häufigkeit der Brushstück‐Ionen auf, die durch Abspaltung von S bzw. CS und deren wasserstoffhaltigen Varianten entsteren. Die Bildungsmöglichkeiten der resultierenden Fragment‐Ionen werden diskutiert.
The effect of a phosphorus bridgehead atom on the loss of neutral species in the mass spectra of bicyclooctanes
Authors: Voorhees Kent J. , Hileman Fred D. , Smith David L. 
Published: May 2005

AbstractThe effect of a bridgehead phosphorus atom, as both the three (phosphate)and five (phosphate) oxidation states, to influence unique mass spectral neutral losses from a 1‐phosphabicyclo[2.2.2]octane system has been investigated. A conventional neutral loss of formaldehyde was found for the phosphites while a unique loss of ethylene was observed for the phosphate. These losses are discussed in terms of the substituent effects from the 4‐position.
Acetylenic ketones. VII—Structural analyses by mass spectrometry of the products obtained from the reaction of acetylenic ketones with nucleophilic sulphur compounds
Authors: Baddar Fawzi G. , Al‐Hajjar Farouk H. , El‐Rayyes Nizar R. 
Published: May 2005

AbstractThe mass spectra of β‐hydroxy‐α‐thiobenzoylstyrene derivatives and (E, Z)‐ or (E, E)‐β,β‐di(α‐aroylstyryl)sulphides as well as β,β′di(α‐aroylstyryl)disulphides are discussed. The fragmentation patterns support their proposed structure and configuration.
Rearrangements and fragmentations of [C2H5S]+ ions
Authors: Broer W. J. , Weringa W. D. , Nieuwpoort W. C. 
Published: May 2005

AbstractFrom deuterium labelling experiments it was concluded that metastable molecular ions of ethyl methyl sulfide lose a methyl radical with the formation of both [CH3SCH2]+ amd [CH3CHSH]+˙ The fragmentation reactions of metastable ions generated with these structure are losses of C2H2, H2S and CH4. These reactoins and the preceding isomerizations have also been studied by means of deuterium labelling. From the results it is concluded that the three fragmentation reactions most probably occur from ions with a CCS skeleton. Appearance energy measurements for ions generated with the two structures above and all give rise to the same ΔHf value for these three isomeric forms. Ab initio molecular orbitals calculations confirm that these three ions fortuitously have very similar heats of formation. A potential energy diagram rationalizing the isomerizations and the principal fragmentation reaction is presented.
Mass spectrometric study of conjugated bifunctional acetylenes. 1—Enynes
Authors: Bachiri M. , Perros P. , Verneuil B. , Mouvier G. , Carlier P. 
Published: May 2005

AbstractThis study on the fragmentation of conjugated enynes demonstrates the relationships between the mass spectra and the structures of these compounds. The rearrangements of the molecular ions and the fragment ions are characterized; the mechanisms by which the most important peaks are formed have been established and detailed analysis of the metastable transitions reveals all the fragmentation steps. A complete scheme is presented for 2‐methyl‐1‐nonene‐3‐yne since it includes all the transitions which can be detected for the lower homologues. The ion kinetic energy spectra for this family of compounds are distinct (even though the conventional spectra are similar) and could very well be used for identification purposes.
The fragmentation of 2‐aminooxazoles under electron impact
Authors: Selva A. , Traldi P. , Rapi G. , Ginanneschi M. , Chelli M. 
Published: May 2005

AbstractThe 70 eV electron impact mass spectra of six 2‐aminooxazoles are discussed in detail with the aid of exact mass measurements, metastable ion detection in the defocused mode and labelling experiments. The fragmentation is markedly influenced by strong electron donating substituents at the 2‐position. Some 2‐acetylamino and 2‐diacetylamino derivatives have also been considered, which lose ketene from [M]+⋅ giving the corresponding aminooxazole molecular ions. The mass spectral behaviour is peculiar and the most important differences between the fragmentation pathways of these compounds and those reported in the literature for oxazole (alkyl and aryl) derivatives are outlined. The mass spectrum of 4‐methyl‐5‐phenylimidazol‐2‐one is compared with that of the isomeric 4‐methyl‐5‐phenyl‐2‐aminooxazole.
Positive and negative ion mass spectra of Aryl‐ONN‐azoxy compounds containing electron withdrawing groups
Authors: Vaglio Gian Angelo , Ferrari Rosa Pia , Mortarini Vittorio , Gasco Alberto , Calvino Rosella 
Published: May 2005

AbstractThe positive and negative ion mass spectra, at 70 eV, of p‐RC6H4N(O)NCOOCH3 (RH, Cl, Br, NO2), C6H5N(O)NCOOC2H5, p‐RC6H4N(O)NCONH2 (RH, Cl, Br, NO2) and p‐RC6H4N(O)NCOC6H5 (RH, Cl, Br, NO2) are reported. The azoxyester derivatives show abundant molecular ions and a number of weak fragment and rearrangement ions in the positive ion mass spectra, whereas weak molecular ions and abundant low mass fragment ions are present in the negative ion mass spectra. Similar behaviour is observed in the mass spectra of the azoxyamides. Conversely, for the azoxycarbonyl compounds the positive molecular ion is absent. A ready cleavage of the NCO bond occurs and only few fragments of low diagnostic value are formed, whereas the negative molecular ion is the base peak for all these compounds with the exception of the p‐NO2 derivative, where [MO]−⋅ is the base peak and [M]−⋅ is the second major ion. The behaviour under electron impact of these classes of compounds is compared with that of azoxycyanides reported previously.