bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the fragmentation of stereoisomeric substituted cyclohexylamines under electron impact. Comparison with corresponding alcohols and ethers
Authors: Weissdorf Miriam , Sharvit Joseph , Mandelbaum Asher 
Published: May 2005

AbstractThe stereospecific elimination of H2O and CH3OH from substituted cyclohexanols and their methyl ethers upon electron impact is not reproduced in the corresponding amines. Ring cleavage α to the amino group is responsible for the non‐stereospecific formation of the most abundant fragments in the amines.
The elimination of metal(I) hydride in the mass spectra of some metal(II) compounds
Authors: Lacey Michael J. , Macdonald Colin G. , Shannon James S. 
Published: May 2005

AbstractMetal(I) hydrides are eliminated as neutral species in the electron impact ionization mass spectra of copper(II) and palladium(II) complexes of ethylene‐N,N′‐3‐benzoylprop‐2‐en‐2‐amine. Deuterium labelling shows that the hydrogen atom of the metal(I) hydride is derived predominantly from the ethylene bridge both for ion source reactions and for metastable ion transitions. Evidence supporting the proposed rationalization for elimination of metal(I) hydride is provided by the observation of an analogous reaction in the mass spectrum of (ethylene‐N,N′‐salicylaldiminato)copper(II). The mass spectrum of ethylene‐d4‐N,N′‐3‐benzoylprop‐2‐en‐2‐amine shows an unusual rearrangement to give [C7H5D2]+ ions involving a formal phenyl‐to‐methylene transfer.
Etude en Spectrométrie de Masse. IX—Fragmentation de Cyclopropanes Dicarboxylate de Méthyle‐1,2 cis et trans Diversement Substitués, et des Homologues Cyclobutaniques, Cyclopentaniques et Cyclohexaniques non Substitués
Authors: Cambon Aimé , Rouvier Emile 
Published: May 2005

AbstractL'étude des spectres de masse de divers cyclopropanes dicarboxylate de méthyle‐1,2 cis et trans, diversement substitués sur les carbones 1,2 et 3, a montré que tous ces composés avaient un comportement identique sous l'impact électronique. Dans tous les cas c'est la rupture du cycle qui conduit aux principaux fragments. Nous avons ensuite comparé les diesters cyclopropaniques non substitués aux homologues cyclobutaniques, cyclopentaniques et cyclohexaniques, afin d'analyser le degré de transmission des effets électroniques des différents cycles.
Electron impact studies on α,β‐unsaturated carbonyl oximes
Authors: Kallury R. Krishna Mohan Rao , Loudon Alexander G. , Maccoll Allan 
Published: May 2005

AbstractElectron impact studies on eight α,β‐unsaturated carbonyl oximes revealed many interesting hydrogen and skeletal rearrangements which were substantiated by deuterium labelling, exact mass measurements and metastable studies. Loss of H· and OH· as well as formation of the indenyl and fluorenyl cations and the [C9H6N]+ fragment proceed through cyclic intermediates. All the ionized oximes undergo a Beckmann rearrangement in the gaseous phase leading to intense aroyl cation peaks. Formation of the styrene radical ions and cleavage of the bond α to the oxime function have also been noticed.
Rearrangements and fragmentations of [C2H5S]+ ions
Authors: Broer W. J. , Weringa W. D. 
Published: May 2005

Abstract[C2H5S]+ ions (m/e 61) with different initial structures were generated in the mass spectrometer from twelve precursor ions. Abundance ratios of competing metastable ion decompositions were used to determine whether these ions decompose through the same or different reaction channels. It was concluded that all [C2H5S]+ ions isomerize to a common structure or mixture of structures prior to decomposition in the first field free region. From 13C labelling experiments it was concluded that [C2H5S]+ ions generated from the molecular ions of 2‐propanethiol‐2‐[13C], partially rearrange to a symmetrical structure before decomposition to [CHS]+ and CH4, whereas in [C2H5S]+ ions generated from the the molecular ions of 1,2‐bis‐(thiomethoxy‐[13C]) ethane, the two carbon atoms become fully equivalent before CH4 loss occurs.
Die massenspektrometrische Fragmentierung von Neopentylpolyolestern. 1—Pentaerythrittetrafettsäureester
Authors: Zeman Alfred , Bartl Peter , Schaaff Albert 
Published: May 2005

AbstractDie Fragmentierung der homologen Fettsäuretetraester des Pentaerythrits (C‐2 bis C‐14) bei Elektronenbeschuß wurde untersucht. Hauptspaltfragmente entstehen durch [MRCOO]+ und [MRCOOH]+. Diese Ionen liegen vermutlich als cyclische Acetale vor. Der weitere Zerfall dieser lonen wird anhand von DADI‐Messungen und Massenfeinbestimmungen geklärt. Ester verzweigter Fettsäuren können anhand charakteristischer Ionen von solchen aus n‐Fettsäuren unterschieden werden. Die massenspektrometrische Identifizierung von isomeren n‐ Fettsäureestern, die gaschromatographisch nicht aufgetrennt werden können, ist ebenfalls möglich.
Negative ion mass spectra of salicylaldehydato and 2‐hydroxy‐1‐naphthylaldehydato complexes of Co(II), Ni(II) and Cu(II): Consecutive and competitive eliminations of CO and H2CO
Authors: Hirata Yukio , Matsumoto Kozo , Takeuchi Tsugio 
Published: May 2005

AbstractThe negative ion mass spectra of some divalent metal complexes, ML2, have been measured, where MCo, Ni and Cu, and LH = salicylaldehyde or 2‐hydroxy‐1‐naphthylaldehyde. All compounds yield intense molecular anions. The mass spectra of these compounds suggest that consecutive and competitive eliminations of CO and H2CO, and various types of hydrogen migrations are involved in the fragmentation of the molecular anions. The mechanism of the fragmentation process and metastable peaks observed are also discussed.
The mass spectra of some 1H‐imidazo[1,2‐a]pyrrolo[3,2‐e]pyridines
Authors: Bancroft Keith C. C. , Brown Kevan , Ward Terence J. 
Published: May 2005

AbstractWe report here the mass spectral fragmentations of some derivatives of a new heterocyclic system 1H‐imidazo[1,2‐a]pyrrolo[3,2‐e]pyridine. These compounds combine structural features of 1H‐pyrrolo[2,3‐b]pyridines and imidazo[1,2‐a]pyridines, but follow fragmentation pathways similar to the former.
Elimination reactions of ions in the gas phase. V—elimination of water in hydroxybornanes and related compounds
Authors: Robbiani R. , Bührer H. , Mändli H. , Kovačević D. , Fraefel A. , Seibl J. 
Published: May 2005

AbstractResults of an investigation of deuterium labelled methylated norborneols and dihydrocarveols are presented to show that the 1,2 elimination of water in borneol and isoborneol is triggered by an initial ring cleavage reaction. Other eliminations of water in borneol and isoborneol are elucidated by specific and stereospecific deuterium labelling in different positions.
Stereospecific elimination of acetic acid in 3‐ and 4‐arylcyclohexyl acetates under electron impact
Authors: Sharvit Joseph , Mandelbaum Asher 
Published: May 2005

AbstractThe elimination of CH3COOH from the molecular ions of trans‐3‐ and 4‐arylcyclohexyl acetates takes place to a greater extent than in the cis isomers. Deuterium labelling shows that the elimination involves mainly the benzylic hydrogen in the trans‐acetates, but not in the cis isomers. This behaviour is similar qualitatively to that of the corresponding alcohols and methyl ethers, but entirely different from that of t‐butylcyclohexyl acetates, which do not exhibit any stereospecificity. Substituent effects on the elimination for both cis and trans isomers are discussed.
Mass spectra of some 4,5‐dihydroimidazole derivatives
Authors: Gioia Bruno , Citerio Luisa , Stradi Riccardo 
Published: May 2005

AbstractThe mass spectra of a series of 4,5‐dihydroimidazole derivatives were determined. Deuterium labelling and high resolution mass spectrometry were utilized in order to elucidate the mechanism of a number of fragmentations. The most significant ions arise from the following processes: (1) elimination of the C‐4 substituent; (2) cleavage of the 1,2‐NC and 4,5‐CC bonds with or without hydrogen migration; (3) cleavage of the 1,5‐NC and 2,3‐CN bonds with charge retention on the N‐1C‐2 moiety.In this paper the standard numbering of the imidazole ring (see structures) is retained for the fragment ions.
Anomalous behaviour is shown by the t‐butoxy derivative; the reasons for this behaviour are discussed.
A predictive model for unimolecular reactions of organic ions
Authors: Bowen Richard D. , Stapleton B. Jane , Williams Dudley H. 
Published: May 2005

AbstractThe slow unimolecular dissociations of six members of the [CnH2n‐3]+ (n = 3‐8) series of unsaturated carbonium ions are explained in terms of a potential surface approach together with some concepts of mechanistic organic chemistry. The occurrence of some dissociations is shown to be precluded because either the reacting configurations or product combinations are inaccessible at energies appropriate to metastable transitions. The approach permits correct predictions to be made concerning the shapes of metastable peaks for dissociations which occur without σ‐bond formation in the final step. In particular, the observation of a composite peak, thus indicating two channels for reaction, for C2H4 loss from [C7H11]+ is naturally accommodated.
Complete isomerization of the molecular ion of 1,3,5‐trimethyl‐2,4,6‐trithian to that of 3,5,6‐trimethyl‐1,2,4‐trithian before decomposition in the gas phase
Authors: Wolkoff Peder , Holmes John L. 
Published: May 2005

AbstractThe complete isomerization of the molecular ion of r‐2‐deuterio‐2, cis‐4,cis‐6‐trimethyl‐1,3,5‐trithian into equal proportions of 3, 5‐ and 6‐d1‐3,5,6‐trimethyl‐1,2,4‐trithian molecular ions adequately accounts for all major fragmentations of the former. These fragmentations are losses of C4H8, C2H4S, S2H˙, C4H8S and C2H4S2. Similar rearrangements are proposed for other 1,3,5‐trithans and 1,3‐dithians.
On the interconversion of o‐methoxybenzaldehyde and 2,3‐ dihydrobenzofuran‐3‐ol molecular ions
Authors: Florêncio Helena , Heerma Wigger 
Published: May 2005

AbstractKinetic energy release measurements show that the similar primary fragmentation reactions in o‐methoxybenzaldehyde and 2,3 dihydrobenzofuran‐3‐ol occur from common ion structures.
Umlagerungen Schiffscher Basen
Authors: Holzmann G. , Rothkopf H. W. , Wöhrle D. 
Published: May 2005

AbstractDie elektronenstoßinduzierten Zerfälle Schiffscher Basen des DMD (Diaminomaleinsäuredinitril) werden durch Cyclisierungsreaktionen der Aminogruppe des DMD‐Restes mit der Azomethingruppierung beherrscht. Die innerhalb der Zerfallsprozesse gebildeten Imidazolsysteme werden durch MI‐ und CA‐ Spektren unter positiven und negativen Ionisierungsbedingungen sowie durch Vergleich des kinetic energy release unter Hinzuziehung von Modellionen bewiesen. Deuterierungsexperimente zeigen, daß die für Anile charakteristische HCN‐Eliminierung nicht unter Angriff der Azomethingruppierung sondern ausschließlich über den DMD‐ Rest ablaüft.
Mass spectra of a series of 2‐p‐substituted phenyl‐1,3,2‐dioxaborolanes
Authors: Kaminski James J. , Lyle Robert E. 
Published: May 2005

AbstractThe mass spectra of a series of 2‐p‐substituted phenyl‐1,3,2‐dioxaborolanes have been examined and compared with the mass spectrum of 2‐phenyl‐1,3,2‐dioxaborolane. Formation of the substituted ion [C7H6X]+ by electron impact induced rearrangement has been found to be influenced significantly by the presence and nature of the substituent at the para position of the phenyl ring.
Collisional activation spectra of [M + Li]+, [M + Na]+ and [M + K]+ ions formed by field desorption of some monosaccharides
Authors: Röllgen F. W. , Giessmann U. , Borchers F. , Levsen K. 
Published: May 2005

AbstractThe collisional activation spectra of monosaccharide ions formed by [Li]+, [Na]+ and [K]+ ion attachment under field desorption conditions are reported. It is shown that the elimination of the alkali ions is determined by the alkali ion affinities of the molecules (M) and competes with a fragmentation of M which is almost independent of the alkali ion attached. Correspondingly the alkali ion is predominantly retained in the fragment ions. The usefulness of this method for the differentiation of underivatized isomers is demonstrated.
A photoionization study of the [C7H8]\documentclass{article}\pagestyle{empty}\begin{document}$\mathop +\limits_.$\end{document} ion formed from some monosubstituted alkyl benzenes
Authors: McLoughlin R. G. , Morrison J. D. , Traeger J. C. 
Published: May 2005

AbstractAppearance potentials for the [C7H8]\documentclass{article}\pagestyle{empty}\begin{document}$\mathop +\limits_.$\end{document}ion produced in the fragmentation of n‐butyl benzene, iso‐butyl benzene and n‐pentyl benzene have been measured by photon impact. The results indicate that, at threshold, the fragment ion has the toluene molecular ion structure.
Artifact peaks in linked electrostatic and magnetic field scans of double focusing mass spectrometers of conventional Nier–Johnson geometry
Authors: Bilton J. N. , Kyriakidis N. , Waight E. S. 
Published: May 2005

AbstractBroad peaks of non‐integral mass in daughter ion spectra obtained by linked scans of double focusing mass spectrometers of conventional Nier‐Johnson geometry are shown to arise from transitions of higher mass ions in the first field free region.
The behaviour of beryllium μ4‐oxo‐μ‐carboxylates under electron impact
Authors: Nekrasov Yurii S. , Sil'vestrova Svetlana Yu. , Grigo'ev Aleksandr I. , Reshetova Lyudmila N. , Sipachev Viktor A. 
Published: May 2005

AbstractThe electron impact mass spectra of eight polynuclear beryllium complexes Be4O(RCO2)6 (RH, CH3, C2H5) and Be4O(RCO2)5OR′ (RCH3, R′H, CH3, C2H5, C3H7; RC2H5, R′C2H5) are reported. The major fragmentations involve the elimination of (RCO)2O (RCOOR′) or Be(RCO2)2 (Be(RCO2)OR′) from the ions [ML]+ and of {(RH)CO}, (R′H), H2O and BeO from the lighter ions. The fragmentation patterns are practically independent of the organic groups present and can be rationalized by stereochemical considerations.
Computerunterstützte Identifizierung von Isotopenmustern in niederaufgelösten Massenspektren
Authors: Kwiatkowski J. 
Published: May 2005

AbstractZur Identifizierung von Isotopenmustern in niederaufgelösten Massenspektren wird ein Computerprogramm beschrieben. Die mit dern Isotopenmusten übereinstimmenden Massen des Massenspektrums werden erkannt und ausgedruckt. Eine Ziffer gibt den Grad der Übereinstimmung des berechneten mit dem gemessenen Isotopenmuster an. Das Programm ist in FORTRAN IV geschrieben und kann auch auf kleineren Rechenanlagen ausgeführt werden.
Nitrile elimination and hydrogen rearrangement upon electron impact in schiff base peptide esters
Authors: Jayasimhulu K. , Day R. A. 
Published: May 2005

AbstractA series of Schiff base peptide esters were examined by gas chromatography mass spectrometry. Electron impact induced elimination of aryl nitriles (ArCN) from Schiff bases magnified image, where R, R′ …are amino acid sidechains formed from aromatic aldehydes and peptide esters was shown to be associated with formation of C‐terminal peptide fragments. Schiff base derivatives prepared from benzaldehyde and α‐deuterobenzaldehyde with several peptide esters indicated that aryl nitrile elimination was accompanied by H(D) transfer to the α‐C of the N‐terminal amino acid residue. Of the many Schiff base peptide esters of different aldehydes studied, HCN elimination of the type observed in some nonpeptide Schiff bases could only be found among N‐methyl pyrrolemethylidene derivatives.
Competing ring cleavages in substituted 4‐arylcyclohexanols and their methyl ethers under electron impact
Authors: Sharvit Joseph , Mandelbaum Asher 
Published: May 2005

AbstractRing cleavage α to the oxygen function leads to [C3H5O]+ and [C4H7O]+ ions in the mass spectra of 4‐arylcyclohexanols and their methyl ethers, respectively. Cleavage α to the aryl group gives rise to [C3H7O]+ (from the alcohols), [C4H9O]+ (from the ethers) and [ArC3H4]+ (from both) ions. The competition between the two ring cleavages explains the effect of the substituents of the aryl groups on the relative abundances of the resulting ions.
Mass spectrometry of transition–metal π‐complexes. V—fragmentation and structure of chromium‐coordinated ions
Authors: Davis R. , Ojo I. A. , Webb M. L. 
Published: May 2005

AbstractMass spectrometric studies have been made of the [(C7H8)Cr]+ ions generated from (η6‐PhCH3)Cr(CO)3 and (η6‐c‐C7H8)Cr(CO)3. Fragmentation behaviour and appearance potential measurements have been used to show that the ions from the two precursors do not achieve a common structure. [(C8H10)Cr]+ generated from (η6‐PhEt)Cr(CO)3 and (η6‐c‐C7H7Me)Cr(CO)3 behave similarly. A study of the α‐d3 toluene complex suggests the structure [CH3C6H4–CrH]+ is appropriate for [C7H8Cr]+ ions generated from (η6‐PhMe)Cr(CO)3 and decomposing to [CrH]+.
Kinetic shift in some para‐substituted acetophenones
Authors: Helal A. I. , Zahran Nagwa F. 
Published: May 2005

AbstractAn Atlas CH4 mass spectrometer has been used in conjunction with the electron ‘Energy Distribution Difference’ technique to investigate the kinetic shift associated with the process of elimination of CH3 from acetophenone, p‐methylacetophenone, p‐chloroacetophenone, p‐fluoroacetophenone and p‐methoxy‐acetophenone. The heats of formation of the ions investigated have been calculated.
Spectrométrie de Masse d'Hétérocycles Azotés. VIII–Comportement sous l'Impact Electronique de Nitroarylazoles
Authors: Atmani Aziz , Aubagnac Jean‐Louis 
Published: May 2005

AbstractLes spectres de masse des nitrophénylimidazoles et des nitrophénylpyrazoles sont étudiés afin d'apprécier l'influence de l'effet de voisinage ortho‐ortho′ sur la fragmentation. Cet effet conduit à des processus spécifiques pour les composés qui ont un groupement nitro en ortho de l'hétérocycle. L'examen des dérivés deutériés permet de confirmer ces processus par la mise en évidence d'un effet isotopique et d'établir dans le cas des o‐nitroimidazoles que le proton H‐2 adjacent aux deux atomes d'azote est concerné dans le départ de OH. La fragmentation de chaque composé est spécifique et son étude peut éventuellement constituer un moyen adéquat pour connaître la structure.
1,3‐Dioxolanylium‐ und 1,3‐Dioxanylium‐Derivate via Protonenkatalysierte SNi‐Reaktionen in der Gasphase
Authors: Respondek J. , Schwarz H. , Van Gaever F. , Van de Sande C. C. 
Published: May 2005

Abstract1,3‐Dioxolanylium‐ und 1,3‐Dioxanylium‐Ionen sind in der Gasphase durch protonenkatalysierte, SNi‐assistierte Heterolysen unter den Bedingungen der Chemischen Ionisation zugänglich. Konstitutionelle und konfigurative Effekte werden diskutiert und mit den Ergebnissen der Heterolyse in kondensierter Phase verglichen. Es wird ferner gezeigt, daß die unimolekulare Eliminierung von HX (X = Br, OAc) aus vicinal disubstituierten [MH]+‐Ionen nicht durch die Protonenaffinität der eliminierten Neutralteile bestimmt wird, so wie es bei monofunktionellen Verbindungen der Fall ist.
Identifikation der Partialstrukturen von unbekannten Steroiden mit einer Schlüsselionenkartei und einem rechnerunterstützten Retrieval‐System
Authors: Spiteller G. , Spiteller Margot , Ende M. , Hoyer G.‐A. 
Published: May 2005

AbstractDie Anwesenheit eines Strukturelementes verursacht oft die Bildung einer Folge von Schlüsselionen, die in threr Gesamtheit von hoher struktureller Spezifität sind. Auf dieser Basis wurde für Steroide ein rechnerunterstütztes Suchsystem geschaffen, das die Bestimmung von Teilstrukturen in unbekannten Verbindungen ermöglicht.
Hydrogen transfer in the retro Diels‐Alder fragmentation of oxygen‐containing heterocyclic Compounds. I—chromanones and 4‐hydroxychromans
Authors: Eguchi Shizuko 
Published: May 2005

AbstractThe mass spectra of 2,2‐dimethylchromanones and 2,2‐dimethyl‐4‐hydroxychromans show peaks corresponding to the ions formed by the retro Diels‐Alder reaction with or without hydrogen transfer to the ion. The hydroxychromans also show peaks corresponding to an ion formed by the loss of hydrogen from the ion formed by the retro Diels‐Alder reaction. Deuterium labelling showed that the hydrogen transferred in the chromanones arises from the gem‐dimethyl groups on C‐2, and the hydrogen atom lost in the case of the hydroxychromans is from C‐4, the carbinyl carbon.
On the mechanism of isomerization in the esters of some α,β‐unsaturated carboxylic acids—II
Authors: Burgers Peter C. , Terlouw Johan K. , Vijfhuizen Peter C. 
Published: May 2005

AbstractThe effect of a phenyl group on the mechanisms of isomerization in the ionized methyl esters of simple α,β‐unsaturated acids (methyl acrylate and related compounds) has been investigated with the aid of deuterium labelling as well as information from mass analysed ion kinetic energy spectra and first field free region metastable peak shapes. Substitution of a hydrogen atom of the OCH3 group by a phenyl group (benzyl acrylate and homologues) greatly enhances the rate of [ester] → [acid] isomerizations (loss of H2O and COOH˙). It is inferred that this is due to an accelerating effect of the phenyl group on the first and the third steps (ring opening of the key intermediate ion which has the structure of the ionized enol form of γ‐butyrolactone) of the reaction whose mechanism is basically the same as that in methyl acrylate. A phenyl group present at the α‐ or β‐position of the vinylic double bond appears to suppress the [ester] → [acid] isomerization in some compounds by promoting other reactions or opening up a new reaction pathway, i.e. the loss of CH2O from ionized methyl atropate for which mechanisms are proposed.
Effects of annulation on the mass spectral behaviour of bicyclo[4.3.0]‐3‐nonene derivatives: Keto esters and ketones
Authors: Tureček F. , Hanuš V. 
Published: May 2005

AbstractThe fragmentation patterns of the title compounds are shown to depend on the nature of the ring annulation. On ionization the cis‐annulated isomers lose a molecule of benzene in contrast to the corresponding trans isomers which do not. A mechanism involving a participation of the π‐electron system in the cleavage of the 5‐membered ring is suggested to explain the observed differences.
Electrohydrodynamic ionization mass spectrometry of sulfonates
Authors: Lai Shook‐T. F. , Evans Charles A. 
Published: May 2005

AbstractElectrohydrodynamic ionization mass spectrometry has been applied to the analysis of 2‐naphthol‐3,6‐disulfonic acid, disodium salt and 4,5‐dihydroxy‐2,7‐naphthalenedisulfonic acid, disodium salt. The negative ion mass spectra indicate ions characteristic of the sample and no fragment ions are observed. Degrees of dissociation of the sulfonates and the ion‐solvent interactions are reflected in the negative ion spectra.
Das Verhalten disubstituierter Benzole RC6H4Si(CH3)2F bei Elektronenstoß
Authors: Dube Gunther , Gey Erhard 
Published: May 2005

AbstractDer elektronenstoßinduzierte Abbau von disubstituierten Benzolen RC6H4Si(CH3)2F (R  p‐N(CH3)2, p‐OCH3, p‐, m‐CH3, H, p‐, m‐Cl, p‐, m‐Br und p‐NO2) besteht hauptsächlich in der Abspaltung eines Methylradikals vom Molekülion. Die Aktivierungsenergien für diese Fragmentierung wurden bestimmt. Sowohl die Intensitäten von Molekül‐ und Fragmentpeak in den Massenspektren als auch die Aktivierungsenergien hängen vom Substituenten R ab. Die änderung der Aktivierungsenergie wird mit der Einwirkung des Substituenten auf die Ladungsverteilung in den Molekülionen erklärt. Die Aktivierungsenergien werden näherungsweise quantenchemisch nach dem Pariser‐Parr‐Pople‐Verfahren berechnet. Die erhaltenen Daten stimmen mit den experimentell ermittelten Energiewerten größenordnungsmäßig überein, und die Tendenz wird richtig wiedergegeben. Durch Intensitätsberechnungen auf der Grundlage der QET wird der Zusammenhang zwischen Aktivierungsenergie und den Peakintensitäten in den Massenspektren bestätigt.