bluuebunny/crossref_metadata_2025_split huggingface dataset:
Über die Strukturen von Fragmentionen im Massenspektrometer: Das Ion m/e 84 aus Lysinmethylester
Authors: Roessler Felix , Hesse Manfred 
Published: May 2005

AbstractDie Entstehungsweise des Ions [C5H10N]+ (m/e 84), Basispeak im Massenspektrum von Lysinmethylester, wurde untersucht. [C5H10N]+ bildet sich in einer Folge von zwei Reaktionen: Aus dem Molekularion ensteht unter Verlust von ·COOCH3 das Primärfragmention [C5H13N2]+ (m/e 101), aus dem durch Abspaltung von Ammoniak m/e 84 generiert wird. Das Aufspaltungsmuster von [C5H10N]+ in den Massenspektren von neun verschieden markierten Lysinmethylestern lässt auf eine hohe Symmetrie im Diaminfragmentation [C5H13N2]+ schliessen. Durch die Ionenstrucktur, welche u.a. eine Äquilibrierung der beiden Stickstoffatome beinhaltet, lassen sich die erhaltenen Resultate am besten erklären.
Massenspektrometrische Untersuchungen an Azoverbindungen: I
Authors: Messmer Karlheinz , Nuyken Oskar 
Published: May 2005

AbstractEine Reihe symmetrischer und unsymmetrischer Azoverbindungen wurde in einer Elektronenstoßionisationsquelle massenspektrometrisch untersucht. In allert Fällen bis auf Azoisobutyronitril folgen die Verbindungen einer zweistufigen Fragmentierung \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm R}^{\rm 1} - {\rm N = N - R}^{\rm 2} } \right]_{}^{_.^ + } $\end{document} → [R1—N2]+(+R2˙) → [R1]+(+N2).
Massenspektrometrische Untersuchungen an Azoverbindungen. II—Ermittlung thermodynamischer Größen
Authors: Nuyken Oskar , Messmer Karlheinz 
Published: May 2005

AbstractAuftrittspotentiale einiger Azoverbindungen und ihrer charakteristischen Bruchstücke wurden gemessen. Aus diesen wurden mittels berechneter Werte für die Bildungsenthalpien der Moleküle die Bildungsenthalpien der Molekülionen und der Fragmentionen sowie deren Ionisationspotentiale berechnet. Aus den Dissoziationsenergien wird auf einen 2‐Schritt‐Zerfallsmechanismus der untersuchten Azoverbindungen geschlossen.
Mass spectra of a series of 3‐halo‐2‐oxazolidinones
Authors: Kaminski James J. , Worley S. D. , Bodor Nicholas 
Published: May 2005

AbstractThe mass spectra of a series of 3‐chloro and 3‐bromo alkyl substituted 2‐oxazolidinones have been investigated and compared with the mass spectra of the corresponding alkyl substituted‐2‐oxazolidinones. Fragmentation of the 2‐oxazolidinone ring system has been found to be significantly influenced by: (1) the presence of an alkyl substituent, (2) the position, number and size of the alkyl substitutents, and (3)replacement of the NH bond by NCI and NBr.
Etude du mécanisme de perte d'ethylène (propène) des N‐ethyl (propyl) bromo‐1,2,4‐triazoles
Authors: Maquestiau André , Van Haverbeke Yves , Flammang Robert , Mispreuve Henri 
Published: May 2005

AbstractLe C‐bromotriazole est généré en ses trois formes tautoméres par élimination d'éthylène à partir de composes N‐éthylés et ces ions tautomères conservent leur structure avant toute fragmentation ultérieure. L'analyse de spectres ‘MIKE’ et ‘CID’ montre que la perte d'éthylbne se déroule suivant un mécanisme non concerté avec un transfert d'hydrogéne à quatre ou cinq centres. Les résultats montrent également que les 3‐et 5‐bromotriazoles contribuent au spectre de masse de l'hétérocycle parent. La perte de propéne de N‐propylbromotriazoles est également discutée.
Metastable ion studies. VII—loss of water from the molecular ion of cyclopentanol
Authors: Holmes John L. , Yuan David , Rye Robin T. B. 
Published: May 2005

AbstractMetastable peaks for the loss of water from the molecular ion of cyclopentanol and six 2H labelled analogues have been studied. The results, together with some thermochemical date and a detailed examination of metastable peak shapes, have allowed the identification of the two mechanisms for water loss, both of which take place from the α‐cleaved molecular ion. Daughter ion structures are proposed.
Mass spectra of ortho substituted 1‐phenyl‐2‐thioureas
Authors: Grehn Leif 
Published: May 2005

AbstractThe mass spectra of some 1‐(o‐alkylphenyl)‐2‐thioureas have been investigated and deuterium labelling shows that the proton lost in the SH⋅ abstraction originates from the α‐hydrogens in the o‐alkyl group. The intensity of the fragment ion formed by loss of the o‐alkyl group increases with the stability of the corresponding alkyl radical.
Charge location and fragmentation under electron impact. V—the ionization potentials of (methylated) phosphoramides, guanidines, formamides, acetamides, ureas and thioureas
Authors: Baldwin M. A. , Loudon A. G. , Webb K. S , Cardnell P. C. 
Published: May 2005

AbstractThe measurement and interpretation of the ionization potentials of some (methylated) phosphoramides, acetamides and formamides is reported. Additivity rules for the prediction of ionization potentials are examined.
A gas phase study of the ions and [C3H3]− generated from the reaction of with propyne
Authors: Dawson J. H. J. , Kaandorp Th. A. M. , Nibbering N. M. M. 
Published: May 2005

AbstractIt is reported that ions gererated in the gas phase by dissociative electron attachment to nitrous oxide react with propyne‐d3 (trideuteromethyl acetylene) to yield the ions ĊDCCH, ĊD2CC−, −CD2CCH and CD3CC−. From their differing reactivity with methyl formate it is suggested that these four ions are distinct stable species.
Mass spectral studies of some π‐benzoylcyclopentadienylmanganese tricarbonyl derivatives
Authors: Gogan Niall J. , Chu Chit‐Kay 
Published: May 2005

AbstractThe loss of three CO groups from derivatives of π‐C6H5COC5H4Mn(CO)3 is a two‐step mechanism in which the loss of two CO groups is followed by a third. Subsequent fragmentations generally involve rearrangement processes which often result in ring closure within the organic substrate. The central metal atoms plays an important part in such rearrangement processes and the positive charge can reside either on the metal or the ligand depending on the nature of the ligand. Fragmentation patterns are proposed for these systems.
Fragmentation sous Impact Electronique du Phényl‐2 Oxétanne
Authors: Brun Jean Pierre , Ricard Michèle , Corval Madeleine , Schaal Catherine 
Published: May 2005

AbstractLes principaux modes de fragmentation du phényl‐2 oxétanne sont étudiés à l'aide des spectres d'espèces diversement marquées aux isotopes stables. L'origine du pic de base [C6H5CO]+ est discutée.
Massenspektrometrische Untersuchungen einiger Catenane und Makrocyclen
Authors: Vetter Walter , Logemann Enno , Schill Gottfried 
Published: May 2005

AbstractDie Massenspektren der Catenane, die in einem der beiden Ringe durch β‐Phenyläthylaza‐, Aza‐, Acetylaza‐, Trideuterioacetylaza‐ oder Trifluoracetylaza‐Gruppen funktionalisiert sind, werden mit den Spektren entsprechend funktionalisierter makrocyclischer und langkettiger Moleküle verglichen. Die Massenspektren der meisten untersuchten Catenane zeichnen sich durch eine dominierende Fragmentierung aus, die durch eine interannulare H‐Übertragung auf die funktionelle Gruppe eingeleitet wird. Fragmentierungen, die durch Ringbrüche eingeleitet werden, treten dagegen zurück. Abgesehen von H‐Übertragungen sind keine interannularen Reaktionen nachweisbar. Bei Anwesenheif, einer β‐Phenyläthylaza‐Gruppe erfolgt der Verlust der Benzylgruppe so rasch, daβ keine bedeutende H‐Übertragungsreaktion zustande kommt. Der Vergleich der Massenspektren der offenkettigen Verbindungen einerseits mit den makrocyclischen und catenan‐artigen andererseits legt die Annahme nahe, daß eine bedeutende Solvatisierung der untersuchten funktionellen Gruppen durch lange Ketten nicht vorliegt.
Entropische und energetische Effekte bei der Bildung cyclischer Oxonium‐, Sulfonium‐ und Bromonium‐Ionen aus ω‐substituierten Phenoxyalkanen
Authors: Schwarz Helmut , Petersen Rolf D. , Van De Sande Christian C. 
Published: May 2005

AbstractMit Hilfe von Auftrittspotentialmessungen wird belegt, daß die bei der Bildung der Titel‐Ionen beobachteten Kettenlängen‐Effekte sowohl durch entropische als auch energetische Faktoren gesteuert werden. Zusätzlich wird gezeigt, daß die Genese der stabilen [M‐PhO]+‐Ionen—unabhängig von der Kettenlänge der reaktiven Molekül‐Ionen‐über einen Übergangszustand erfolgt, der zu cyclischen Produkten fiihrt. Acyclische Spezies oder solche, die durch komplexe Umtagerung des Kohlenstoffgerüstes entstehen könnten, sind wahrscheinlich auszuschließlen.
Expulsion of the CHO radical from the molecular ion of homochromones
Authors: Nakayama Mitsuru , Yamaoka Hiroshi , Eguchi Shizuko , Hanafusa Terukiyo , Hayashi Shûichi 
Published: May 2005

AbstractFor some homochromones, it was confirmed by labelling C‐9 with deuterium that the CHO radical expelled from the molecular ion contains either the methine hydrogen or one of the methylene hydrogens of the cyclopropane ring. The origin of the CO group in the expelled CHO radical was also inferred, and a plausible mechanistic interpretation is presented.
The mass spectra of some 4‐arylhydrazono‐3‐methyl‐2‐pyrazolin‐5‐ones
Authors: Amer Fathy A. , Strand Linda P. , Francis George W. 
Published: May 2005

AbstractThe mass spectra of the title compounds, having various substituents on the aryl group are presented and discussed. High resolution mass measurements and metastable ions allow the fragmentation to be rationalized. The system is typified by the occurrence of intense molecular ions and of ions due to consecutive decomposition of the nitrogen‐containing part of the molecule. Ions attributable to substituted, aniline‐like fragments, and their decomposition products, are also abundant and may be used to identify the aryl group present.
A three‐dimensional representation of metastable peaks from double focusing mass spectrometers
Authors: Lacey Michael J. , Macdonald Colin G. 
Published: May 2005

AbstractThe ion current transmitted by the collector slit of a double focusing mass spectrometer is considered as a function of two variables which independently reflect the effects of the instrument's electric and magnetic sectors. The ionic products of reactions occurring in the source and in various regions of the flight tube give rise to peaks or ridges with distinctive shapes and positions in the surface so derived. Volumes under peaks are proportional to abundances of ions. The surface provides a unified view of the alternative methods of scanning and facilitates understanding of the contrasting perspectives of metastable peaks which they reveal. The method, which may be applied with instruments of either conventional or reversed geometry, is illustrated for the former by reference to that part of the surface for toluene which relates to the loss of H from the molecular ion.
Secondary hydrogen‐deuterium isotope effects on electron impact induced fragmentations
Authors: Eadon George , Zawalski R. 
Published: May 2005

AbstractSecondary hydrogen‐deuterium isotope effects have been observed in the mass spectra of cis‐4‐t‐butylcyclohexyl iodide, 5‐iodononane and 2‐iodopropane. Under conditions which suppress competing and second generation fragmentations, β‐deuterium substitution decreases the intensity ratio \documentclass{article}\pagestyle{empty}\begin{document}$ ([{\rm M} - {\rm I]}^{\rm + } /[{\rm M]}^{\mathop + \limits_ \cdot } ) $\end{document}, a result analogous to a normal isotope effect. The decrease is larger in the spectrum of cis‐4‐t‐butylcyclohexyl iodide‐trans‐2‐d than in the spectrum of the cis‐2‐d derivative. Since these effects parallel those in the better understood solvolysis reaction, both effects may have a common origin. In contrast, deuteration of more remote positions in cis‐4‐t‐butylcyclohexyl iodide and 5‐iodononane increases the indicated intensity ratio, an apparent inverse isotope effect. Although similar effects have been observed in solvolysis reactions, the mass spectral effect may be attributable to an increase in the nonfixed energy available for fragmentation. These results suggest that secondary isotope effects can be readily measured in certain cases, and that they may eventually become useful probes into the mechanisms of mass spectral fragmentations.
Skeletal and hydrogen rearrangements in the electron impact mass spectrum of propene
Authors: Harrison Alex. G. , Dymerski Paul P. 
Published: May 2005

AbstractThe mass spectrum of propene‐2‐[13C] shows 81% retention of C‐2 in the [C2H3]+ fragment ion at 70 eV electron energy, decreasing to 75% C‐2 retention at low electron energies. The mass spectra of propene‐2‐d1, propene‐1,1,3,3,3‐d5, propene‐1,1,2‐d3 and propene‐3,3,3‐d3 also have been examined at a resolution sufficient to resolve H2‐D doublets. The results at 70 eV electron energy show complete H/D randomization prior to fragmentation to form [C3(H, D)5]+ but, in agreement with the 13C labelling data, incomplete H/D interchange prior to fragmentation to form [C2(H, D)3]+. The results are interpreted in terms of a reversible isomerization of the propene molecular ion to a cyclopropane structure in competition with fragmentation.
Rearrangement ions in the mass spectra of bis‐ trimethylsilyl derivatives of simple boronic acids
Authors: Vandenheuvel W. J. A. , Smith J. L. , Firestone R. A. 
Published: May 2005

AbstractThe mass spectra of bis‐trimethylsilyl derivatives of simple boronic acids have been determined and found to contain two rearrangement ions involving loss of MeBO. Mechanisms based largely on 1, 3 shifts to electron deficient silicon and boron are presented to explain the formation of these ions. The mechanisms are supported by deuterium labelling experiments and metastable transtions.
Fragmentations Principales de Mono‐, Di‐, Triet Tetra‐azaindolizines Sous L'Impact Electronique
Authors: Daunis Jacques , Lopez Hélàne , Maury Georges 
Published: May 2005

AbstractLes fragmentations principales de 41 azaindolizines de structure imidazo [1,2‐a]pyridine, imidazo [1,5‐a]pyrimidine, imidazo[1,5‐b]triazine‐1,2,4 triazolo[2,3‐b], ‐[4,3‐b], ‐[3,4‐c] et ‐[3,2‐c]triazine‐1,2,4 sont décrites. Il est montré que chaque système possède une fragmentation caractéristique de sa structure sauf lorsqu'une réaction de transposition de Dimroth en composé peut‐être envisagée. Leur schéma de dégradation est lié au nombre et à la position des atomes d'azote.
Comportement de quelques Arylbenzo[b]‐furannes sous l'Impact électronique
Authors: Vebrel J. , Roche M. , Gore J. 
Published: May 2005

AbstractUn mécanisme de fragmentation des arylbenzo[b]furannes est proposé qui rend compte de la similitude des spectres obtenus avec divers couples d'isomères d'aryl‐2 et d'aryl‐3 benzofurannes. Ce mécanisme implique la migration du groupe aryle lors de la décomposition des isoères substitués en −2.
Mass spectra of ferrocenophanes. Cyclic peroxide derivatives
Authors: Hisatome Masao , Yamakawa Koji 
Published: May 2005

AbstractThe electron impact mass spectra of two 6‐membered cyclic peroxides of ferrocenophane depend sensitively on the temperature of the sample heater of the direct inlet system. It is confirmed that their spectra contain some fragment ion peaks arising from thermal decomposition or rearrangement products, but that the ion at m/e (M–28) is due to elimination of ethylene from the molecular ions of the peroxides by a retro Diels‐Alder type reaction.
Massenspektren der von Aminosäuren bzw. Peptiden abgeleiteten Triazin‐Derivate
Authors: Maekawa Kazuyuki , Taniguchi Eiji , Kuwano Eiichi 
Published: May 2005

AbstractDie massenspektrometrische Untersuchung von etwa dreißig Triazin‐Verbindungen, die das C‐Ende (Car‐boxylgruppe) von Aminosäuren und Peptiden in den Ring setzten, wird beschrieben. In Gegensatz zu den bisher untersuchten Massenspektren von Aminosäure‐bzw. Peptidestern ergeben sie immer charakteristische Fragmente, die den Triazinring am Ende aufweisen. Unter Anwendung diese Peaks als Merkmal ist es leicht, das C‐Ende von Peptiden festzustellen. Bei Dipeptiden werden N‐Ende und C‐Ende zugleich bestimmt.
Das [C8H8]+‐Problem: Der Verlust von Äthylen aus dem Molekülion von Tetralin
Authors: Stolze R. , Budzikiewicz H. 
Published: May 2005

AbstractEs wird gezeigt, daß die Abspaltung von Äthylen aus Tetralin ein komplexer Prozeß íst, bei dem neben, vollständigem C‐ und H‐Scrambling (etwa 10%) wenigstens zwei konkurrierende Prozesse ablaufen.
The electron impact induced fragmentation of 1,3‐diphenyl‐2‐pyrazoline
Authors: Srzić D. , Klasinc L. , Noppel H. E. , Güsten H. 
Published: May 2005

AbstractThe electron impact induced fragmentation of 1,3‐diphenyl‐2‐pyrazoline was studied by nitrogen‐15, carbon‐13 and deuterium labelling, substitution in the para position of one of the phenyl rings by fluoro and methoxy groups, and ion kinetic energy spectroscopy, as well as accurate mass measurements. In the fragmentation pathway observed all the ions in the mass spectrum of 1,3‐diphenyl‐2‐pyrazoline (except m/e 103) originate from the molecular ion, which in all compounds is the base peak. The formation of prominent fragment ions is discussed.
Hydrogen rearrangement in molecular ions of alkyl benzenes: Mechanism and time dependence of hydrogen migrations in molecular ions of 1, 3‐diphenylpropane and deuterated analogues
Authors: Kuck Dietmar , Grützmacher Hans‐Fr. 
Published: May 2005

AbstractHydrogen migrations in the molecular ions of 1,3‐diphenylpropane, preceding the fragmentations to [C7H7]+ and [C7H8]+ ions, have been investigated by use of deuterated derivatives. By comparing the distribution of deuterium labels in the [C7(H, D)8]+ products from metastable molecular ions with the distribution patterns calculated for various exchange models, it is shown that the H migrations occur by two processes linked by a common intermediate: (i) exchange between hydrogen isotopes at the γ‐methylene group and at the ortho positions of the phenyl group: (ii) exchange between hydrogen isotopes at the ortho and orthó positions in the intermediate. In these mechanisms the eight hydrogen isotopes at both benzylic positions and both the ortho and orthó positions of 1,3‐diphenylpropane participate in a mutual exchange. A statistical equipartition of the hydrogen isotopes at these eight positions is not reached in metastable molecular ions, however. The distribution pattern of [C7(H, D)8]+ ions from the deuterium labelled compounds as a function of the mean number n of exchange cycles has been calculated according to this reaction model and compared with experimental results for unstable molecular ions, generated by 70 eV and 12 eV electrons, respectively, and metastable molecular ions. Good agreement is obtained for all compounds and n = 0.4–0.8 for unstable molecular ions and n = 5–8 for metastable ions. Therefore, the hydrogen exchange in the molecular ion of 1,3‐diphenylpropane is a rather slow process. These results firmly establish the isomerization reaction involving the conversion of the molecular ion of 1,3‐diphenylmethane to the intermediate and hence to the molecular ion of 7‐(2‐phenylethyl)‐5‐methylene cyclohexa‐1,3‐diene and preceding the fragmentations. The postulated intermediate is a true one which corresponds to a s̀‐complex type ion and which fragments to [C7H8]+ ions. Surprisingly, no isomerizations of the intermediate by hydrogen shifts within the protonated aromatic system (‘ring walks’) are observed.
Hydrogen migrations in mass spectrometry. V—loss of olefin from n‐propyl esters following chemical ionization
Authors: Benoit Frank M. , Harrison Alex. G. 
Published: May 2005

AbstractThe sources of the migrating hydrogen in the elimination of propylene from the protonated and ethylated n‐propyl acetate and n‐propyl benzoate molecules have been determined by studying the CH4 and H2 chemical ionization mass spectra of esters specifically deuterated in the propyl group. It is shown that the migrating hydrogen originates from C‐1 ( ∼ 27%), C‐2 ( ∼ 23%) and C‐3 ( ∼ 50%) of the propyl group, independent of ester and mode of ionization. It is argued that the observed reaction involves specific competing H‐migration reactions from each propyl position to the ether oxygen in a keto‐protonated (ethylated) ester molecule.
Energy partitioning in the metastable fragmentation [C3H7]+ → [C3H5]+ + H2
Authors: Holmes John L. , Osborne Alexander D. 
Published: May 2005

AbstractThe dish‐topped metastable peak for the fragmentation [C3H7]+ → [allyl]+ + H2 is generated by the threshold fragmentation. The fraction of the reverse activation energy which is partitioned as translational energy of the products is 0.9 ± 0.1. It is proposed that a similar partitioning coefficient applies to the excess internal energy above threshold.
The site of ionization in the acetylation of aliphatic esters by [(CH3CO)3]+
Authors: Cobb Christine S. , Bursey Maurice M. , Rhyne Lee D. 
Published: May 2005

AbstractA series of esters RCOOR′ (where R, R′ = CH3, CH3CH2, (CH3)2CH, (CH3)3C) were reacted with the [(CH3CO)3]+ ion from biacetyl in an ion cyclotron resonance spectrometer. A steric effect influences the rate of formation of stable products [RCOOR′·CH3CO]+ and is used to determine that either oxygen of the ester may be initially acylated by [(CH3CO)3]+.
Studies in chemical ionization mass spectrometry of some flavonoids
Authors: Yinon J. , Issachar D. , Boettger H. G. 
Published: May 2005

AbstractFormation of ions in chemical ionization mass spectrometry of flavonoid compounds has been studied. Production of adduct ions and fragment ions as a function of ring substituents and of reagent gas has been observed. Pressure and repeller field dependence of ions has been found as a function of ring substituents.
Nachbargruppenbeteiligung bei der elektronen‐stoßinduzierten Fragmentierung von elektronenarmen 2,2′‐Biphenolbenzoaten
Authors: Schwinger Gerhard , Spitzner Dietrich 
Published: May 2005

AbstractBeim elektronenstoßinduzierten Zerfall von elektronenarmen 2,2′‐Biphenolbenzoaten wird die Abspaltung von Benzoesäureanhydrid beobachtet. Die Messung nach der DADI‐Methode macht für diese Abspaltung sowohl einen Synchronprozeß als auch einen schrittweisen Zerfall wahrschinlich.
Electron impact studies on 2‐hydroxyimino‐N‐aryl acetamides
Authors: Kallury R. Krishna Mohan Rao , Loudon Alexander G. , Maccoll Allan 
Published: May 2005

AbstractThe mass spectra of 13 2‐hydroxyimino‐N‐aryl acetamides contain abundant arylamine, isocyanate and protonated benzimidazole ions, the mechanisms of formation of which were established by deuterium labelling and formulae by exact mass measurements. Loss of OH˙ and NO˙ were postulated to proceed through cyclic and acyclic intermediates respectively. Considerable hydrogen scrambling and rearrangement could be noticed in all the processes.
Mass analysed collisional activation mass spectra of organic salt cations produced by field desorption linked magnetic and electric field scanning
Authors: Veith H. J. 
Published: May 2005

AbstractThe collisional activation mass spectra of some organic salt cations produced by field desorption are reported. The principal fragmentations of these ions are discussed. The collisional activation mass spectra were obtained, with good mass resolution, by linked scanning of the electric and magnetic fields in a double focusing mass spectrometer.
Positive and negative ion mass spectra of oxygen, sulphur and selenium 2,1,3‐benzodiazoles
Authors: Arshadi Mohammed R. 
Published: May 2005

AbstractThe 70 eV positive and negative ion mass spectra of the oxygen, sulphur and selenium 2,1,3‐benzodiazoles have been studied. The influence of hetero atom on the fragmentation modes of the benzodiazole molecular ions has been discussed.