bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mass spectrometry of phenothiazines—I. 10‐alkylphenothiazines
Authors: Simov D. , Taulov I. G. 
Published: May 2005

AbstractThe fragmentation of six substituted 10‐alkylphenothiazines is discussed. Predominant expulsion of OH, SO and O occurs from the molecular ions of 10‐alkylphenothiazine‐5‐oxide derivatives, the relative extent depending upon the configuration of the 10‐substituent. The simultaneous elimination of two OH radicals from the molecular ion of 10‐alkylphenothiazine‐5‐sulphone derivative is also observed.
Oligosaccharide sequencing by means of mass spectrometry‐II: Acetates of N‐arylglycosylamines
Authors: Chizhov O. S. , Kochetkov N. K. , Malysheva N. N. , Shiyonok A. I. , Chashchin V. L. 
Published: May 2005

AbstractThe fragmentation of the N‐arylglycosylamines of some di‐, tri‐ and tetrasaccharides under electron‐impact has been studied. The results indicate that these derivatives can be used successfully for the determination by mass spectrometry of the molecular weight, sequence of monosaccharide units and, in some cases, for the elucidation of the positions of glycosidic linkages.
Studies in organic mass spectrometry—IX: The fragmentation of alkylsubstituted 1,3‐cyclopentanediones
Authors: Cant E. , Vandewalle M. 
Published: May 2005

AbstractThe mass spectra of 2‐ and 4‐substituted 1,3‐cyclopentanediones are discussed. Methyl substituted compounds display mostly ring degradation, while for longer alkyl groups fragmentations in the side chain are responsible for most of the total ionization. As was found for other 1,3‐diketones the spectra of 1,3‐cyclopentanediones show typical and separate fragmentations for both diketoand enol‐molecular ions.
The mass spectral fragmentation of 2‐aryl‐N, N′‐dimethyl‐1,3‐imidazolidines and 2‐aryl‐1‐3‐dioxolanes
Authors: Horodniak J. W. , Wright J. , Indictor N. 
Published: May 2005

Abstract2‐Aryl‐N,N'‐dimethyl‐1,3‐imidazolidines and 2‐aryl‐1,3‐dioxolanes were subjected to 70 eV spectral analysis. Fragmentation pathways for both series of compounds are suggested. Aryl vs. benzylic hydrogen fragmentations were subjected to Hammett σ+  ρ plots. Incipient charge on the benzyl carbonium ion was stabilized by electron donating groups in both series of compounds. Dioxolanes were more sensitive to substituent effects (ρ = −0.639) than the imidazolidines (ρ = −0.251) implying that the positive charge on the fragmenting ion is more localized at the benzylic position of the imidazolidines than of the dioxolanes.
Studies in mass spectrometry—XVI. The striking difference between the mass spectra of stereoisomeric cyclic anhydrides
Authors: Karpati Annie , Mandelbaum Asher 
Published: May 2005

AbstractElimination of CO gives rise to prominent peaks in the mass spectra of cis‐1,2,3,6‐tetrahydrophthalic anhydride (Ia) and its 4,5‐dimethyl analogue which are almost absent in the corresponding trans‐isomers. The striking difference in the fragmentation of the isomers shows that practically no rearrangement in the molecular ion occurs prior to this fragmentation. In this case a high degree of stereospecificity is observed, although hydrogen migration is apparently not involved in the process.
Mass spectra of steroidal alkyl ethers—I
Authors: Narayanan C. R. , Lala A. K. 
Published: May 2005

AbstractThe mass spectral fragmentation of saturated and unsaturated steroidal methyl and ethyl ethers and ethers of 4,4‐dimethyl steroids are studied and compared to the fragmentation of steroidal alcohols, trimethylsilyl ethers and ethylene ketals. Unlike the trimethylsilyl ether the small fragment containing the alkoxy group is neither the base peak nor a very strong peak in the spectrum. A significant peak occurs at [M — ROH]+·, however, sometimes even constituting the base peak of the spectrum. The fragmentations of the alkyl ethers are largely dependent on their environments. The present results also show the generalization that methyl ethers are better leaving groups than the corresponding alcohols in fragmentation processes, is not always valid.
The mass spectra of some O‐methyloximes of aliphatic aldehydes and ketones
Authors: Middleditch B. S. , Knights B. A. 
Published: May 2005

AbstractThe mass spectra of O‐methyloximes of fifteen aliphatic aldehydes and ketones of various molecular weights and degrees of branching have been examined. All give molecular ions, and many of the fragmentations parallel those of aldoximes and ketoximes. The formation of some ions is better explained by the initial production of a novel substituted cyclopropene ion. O‐Methyloximes of of the long‐chain aldehydes and methyl ketones are readily distinguished by the masses of abundant products of McLafferty rearrangement at m/e 73 and 87, repectively.
Formation of benzoyl ions: A complicated simple cleavage reaction
Authors: Turk Jonathan , Shapiro Robert H. 
Published: May 2005

AbstractCharge exchange and electron‐impact induced cleavages of some N‐phenyl benzamides, phenyl benzoates and benzophenones are reported. The data obtained appear to be consistent with energy being lost from ions by photon emission or stored in isolated states of the molecular ions.
The electron‐impact promoted fragmentation of aurone epoxides
Authors: Brady B. A. , O'Sullivan W. I. , Duffield A. M. 
Published: May 2005

AbstractThe mass spectra of six aurone epoxides have been rationalized with the aid of high resolution mass spectrometry and metastable ion evidence. These compounds fragment in a well defined manner and mechanisms are proposed for the formation of their characteristic ions. Some similarity was observed between the mass spectra of 6‐methoxyaurone epoxide (II), 4‐hydroxy‐7‐methoxy‐3‐phenylcoumarin (VII) and 7‐methoxyflavonol (IX). The possibility that VII and IX are intermediates in the fragmentation of epoxide II is discussed. Thermal rearrangement of aurone epoxide II was shown to yield the corresponding flavonol IX and coumarin VII.
Mass spectrometry of onium compounds—X: on the evaporation of pyridinium‐3‐oxides ionization potential measurements
Authors: Grønneberg Truls , Undheim Kjell 
Published: May 2005

AbstractIonization potentials of a number of substituted pyridines have been measured. The ionization potential is dependent on the substituent properties. Derivatives of pyridinium‐3‐oxide are unusual in that they have considerably lower IP values than isomeric covalent structures.
Charge localization: The ion kinetic energy spectra of pyrazine, pyrimidine and pyridazine
Authors: Beynon J. H. , Caprioli R. M. , Ast T. 
Published: May 2005

AbstractThe ion kinetic energy (IKE) spectra of pyrazine, pyrimidine, pyridazine, pyrazine‐d4, pyrimidine‐d4 and pyridazine‐d4 have shown that these compounds can more readily be distinguished on the basis of IKE spectra than mass spectra. Studies of the fragmentation of various doublycharged ions have given information about the localization of charge on the heteroatoms and on the structures of the ions themselves. Transition states from which fragmentation occurs for doublycharged ions with loss of either [H]+ or [D]+ have shown large differences of the order 1 Å between the intercharge distances in the two cases.
The mass spectra of 3‐substituted furans
Authors: Baarschers W. H. 
Published: May 2005

AbstractA fragmentation pattern characteristic of 3‐substituted furans, in which the 3‐substituent carries an oxygen function, is discussed. Examination of the spectra of some meliacins, as well as those of some synthetic model compounds, illustrates the diagnostic value of this particular fragmentation. In addition the spectrum of methyl limonilate (III, R = CH3) is discussed in some detail.
Mass spectrometry in structural and stereochemical problems—CCXVI: Anomalous cleavage ions in bifunctional compounds resulting from participative interaction
Authors: Dias Jerry Ray , Djerassi Carl 
Published: May 2005

AbstractTwo types of remote group interaction after electron‐impact are possible: one involving the transfer of an atom or group of atoms and the other involving expulsion of a group of atoms concomitant with ring closure. These interactions were examined in a homologous series of polyfunctional compounds at high and low ionizing voltages. Fragmentation resulting from remote group interaction in hydroxy ethyleneketals occurs exclusively via 5‐, 6‐ and 7‐membered rings. This is contrasted with the remote group interaction of keto esters, diesters and other literature examples in which ring size (e.g. 5‐15‐membered) plays no significant role.
Electron‐impact studies—LXX. Substituent effects in the negative‐ion spectra of nitroaryl esters
Authors: Bowie J. H. , Nussey B. 
Published: May 2005

AbstractThe negative‐ion mass spectra of a variety of substituted nitroaryl benzoates and aryl nitrobenzoates have been studied. Pronounced proximity effects are observed in the spectra of ortho‐substituted compounds. The meta and para pairs fragment in a similar manner. Linear plots are observed for many cleavages using either the McLafferty or Harrison methods. Evidence is provided which suggests that the fragmentations of meta and para isomers may proceed by the same mechanistic pathway. The magnitude of ρ does not appear to provide precise information concerning the nature of the transition state for a particular reaction of a negative ion.
Mechanism of the elimination reactions in α,δ diols and their halogenated derivatives under electron‐impact
Authors: Horváth Gy. , Kuszmann J. 
Published: May 2005

AbstractMass spectrometric investigations of α,δ diols and their halogenated derivatives revealed the necessity of postulating a mechanism for both their elimination of water and of haloid acid. This mechanism proceeding via a transition state of larger ring‐size than described for similar monofunctional aliphatic compounds was confirmed by deuterium labelling.
A labeling study of π‐cycloheptatrienetricarbonylchromium(0)
Authors: Tibbetts Fred E. , Bursey Maurice M. , Little William F. , Willeford Bennett R. , Benezra Steven A. , Hoffman Michael K. , Jennings Paul W. 
Published: May 2005

AbstractPeaks of different intensities in the mass spectra of π‐toluenetricarbonylchromium and π‐cycloheptatrienetricarbonylchromium were studied by deuterium labeling of the latter compound. Incomplete hydrogen randomization in cycloheptatriene ligands preceding different reactions was observed, in contrast to the results for cycloheptatriene itself.
The mass spectra of carboxylic acids—V: Carboxyl‐carboxyl interaction in the fragmentation of some cycloalkene‐1,2‐dicarboxylic acids
Authors: Benoit F. , Holmes J. L. 
Published: May 2005

AbstractThe fragmentation mechanisms of the six isomeric cyclohexene‐1,2‐dicarboxylic acids are discussed. Only the 1‐cyclohexene acid, by virtue of the major sequential losses of H2O and CO2 from the molecular ion, is readily distinguishable from its isomers, all of whose mass spectra are closely similar. In contrast to cis and trans cyclohexane‐1,2‐dicarboxylic acids, whose mass spectra were markedly different, the cis and trans cyclohexene‐1,2‐dicarboxylic acids fragment in a similar fashion. The mass spectra of 1‐cyclopentene‐1,2‐dicarboxylic acid and 1‐cyclobutene‐1,2‐dicarboxylic acid also exhibit a strong carboxyl‐carboxyl interaction; the fragmentation behaviour of the 1‐cyclopenteneacid is, however, more complex than that of the 1‐cyclohexene and 1‐cyclobutene acids.
Spectrometrie de Masse des Acetates de la Serie Bicyclo‐(2.2.1) heptane. Elimination de Cetene et Fragmentation Type
Authors: Kossanyi J. , Furth B. , Morizur J. P. 
Published: May 2005

AbstractL'élimination de cétène à partir acéates de la série bicyclo [2.2.1] heptane se produit par un mécanisme à quatre centres qui conduit à l'alcool correspondant. Une fragmentation type, apparentée aux réarrangements connus pour les carbocations del al série, est mise en évidence lorsqu'il y a une insaturation exocyclique en 3.
Mass spectra of some sulphonyl azides
Authors: Campbell M. M. , Dunn A. D. 
Published: May 2005

AbstractA series of sulphonyl azides decomposed upon electron‐impact with loss of azide radical. This fragmentation was in marked contrast to the photochemical behaviour of the compounds. An interesting ortho‐extrusion process occurred in the mass spectrum of 2,4,6‐triisopropylbenzenesulphonyl azide.
The mass spectra of styryl sulfoxides and sulfones
Authors: Kinstle Thomas H. , Oliver William R. 
Published: May 2005

AbstractA variety of rearrangement reactions have been documented in the gas phase ion chemistry of styryl sulfoxides and sulfones. The styryl group rearranges from sulfur to oxygen as evidenced by loss of SCH3 from methyl styryl sulfoxide and loss of SOCH3 from the corresponding sulfone. The resulting m/e 119 ion loses carbon monoxide in one fragmentation route and alternatively loses a hydrogen atom from the aromatic nucleus to produce the benzofuran molecule ion via an electrophilic aromatic ring closure reaction. Styryl sulfoxides lose both carbon monoxide and formyl radicals directly from their molecule ions, but the corresponding sulfones do not fragment in this manner. The mechanisms of the above reactions, as well as others, were investigated using substituent and deuterium labeling. The styryl group has been shown to migrate in preference to a phenyl or substituted phenyl group by investigation of the mass spectra of appropriate aryl styryl sulfoxides and sulfones.
Studies on morphine alkaloids—IX. The mass spectra of indolinocodeine and its derivatives
Authors: Abe K. , Onda M. , Okuda S. 
Published: May 2005

AbstractThe mass spectra of indolinocodeine and its derivatives have been determined. Some of the fragmentation pathways are discussed on the basis of high‐resolution mass spectrometry and deuterium labelling. Although basic fragmentation patterns for this series of compounds are similar to each other, the substituents in B‐ and/or C‐ring were found to determine the course of the fragmentation.
Mass spectra of cobalt carbonyl complexes
Authors: Gambino O. , Vaglio G. A. , Ferrari R. P. , Valle M. , Cetini G. 
Published: May 2005

AbstractThe mass spectra of the following acetylenic derivatives of Co2(CO)8 are reported: Co2(CO)6C2H2Co2(CO)6C 2,(CH3)2, Co2(CO)6 C2(CH2Cl)2, Co2(CO)6C2 (CF3)2, Co2(CO)2C2(C6H5)2 and Co2(CO)6C2(COOCH3)2. The effect of different C2RR′ on fragmentation modes is investigated. When R and R′ are aromatic groups, the major controlling factor is the stability of charged fragments; in other cases, it seems to be the loss of a stable neutral moiety. Transfer processes of alkoxylic groups are observed in Co2(CO)6C2(COOCH3)2, as well as in Co3(CO),9CCOOCH3, and Co3(CO)9CCOOC2H5. It is suggested that both cobalt and carbon atoms may be the migration sites.
Studies in chemical ionization mass spectrometry: 17‐hydroxy steroids
Authors: Michnowicz John , Munson Burnaby 
Published: May 2005

AbstractThe chemical ionization mass spectra of several hydroxy steroids were obtained using methane as the reactant gas. The spectra are much less complex than the electron ionization spectra and little fragmentation of the steroid nucleus is observed. The major fragment ions involve the loss of water from [M + H]+. A 3‐keto group in the steroids was characterized by an abundant [M + C2H5]+ ion. 5α‐ and 5β‐Dihydrotestosterone could be distinguished by their spectra, with H2 as the reactant gas by marked differences in amounts of [M + H]+, [M + H − H2O]+ and [M + H − 2H2O]+. Substituted 3α‐X‐, 17 β‐ol compounds, (X = Cl, Br) were also studied to obtain relative amounts of protonation at these sites.
Mass spectrometric comparison of ordinary and fully deuterated α‐ and β‐carotene
Authors: Svec W. A. , Harkness A. L. , Strain H. H. , Katz J. J. 
Published: May 2005

AbstractThe individual, deuterated, isomeric α‐ and β‐carotenes were isolated from the green alga, Scenedesmus obliquus, cultivated in D2O containing 99·7 to 99·8 atom percent deuterium. Mass spectroscopy showed that both the α‐ and β‐deuterio‐carotene preparations contained principally the fully deuterated pigment molecules (C40D56), small quantities of deuterated molecules with one proton (C40D55H) and yet smaller quantities of deuterated molecules with two protons (C40D54H2). From statistical calculations the deuterio‐carotene preparations also contained one to several isotopically‐substituted deuterio‐carotenes of each mass in the mass range 585 to 599 because of variation of the number of 13C and H atoms per molecule. The mass fragmentation of the deuterated pigments was analogous to that of the respective ordinary α‐ and β‐carotene. It indicated that the protons in the C40D55H and C40D54H2 molecules were distributed approximately randomly in various parts of the structure as in the terminal rings and in the ends and central portions of the polyene chain.
Cyclization of molecular ions: The mass spectrometric fragmentation of allene‐carboxylic esters
Authors: Liehr J. G. , Runge W. , Richter W. J. 
Published: May 2005

AbstractA series of six 2,4,4‐substituted allenecarboxylic esters R1R2CCC(R3)COOAlk has been found to exhibit O‐Alkyl cleavage as the most prominent feature of both their 70 and 12 eV mass spectra. Loss of linearity of the allene system upon ionization, followed by conversion of the molecular ion to a 5‐membered cyclic isomer, is thought to induce this unusual mode of bond rupture. Oxygen‐migration from the ester function to C‐4 as is indicated by the subsequent decomposition of the [M — Alk] ions to [R1CO]+ and [R2CO]+ fragments can be taken as direct evidence in favour of this rationale.
Rearrangement of the benzyl benzoate molecular ion to lose H2O
Authors: Beynon J. H. , Caprioli R. M. , Shapiro R. H. , Tomer K. B. , Chang C. W. J. 
Published: May 2005

AbstractThe molecular ion of benzyl benzoate undergoes several decompositions, two of which are the loss of H2O and COOH·. To study these processes, the mass and IKE spectra of benzyl benzoate together with various deuterated benzyl benzoates and some of its isomers were studied. Evidence is presented to support the rearrangement processes of the molecular ion. A decomposition scheme is proposed to explain the observed transitions.
Migration of dimethylsilyl substituents upon electron‐impact: The fragmentation of methyl 12‐dimethylsilyloxyoctadecanoate
Authors: Hunneman D. H. , Richter W. J. 
Published: May 2005

AbstractFragmentation of the dimethylsilyl (DMS) derivative of methyl 12‐hydroxyoctadecanoate is found to be closely analogous to that of the previously studied trimethylsilyl (TMS) derivative, including migration of the silyl substituent from C‐12 to the ester carboxyl function. besides establishing comparable migratory aptitudes of the TMS and DMS substituents, details of several other processes were revealed by use of deuterium labelling of selected positions and compared with related fragmentation of simple long‐chain alcanoic esters.
Substituent effects in the field ionization mass spectra of acetophenones
Authors: Beckey H. D. , Migahed M. D. 
Published: May 2005

AbstractSubstituent effects in the electron‐impact and field ionization mass spectra of acteophenones are compared. No Hammett correlation could be found for the fragments formed on the surface of the field anode. A straight line log z/z0 versus σ+ was observed, however, for the metastable decomposition of para‐substituted acetophenones (and also some benzophenones). Meta‐substituted compounds did not yield such straight lines.
Mass spectra of the aminoisoquinolines and 5‐amino‐15N‐isoquinoline
Authors: Brown Ellis V. , Mitchell Stanley R. 
Published: May 2005

AbstractThe mass spectra of the isomeric aminoisoquinolines and 5‐amino‐15N‐isoquinoline are reported. In the aminoisoquinolines, the major fragmentation pathway was the loss of two molecules of HCN and a hydrogen atom to give the m/e 89 fragment ion. Two additional pathways culminating with this ion were observed. The mass spectrum of 5‐amino‐15N‐isoquinoline showed a preference of 4 to 1 for loss of HC15N (benzenoid amine group) over HC14N (heterocyclic nitrogen) from the molecular ion.
Dimethyl ketals of methylcyclohexanones as fragmentation‐directing derivatives
Authors: Manni Peter E. , Cooper Ralph D. , Hardesty Clifford L. 
Published: May 2005

AbstractThe mass spectra of dimethyl ketal derivatives of cyclohexanone and the 2‐, 3‐ and 4‐methylcyclohexanones are discussed relative to their usefulness in indicating the point of alkyl substitution. Major fragments in the spectra (m/e 101 and m/e 115) arise by α‐cleavage, hydrogen rearrangement and further cleavage to give even‐electron species. The spectra yield structural information equivalent to that obtained from the corresponding ethylene ketals. The ease of preparation of dimethyl ketals and the mildness of reaction conditions relative to ethylene ketals warrant further exploitation of dimethyl ketals as fragmentation‐directing derivatives in mass spectrometry.
Ring expansion and hydrogen scrambling in the molecular ion of 3‐methylthiophene
Authors: Wakkers P. J. M. , Janssen Matthijs J. , Weringa W. D. 
Published: May 2005

AbstractThe ratio [M  D]/{[M‐D] + [M  H]} in the 70 eV mass spectra of six deuterated 3‐methylthiophenes has been determined. From these values the mole fractions of the molecular ions that lose hydrogen atoms specifically from the various positions of the molecule were calculated, as well as the mole fraction in which the hydrogen atoms are fully scrambled before hydrogen elimination. It appears that hydrogen atoms are mainly lost from a fully scrambled [C5H6S]+· ion and from the α‐position of the original molecular ion. A deuterium isotope effect of 1·60 to 1·72 was calculated for the hydrogen elimination. The reaction was also studied at low electron energies. In order to determine the degree of scrambling in the [C5H5S]+ ions, some decomposition reactions of this ion were investigated.
The mass spectra of alkylbenzenes—II. The formation of [M  methyl]+ from tri‐ and tetra‐methylbenzenes
Authors: Dawson R. M. , Gillis R. G. 
Published: May 2005

AbstractA study of the [M  methyl]+ ion in the mass spectra of ring‐deuterated tri‐ and tetramethylbenzenes has confirmed the partial randomisation of hydrogen and deuterium atoms observed by other workers. The results can be explained by postulating randomisation of the peripheral entities, followed by several cycles of ring expansion and contraction, prior to fragmentation.
The mass spectra of some 7‐methoxycoumarin derivatives with differing 6‐substituted C5 isoprenoid sidechains
Authors: MacLeod J. K. 
Published: May 2005

AbstractThe mass spectra of several biogenetically and chemically inter‐related coumarins (I to XVII) have been examined, and fragmentation pathways proposed on the basis of metastable evidence and deuterium labelling studies. The particular modification of the isoprenoid sidechain present in each compound directs fragmentation and gives rise to characteristic mass spectral cleavage patterns which may be useful for structural elucidation.
Mass spectral studies on steroidal compounds—I: Steroidal 6‐one ethylene acetals
Authors: Ahmad M. S. , Ansari G. A. S. 
Published: May 2005

AbstractThe mass spectra of several steroidal 6‐one ethylene acetals have been examined. The spectra of I and II are conspicuous by an intense [M — 55] peak. This differentiates them from other acetals reported in the present study. The acetals III, IV, V, VI, VII and VIII show the expected behaviour related to the acetal IX. The fragmentation pathways suggested are supported by accurate mass measurement of the salient fragment ions and in some cases also by appropriate metastable peaks.
Mass spectral studies on steroidal compounds—II: 7a‐aza compounds in the cholestane series (ring Bε‐lactams)
Authors: Ahmad M. S. , Mushfiq M. 
Published: May 2005

AbstractThe mass spectra of four structurally related 7a‐aza compounds in the cholestane series have been examined. These spectra are conspicuous by the presence of a fragment ion peak at m/e 222 (C15H28N). which can be of diagnostic value in characterisation of such ε‐lactams. The fragmentation pathways are supported by accurate mass measurement of the salient fragment ions and in some cases by appropriate metastable peaks.