bluuebunny/crossref_metadata_2025 huggingface dataset:
On the formation and decomposition of the [M  HNO]+ ion from o‐nitrobenzaldoxime
Authors: Vijfhuizen Peter C. , Heerma Wigger , Nibbering Nico M. M.
Published: May 2005

The molecular ion of o‐nitrobenzaldoxime appears to eliminate a molecule of HNO, the latter as shown by deuterium labelling containing the hydroxyl hydrogen atom. This reaction may be followed either by loss of CO2 or C2O2 (2 × CO), which requires complicated skeletal rearrangements. To determine the structure of the [M  HNO]+ ion, the kinetic energies, released in the loss of CO2 and of C2O2 from this ion, have been measured. Similar measurements have been made on the appropriate metastable ions from o‐nitrosobenzaldehyde, 2,1‐benzisoxazoline‐3‐one, 2‐benzoxazolinone and 3‐hydroxy‐1,2‐benzisoxazole, whose molecular ions have the same elemental composition as the [M  HNO]+ ion from o‐nitrobenzaldoxime.

In the loss of HNO from the molecular ions of o‐nitrobenzaldoxime o‐nitrosobenzaldehyde molecular ions are generated first, which then, at least upon decomposition, rearrange further to 2,1‐benzisoxazoline‐3‐one molecular ions. Part of the latter finally rearrange to 2‐benzoxazolinone molecular ions, which eliminate CO via two routes. One of these corresponds to a low energy process and the other to a higher energy path whose excess energy induces the subsequent rapid loss of a second CO molecule. The observed effect of the rate‐determining isomerizations of the molecular ions of o‐nitrobenzaldoxime, o‐nitrosobenzaldehyde, 2,1‐benzisoxazoline‐3‐one and 3‐hydroxy‐1,2‐benzisoxazole to 2‐benzoxazolinone on the intensity and shape of the metastable peak for the low energy process for CO expulsion from the molecular ions of 2‐benzoxazolinone supports the proposed rearrangements.
Etude en Spectrometrie de Masse. VIII—Fragmentation de Qulques Benzalacetophenones et Benzalacetones Diversement Substituees sur le Cycle Aromatique
Authors: Rouvier Emile , Medina Haïm , Cambon Aimé
Published: May 2005

Nous présentons dans ce travail und étude comparative en spectrométrie de masse, du comportement des diphényl‐1,3 propénones (ou benazlacétophénones) et des phényl‐4 butanones‐2 (ou benazlacétones) dieversement substituées. La grande conjugaison qui s'étend á la quasi totalité de Ia molécule en fait des composés trés stables sous l'impact électronique. La présence d'un groupemen sur le cycle aromatique donne des fragements caratéristiques dont nous avons pu apprécier l'importance.
Intramolecular hydrogen exchanges during the electron impact‐induced fragmentation of complex alicyclic amines
Authors: Longevialle Pierre , Marazano Christian
Published: May 2005

The three‐step mechanism of formation of the important fragment ion of mass 84 from 3‐dimethylaminosteroids under electron impact is accompanied by intramolecular hydrogen exchanges, as shown by the mass spectra of deuterium labelled derivatives. The hydrogen exchanges are shown to occur in the ring A opened molecular ion, i.e. after the initial C‐3–‐C‐4 bond rupture, and to compete with the final C‐1–‐C‐10 bond rupture. (The intensity of hydrogen‐deuterium exchange reactions depends upon the activation energy of the final rupture.) The electron impact‐induced‐fragmentation of large alicyclic molecules bearing a strong charge stabilizing functional group, such as amines, appears to be the result of a series of displacements of the radical over different sites of the molecular ion through hydrogen (or carbon) rearrangements, with some of the radical sites being in the appropriate position to induce a final rupture.
A study of the electron impact‐induced fragmentation of 1,6‐diaminohexane
Authors: Blac Pierre‐Alain , Singy Gérard A. , Buchs Armand
Published: May 2005

The mass spectrometric behaviour of 1,6‐diaminohexane has been studied with the help of deuterium labelling in every position of the molecule. Extensive intramolecular exchange reactions between the hydrogen atoms of the amino groups and those of the hydrocarbon chain are responsible for the apparent complexity of the fragmentation mode.
Mass spectra of sulfinamide derivatives and identification of their thermal decomposition products
Authors: Ueda Yo , Mori Kōichi , Kouno Keiki , Nhya Tokihiro
Published: May 2005

The mass spectra of 30 sulfinamide derivatives (RSONHR', R' alkyl or p‐XC6H4) are reported. Most of the spectra had peaks attributable to thermal decomposition products. For some compounds these were identified by pyrolysis under similar conditions to be: RSO2NHR', RSO2SR, RSSR and NH2R' (in all kinds of sulfinyl amides); RSNHR' (in the case of arylsulfinyl arylamides); RSO2C6H4NH2, RSOC6H4NH2 and RSC6H4NH2 (in the case of arylsulfinyl arylamides of the type of X = H)

The mass spectra of the three thermally stable compounds showed that there are several kinds of common fragment ions. The mass spectra of the thermally labile compounds had two groups of ions; (i) characteristic fragment ions of the intact molecules and (ii) the molecular ions of the thermal decomposition products. It was concluded that the sulfinamides give the following ions after electron impact: [M]+, [M  R]+, [M  R + H]+, [M  SO]+, [RS]+, [NHR']+, [NHR' + H]+, [RSO]+, [RSO + H]+, [R]+, [R + H]+, [R']+ and [M  OH]+, and that the thermal decomposition products give the following ions: [RSO2SR]+, [RSSR]+, [M  O]+, [M + O]+ and [RSOC6H4NH2]+.
Hydrogen migrations in mass spectrometry. II—single and double hydrogen migrations in the electron impact fragmentation of n‐propyl benzoate
Authors: Benoit Frank M. , Harrison Alex G.
Published: May 2005

The sources of the migrant hydrogen atom(s) in reactions (a) and (b) in the electron impact mass spectrum of n‐propyl benzoate have been investigated: (a) [C6H5CO2C3H7]+ →[C6H5CO2H]+ + C3H6; (b) [C6H5CO2C3H7]+ → [C6H5CO2H2]+ + C3H5sdot;. Deuterium labelling of the propyl group showed that, for reaction (a) at 70 eV ionizing energy 3 ± 1% of the hydrogen originates from C‐1 of the propyl group, 86 ± 4% from C‐2 and 11 ± 3% from C‐3. The specificity of the transfer from C‐2 increases as the internal energy of the fragmenting ions decreases, indicating that the results cannot be rationalized in terms of H/D interchanges between positions in the propyl group, but rather that the reaction involves specific, competing, H transfer reactions from each propyl position, in contrast to the high site specificity characteristic of the McLafferty rearrangement. Reaction (b) involves, almost exclusively, transfer of one hydrogen from C‐2 and one from C‐3 with only very minor participation of C‐1 hydrogens. The [C6H5COOH]+ ion produced in reaction (a) fragments further to [C6H5CO]+ + OH. and the labelling results indicate some interchange of the carboxylic hydrogen with (ortho) ring hydrogens for those ions fragmenting in the first drift region. The extent of interchange is less than that observed for fragmentation of the same ion produced by direct ionization of benzoic acid or by reaction (a) in ethyl benzoate.
The mass spectrometric [M  C2H4O]+ process in cyclic ketones. I—the nature of the C2H4O losss in bicyclo[3.3.1]nonan‐2‐one and 3‐one
Authors: Cable J. , MacLeod J. K.
Published: May 2005

Although the loss of a C2H4O molecule from the molecular ions of the isomeric bicyclo[3.3.1]nonan‐2‐ and 3‐ones gives rise to the base peak at m/e 94 in both spectra, deuterium labelling results show that the processes leading to this ion are markedly different in the two cases. While the 2‐one follows essentially (>80%) the same [M  C2H4O]+ fragmentation pathway described for other 2‐alkylcyclohexanones, the 3‐one exhibits a more complex decomposition pathway in which one α‐hydrogen is transferred away from the departing C2 unit and three hydrogen atoms are subsequently rearranged to the eliminated C2H4O molecule. Similar competing fragmentation schemes have been invoked to explain deuterium labelling results in cycloheptanone, 2‐methylcycloheptanone and cyclooctanone.
Electron impact studies. CV—negative ion mass spectra of functional groups. The trimethylsilyl group. Singly charghed and doubly charged ions
Authors: Bowie John H. , Hale Barbara A.
Published: May 2005

The 70 eV negative ion spectra of m‐ and p‐nitrophenyltrimethylsilyl‐ethers and ‐esters show pronounced molecular anions and simple fragmentation patterns. The spectra of the corresponding ortho isomers show peaks produced by rearrangement processes; these reactions have been studied by 2H and 18O labelling. p‐Nitrobenzoyl derivatives of amino trimethylsilyl esters are of limited use for characterization of amino acids. Certain of the compounds studied produce a variety of dianions.
Zum Mechanismus Massenspektrometrischer Fragmentierungsreaktionen. XVI—hydrid‐Wanderungen bei der Fragmentierung von αω‐Dimethoxyalkyl‐Ionen
Authors: Neuert Ulrich , Grützmacher Hans‐Fr.
Published: May 2005

Das Isomeisierungs‐und Fragmentierungsverhalten von α,w‐dimethoxyalkylionen a (CH3OCH2(CH2)n CH+OCH3, n = 1‐6) wird mit Hilfe von Deuteriummarkierungen untersucht. Es wird gezeigt, daß vor eine Methanol‐Eliminierung a durch einen Hydrid‐Übertragung von der w‐ständigen CH2‐Gruppe auf das positive Ladungszentrum am α‐C‐Atom zu a' isomerisiert und bide Methoxygruppen als Methanol abgespalten werden können. An Hand der Alken‐Eliminierung aus [a ‐CH3OH]+‐Ionen in deuterierten Derivaten von A word auf den Isomerisierungsgrad geschlossen. Bei 70 eV treten danach im Mittel bis zu drei Umlagerungsschritte auf, bei denen ejweils eine Hydrid‐Übertragung stattfindet.
The computer processing and interpretation of mass spectral information. I—The reduction of raw mass spectra to monoisotopic form
Authors: Sukharev Yu. N. , Nekrasov Yu. S.
Published: May 2005

An algorithm of the AELITA program (Atomic‐Element Identification) is described which enables both low and high resulution mass spectra to be processed to give the elemental composition and ion abundances of the mass spectra in monoisotopic form. The program has no limitations in respect of the elemental composition and spectrum complexity. The criterion for the choice of the most probable solution is based either on the accuracy of measurement of the peak abundances and/or the masses. The program is written in ALGOL, run on a BESM‐6 computer, and occupies about 19K core memory.
Metastable ion Characteristics. XXXXIII—separation and comparison of collisional activation spectra and metastable ion spectra
Authors: Wachs Timothy , Van De Sande C. C. , McLafferty F. W.
Published: May 2005

Additional ion acceleration in a separate collision chamber in the field free drift region makes it possible to add extra kinetic energy to those ions undergoing decomposition in the chamber. In this way product ions formed in the collision chamber (the [collisional activation] spectrum) can be distinguished from ions formed from decompositions in the low pressure portion of the field free drift region (the [metastable ion] spectrum). This technique is used to show that often a relatively small proportion of the ions in the [pure] collisional activation spectrum arises from processes which produce the metastable ion spectrum.
An investigation of the decomposition of the common intermediate ions produced by electron impact. IV—[C6H5CO]+ ions from several alkyl benzoates
Authors: Tajima Susumu , Azami Tadashige , Tsuchiya Toshikazu
Published: May 2005

The decomposition of the [C6H5CO]+ ions produced from eight alkyl benzoates by electron impact has been studied. By calculating the heat of formation of [C6H5CO]+ ions from the appearance potential value, it is shown that the ions from C6H5COOR when RH, CH3, C2H5 have some excess energy, and those where R = n‐C3H7, iso‐C3H7, n‐C4H9, iso‐C4H9, iso‐C5H11 are produced with more excess energy. It is also shown that by taking this excess energy into account, there is a linear relationship between the heat of formation of the activated complex produced in the reaction [C6H5CO]+→[C6H5]+ + CO and the vibrational degree of freedom of the neutral fragment OR.
Electron impact and chemical ionization mass spectra of alkyldiphenylphosphine oxides
Authors: Goff Susan D. , Jelus Barbara L. , Schweizer Edward E.
Published: May 2005

In the 70 e V electron impact mass spectra of a series of alkyldiphenylphosphine oxides (Rϕ2PO, R = Me, Et, n‐Pr, i‐Pr, n‐Bu, i‐Bu, t‐Bu, neopentyl, n‐decyl), molecular ions of low abundance are observed and [M + H]+ ions are formed to a small extent at high sample pressures. The major ions include [ϕ2PO]+, [ϕ2POH]+; [ϕ2CH2PO]+ and [ϕ2CH2POH]+ which are formed by rearrangement and cleavage processes. The chemical ionization mass spectra obtained with methane and isobutane reagents consist of [M + H]+ ions. The proton affinity of Rϕ2PO was found to be 219 ± 2.5 kcal mol−1.
Über die Strukturen von Fragmentionen im Massenspektrometer: Das Ion m/e 84 aus Lysinmethylester
Authors: Roessler Felix , Hesse Manfred
Published: May 2005

Die 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

Eine 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

Auftrittspotentiale 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

The 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

Le 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

Metastable 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.
Genesis of the trimethylsilyl cation in the electron impact mass spectra of t‐butyldimethylsilyl derivatives
Authors: Phillipou G.
Published: May 2005

The formation of the trimethylsilyl cation in the electron impact mass spectra of t‐butyldimethylsilyl derivatives is shown to involve rearrangement of the t‐butyl group bound to silicon.
Mass spectra of ortho substituted 1‐phenyl‐2‐thioureas
Authors: Grehn Leif
Published: May 2005

The 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

The 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

It 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

The 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

Les 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

Die 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

Mit 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

For 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

The 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

The 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

Secondary 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

The 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

The 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

Les 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

Un 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

The 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

Die 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

Es 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

The 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

Hydrogen 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

The 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

The 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

A 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

Formation 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

Beim 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

The 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

The 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

The 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.
On the mechanism of isomerization reactions in the esters of some simple α,β‐unsaturated carboxylic acids
Authors: Burgers Peter C. , Terlouw Johan K. , Vijfhuizen Peter C. , Holmes John L.
Published: May 2005

It is shown from a detailed examination of first field free region metastable peak shapes that the molecular ion of the methyl ester of acrylic acid rearranges into 2‐ and 3‐butenoic acid ions prior to metastable fragmentations involving the losses of H2O, CH3˙ and CO. The key intermediate ion in this ester‐acid isomerization is shown to be the enol form of ionized γ‐butyrolactone. The C‐5 homologues methylmethacrylate and ethylacrylate display a similar mechanism for H2O loss, but the loss of CH3˙ shows additional mechanistic complexities. It was shown from the metastable peak shapes of 13C and deuterium labelled compounds that the larger part of the methyl loss does not occur from acid type ions, but directly from methyl substituted enol ions of γ‐butyrolactone. The mechanistic proposals also account for the presence of a pronounced loss of CH3˙ from the isomeric ester methylcrotonate and the absence of H2O loss in both methylcrotonate and the methyl ester of 3‐butenoic acid.
Electron impact mass spectra of some salts of carboxylic acids with alkali (group Ia) metals
Authors: White V Edward
Published: May 2005

Thirteen of the salts of the alkali metals (Li, Na, K, Rb, Cs) with acetic, 2,2‐dimethylpropionic, trifluoroacetic and heptafluorobutyric acid have been found to be sufficiently volatile to give mass spectra under normal electron impact conditions. The metal containing ions observed include (M=metal): [M]+, [MO]+, [MCO2]+, [M2]+·, [M2O]+·, [M2CO2]+· and the cluster ions [Mn (carboxylate)n‐1]+ for n = 2–8.
The time dependence of the competing processes leading to the loss of C2H4 from tetralin
Authors: Levsen K. , Borchers F. , Stolze R. , Budzikiewicz H.
Published: May 2005

Field ionization kinetic measurements indicate that loss of C2H4 from the molecular ion of tetralin occurs via competing processes, viz. (a) at short times the retro Diels‐Alder decomposition which is a high energy process, (b) loss from positions 1+2 (=3+4) and (c) loss after complete C and H scrambling which gains in importance for long ion lifetimes.
Effects of annulation on the mass spectral behaviour of monosubstituted bicyclo[4.3.0]‐3‐nonenes and bicyclo[4.3.0]‐3,7‐nonadienes
Authors: Tureček František , Hanuš Vladimir
Published: May 2005

The mass spectra of the title compounds differ considerably depending on the annulation of the bicyclic skeleton. For a series of alkyl derivatives the cis‐annulated compounds show a higher abundance of the products due to the retro Diels‐Alder cleavage than the corresponding trans isomers. The cis‐annulated esters and alcohols lose a molecule of ethanol and water, respectively, more easily than the corresponding trans isomers. Effects of conformation and configuration are discussed.
Electron impact induced formation of ions by skeletal rearrangement of some phenyl substituted cyclic ketones
Authors: van den Heuvel C. G. , Nibbering N. M. M.
Published: May 2005

The base peak at 70 eV for 7‐phenylbicyclo [3.1.1] heptan‐6‐one is due to the ion only. The direct formation of this ion from the molecular ion, as deduced from metastable ion decompositions in the field free regions, involves a rearrangement of 7‐phenylbicyclo [3.1.1] heptan‐6‐one to its 7‐phenylbicyclo [3.2.0]‐heptan‐6‐one isomer. Evidence for this rearrangement has been obtained from 13C labelling of 7‐phenyl‐bicyclo [3.1.1] heptan‐6‐one, from investigation of its independently synthesized bicyclic [3.2.0] isomer and of related compounds, and from measurements of kinetic energy release in fragmentations generating the various ions.
Chemical ionization of aliphatic nitro compounds
Authors: Chizhov Oleg S. , Kadentsev Valentin I. , Palmbach Galina G. , Burstein Konstantin Ia. , Shevelev Svyatoslav A. , Feinsilberg Albert A.
Published: May 2005

The chemical ionization mass spectra of various aliphatic nitro compounds have been studied. Almost all the nitro compounds form stable [M+H]+ ions in sharp contrast to the instability of their ions produced by other ionization techniques. The fragmentations of the [M+H]+ ions are discussed, the mechanisms and structures of fragment ions proposed being supported by quantum mechanical calculations. Correlations between chemical ionization mass spectra and structures of compounds studied are outlined. Reliable identification of mono‐ and polynitroalkanes and some related derivatives may be made by analysis of their chemical ionization mass spectra.
Stable gaseous aziridinium ions
Authors: Van de Sande Christian C. , Ahmad Syed Zahoor , Borchers Friedrich , Levsen Karsten
Published: May 2005

Gaseous protonated aziridine ions are produced at the threshold from β‐phenoxyethylamine molecular ions. The evidence for this is collisional activation spectra, using various precursors (including labelled analogues) under electron impact and field ionization conditions. Partial conversion to the acyclic \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH = }\mathop {\rm N}\limits^ + {\rm H}_{\rm 2} $\end{document} isomer occurs at higher electron energies and is rationalized by means of a potential energy surface constructed from energetic data.
Ionization and appearance potentials in organic chemistry. I—energetic aspects of the mass spectra of stereoisomeric 4‐substituted N‐alkyl‐2‐methyldecahydroquinol‐4‐ols
Authors: Zaikin V. G. , Wulfson N. S.
Published: May 2005

The ionization potentials for the stereoisomers of trans‐fused 1,2‐dimethyl‐ and 1‐ethyl‐2‐methyl‐4‐R‐decahydroquinol‐4‐ols (RCCH, CHCH2 or C2H5) and the appearance potentials for the [M–CH3]+ and [M–C2H5]+ ions (loss of 2‐CH3 and 4‐C2H5 groups potential, respectively) were measured by using the electron impact method. The ionization and appearance potential for [M–CH3]+ are always lower for the isomers with the axial 2‐CH3 group. For the C‐2 epimers, the difference between the appearance potentials for the [M–CH3]+ ion values is likely to be equal to the enthalpy differences between the ground states of the epimers and the dissociation energy differences between the axial and equatorial C2–CH3 bonds. The appearance potentials for [M–C2H5]+ for the C‐4 epimers possessing the 4‐C2H5 group were very similar. At the same time, the appearance potentials for the [M–CH3]+ ions were lower for less stable epimers which had an axial 4‐C2H5 group.
Reactions of [CH3]+ and [CD3]+ with alcohols
Authors: Smith Richard D. , Futrell Jean H.
Published: May 2005

The reactions of [CH3]+ and [CD3]+ with a number of C1 to C5 alcohols were studied at approximately thermal energies (0.1 eV) using a tandem Dempster ion cyclotron resonance mass spectrometer. Branching ratios obtained under single collision conditions are reported for [CH3]+ and [CD3]+ with methanol, perdeutero methanol, ethanol, allyl alcohol, 1‐propanol, 2‐propanol, perdeutero‐2‐propanol, 1‐butanol, 2‐butanol, t‐butanol, cyclopentanol and 1‐pentanol. The results are examined in terms of the mechanism of reactions and indicate that upon progression to larger alcohols, the formation of a long‐lived adduct becomes less important in determining the reaction products.
Mass spectrometry of heterocyclic compounds. XV—The mechanism of the fragmentation under electron impact of 3‐p‐NH2‐phenyl‐5‐phenyl‐1,2,4‐oxadiazole. A CNDO/2 treatment
Authors: Selva A. , Traldi P. , Fantucci P.
Published: May 2005

Molecular orbital calculations using the semi‐empirical CNDO/2 method were carried out on the molecular ion of 3‐p‐NH2‐phenyl‐5‐phenyl‐1,2,4‐oxadiazole, whose structure had been determined by X‐ray diffraction. The calculated diatomic interaction energy values are consistent with the mechanistic proposals made previously in terms of the quasi‐equilibrium theory concerning the cleavage of the heterocycle ring after electron impact.
Potential energy profiles for unimolecular reactions of organic ions: [C3H8N]+ and [C3H7O]+
Authors: Bowen Richard D. , Williams Dudley H. , Hvistendahl G. , Kalman John R.
Published: May 2005

The unimolecular decompositions of two isomers of [C3H8N]+, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} {\rm CH} = \mathop {\rm N}\limits^ + {\rm H}_2 $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} \mathop {\rm N}\limits^ + {\rm H = CH}_{\rm 2} $\end{document}, are discussed in terms of the potential energy profile over which reaction may be considered to occur. The energy needed to promote slow (metastable) dissociations of either ion is found to be less than that required to cause isomerization to the other structure. This finding is supported by the observation of different decomposition pathways, different metastable peak shapes for C2H4 loss, the results of 2H labelling studies, and energy measurements on the two ions. The corresponding potential energy profile for decomposition of the oxygen analogues, \documentclass{article}\pagestyle{empty}\begin{document}${\rm CH}_{\rm 3} {\rm CH}_{\rm 2} {\rm CH =\!= }\mathop {\rm O}\limits^ + {\rm H} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm CH}_{\rm 3} {\rm CH}_{\rm 2} \mathop {\rm O}\limits^ + {\rm = CH}_{\rm 2} $\end{document}, is compared and contrasted with that proposed for the [C3H8N]+ isomers. This analysis indicates that for the oxygen analogues, the energy needed to decompose either ion is very similar to that required to cause isomerization to the other structure. Consequently, dissociation of either ion is finely balanced with rearrangement to the other and similar reactions are observed. Detailed mechanisms are proposed for loss of H2O and C2H4 from each ion and it is shown that these mechanisms are consistent with 2H and 13C labelling studies, the kinetic energy release associated with each decomposition channel, the relative competition between H2O and C2H4 loss and energy measurements.
Formation of doubly charged ions in field ionization mass spectra of para substituted acetophenones
Authors: Helal A. I. , Zahran Nagwa F.
Published: May 2005

The doubly charged [M]2+, [M+1]2+ and [M‐O]2+ ions are observed in the field ionization mass spectra of para substituted acetophenones. The effect of the type of the substituent on the formation of the doubly charged ions is described.
Intermolecular methyl transfer on pyrolysis of carpronium chloride
Authors: Ohya Kazumi , Yotsui Yasuhiko , Sano Mitsuji
Published: May 2005

The methyl transfer occurring in the production of methyl N,N‐dimethyl‐γ‐aminobutyrate by pyrolysis of carpronium chloride was examined by means of pyrolysis gas chromatography mass spectrometry with the aid of some deuterated compounds. The mass spectra of methyl N,N‐dimethyl‐γ‐aminobutyrate, produced from deuterated derivatives of carpronium chloride, showed inter alia, characteristic molecular ion peaks which indicated that the methyl of the trimethylammonium group transfers and displaces the methyl of the carbomethoxy group of the tertiary amino compound. The results show that an intermolecular methyl transfer occurs in part on pyrolysis of carpronium chloride, to form methyl N,N‐dimethyl‐γ‐aminobutyrate in which the methyl oxygen is replaced by a methyl from the nitrogen of the original compound. The mechanism presented involves the bimolecular reaction between zwitterionic intermediates formed by ionic O‐demethylation of carpronium chloride.
The use of a mass spectrometer of mattauch‐herzog geometry for the determination of the kinetic energy release in ionic decompositions
Authors: Herzig Ulrike , Krenmayr Peter
Published: May 2005

A double focusing mass spectrometer of Mattauch‐Herzog geometry has been modified to allow the evaluation of the kinetic energy (T) released during ionic fragmentations within the first field free region. The data obtained are consistent with, though less accurate than those determined on Nier‐Johnson type mass spectrometers. Kinetic energy release values for the decomposition of metastable [C2H3O]+ ions formed from a series of compounds containing the acetyl group are reported. A ‘degrees‐of‐freedom’ effect on T was not detected.