bluuebunny/crossref_metadata_2025 huggingface dataset:
Fragmentation and rearrangement processes in the high resolution mass spectra of diphenylsilyl compounds
Authors: Ho Benedic T. Y. K. , Spialter Leonard , Smithson Lee D.
Published: May 2005

High resolution mass spectra of a series of diphenylsilyl compounds, Ph2SiX2(X=H, F, Cl) and Ph2Si(oy)2 (Y=Et, Me, H), were recorded. Results from selected metastable defocusing experiments showed that if X or OY can be readily lost stepwise, the relative abundance of the biphenyl radical rearrangement ion (d) is small; if neutral silicon species such as :SiX2, SiX or :Si(OY)2 are readily eliminated, the relative abundance of the ion d will be large. The ion d originates from both odd‐ and even‐electron ions, thus making the radical site mechanism, which requires a phenyl radical to polarize the other phenyl group, rather unlikely to be an important general driving force. The condensation of phenyl groups could be more appropriately viewed in terms of bond liability and product stability. In the special case of diphenylsilyl catecholate, in addition to geminal cleavage of phenyl groups, complex fragmentation and rearrangement processes were also observed.
MASSENSPEKTROMETRISCHE UNTERSUCHUNGEN ZUR STRUKTUR STABILER [mCH2COOH3]+‐IONEN AUS α,ω‐DICARBONSäREDIMETHYLESTERN
Authors: Schwarz Helmut
Published: May 2005

Mit Hilfe von Auftrittspotential‐Messungen wird gezeigt, daß die stabilen [M  CH2COOCH3]+‐Ionen aus den Titelverbindungen im Fall von n= 4,5 und 6 eine cyclische Struktur besitzen. Die Bildung freier Carbenium‐Ionen oder Ionen einer isomersen Struktur wird diskutiert.
Mass spectrometric beheviour of some 5,5‐diphenylglycocyamidine and ‐hydantoin derivatives
Authors: Tamás J. , Czira G. , Simig Gy. , Lempert K.
Published: May 2005

The mass spectra and main fragmentation pathways are presented for thirteen 1‐ and 3‐substituted 5,5‐diphenylglycocyamidine and ‐hydantoin derivatives. The principal decomposition routes of these compounds are also of diagnostic value for ascertaining positional isomerism when the substituents are eliminated in the initial stage of fragmentation.
FRAGMENTATION DES AMINO‐2 STEROIDES EN SPECTROMETRIE DE MASSE
Authors: Marazano Christian , Longevialle Et Pierre
Published: May 2005

La fragmentation des diméthylamino‐2 stéroides en spectrométrie de masse est étudiée et des interprétations proposées pour la formation des principaux ions formés. L'étude comparée avac Ie spectre d'un β‐amino‐alcool (OH en 3) permet de déterminer Ia rupture initiale dans Ie mécanisme de formation des principaux ions. Une comparaison est faite entre Ia fragmentation des amino‐3 et celle des amino‐2 stéroides.
EI and IKE spectra of some aldosyl disaccharide peracetates
Authors: Das K. G. , Thayumanavan B.
Published: May 2005

The electron ionisation and ion kinetic energy spectra of some aldosyl disaccharide peracetates are discussed. The diagnostic value of the data in differentiating between the various types of glycosidic linkages is emphasised.
MASSENSPEKTROMETRISCHE UNTERSUCHUNG ZUM MECHANISMUS DER METHYLABSPALTUNG AUS VICINALEN METHYLFURANCARBONSÄURE‐METHYLESTERN
Authors: Schwarz Helmut , Bornowski Hans , Petruck Gerd‐Michael
Published: May 2005

Die Methyl‐Eliminierung aus den Titelverbindungen wird durch die Untersuchung mehrerer Modellverbindungen aufgeklärt. Es wird gezeigt, daß die Reaktion unter Nachbargruppenbeteiligung verläuft und daß der Abstand zwischen dem Wasserstoffdonator und demakzeptor von entscheidender Bedeutung für die Bildung der [M‐CH3]+‐Ionen ist.
On the formation of anisole from phenoxyacetamides
Authors: Tomer Kenneth B.
Published: May 2005

A major fragmentation route of N‐t‐butyl‐N‐isopropyl‐and N‐ethylphenoxyacetamide is the formation of [C7H8O]+. Deuterium labeling implicates hydrogen transfer from nitrogen in all three species and from the t‐butyl groups of the t‐butylamide. The anisole structure is assigned to the [C7H8O]+· ion on the basis of its secondary fragmentation.
Electron‐impact‐induced rearrangement of organic hypophosphates
Authors: Stec W. J. , Zielińatska B. , Van Wazer J. R.
Published: May 2005

Preliminary investigation of electron‐impact behavior of organic hypophosphates and their mono and dithio derivatives has shown that they undergo skeletal rearrangement to the anhydride type of structure magnified image,and that this anti‐Arbuzov rearrangement is of electron‐impact origin.
Mass spectral fragmentation of some phosphaaromatic compounds
Authors: Jongsma C. , Bickelhaupt F.
Published: May 2005

The behaviour of 2‐phosphanaphthalene, 3‐methyl‐phosphanaphthalene and 10‐methyl‐9‐phosphaanthracene upon electron‐impact has been compared with that of the carbon and nitrogen analogues. A close resemblance to the fragmentation pattern of the [M  H]+ ions of 2‐methyl‐and 2‐ethylbenzo[b]thiophene has been observed. It is concluded from the σ40 intensities of the molecular ions, the relatively high intensities of the doubly charged molecular ions and the fragmentation patterns, that these phosphorin derivatives behave as aromatic compounds under electron‐impact. From the molecular ion of 2‐phosphanaphthalene a remarkable expulsion of a phosphours atom is observed.
MASSENSPEKTROMETRISCHE UNTERSUCHUNGEN VON DIARYLMETHYLEN‐BIS‐XANTHOGENATEN UND DIARYL‐DITHIOACETALEN: II
Authors: Schumann Dieter , Frese Emil , Praefcke Klaus , Knöfel Werner
Published: May 2005

Das massenspektrometrische Verhalten der Diarylmethylen‐bis‐xanthogenate wird beschrieben und mit dem der Dithioacetale verglichen. Charakteristisch für alle untersuchten Verbindungen ist das Auftreten eines primär gebildeten Sulfenium‐Kations, das für die Verbindungen ein den Thioestern analoges Fragmentierungsverhalten zeigt. Hervorzuheben ist das mit Thioketonstrukturen, deren Bildung mit der thermolytischen verglichen und diskutiert wird. Dabei ist bemerkenswert, dass die als Beleg dienenden metastabilen Signale für die Bildung des Fragments d aus dem 1. feldfreien Raum erst bei höheren Temperaturen auftreten und somit Abhängigkeit von der thermischen Überschussenergie zeigen.
The significance of field ionisation kinetics to ion structure: Isomerisation and decompostition of [C4H8]+· radical ions
Authors: Morgan Roger P. , Derrick Peter J.
Published: May 2005

The kinetics of formation of [C3H5]+[M  CH3]+, [C3H4]+·[M  CH4]+· and [C2H4]+·[M  C2H4]+· from but‐1‐ene, cis‐ and trans‐but‐2‐ene, 2‐methylpropene, cyclobutane and methylcyclopropance following field ionisation have been determined as a function of time 20 (or 30) picoseconds to 1 nanosecond and at two points in the microsecond time‐frame. The results are consistent with the supposition that at the shortest accessible times (20 to 30 picoseconds) the structure of the [C4H8]+· molecular ion qualitatively resembles that of its neutral precursor, but suggest that prior to decomposition within nanoseconds the various molecular ions (excepting cyclobutane where the processes are slower) attain a common structure or mixture of structures. Reaction pathways of the presumed known ion structures are delineated from the nature of decompostion at the shortest times.
MASSENSPEKTROMETRISCHE UNTERSUCHUNG ORGANISCHER STICKSTOFFVERBINDUNGEN XVIIIMECGABUSNEB;ndash DER NH3‐ ELIMINIERUNG AUS 3‐PHENYL‐PROPYL‐ UND 5‐PHENYLPENTYLAMIN
Authors: Schwarz Helmut , Wesdemiotis Chrysostomos , Hess Bernd , Levsen Karsten
Published: May 2005

Mit Hilfe von 2H‐markierten Verbindungen, Bestimmungen, Bestimmung der Bildungsenthalpien der [pM  NH3]+·‐Ionen aus Auftrittspotential‐Messungen und Vergleich der Stoßakitiverungs‐spektren dieser Ionen mit denen der entsprechenden Phenylalkene werden die Mechanismen der Ammoniak‐Eliminierung aus den Titelverbindungen untersucht und möliche Ionenstrukturen als Funktion der Lebensdauer diskutiert.
Mass spectrometric study of hexamethyldisilazane and some of its N‐substituted derivatives
Authors: Tamás J. , Miklós P.
Published: May 2005

The electron‐impact‐induced decomposition of the title compounds has been investigated in detail. Deuterium labelling was used to study the mechanisms of fragmentation and the structures of ions generated. Hydrogen, methyl and phenyl group migrations to one of the silicon atoms were observed as significant secondary processes. These processes are usually γ‐transitions, from which it is inferred that these rearrangements occur via 4‐membered cyclic transition complexes.
Formation of aniline‐like ions by electron‐impact‐induced elimination of CO from formanilide
Authors: Hammerum Steen
Published: May 2005

The metastable peak intensity ratios for elimination of HNC vs DNC from the [M  CO]+· ion of deuterium labelled analogues of formanilide show that the formyl hydrogen atom migrates to nitrogen prior to or during CO expulsion to form a [C6H7N]+· ion of aniline‐like structure. An examination of metastable peaks does not allow similar conclusions to be reached for methyl substituted formanilides. Low abundance [C6H6O]+· ions are formed by HNC elimination from the formanilide molecular ion in a reaction where three covalent bonds to the formyl carbon are broken.
Spectrometrie de masse d'heterocycles azotes. IV—comportement sous l'impact electronique d'iodures de pyrazoliniums‐2
Authors: Aubagnac J.‐L. , Bourgeon D. , Jacquier R.
Published: May 2005

Le comportement d'iodures de pyrazolinium‐2 en spectrométrie de masse est étudié. Les réactions de substitution de l'anion iodure sur les substituants portés par l'azote en 1 entraǐnent la formation de quatre molécules neutres dont on observe simultanément la fragmentation. Les réactions se produisent donc tant dans des solutions protiques, ainsi que des travaux précédents l'ont montré, qu'en phase gazeuse et sous l'impact électronique.
Studies in mass spectrometry. III—formation of a common intermediate in the primary fragmentation process of 1‐phenylcyclobutene and of 2‐phenyl‐1,3‐butadiene
Authors: Derocque Jean‐Luc , Jochem Martin
Published: May 2005

The mass spectra of the title compounds show peaks corresponding to the primary fragmentation of H, CH3 and (H2 + C2H2). Kinetic study suggests that the molecular ion of 1‐phenylcyclobutene and 2‐phenyl‐1,3‐butadiene loses H and CH3 through formation of a common intermediate. This is confirmed by appearance potential and ionisation potential measurements, fragmentation of deuterium labelled compounds and the corrected Z values.
Fragmentation d'azoles sous l'impact electronique. X—etude de rearrangements cycliques en serie alkylamino‐1,2,4‐triazole
Authors: Maquestiau A. , Van Haverbeke Y. , Flammang R. , Cooks R. G.
Published: May 2005

La formation in situ de tautomères individuels par des réactions de fragmentation dans le spectromètre de masse constitue une méthode de réarrangements tels que les équilibres prototropiques. Le C‐aminotriazole est généré en ses différentes formes tautomères par élimination d'éthylène à partir des composés N‐éthylés et ces tautomères sont isomérisés en une structure commune avant fragmentation. L'élimination d'éthylène se déroule via un état de transition à quatre centres pour deux éthylaminotriazoles isomères et via un état de transition à cinq centres pour le troisième comme le montrent les termes de partition d'énergie associés aux réactions aux réactions d'ions métastables. Ces conclusions mécanistiques sont étayées par l'étude d'effects isotopiques (méthode de caractérisation de facteurs de fréquence). L'élimination de propène à partir de propylaminotriazoles est abordée par des méthodes analogues. Les termes de partition d'énergie et l'étude d'effets isotopiques primaires sont en accord avec une élimination non concertée de propène ou avec un mécanisme de transfert de l'hydrogène β via un complexe transitoire à cinq centres.
Mass spectra of some neopentylphosphorus derivatives
Authors: King R. B. , Cloyd J. C. , Reimann R. H.
Published: May 2005

The fragmentation patterns and major metastable ions of the mass spectra of the neopentyl‐phosphorus derivatives [(CH3)3CCH2]3P, [(CH3)3CCH2]2P(O)H, [(CH3)3CCH2]nPX3‐n (n = 1 and 2; X = H, Cl, C6H5 and CH = CH2), [(CH3)3CCH2]3PS, [(CH3)3CCH2]nP(S)R3‐n (n = 1 and 2; R = C6H5 and CH = CH2), [(CH3)3 CCH2]2PCH2CH2P[CH2C(CH3)3]2, ([CH3)3CCH2]2PCH2PCH2‐CH2P(H)C6H5 and [(CH3)3CCH2]2PCH2CH2P(S)(CH3)2 are described. Fragmentation of a neopentyl group by elimination of either C4H8 or CH3 is very favourable when the neopentyl group is bonded to either a tricoordinate or tetracoordinate phosphorus atom. In neopentylphosphines with two or three neopentyl groups, stepwise elimination of C4H8 from all of the neopentyl groups occurs very readily. The resulting [(CH3)nPX]+.3‐n ions are often the most intense ions in the mass spectra.
Isomere N‐Aryltetrazole. III—Massenspektren
Authors: Könnecke A. , Lippmann E.
Published: May 2005

Die niedrigaufgelösten massenspektren von vier Paaren isomerer N‐Aryltetrazole sind untersucht worden, um die Anwendbarkeit der Massenspektrometrie zur Unterschiedung der Isomeren zu überpuüfen. die Fragmentierung beginnt in Reihen durch aufeinanderfolgende Abspaltung von N2 und HCN unter Bildung von Ionen der gleichen Massenzahlen, die vielleicht auf Grund verschiedener Struktur mit unterschiedlicher Häufigkeit auftreten. Dies ermöglilcht die eindeutige Identifizierung der Isomeren.
Hydrogen rearrangements in cyclic phosphates during the electron impact‐induced fragmentation
Authors: Murai Asao , Kainosho Masatsune
Published: May 2005

The fragmentation upon electron impact of a cyclic phosphate, 5,5‐dimethyl‐2‐oxo‐2‐phenoxy‐1,3,2‐dioxaphosphorinane, was investigated. Using its deuterated analogue, it was shown that no randomization of hydrogen atoms among methyl, methylene and phenyl groups occurred within the molecular ion. The majority of the fragmentations involved single, double or triple hydrogen transfers. The origin of hydrogen(s) transferred in the formation of C‐5 ions was also estimated. The existence both specific and nonspecific hydrogen rearrangement mechanisms was also revealed. The specific hydrogen rearrangement involves a methyl hydrogen transferring to the PO group and this process seemed to be the initial step in the formation of many of the ions.
Anwendung der Massenspektrometrie zur Identifizierung isomerer Amino‐oxadiazole
Authors: Kraft R. , Henklein P. , Etzold G. , Zöpfl H.‐J. , Westphal G. , Schmidt R.
Published: May 2005

Die massenspektrometrischen Zerfallsprodukte der vier isomeren phenyl‐substituierten Amino‐oxadiazole, 2‐Amino‐5‐phenyl‐l.3.4‐oxadiazol, 3‐Amino‐5‐phenyl‐l.2.4‐oxadiazol, 5‐Amino‐3‐phenyl‐l.2.4‐oxadiazol und 3‐Amino‐4‐phenyl‐l.2.5.oxadiazol, unterscheiden sich sowohl hinsichtlich der Art der Fragmentzusamrnensetzung als auch der Signalintensitäten so charakteristisch, daß eine eindeutige Differenzierung von Ring‐ und Stellungsisomeren moglich ist. Die wichtgsten Fragmentierungswege, die zu den strukturspezifischen Ionen führen, werden diskutiert.
Elektronestossinduzierte Fragmentierung von Acetylenverbindungen. XIV—Wasser‐Eliminierung Durch OH/OH‐Wechselwirkung bei α,ω‐DIIN‐Diolen
Authors: Schwarz Helmut
Published: May 2005

Die Mechanismen der elektronenstroßinduzierten Wasser‐Eliminierung aus den Titelverbindungen werden untersucht. Es wird gezeigt, daß beide Hydroxylgruppen an diesem Prozeß beteiligt sind und daß die ungewöhnliche Wechselwirkung nichtgebundener Zentren wahrscheinlich durch winkeldeformationen der Diine verursacht wird.
Structure in metastable peaks arising from reactions in which[C3H3]+ ions are produced
Authors: Sen‐Sharma D. K. , Jennings K. R. , Beynon J. H.
Published: May 2005

The metastable peak resulting from the fragmentation of [C7H7]2+⋅ ions fram a variety of sources shows structure due to the presence of two reactions releasing different amounts of translational energy. The translational energy differences has been measured as 0.52 ± 0.04eV and is thought to be due to the formation of product ions of different structure via competing reactions from a single transition state. The possible structures of these ions are discussed, and it is proposed that the effect observed is due to the formation of [C3H3]+ ions in two forms, cyclopropenyl and proparg1. The metastable singly charged ions which also lead to product ions of formula [C3H, 3]+.
Mass spectral studies of unsaturated carboxylic acids. II—Some acids containing two double bonds
Authors: Bigley D. B. , Todd J. F. J. , Weatherhead R. H.
Published: May 2005

The mass spectra of some doubly unsaturated carboxylic acids are reported. Where C‐2 is quaternary, the fragmentation pathway is similar to that previously demonstrated for βγ‐unsaturated acids. The unbranched acids show different behaviour, similar to their thermal pyrolysis.
Chemical ionization of cyclopropyl ethers
Authors: Andrist A. Harry , Wilburn Bruce E. , Zabramski Joseph M.
Published: May 2005

Chemical ionization of the isomeric 2,3‐dimethylcyclopropyl methyl ethers has been examined with hydrogen, methane and ammonia as reagent gases. The relative ion intensities for loss of methanol from each protonated isomer are consistent with the operation of the DePuy‐Hoffmann‐Woodward Rule in the gas phase.
Slow metastable transitions in aromatic species
Authors: Smith Richard D. , Furtell Jean H.
Published: May 2005

A tandem Dempster‐ion cyclotron resonance mass spectrometer was used to examine metastable transitions in benzene, toluene, anisole and anisole 1,3,5‐d3. The tandem‐ion cyclotron resonance technique examines all unimolecular reactions of the injected, mass‐selected ion, which occur between the injection time of several microseconds and the ion cyclotron resonance reaction section residence time of several milliseconds. The long sampling interval results in different relative intensities and considerably larger isotope effects than have been observed in previous studies.
Stereoselective H2O eliminations in 3‐ and 4‐arcylcyclohexanols under electron impact
Authors: Sharvit Joseph , Mandelbaum Asher
Published: May 2005

The elimination of H20 from the molecular ions of trans‐4‐ and trans‐3‐arylcyclohexanois takes place to a greater extent than in the corresponding cis isomers. The remarkable differences in abundance taken together with substituent effects and the results of deuterium labelling, show that configuration is retained in the molecular ions which undergo the elimination, and that this process is a cis‐1,4 and cis‐1,3 elimination in the trans‐4‐ and trans‐3‐ arylcyclohexanois, respectively. Possible mechanisms for the elimination in the cis isomers are discussed.
Die massenspektrometrische Identifizierung von Alkyl‐1, 3‐thiazolen
Authors: Haag Armin , Werkhoff Peter
Published: May 2005

Stellungsisomere Mono‐, di‐ und Trialkyl‐1,3‐thiazole Können anhand ihrer Elektronenstossmassenspektren eindeutig identifiziert und von isobaren Deivaten unterschieden werden. Die entscheidenden Kriterien hierfür ergeben sich suc den Massenzahlen und den relativen Intensitäten signifkanter schlüsselionen, isbesondere der Molkülionen, der [M – 1]+,‐Ionen, der Thiazolylmethly‐carbokationen bzw. ihrer zur Thiaziniumstruktur ringerweiterten Formen, sowkie der durchringverrengende Nitrileliminierung gebildeten Thiitren‐Radikalionen. Auf diese Weise wurden durch Gaschromatographie‐Massenspektroskopie im Glaskapillar‐Gaschromatogramm von Röstkaffeearoma 22 Thiazolderivate erkannt. Ihre Zuordnung wurde durch Messungen an einer Reihe authentischer Vergleichspräparate voll bestätigt.
Mass spectrometric identification of amino acid thiohydantoins
Authors: Suzuki Tateo , Song Kyung‐Duck , Itagaki Yasuhiro , Tuzimura Katura
Published: May 2005

Amino acid thiohydantoins were identified using electron impact and chemical ionization mass spectrometry. Some fragmentations of thiohydantoin ring were also identified. These results suggest that the thiohydantoin method should be useful for the stepwise peptide sequence analysis starting from the carboxyl terminus. The sequence of a model tripeptide was determined by the combination of the thiohydantoin method and mass spectrometry. In the case of peptide which contained a proline residue as their C‐terminal peptide, cleavage of the peptide bond cannot be achieved.
Fragmentation in doubly charged ion mass spectra of anhydropisatin and related compounds
Authors: Eguchi Shizuko , Nakayama Mitsuru , Hayashi Shûichi
Published: May 2005

The doubly charged ion mass spectra of anhydropisatin, 4‐methoxyanhydropisatin, 3, 8, 9‐trimethoxypterocarpen and 3, 4, 8, 9‐tetramethoxypterocarpen were determined, and the fragmentation was explained by assuming that the paired electrons were partially localized in the fragmentations and by comparing the spectra with that of 3‐(CD3)‐anhydropisatin. Conventional mass spectra of these compounds were very simple, but the doubly charged ion spectra were sufficiently characteristic for the reliable identification.
Hydrogen migrations in mass spectrometry. I—The loss of olefin from phenyl‐n‐propyl ether following electron impact ionization and chemical ionization
Authors: Benoit Frank M. , Harrison Alex G.
Published: May 2005

Using specifically labelled compounds we have made a detailed study of the source of the hydrogen transferred in the elimination of C3H6 from the molecular ion of phenyln‐propyl ether following electron impact ionization and from the protonated (and ethylated) molecule following chemical ionization. The migrating hydrogen originates from all three positions of the npropyl group but not in the ratio expected for randomization of the alkyl hydrogens prior to transfer. The source of the migrating hydrogen is similar for both electron impact ionization and chemical ionization, indicating that the factors governing the rearrangement are the same for both modes of ionization. From a comparison of the results for labelled 2,6‐dimethyl phenyl n‐propyl ethers with the results for the unsubstituted ether it is concluded that hydrogen transfer occurs only to the ether oxygen and not to the phenyl ring. A two‐step mechanism involving a set of competing reversible hydrogen transfer reactions followed by CO bond cleavage is proposed to explain the results.
Mass spectrometry and organic analysis. XV—esters of αβ‐unsaturated acids (tiglates and angelates)
Authors: Thomas Alan F. , Willhalm Bruno
Published: May 2005

The unambiguous differences between the mass spectra of Z and E isomers of esters of 2‐methylbut‐2‐enoic acid enable the double bond geometry to be determined.
A standard form for the presntation of field ionization kinetics data
Authors: Beckey H. D. , Levsen K. , Derrick Peter J.
Published: May 2005

It is suggested that division of the rates of molecular ion decomposition by the measured mass‐resolved molecular ion current be adopted as the standard method of normalizing these data obtained through the field ionization kinetics technique.
Hydrogen randomization and the loss of CH3N in the mass spectra of 2‐dimethylaminopyridines
Authors: Whittle C. P. , Lacey M. J. , Macdonald C. G.
Published: May 2005

The electron impact mass spectra of some deuterium labelled 2‐dimethylaminopyridines are consistent with hydrogen randomization within the dimethylamino group prior to the loss of the elements of methylenimine.
Charge stripping and E/2 mass spectra
Authors: Kemp D. L. , Beynon J. H. , Cooks R. G.
Published: May 2005

The stabilities of doubly charged ions have been investigated by comparing the relative abundances of these ions in charge stripping spectra with their precursor ions in normal mass spectra. This study reveals differences in cross‐section for charge stripping of isobaric ions with different elemental compositions, and information is presented on the competition between collisional dissociation and collisional ionization.
The analysis of mixtures: V
Authors: Halket J. McK. , Reed R. I.
Published: May 2005

The work previously discussed has been extended. Product‐moment correlation coefficients are shown to be useful in reducing the conditions hitherto necessary for the resolution of pure component spectra from an array of mixtures spectra. The method is illustrated by the solution of a five component calculated mixture in which there is only one unicomponent peak.
Computer‐aided interpretation of mass spectra. Increased information from neutral loss data
Authors: Dayringer Henry E. , McLafferty F. W. , Venkataraghavan Rengachari
Published: May 2005

The performance of the [Self‐Training Interpretive and Retrieval System] for unknown mass spectra has been improved by modifications to the data classes utilizing information concerning the masses of neutral fragments lost from the molecular ion. Modifications include use of overlapping mass ranges, sets of homologous series of losses and an arithmetic combination of the data class rankings to give an [overall match‐factor] for neutral loss data.
Mass spectra and fragmentation patterns of malonaldehydedianil and some of its metal complexes
Authors: Richards C. P. , Delderfield J. , Webb G. A.
Published: May 2005

Under electron impact malonaldehydedianil and its bis Co(II), Ni(II) and Zn(II) complexes produce a stable molecular ion. The Cu(II) complex appears to decompose prior to ionization. The free dianil molecular ion fragments by expulsion of the azomethine proton or by fission of C‐N bonds. The molecular ions of the metal complexes usually expel a complete ligand before undergoing demetallation.
Etude en Basse Tension de l'Androstane Dione‐3,17—Application a la Localisation du Deuterium
Authors: Viger Antoinette , Marquet Andrée , Tabet Jean‐Claude
Published: May 2005

Les fragmentations de al (5α) androstanedione‐3,17 ont été étudiées en vue de localiser le deutérium entre les positons 4 et 6. Ceci est possible en basse tension: on trouve un pic à m/e 216, provenant d'une élimination du cycle. A qui permet le dosage de molécules deutériées en 4 et (ou) 6.
Application of molecular orbital theory to the interpretation of mass spectra study of substituent effect on a series of acetophenones
Authors: Loew Gilda H. , Kirchner Robert F. , Lawless James G.
Published: May 2005

Semi‐empirical molecular orbital calculations have been used to study the substituent effect on the intensity of the m/e 43 peak ([COCH3]+) in the mass spectra of a series of 25 substituted acetophenones. The two most relevant molecular properties calculated appear to be the ionization potential and the bond density of the fragmenting bond. A semi‐logarithmic plot of relative peak intensities[the ratio of m/e (43/[M]+)] versus the ratio of ionization potential to bond density for these compounds produced a linear relationship with a correlation coefficient of 0.90 from the INDO method and 0.93 from the IEHT method. The use of two different semi‐empirical methods to calculate ionization potentials and bond densities, together with the qualitative agreement between the two methods and with available experimental data, substantiates the correlations obtained. In addition, the molecular orbital calculations were used to understand the anomalous behavior of the teritary butyl and para‐phenyl substitutes.
Mass spectra of perfluoroalkyl and perfluoroalkylether nitriles and acyl halides
Authors: Paciorek Kazimiera J. L. , Nakahara James H. , Rratzer Reinhold H.
Published: May 2005

Electron impact fragmentation patterns were obtained for perfluoroalkylether nitriles, C,F,O[CF(CF3)CFIO]ICF(CF3)CN (x = 1 and 2), perfluoroalkylether acyl halides, CSF,OCF(CF,)‐CF2OCF(CF3)COX (X = F and Cl), n‐perfluorooctanonitrile and n‐perfiuorooctanoyl chloride. The perfluoroalkyl and perfluoroalkylether nitriles afforded ions characteristic of the nitrile function. The major fragment from the acyl chlorides was the [COClJ]+ ion; the presence of chlorine was evidenced also by rearrangement ions of the general form [RfCl] t. The perfluoroalkylether compounds appeared to undergo a typical fragmentation governed by the cleavage of the carbon‐oxygen bond.
Mass spectra of heterocyclic compounds. II‐Hexahydro‐1,3,5,‐triazines
Authors: Corral Renée A. , Orazi Orfeo O.
Published: May 2005

The twelve tri‐N‐sulphonylhexahydro‐1,3,5‐triazines (R = alkyl or aryl) exhibit a common fragmentation pattern; most of the fragments are directly or indirectly generated from the [M  RSO2]+ ion. Tri‐N‐Benzylsulphonylhexahydro‐1,3,5‐triazine (R = PhCH2) departs from the others mainly because the key ion [M  RSO2]+ suffers a skeletal rearrangement with loss of SO2. The rationalizations presented are supported by metastable evidence, accurate mass measurements and deuterium labelling.
The mass spectra of [17‐13C]phyllocladene and [3‐13C]methylenecholestane—III
Authors: Cruz R. A. , Castillo R. C. , Garcia F. J. , Reed R. I.
Published: May 2005

The mass spectra of [17‐13C]phyllocladene and [3‐13C]methylenecholestane have been examined. It is shown that there are some rearrangements at 70 e V as in the case of [17‐13C]kaurene. However, no extensive randomization is evident at the molecular ion level. The results are interesting because very little is known about 13C randomization in polycyclic aliphatic hydrocarbons. The percentage retention of label was calculated for each ion.
Regiospecificity for water elimination. A mass spectral study of 1‐tetralol and 2‐tetralol
Authors: Gross M. L. , Chiu E. , Pokorny D. , Deroos F. L.
Published: May 2005

In order to provide a comparison with the extensive research on the mechanism for elimination of water from various cyclohexanols, the mass spectra of 1‐tetralol(1,2,3,4,‐tetrahydro‐1‐naphthalenol) and 2‐tetralol(1,2,3,4‐tetrahydro‐2‐naphthalenol) have been investigated. Deuterium labeling experiments show that the 1‐tetralol molecular ion expels water by a highly specific 1,4 elimination, whereas 2‐tetralol undergoes a 1,3 elimination. Both of these processes are competitive with cycloreversion reactions. The ionization potentials and appearance potentials for the major fragments \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm M - H}_{\rm 2} {\rm O}} \right]_{}^{_.^ + } $\end{document} and the cycloreversion products hae been measured using the Electron Distribution Difference method. In addition, the kinetic energy release in the metastable decompositions to lose water have been measured. It has been found that the 1,4 elimination for 1‐tetralol releases over 50% of the available energy in the transition state, which is unexpected in view of the 6‐membering ring transition state involved. This research also includes an investigation of the nature of the various \documentclass{article}\pagestyle{empty}\begin{document}$ \left[{{\rm C}_{{\rm 10}} {\rm H}_{{\rm 10}} } \right]_{}^{_.^ + } $\end{document} ions formed in the rearrangement reaction to lose water.
Spectrométrie de Masse D'Hétérocycles Azotés. VI—Tautomérie en Phase Gazeuse d'Isoxazolones‐5
Authors: Aubagnac Jean‐Louis , Bourgeon Dominique
Published: May 2005

La comparaison de la fragmentation sous l'impact électronique d'isoxazolones‐5 avec celles des dérivés méthylés: méthoxy‐5 isoxazoles, méthyl‐2 isoxazolones‐5 et diméthyl‐4,4 isoxazolones‐5 conduit à la conclusion qu'à l'état gazeux et avant fragmentation, les isoxazolones‐5 existent sous la forme du tautomère CH. En outre, il a été établi dans le cas des méthoxy‐5 isoxazoles que le réarrangement isoxazole→azirine→oxazole qui se produit par voie thermique entraǐne pour ces composés une modification des intensités de certains ions en fonction des conditions opératoires.
Zur wecheslwirkung der amidfunktion mit dem β‐C‐atom bei zerfällen α,β‐ungesättigter amid: Sauerstoff‐ odder stickstoff‐attacke?
Authors: Levsen K. , Berendsen G. E. , Nibbering N. M. M. , Schwarz H.
Published: May 2005

Durch die Untersuchung 13C‐markierter Crotonsäureamide und die Analyse von ‘collisional activation’ (CA)‐Spektren geeigneter Referenzverbindungen wird belegt, daß die durch eine Nachbargruppenwechsel‐wirkung zwischen β‐C‐Atom und Amidfunktion verursachte Radikal‐Eliminierung vom β‐C‐Atom im wesentlichen durch eine Stickstoff‐Attacke und nur untergeordnet durch einen Angriff des Carbonylsauerstoffs eingeleitet wird. Die resultierenden Ionenstrukturen werden diskutiert.
The structure of the ion: An ion kinetic energy spectrometry study
Authors: Hoffman Michael K. , Friesen Marlin D. , Richmond Geraldine
Published: May 2005

The kinetic energy release (T) values for the loss of CO from ions from five compounds have been obtained and are consistent with at least two different structures for the ion. This result is supported by the T value obtained for the decomposition of the molecular ions.
The formation and structure of radical cations
Authors: van Thuijl J. , van Houte J. J. , Maquestiau A. , Flammang R. , de Meyer C.
Published: May 2005

ions generated from a number of different presursors have been studied by high kinetie energy ion—molecule reations. It has been shown that at least four distinct stable species oeeur, of which acetonitrile and methyl isoeyanide retain their original structure. With imidazole or pyrazole as precursors, a mixture of open thain radical cations, not identical to the above species and probably interconvertible via the 1H‐azirine radocal cation, is formed. From butrynitrile, pyrrole, crotonitrile, allyl interconvertible via the and cyanocyopropane a fourth species, probably the vinylidenimine ion, is formed.
Reversible cyclomerization and long range hydrogen abstraction by electron impact of 7‐coumarinyl diesters ROOC(CH2)nCOOR
Authors: Compernolle F. , Schouteden E. , De Schryver F. C.
Published: May 2005

The mass spectra of 4‐methyl‐7‐coumarinyl and 7‐coumarinyl diestes ROOC(CH2)nCOOR (n = 2‐12) have ben studied by appearance potential measurements, deuterium labelling and by comparison with suitable reference compounds such as the mised diestes ROOC(CH2)nCOOR′ (R=4‐methyl‐7‐coumarinyl and R′ = methyl and phenyl) and 3.4‐dihydro‐4‐methyl‐coumarinyl diestes. Observations on the fragment ions of m/e 324, produced from the 7‐coumrinyl diestes and their photocyclomers, by elimination of the central bridge as OCCH(CH2)n–2CHCO, demonstrate the existence and reversible formation of cyclomeric molecular ions. A stable bound system between the coumrin end groups is formed only at high internal energies by expulsion of a hydrogen atom, followed by elimination of the central bridge from the [MH]+ ion. It is also shown that the lifetime of the open form molecular ions decreases remarkably for chain lengths with n larger than 6.
Mass spectral aspects of 7‐phenacylxanthopterins
Authors: Iwanami Yasuo , Inagaki Takeshi , Sakata Hisanori
Published: May 2005

7‐Phenacylxanthopterin and its para‐substituted derivatives, which exist in the chelate rign form initially lose CO from pyrazine rings followed by a hydrogen atom. This ion can also be formed in the reverse order, but not for the 4‐amino analogues. Fragmentation of the intramolecularly hydrogen bonded sidechain also occurs involving loss of a benzoyl or phenyl radical. Linear plots at 40 eV for the loss of the benzoyl radical were obtained for log (Z/Z0) against the Hammet σ constants not only for the fragmentation of the xanthopterins but also for that of the amino analogues.
Electron impact studies on some aryl heteryl ketoximes
Authors: Kallury R. Krishna Mohan Rao , Rao P. L. K. Marutatmaja
Published: May 2005

The mass spectra of nine aryl heteryl ketoximes indicated that a gaseous phase Beckmann rearrangement occurs to a significant extent, as confirmed by the exact mass measurements of the resulting aroyl cation peaks. Loss of oxygen, hydroxyl radical and migration of the oxime hydrogen to the heterocycle is observed to take place in varying proportions.
Surface ionization of unpolar molecules by [Li]+ ion attachment
Authors: Borchers F. , Giessmann U. , Röllgen F. W.
Published: May 2005

It is shown that unpolar molecules can also be ionized by [Li]+ surface ionization. This is demonstrated with cyclohexane, neopentane and tetrachloromethane.
Mass spectrometry of heterocyclic compounds. I—the behaviour of some quaternary heterocyclic iodides under electron impact
Authors: Bologa Margareta , Palibroda N. , Moldovan Z. , Ciurdaru Gh.
Published: May 2005

The mass spectra of five quaternary heterocyclic iodides have been investigated. The main thermal process is the anhydro base formation by HI elimination. The influence of the second heteroatom, X, on the fragmentation mode of the thermally produced anhydro bases is analysed.
On the characterization of dihydro‐oxazin‐6‐ones and N‐acetylazetidin‐2‐ones by mass spectrometry
Authors: Bexon J. J. , Todd J. F. J. , Drey C. N. C. , Ridge R. J.
Published: May 2005

Mass spectrometry has been used in an attempt to resolve the ambiguity in the structures of the isomeric dihydro‐oxazin‐6‐ones and N‐acyl‐azetidin‐2‐ones.
Secondary ion mass spectrometery: A new analytical technique for biologically important compounds
Authors: Benninghoven A. , Sichtermann W.
Published: May 2005

The secondary ion emission of about 40 biologically important compounds including amino acids, peptides, drugs, vitamins, pharmaceuticals, etc. has been determined by static secondary ion mass spectrometry. Unexpected ‘parent‐like’ secondary ions such as [M + H]+ and [M − H]−, as well as fragment ions, correlated with functional groups, are emitted with relatively high absolute yields. The secondary ion mass spectra allow an unambiguous identification of all samples with detection limits in the 10−12 g range.
The loss of CH3⋅ from some unsaturated dithioesters
Authors: Burgers Peter C. , Terlouw Johan K. , Meijer John , Dijkstra Geo
Published: May 2005

The mechanism for the loss of CH3⋅ (and C2H5⋅) from the molecular ions of some unsaturated dithioesters of the type magnified image with n=0, 1, 2, has been studied. Based on first field free region metastable ion characteristics it is proposed that 1,3‐dithiolium type product ions are generated. Deuterium labelling experiments indicated that the molecular ions of the 2‐alkenyl alkanedithioates magnified image undergo a rearrangement prior to fragmentation which resembles the [3,3]sigmatropic rearrangement in solution chemistry.
Electron impact induced fragmentations and rearrangements of some phenyl substituted phosphine oxides
Authors: Koch Charles W. , Eargle Dolan H. , Kenyon George L.
Published: May 2005

Electron impact induced fragmentations and rearrangements of 1‐phenyl‐2,2,3‐trimethylphosphetane 1‐oxide, 1‐phenylphospholane 1‐oxide and 1‐phenylphosphorinane 1‐oxide were investigated. A process common to all of these phosphine oxides was electron impact induced formation of new carbon‐carbon bonds involving the phenyl rings. Evidence for such rearrangements included observation of hydrocarbon fragment ions containing seven or more carbons.
Electron impact and chemical ionization mass spectrometry of cyclic boronate derivatives of sphingosines and related compounds
Authors: Simon J. Gaskell , Charles J. W. Brooks
Published: May 2005

Electron impact and isobutane chemical ionization mass spectrometric data are reported for cyclic boronate esters of sphinganine and 4‐sphingenine and of the related N‐ethyl, N‐dimethylaminomethylene and acetone Schiff base compounds. Fragmentation of the 6‐membered boronate ring is promoted by the presence of the 2‐amino or 2‐imino substituent and by Δ4 unsaturation. Evidence is presented for a transannular interaction stabilizing the ion formed by loss of the alkyl or aryl group, attached to the boron atom, in the case of the N‐dimethylaminomethylene derivatives. An NH2 migration is postulated to occur in 4‐sphingenine boronates under electron impact. Mass spectrometric data are also reported for 4D‐hydroxysphinganine bis‐boronates.
A study of the decomposition of field ionized doubly charged molecular ions
Authors: Migahed M. D. , Allam S. H.
Published: May 2005

The dissociation of field ionized doubly charged organic molecular ions into doubly charged fragment ions and neutral fragments is discussed. The kinetic energy released during the dissociation of the singly and doubly charged molecular ions rules out the possibility of a direct correlation between their mechanisms of formation. Further, the pressure as well as the temperature dependence revealed that the singly charged molecular ions are formed by direct ionization of the neutral molecules, while the doubly charged molecular ions are formed through a second ionization process of the adsorbed molecular ions on the field anode surface.
Einfluß der chemischen Struktur auf die EA‐Massenspektren von aromatischen Kohlenwasserstoffen sowie von N‐ und S‐Heteroanaloge
Authors: Albers Georg , Knof Hans
Published: May 2005

Der Einfluß der chemischen Struktur von aromatischen Kohlenwasserstoffen mit Molekulargewichten über 100 und ihren N‐ und S‐Heteroanalogen auf die Bruchstückbildung und die Ionenintensitäten bei der Elektronenanlagerungsmassenspektrometrie wird untersucht. Die Ausbeute negativer Ionen hängt haupsächlich von der chemischen Struktur und nicht so sehr von den Heteroatomen ab. Eine Ausnahme zu dieser Regel ist die Bildung von Sulfidanionen, die mit einer sehr hohen Ausbeute an Molekularionen abläuft.
Fragmentation de Quelques Hydrazines, Tétrahydrocinnolines et Pyrazolidines sous I'Impact Electronique
Authors: Cauquis G. , Chabaud B. , Ulrich J.
Published: May 2005

Les spectres de masse de diverses hydrazines, tétrahydrocinnolines et pyrazolidines, issues de la condensation d'une cation diazénium ou de sa base conjguée sur des oléfines sont discutés. Le mode de fragmentation principal des hydrazines trisubstituées correspond à un processus de rétroaddition libérant le cation diazénium et l'oléfine. On Observe aussi une rupture de la liaison NN qui peut s'expliquer par une délocalisation de la charge de l'ion moléculaire sur les noyaux phényles que toutes les hydrazines considérées protent sur l'un de leurs atomes d'azote. Cette rupture de la liaison NN est la fragmentation dominante dans le cas des tétrahydrocinnolines. Par contre, elle n'est pas observable chez les pyrazolidines. Ces dernières subissent principalement une fragmentation voisine d'une rétroaddition de type dipolaire‐1,3. Celle‐ci libère le cation diazénium dont la base conjuguée qui est une imine d'azométhine a été utilisée dans la synthèse.
A collisional activation study of ions generated from the molecular ions of 2‐phenoxyethyl halides
Authors: Borchers F. , Levsen K. , Theissling C. B. , Nibbering N. M. M.
Published: May 2005

Collisional activation spectra of ions generated from phenol, [2,2,2]oct‐2‐en‐5,7‐dione and site specifically deuterium labelled 2‐phenoxyethyl halides, , have shown that 2,4‐cyclohexadienone and phenol ions are distinct stable species in the gas phase for ≥ 10−5 s.
Fragmentation in chemical ionization mass spectrometry and the proton affinity of the departing neutral
Authors: Harrison Alex. G. , Onuska Francis I.
Published: May 2005

Chemical ionization mass spectra of six 5,6‐dihydro‐2‐methyl‐1,4‐oxathiins, and some of the sulfoxides and sulfones derived therefrom, have been determined employing hydrogen, methane and isobutane as reagent gases. The major fragmentation reaction of the protonated molecule, [R′COX·H]+, involves loss of the neutral HX molecule. For the sulfides and sulfones, with X ranging from OH to N(CH3)C6H5, it is observed that the importance of this fragmentation is inversely correlated with the proton affinity of the departing HX molecule in both the H2 and CH4 chemical ionization. For the sulfoxides no consistent correlation is observed and this is attributed to the interference of competing and/or consecutive fragmentation reactions. In the isobutane chemical ionization mass spectra only the protonated molecule is observed for most of the compounds studied.
Thiosugars. VI—mass spectrometry of 2,3‐epithio‐D‐allose derivatives
Authors: Yamaguchi Tadatoshi , Kojima Masaharu
Published: May 2005

The behaviour under electron impact of methyl 2,3‐dideoxy‐2,3‐epithio‐α‐D‐allopyranoside, methyl 2,3‐dideoxy‐2,3‐epithio‐β‐D‐allofuranoside, 1,6‐anhydro‐2,3‐dideoxy‐2,3‐epithio‐β‐D‐allopyranose, 1,6‐anhydro‐2,3‐dideoxy‐2,3‐epithio‐β‐D‐allofuranose and 2,3‐dideoxy‐2,3‐epithio‐β‐D‐allofuranose has been examined. The fragmentation pathways have been deduced by determination of the fragment ions elemental compositions, assignment of the metastable ions fröm the mass number shifts resulting from deuterium replacement, and by the comparison with an epoxide analogue.
Ionisation et Fragmentation en Spectrométrie de Masse. VII—Structure de l'Ion [C6H6O]+ Issu de la Décomposition du Phényléthyléther Sous Impact Electronique
Authors: Bouchoux Guy
Published: May 2005

L'energie d'activation de la fragmentation [C6H5OC2H5]+ → [C6H6O]+ +C2H4 est calculée. Après évaluation de la variation d'enthalpie correspondante, une structure de type phénol est déterminée pour l'ion [C6H6O]+. L'énergie d'activation de la réaction inverse est comparée à l'énergie moyenne de translation des fragments [C6H6O]+ et C2H4. L'aspect concerté ou non concerté du mécanisme de cette fragmentation est discuté.
Pyrones. II—the mass spectra and fragmentation mechanisms of methyl maltol (3‐methoxy‐2‐methyl‐4H‐pyran‐4‐one) and methyl allomaltol (5‐methoxy‐2‐methyl‐4H‐pyran‐4‐one)
Authors: McGillivray David L. , Poulton Gerald A.
Published: May 2005

The mass spectra of methyl maltol (3‐methoxy‐2‐methyl‐4H‐pyran‐4‐one) and methylallomaltol (5‐methoxy‐2‐methyl‐4H‐pyran‐4‐one) and a number of deuterium labelled analogues have been studied in detail. The two pyrones have common fragmentation pathways, all of which can be traced back to a primary rearrangement of the molecular ion. The loss of water from the molecular ion occurs by two processes, both involving the methoxymethyl protons. The loss of methyl from the molecular ion also occurs by two routes, only one of which involves the methoxy methyl protons directly.
Recherches en série diazépine‐1,4 et triazépine‐1,2,4. XI—etude en spectrométrie de masse des fragmentations de triazépines‐1,2,4
Authors: Hasnaoui A. , Lavergne J.‐P. , Viallefont Ph.
Published: May 2005

Les spectres de masse de onze triazépines‐1,2,4 présentant cinq types de structure et possédant les groupes oxo, thioxo, méthoxy ou méthylmercapto dans les positions 3 et 5 sont déorits. Chaque structure est caractérisée par un ensemble original de ruptures. Pour certains composés la participation à ľéquilibre, à ľétat vapeur, de certaines formes tautomères a été discutée.
The dependence of the extent of C2H6 elimination on the orientation of the C2H5 group in ethylbicyclo [4.4.0]decanes
Authors: Zaikin V. G. , Smetanin V. I. , Musaev I. A. , Kurashova E. Kh.
Published: May 2005

The elimination of C2H6 from the molecular ions of trans‐fused 2‐ and 3‐ethylbicyclo [4.4.0] decanes with the axial C2H5 group takes place to a greater extent than in the corresponding equatorial epimers.
Mass spectral studies on steroidal compounds. VIII—a comparative study of 6‐ and 7‐oxalactones
Authors: Ahmad M. S. , Moinuddin G. , Khan I. A.
Published: May 2005

The mass spectra of three steroidal ring B 7‐oxalactones and one 6‐oxalactone have been examined and comparison made with previously studied spectra of 6‐oxa isomers. Whereas the mass spectra of 6‐oxalactones are conspicuous by an intense peak at m/e 318, no such peak was found for 7‐oxalactones. On the contrary, the 7‐oxalactones showed characteristic [M  CH2O]+ ions. Thus, mass spectrometry offers an excellent means of differentiating between isomeric 6‐ and 7‐oxa ϵ‐lactones in the cholestane and β‐sitostane series. The fragmentation pathways suggested are supported by accurate mass measurement of some of the salient fragment ions.