bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for anchimeric assistance in the expulsion of bromine from ring‐substituted β‐phenylethyl bromides: When is a simple cleavage a rearrangement?
Authors: Shapiro Robert H. , Jenkins Thomas F. 
Published: May 2005

AbstractUsing the principles of the quasi‐equilibrium theory, substituent effects, deuterium labeling and comparison of compound behavior, we provide strong evidence for aryl participation in the expalsion of Br· from the molecular ion of β‐phenylethyl bromide and eleven of its ringsubstitued derivatives. This reaction shows a kinetic behavior which is typical of rearrangements, its activation energy is lower than that of similar reactions where participation is partially or completely precluded and substitute effects are not only consistent with a particular process, but are also consistent with those predicted from solution chemistry.
Die McLafferty‐Umlagerung als Hauptabbaureaktion 1,1‐di‐, tri‐und tetra‐alkylsubstituierter Äthylenderivate
Authors: Kraft Manfred , Spiteller Gerhard 
Published: May 2005

AbstractIm Gegensatz zu den Olefinen I und II unterliegen die an der Doppelbindung alkylsubstituierten Olefine II bis IX keiner der Bruchstückbildung vorausgehenden Isomerisierung unter Wasserstoffwanderung. Bei den Olefinen III bis VIII ist die McLafferty‐Umlagerung die nahezu einzige Abbaureaktion der Molekülionen. Aus den Isomeren III und IV bzw. V und VI entsteht das gleiche McLaffetty‐Abbauprodukt, so daß die Spektren praktisch identisch sind.Es wird ein allgemeingültiges Schema für das Auftreten identischer Massenspektren isomerer Verbindungen angegeben.Ein Olefin der Struktur IX, bei dem die McLaffetty‐Umlagerung nicht möglich ist, zeigt bei Electronenbeschuß vorzugsweise. Befindet sich ein weiterer Alkylsubstitutent in der Kette, so tritt als Konkurrenzreaktion zur McLaffety‐Umlagerung der Bindungsbruch an der Verzweigungsstelle ein.
Metastable transitions in the mass spectra of ketals and ketones. Competition between loss of small and large radicals
Authors: Cooks R. Graham , Yeo Adrian N. H. , Williams Dudley H. 
Published: May 2005

AbstractAn investigation of competing metastable transitions in the mass spectra of ethylene ketals RSRLC(OCH2)2 (where RL is a larger n‐alkyl group than RS) has established that in most cases RS is lost with a lower activation energy than RL. This technique has also been applied to ketones RSRLCO, to show again that RS is usually lost with the lower activation energy (thus supporting earlier data based on relative daughter ion abundances at the threshold). In the classes of compounds so far investigated, although [M+ − RS] ions are formed with lower activation energies than [M+ − RL] ions, the ion yield of [M+ − RS] ions is anomalously low from ions of high internal energy. Factors which may influence the [M+ − RS]/[M+ − RL] ratio of daughter ion intensities are examined. It is suggested that at the threshold [M+ − RS] and [M+ − RL] ions may be formed with rearrangement, or from an electronic state that cannot be effectively populated from molecular ions of high internal energies.
Decomposition of 1‐(2‐thienyl)alkylalkanones under electron‐impact
Authors: Foster Norman G. , Higgins Robert W. 
Published: May 2005

AbstractThe major fragmentation paths of the 1‐(2‐thienyl)alkylalkanones ionized by electron impact are delineated by means of isotopically labeled molecules, metastable ion peaks and low ionization voltage data. A prominent process is cleavage of the bond beta to the carbonyl group with the concurrent rearrangement of a hydrogen atom. Another important process is cleavage alpha to the carbonyl group to produce the thienoylium ion analogous to the benzoylium ion. As expected, the data show that increasing the chain length by two methylene groups increases the total ion current. The bulk of this increase is found in the increased ion current of the rearrangement ion with the remainder being associated with alkyl fragments and oxygenated ion species.
Electron‐impact induced oxygen migration in the mass spectra of β‐ketoalkylidenephosphoranes
Authors: Aplin R. T. , Hands A. R. , Mercer A. J. H. 
Published: May 2005

AbstractThe mass spectra of six β‐ketoalkylidenephosphoranes have been examined. The spectra all exhibit an electron‐impact induced migration of oxygen to phosphorus reminiscent of their thermal decomposition.
Charge separation and ion‐pair formation in cations subsequent to electron‐impact
Authors: Seibl J. 
Published: May 2005

AbstractInvestigation of metastable ion transitions shows, that spontaneous charge separations (loss of an electron from a cation) and ion‐pair formations (loss of negative ions from positive ones)are taking place in conventional mass spectrometry. Such processes may be important factors in formation of doubly charged ions.
Analysis of the chemical composition of solid petroleum hydrocarbons by electron attachment (EA) mass spectrography with negative ions
Authors: Kajdas Czesław , Tümmler Rudolf 
Published: May 2005

AbstractThe composition of solid saturated hydrocarbons from slack‐wax after reaction with urea has been investigated by electron‐attachment (EA) mass spectrography with negative ions. From the spectra of the samples the content of paraffin hydrocarbons, monocyclic, dicyclic and other polycyclic naphthenes was calculated. The presence of n‐paraffins up to C46, isoparaffins and cycloalkanes up to C52 has been confirmed. In the paraffin series the concentration of normal paraffin hydrocarbons containing one and two 13C atoms was determined. On the basis of the results obtained the constitution of the samples and the possible structures of the hydrocarbons were discussed. The results obtained have shown that the solid hydrocarbons which react with urea not only consist of one‐ or two‐ring systems, but also of systems with up to five and six rings.
Negative ion mass spectra of highly fluorinated compounds
Authors: Chait E. M. , Askew W. B. , Matthews C. B. 
Published: May 2005

AbstractThe negative ion mass spectra of highly fluorinated molecules with varying functionality are discussed. Attempts to obtain negative molecular ions where no positive molecular ion was observed met with little success. An interesting structural correlation for fluorinated ethers was developed based upon the observation of the abundant perfluoro alkoxide anions, CF3O− and CF3(CF2)2O−, in the negative ion mass spectrum.
The mass spectra of griseofulvin analogues. Characteristic fragmentation processes in the mass spectra of spiro‐cyclohexenones and spiro‐cyclohexanones containing the griseofulvin skeleton
Authors: Ballantine J. A. , Fenwick R. G. 
Published: May 2005

AbstractThe mass spectra of a number of griseofulvin analogues have been examined and the fragmentations, which are characteristic of the basic skeleton of the molecule, have been determined. In all of the different structural types examined, the ring cleavages which predominate are found tol occur by fission of one or more of the bonds attached to the spiro carbon atom.The degree of unsaturation in the spiro‐cyclohexane ring system is found to controll the type of fragmentation which occurs and the type of ring system which is present can therefore be identified by its mass spectrum.
Etude de la fragmentation de derives de L'uracile et de la thymine par Spectrometrie de masse
Authors: Ulrich J. , Teoule R. , Massot R. , Cornu A. 
Published: May 2005

AbstractNous présentons und série de spectres de masse originaux, de dérivés de l'uracile et de la thymine, ainsi que les schémas de fragmentation correspondants.L'étude d'une première série de molécules, à caractère aromatique, dont une marquée au 14C, a permis de confirmeer le mécanisme de base de la fragmentation comme étant un ‘retro Diels Alder’.Une deuxième série, Saturée en positoin 5,6 du noyau, montre le caractère totalement différent de ces molécules, plus fragiles, plus sensibles à la nature des substituants et donnant un ion protoné [MH]+, responsable d'une partie des fragments observés.
The mass spectra of some α‐lactams
Authors: Lengyel István , Uliss David B. , Nafissi‐V M. Mehdi , Sheehan John C. 
Published: May 2005

AbstractThe electron‐impact induced fragmentation of eight aziridinones has been studied by conventional as well as by high resolution mass spectrometry. All α‐lactams exhibit a molecular ion. The major primary step, in the fragmentation, is the ejection of carbon monoxide from the molecular ion. Ions of the general formula R1NC and R2R3CO were found in the mass spectra of all α‐lactams investigated. A skeletal rearrangement to rationalize these ions is proposed. The fragmentation of the molecular ion is affected by the N‐substituent. Exact mass measurement and specific deuterium labeling indicate the absence of McLafferty rearrangement from either the N‐ or C‐substituent.
Zur Kenntnis des chinoiden Zustandes—XVI. Massenspektrometrische untersuchungen an chinonen, diphenochinonen und stilbenchinonen
Authors: Heiss J. , Zeller K.‐P. , Rieker A. 
Published: May 2005

AbstractAußber den o‐Benzochinonen und o‐Naphthochinonen zeigen auch p‐Chinone, sowie Diphenochinone und Stilbenchinone [M + 2]+·‐Peaks. Diese beruhenim wesentlichen auf der Restfeuchtigkeit mi Massenspektrometer und hängen stärker vom Partialdruck dersubstanzen bzw. des Wassers als von der Temperatur ab. Die Spektren der [M + 2]+·‐Ionen entsprechen denjenigen der zugehörigen ionisierten Hydrochinone. Zwischen dem Redoxpotential und der Instensität des [M + 2]+·‐Peaks p‐chinoider Systeme besteht ein Zusammenhang. Die elektronenstoßinduzierte Fragmentierung von 2.6‐Di‐tert.‐butyl‐benzochinon‐(1.4) und 3.5‐Di‐tert.‐butylbenzochinon‐(1.2) wird diskutiert.
The electron‐impact induced loss of CHNO from 1,3‐bis‐(3‐m‐tolyl‐1,2,4‐oxadiazol‐5‐yl)hexafluoropropane
Authors: Cotter J. L. , Dickinson Hilary 
Published: May 2005

AbstractHigh resolution mass measurement established that the m/e 425 peak in the mass spectrum of 1,3‐bis‐(3‐m‐tolyl‐1, 2,4‐oxadiazol‐5‐yl)hexafluoropropane corresponds to [M  CHNO]. This peak is absent from the mass spectrum of the para isomer.
Electron‐impact‐induced fragmentation of aromatic cyclic diazoketones
Authors: Dejongh D. C. , Van Fossen R. Y. , Dusold Laurence R. , Cava M. P. 
Published: May 2005

AbstractThe mass spectra of eleven diazoketones have been obtained. High resolution mass measurements of selected ions have shown initial loss of nitrogen followed by loss of carbon monoxide. In many of the spectra, flat‐topped metastables were observed.
Mass spectra of 2H‐1,4‐benzoxazine and‐benzothiazine hydroxamic acids
Authors: Coutts R. T. , Hindmarsh K. W. 
Published: May 2005

AbstractThe mass spectra of various benzoxazine and benzothiazine hydroxamic acids and related lactams have been recorded and interpreted. Proposed fragmentations have been substantiated by means of deuterium‐labeling and accurate mass measurements. Abundant molecular ions were observed in all spectra. The benzoxazine hydroxamic acids fragmented initially by expelling an oxygen atom and a COOH radical from the molecular ion. The corresponding benzothiazine hydroxamic acids lost an oxygen atom and an OH radical, whereas their 1,1‐dioxides decomposed by losing an oxygen atom and a ketene or substituted ketene molecule. The expulsion of CO, HCN, CS and SO2 molecules, as well as alkyl and NO radicals were common subsequent fragmentations.
Timing of hydrogen randomization in substituted diphenyl acetylenes
Authors: Safe S. 
Published: May 2005

AbstractThe mass spectra of halogenosubstituted diphenylacetylenes show hydrogen scrambling between the two phenyl rings. As with the halogenobenzenes the randomization process occurs i the molecular ion rather than in the [M – 1] ion as is the case for methyldiphenylacetylene (I, × = CH3).
Field‐ionization mass spectrometry—fragmentation and metastables
Authors: Chait E. M. , Kitson F. G. 
Published: May 2005

AbstractField‐ionization (FI) mass spectrometry is an established method for obtaining abundant molecular ions1 of a variety of compounds, and recently has been used in conjunction with exact mass measurements for determination of elemental compositions of molecules.2,3 Very little, however, has been reported on the value of normal fragment ions and metastable ions appearing in the FI spectrum as a source of structural information.
The high‐resolution mass spectra of aliphatic aldehydes
Authors: Harrison A. G. 
Published: May 2005

AbstractThe mass spectra of the C3 to C9 n‐alkanals and a number of branched aldehydes have been obtained at a resolution sufficient to resolve the OCH4 doublets. From the resolved spectra, a study of metastable transitions, and the spectrum of one deuterium‐labelled alkanal, (n‐hexanal‐2,2‐d2) the major fragmentation reactions have been elucidated. Of particular interest are the γ‐cleavage reaction, leading to [C3H5O]+ in the n‐alkanals, which proceeds both by a simple cleavage and by cleavage preceded by hydrogen interchange, and the loss of C2H4, which involves loss of the C2 and, probably C3, carbons.
Mass spectrometry—III: Further studies of the unimolecular decomposition of acetophenone azine in the gas phase induced by electron‐impact
Authors: Scheppele Stuart E. , Grigsby Ronald D. , Whitaker Donald W. , Hinds Susan D. , Kinneberg Keith F. , Mitchum Ronald K. 
Published: May 2005

AbstractMass spectra of acetophenone azine‐d10 (II) and acetophenone azine‐d6 (III) were obtained to ascertain the validity of the proposed mass spectral fragmentation mechanisms proposed for acetophenone azine (I). Data from II and III reveal that the [M –1] ion in the spectrum of I is formed via loss of ring hydrogen. Within experimental uncertainty the major fragmentation reactions of the molecular ion of I, the [M –1] ion, and the [M –15] ion occur without loss of structural identity of the phenyl and methyl moieties. Ionization of I occurs with a high degree of structural integrity.
Reactions of aliphatic aldehydes under electron‐impact
Authors: Meyerson Seymour , Fenselau Catherine , Young J. L. , Landis W. R. , Selke Edward , Leitch L. C. 
Published: May 2005

AbstractThe mass spectra of hexanal, heptanal and nonanal variously labeled with deuterium confirm γ‐hydrogen migration and β cleavage as the mechanism leading to [C2H4O]+˙ and [M  C2H4O]+˙, although the data on the latter are complicated by contributions from other, related paths. In addition, they show that three other major primary decomposition products, [M  C2H4]+˙, [M  H2O]+˙ and [C3H5O]+, all arise in large part by processes involving γ‐hydrogen migration to the oxygen atom. The ethylene lost to yield the first of these products consists of the α and β methylene groups. The loss of ethylene most likely occurs by way of a cyclobutanol intermediate, which, via alternative reaction paths, may well contribute to the yields of the other two products as well. These findings further extend the range of parallelism between photochemical and electron‐impact‐induced reactions.
The mass spectra of N‐adamantoylpeptides
Authors: Lengyel István , Salomon Ramon A. , Biemann Klaus 
Published: May 2005

AbstractThe N‐adamantoyl derivatives of the esters of twenty‐one di‐peptides and eight tri‐peptides containing the amino acids glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, glutamic acid, lysine, histidine, serine, threonine, methionine, S‐benzylcysteine and tyrosine were prepared and their mass spectra determined. The spectra of all compounds were suitable for amino acid sequence determination. Mixtures containing N‐adamantoyl dipeptide and tripeptide methyl esters were separated by thin‐layer chromatography and the components identified by high resolution mass spectrometry. The mass spectrometric features of N‐adamantoyl peptide esters are discussed and compared with those of other N‐acyl peptide derivatives.
Mass spectra of selected beta‐carbolines [β‐9H‐pyrido(3,4‐b)indoles]
Authors: Coutts R. T. , Locock R. A. , Slywka G. W. A. 
Published: May 2005

AbstractThe mass spectra of fifteen β‐carbolines have been interpreted and proposed fragmentations have been substantiated by means of deuterium‐labeling and accurate mass determinations. Most decompositions were predictable. An interesting fragmentation was observed in the spectra of 1‐alkyl‐1,2,3,4‐tetrahydro‐β‐carbolines, which rearrange to expel an alkylamino (RNH) radical from the molecular ion.
Skeletal rearrangement in the mass spectra of tetrasilaadamantanes
Authors: Gohlke R. S. , Robinson R. J. 
Published: May 2005

AbstractThe loss of methyl group giving a peak of high intensity is observed in the mass spectra of 1,3,5,7‐tetrasilaadamantanes. This skeletal rearrangement must involve the simultaneous rupture of three bonds and concomitant hydrogen transfer. The spectra of the tetrasilaadamantanes are considerably different from the spectrum of adamantane.
Mass spectrometry in structural and stereochemical problems–CLXXXIX: Electron‐impact induced fragmentations and rearrangements of alkoxycyclohexanol trimethylsilyl ethers and alkoxycyclohexyl trimethylsilanes
Authors: Gray Robin T. , Diekman John , Larson G. L. , Musker W. K. , Djerassi Carl 
Published: May 2005

AbstractIn view of the current interest in the electron‐impact induced rearrangements of both trimethylsilyl derivatives and bifunctionalized cyclohexanes, the mass spectral properties of several alkoxycyclohexanol trimethylsilyl ethers and alkoxycyclohexyl trimethylsilanes have been investigated. Using deuterium labeling, the basic fragmentation modes incurred upon electron‐impact of ethanol trimethylsilyl ether were elucidated. The major peaks in the spectrum of this simple ether occur also in those of the title compounds, the latter fragments having been formed by interaction of the two functional groups. Thus the initial rearrangement ion of mass 103 (e) from electron bombardment of 4‐ethoxycyclohexanol trimethylsilyl ether and 2‐ethoxycyclohexyl trimethylsilane corresponds to the [M  CH3] ion from ethanol trimethylsilyl ether. Its further fragmentation has been studied using high resolution and metastable ion measurements, and the scope of the interaction between the alkoxy and trimethylsilyl groups, when silicon is attached both to oxygen and to carbon, has been determined. In addition, the origin of every ‘characteristic’ fragment ion has been elucidated on the basis of each corresponding peak in the spectra of several derivatives labeled specifically with deuterium. Peaks derived from initial ionization of both functionalities in each compound have been observed, although the majority of ions in the spectra of both series seem to be directed by fragmentations associated with the trimethylsilyl ether moiety.
The mass spectra of reissert compounds
Authors: Popp F. D. , Potts K. T. , Armbruster R. 
Published: May 2005

AbstractA series of Reissert compounds containing the quinoline, isoquinoline and phthalazine nuclei show the common feature in their mass spectra of the initial loss of the N‐substituent and either of the substituents attached to the adjacent carbon atom.
Fragmentations de Molecules Aliphatiques Bifonctionnelles: Aminoesters a Longue Chaine
Authors: Caspar Alain , Teller Gérard , Wolff Robert E. 
Published: May 2005

AbstractL'élimination de CH3OH à partir d'un des ions de coupure α produits par la fragmentation des esters des aminoacides à longue chaîne est induite par l'interation des deux fonctions même lorsque celles‐ci sont éloignées l'une de l'autre dans la molécule. Elle met en cause en partie un atome d'hydrogène du groupe NH2, en partie un atome d'hydrogène du CH2 en α du carbone qui porte le groupe NH2. Des mécanismes sont proposés et une comparaison est faite avec les fragmentations des ω‐aminoesters, déjà étudiés.
The mass spectra of some phenanthro (9,10‐d) heterocycles
Authors: Cooper J. L. , Lipsky S. R. , McMurray W. J. 
Published: May 2005

AbstractThe mass spectra of six phenanthro(9,10‐d)‐oxazoles, thiazoles and imidazoles are reported. The decompositions of the phenanthro(9,10‐d) derivatives resemble the corresponding benzo heterocycles. A C13H7 fragment was found to be characteristic of these phenanthro compounds. Deuterium labeling was used to show that there is no correlation between the formation of the C13H7 from the phenanthro compounds and the C13H9 observed in the spectra of 4,5‐diphenyl substituted heterocycles.
The ‘preference factor’ and isotope effect in the loss of hydrogen or deuterium from labeled toluenes
Authors: Beynon J. H. , Corn J. E. , Baitinger W. E. , Caprioli R. M. , Benkeser R. A. 
Published: May 2005

AbstractMetastable ion decompositions involving the loss of hydrogen and deuterium from partially deuterated toluene ions were studied using a double focusing mass spectrometer. The electric sector voltage was adjusted so that the only ions transmitted were those which lost a particular fraction of their kinetic energy in decompositions taking place in front of the electric sector. Transitions involving loss of mass 1 or mass 2 from the molecular ions of toluene‐α‐d3 and toluene‐2,3,4,5,6‐d5 were studied. The results showed that in these slow reactions, the ‘preference factor’ defined as the ratio of the probability of loss of a hydrogen atom from a side‐chain position to loss of a hydrogen atom from a ring position was 1.00. The ‘isotope factor,’ defined as the ratio of the probability of loss of a hydrogen atom from any position to that for the loss of a deuterium atom from the same position was found to be 3·50.
Mass spectral and pyrolytic fragmentation paths for o‐nitroanisole
Authors: Mamer O. A. , Kominar R. J. , Lossing F. P. 
Published: May 2005

AbstractThe mass spectral and pyrolytic dissociations of o‐nitroanisole are reported. The parent ion dissociates by two pathways, principally through loss of CH2O, but a significant fraction through loss of NO. The parent‐less‐30 peak is therefore a doublet, as shown by high resolution measurements. The thermal decomposition at 600°C and above proceeds also by two pathways, but these are the loss of HNO and HNO2, to form 1,2‐methylenedioxybenzene and benzaldehyde respectively.
The mass spectra of some diterpene lactones
Authors: Hodges R. , Cambie R. C. , Joblin K. N. 
Published: May 2005

AbstractThe molecular ions of some diterpenoid trans‐γ‐and δ‐lactones have been shown to lose the elements of carbon dioxide. The corresponding cis‐lactones do not undergo fission in this manner. A mechanism for this stereospecific fragmentation is proposed.
Kinetic shifts and metastable transitions
Authors: Hickling R. D. , Jennings K. R. 
Published: May 2005

AbstractDifferences in the appearance potentials of normal fragment ions and of metastable transitions leading to the formation of the same fragment ions have been measured in the mass spectra of a number of compounds. The differences varied from 0.1 to 1.0 eV and were attributed to the measurable part of the kinetic shift. An approximate correlation was found between the intensity of a ‘metastable peak’ and the observed difference in appearance potentials, and it is suggested that the full kinetic shift for processes giving rise to intense ‘metastable peaks’ is substantially larger than the measurable part. The implications of this in thermochemical calculations are discussed.
Calculation of mass spectra of some organic compounds undergoing two consecutive reactions from the molecular ions
Authors: Yeo Adrian N. H. , Williams Dudley H. 
Published: May 2005

AbstractThe molecular ions of phenyl benzoate, methyl benzoate, t‐butylbenzene, phthalic anhydride, p‐dimethoxybenzene, o‐dimethoxybenzene and acetophenone each undergo two consecutive reactions ([M]+.→[A]+→[B]+). These unimolecular reactions are treated within the framework of the quasi‐equilibrium theory (QET); a simple modification of the original equation relating the rate constant (k) with the internal energy (E) was used to calculate mass spectra of the above compounds from 12 to 20 eV. Good agreement between calculated and observed spectra is obtained.