bluuebunny/crossref_metadata_2025_split huggingface dataset:
An unusual rearrangement observed in the mass spectra of several 1‐alkyl‐2‐substituted‐5‐nitroimidazoles
Authors: Van Lear George E. 
Published: May 2005

AbstractThe mass spectra of several l‐alkyl‐2‐substituted‐5‐nitro imidazoles exhibit prominent rearrangement ions corresponding to the loss of CnH2nO from the molecular ion. The effect on this rearrangement upon variation of the group at position 2 is discussed.
Mass spectrometry of 1,1′‐diacetylferrocene and 1,1′‐dipropionylferrocene: Evidence for intraannular interaction between alkanoyl substituents
Authors: Sheley Curtis F. , Fishel Derry L. 
Published: May 2005

AbstractThe mass spectra of 1,1′‐diacetylferrocene, 1,1′‐dipropionyl ferrocene and their deuterium and Fe57 isotope labeled analogs are herein reported and discussed. Fragmentation pathways are established and evidence is presented that in the process of fragmentation there is extensive interaction between substituents on the two ferrocene rings. This process apparently has little precedent in the mass spectrometry of ferrocene derivatives. Specifically, the experimental results suggest the simultaneous elimination of two molecules of carbon monoxide, or in another case, of carbon monoxide and ethylene from ions produced in the mass spectrometry of the above compounds.
Mass spectral studies of unsaturated carboxylic acids—I: Some cyclic and acyclic βγ‐unsaturated acids
Authors: Alexander R. G. , Bigley D. B. , Todd J. F. J. 
Published: May 2005

AbstractThe mass spectra of a series of βγ‐unsaturated cyclic and acyclic carboxylic acids are reported. Metastable ion studies and precise mass measurements have been employed in demonstrating that the ten compounds studied conform to one or other of two generalised fragmentation pathways.
Positive chemical ionization mass spectra of polycyclic chlorinated pesticides
Authors: Biros Francis J. , Dougherty Ralph C. , Dalton John 
Published: May 2005

AbstractMethane chemical ionization (CI) mass spectra for a series of ten polycyclic chlorinated insecticides and metabolites have been examined. In all cases except heptachlor epoxide the base peak corresponded to elimination of Cl, or OH from the molecule ion. In the spectrum of heptachlor epoxide the [M + H]+ and [M − Cl]+ clusters were of approximately equal intensity. The CI spectra were remarkably simple, invariably less complex than the corresponding electron‐impact (EI) mass spectra and the intensity of the ions with high information content, e.g. [M − CI]+ was uniformly high. All of these features are important to the analytical potential of these studies. Retro Diels‐Alder (RDA) fragments were observed for the chlordanes, aldrin, isodrin, nonachlor and heptachlor epoxide. The reported preliminary data suggest that the relative intensity of RDA ions in CI mass spectra may be useful in establishing molecular configurations.
Negative chemical ionization mass spectra of polycyclic chlorinated insecticides
Authors: Dougherty Ralph C. , Dalton John , Biros Francis J. 
Published: May 2005

AbstractNegative ion mass spectra obtained under chemical ionization conditions (NCI) employing methane, isobutane or methylene chloride as the enhancement gas are presented for a series of chlorinated polycyclic insecticides. All of the compounds examined except 1‐hydroxychlordene yielded molecular anions of substantial relative abundance (6 to 39%). The most significant features of the spectra are the prominent peaks at masses greater than that of the molecule ion formed via ionmolecule association reactions. Peaks representing association of the parent molecule with ionic species such as H−, O−, OH−, Cl−, H2OCl−, HCl2−, ClO− and Cl3− were observed in some cases. The base peak in all spectra was associated with the isotopic group of the [M + Cl]− on if contributions from other negative, even electron ions of low mass values present in high concentrations (Cl−, H2OCl− Cl2− and HCl2−) are neglected. Fragmentation processes were limited to elimination reactions involving loss of combinations of the even electron neutral species H, Cl and HCl. In addition, fragmentation resulting from a nucleophilic radical displacement of Cl by O− from the parent molecule was observed in all cases except 1‐hydroxychlordene when the source was modestly wet (methane as reactant gas). NCI mass spectra of polycyclic chlorinated pesticides are reproducible, intense, interpretable in terms of classical carbanion chemistry and thus may have important analytical utility, particularly when used in conjunction with positive electron‐impact and chemical ionization mass spectral methods and selective use of different enhancement gases.
Mass spectrometry of organic compounds in the group V elements—II: Branched chain aliphatic derivatives
Authors: Kostyanovsky R. G. , Plekhanov V. G. , Elnatanov Yu. I. , Zagurskaya L. M. , Voznesensky V. N. 
Published: May 2005

AbstractThe behaviour of compounds I to XII under electron‐impact (electron voltages 30 and 12 eV) was investigated. The abundance of the ions characteristic of amines was shown to decrease drastically with an increase of chain branching in alkylphosphines. Comparison of the spectra of VII and X led to the conclusion that the unshared electron pair of phosphorus does not affect the fragmentation. The main peaks in the spectra of phosphines corresponded to hydrocarbon fragments. The origins of the main fragment ions were confirmed by metastable peaks.
Mass spectra of lincomycin, lincomycin analogs and degradation products
Authors: Kagan Fred , Grostic Marvin F. 
Published: May 2005

AbstractThe principal ions observed in the mass spectra of lincomycin hydrochloride, some of its analogs and two degradation products are discussed. Lincomycin‐related compounds can be characterized by examination of the molecular ion and four other ions. Plausible mechanistic interpretations of these ions are presented.
The study and characterization of nucleosides by mass spectrometry—I: The mass spectra of pyrimidine 2,2′‐anhydronucleosides and their derivatives
Authors: Westmore J. B. , Lin Denis C. K. , Ogilvie K. K. , Wayborn H. , Berestiansky J. 
Published: May 2005

AbstractThe mass spectra of 2,2′‐anhydrouridine, 2,2′‐anhydrothymidine and 2,2′‐anhydro‐4‐thiouridine are reported. The acetyl, trifluoroacetyl, trityl, pivaloyl and trimethylsilyl ether derivatives were also studied. Deuterium labeling in acetyl and trimethylsilyl groups aided characterization of many ions in the spectra, as well as helping to clarify hydrogen migration processes. The anhydronucleosides and their derivatives are readily distinguished from natural nucleosides by the presence of an ion containing the base moiety plus the anhydro‐ring plus one hydrogen atom from the rest of the molecule. As for natural nucleosides the [base + H]+ and [base + 2H]+ ions are usually prominent, but in contrast to natural nucleosides, ions characteristic of the sugar moiety do not retain the 2′‐oxygen atom (i.e. the oxygen atom of the anhydro‐ring). The mass spectra of deuterium labeled derivatives suggest a test for the presence of a 3′‐O‐acetyl function (the O‐acetyl group is lost from the molecular ion much more readily from the 3′‐ than from the 5′‐carbon atom). The trimethylsilyl derivatives showed evidence in their mass spectra for migration of trimethylsilyl groups in addition to hydrogen atoms.
Electron‐impact fragmentations of 1,3‐ and 1,4‐bis‐(cyclopentadienyliron dicarbonyl)tetrafluorobenzenes
Authors: Cohen Stuart C. 
Published: May 2005

AbstractAlthough 1,4‐bis(cyclopentadienyliron dicarbonyl)‐tetrafluorobenzene fragments under electron‐impact, losing four CO groups stepwise prior to other observed fragmentations, the corresponding 1,3‐derivative eliminate HF after loss of only two CO groups.
Substituent effects in mass spectrometry: The correlation of the ionisation potentials of substituted benzenes with σp+
Authors: Benoit F. 
Published: May 2005

AbstractIt is demonstrated that the ionisation potentials of mono‐ and di‐substituted benzenes are related to the sum of Brown's σp+ of the substituents for both the meta and para isomers. From this it is concluded that the charge, in substituted arenes, lies predominantly on the aromatic ring rather than on either of the substituents. An empirical equation relating the IP's of mono‐ and disubstituted benzenes to the sum of σp+ is presented.
Appearance potentials as an analytical aid in the evaluation of of non‐bonded interactions. Recalculation of strain energies for some methyl phenanthrenes
Authors: Jalonen Jorma , Pihlaja Kalevi 
Published: May 2005

AbstractRecently, Dougherty et al.1 reported ionisation potentials for the [M]+· and appearance potentials for the [M  CH3]+ ions of 2,7‐dimethyl‐ (I), 4,5‐dimethyl‐ (II), 2,4,5,7‐tetramethyl‐ (III) and 3,4,5,6‐tetramethyl‐phenanthrenes (IV). For evaluation of strain energies they used the assignments presented by Arnett et al.2 The expression used is shown to be thermodynamically irrelevant and the strain energies of II and IV in comparison to I and III are re‐estimated with the aid of thermodynamically relevant assumptions. A close agreement prevails between the present results and those obtained with comparison of heats of formation.
Transfer processes of alkoxyl groups in iron carbonyl complexes
Authors: Gambino O. , Vaglio G. A. , Cetini G. 
Published: May 2005

AbstractThe mass spectra of Fe2(CO)6C4(COOCH3)4 and Fe2(CO)6C4(COOC2H5)4 are reported. Transfer processes of alkoxyl groups and hydrogen rearrangements are observed, and confirmed by deuterium labelling and the observation of metastable transitions. Fe3(CO)8C4(COOCH3)4 and Fe3(CO)8C4(COOC2H5)4 give similar breakdown patterns. Likely fragmentation schemes are suggested.
Etude de la Fragmentation du Benzisothiazole et de Quelques Benzoselenazoles et Benzisoselenazoles
Authors: Croisy A. , Jacquignon P. , Weber R. , Renson M. 
Published: May 2005

AbstractLes spectres de masse du benzisothiazole, de trois benzosélénzoles et de trois benzisoséléazoles not été mesurés et comparés à ceux des benzothiazoles correspondants. La perte de CS mise en évidence chez ces derniers est confirmée dans le cas du benzisothiazole, mais un mécanisme différent est proposé.La fragmentation des analogues séléniés conduit à des ions du même type que dans le cas des benzothiazoles et du benzisothiazole par perte de molécules du type CN—R, cependant, la perte de l'hétéroatome ne s'accompagne pas de perte de carbone. En outre, il semble que la structure isosélénazole soit plus sensible à l'electronolyse que son isomére.Les six hétérocycles séléniés étudiés ont tous donné naissance à deux ions (130 et 132) provenant d'une recombinaison de divers fragments. Ce phénomène laisse à penser qu'il s'agit là d'un élément caractéristique dans la fragmentation électronique de tels composés.
The electron‐impact induced fragmentation of substituted 4‐styrylquinolines
Authors: Güsten H. , Klasinc L. , Stefanović D. 
Published: May 2005

AbstractThe fragmentation of 4‐styrylquinoline (I), 4‐(p‐nitrostyryl)‐quinoline (II), 4‐(p‐chlorostyryl)‐quinoline (III), 4‐(p‐hydroxystyryl)‐quinoline (IV), 4‐(p‐methoxystyryl)‐quinoline (V), 4‐(p‐dimethylaminostyryl)‐quinoline (VI) and 4‐(p‐cyanostyryl)‐quinoline (VII) under electron‐impact in the mass spectrometer is reported. The role and the influence of substituents on the fragmentation scheme is discussed. The loss of the substituents from the molecular ion is correlated with LCAOMO quantities.
Elektronenstossinduzierte Fragmentierung von Acetylenverbindungen—V: Vergleich der Isomeren Naphthyl‐ und Phenyl‐Pentinen‐Alkohole
Authors: Schwarz Helmut , Bohlmann Ferdinand 
Published: May 2005

AbstractDie Unterschiede im Fragmentierungsschema der isomeren Naphthyl‐ und Phenylpentinen‐aklohole sind durch Untersuchung der 2H‐ und 13C‐markierten Derivate nachgewiesen worden. Wie durch hochauflösende Massenspektrometrie gezeigt werden kann, wird im Falle der Acetylenverbindung IOn [C9H7]⊕ hauptsächlich durch Keten‐eliminierung aus dem [M – 1]+‐Ion und bei den Naphthalinen durch Abspaltung von Acetylen aus dem Benztropylium‐Ion gebidet. Der vorgeschlagene Mechanismus der CO‐ und CHO‐Abspaltung füBenzylalkohol kann nicht auf die untersuchten Verbindungen übertragen werden.
Fragmentation of reduced dibenzo[b,f][1,4]‐diazocines, ‐oxazocines and ‐thiazocines on electron‐impact
Authors: Millard B. J. , Saunders A. , Sprake J. M. 
Published: May 2005

AbstractAn investigation of the mass spectral behaviour of the title compounds is reported. Two processes have been studied by deuterium labelling. One, which occurs with all three ring systems, results in the loss of a C7H7 radical, whilst the other, which occurs only in the dibenzothiazocine, leads to the loss of a C6H6N radical.
Mass spectra of organoarsenic compounds—I: Electron‐impact‐induced fragmentations of esters of arsenious and thioarsenious acid
Authors: Frøyen Paul , Møller Jørgen 
Published: May 2005

AbstractThe mass spectra of a series of esters of arsenious and thioarsenious acid have been studied, together with that of diethyl methylarsonite. The main fragmentation pathways have been determined with the use of high resolution mass measurements and application of the metastable defocusing technique.The major fragment ions all contain arsenic and may be ascribed structures implying divalent/trivalent arsenic. Ions implying tetravalent/pentavalent arsenic as well as double hydrogen rearrangement processes are hardly recognisable; this is in contrast to the findings reported for the corresponding phosphorous compounds, with which a comparison is made.The present results are in accordance with the view that arsenic is less capable than phosphorous of achieving multiple bonding to other atoms by means of its empty d orbitals.
Quantitative mass spectrometry by internal standardisation using a single focusing mass spectrometer and the peak switching facilities of a peak matching device
Authors: Seiler N. , Knödgen B. 
Published: May 2005

AbstractA quantitative mass spectrometric method for the determination of small sample sizes is described. This method is applicable to both single and double focusing mass spectrometers, if a conventional peak matching device or any other suitable peak switching facility is attached to the instrument.In the conventional integrated ion current technique a constant pressure of the vapour of hepta‐cosafluoro‐tri‐n‐butylamine or a comparable standard is maintained in the analyser. By contrast to this in our method the calibrating substance is evaporated together with the sample from the same capillary of the probe. Substances with a similar chemical structure (in most cases higher or lower homologues) can be used as internal standards. Since thermal effects in the probe and sensitivity changes of the mass spectrometer during the flash evaporation of the substances affect the integrated ion current curves of both sample and standard equally, the ratio of the curves is largely independent of these parameters.With a single focusing mass spectrometer (CH‐5 Varian, MAT) reproducibilities of the determinations were within ±10%, with substance amounts in the range between 10−10 to 10−11 mole.
Mass spectrometric identification of oleanolic and ursolic acids
Authors: Grilanc P. , Milivojević D. 
Published: May 2005

Abstractp‐Toluidides of 3‐acetoxy ursolic and 3‐acetoxy oleanolic acids were prepared. On the basis of different intensities of the m/e 452 and 453 peaks the identification of oleanolic and ursolic acids is possible.
Isotope effects upon hydrogen atom loss from molecular ions
Authors: Bertrand M. , Beynon J. H. , Cooks R. G. 
Published: May 2005

AbstractThe isotope effect (TH/TD) upon the kinetic energy release and the isotope effect (kH/kD) upon ion abundance for unimolecular H· loss from molecular ions has been determined for several compounds. It is suggested that the isotope effect upon abundance might provide a convenient method of estimating the relative life‐time of ions which fragment in the metastable region for different instruments or different experimental conditions. The value of kH/kD varies from <2 to >1000 for different molecular ions and this variation is apparently largely due to the rate of increase of the reaction rate with internal energy in the threshold region. The magnitude of the isotope effect is thus related to the entropy of activation. The isotope effect upon energy release was found to be slightly less than unity in almost every case studied; this included both reactions in which the reverse activation energy is very small and those in which it is appreciable.
The mass spectra of some selenoureas and selenothiocarbamic esters
Authors: Kirkien Alicja M. , Shine Robert J. , Plimmer Jack R. 
Published: May 2005

AbstractThe mass spectra of five selenoureas and two selenothiocarbamic esters are reported and discussed. Fragmentation modes are compared with those reported for the ureas, thioureas, carbamates and thiocarbamates.
Some aspect of the doubly‐charged ion chemistry of armoatic amines and diamines
Authors: Ast T. , Beynon J. H. 
Published: May 2005

AbstractDoubly‐charged ion mass spectra of aromatic amines and diamines, as opposed to those of the aromatic hydrocarbons, show strong correlation with empirical formula.[M]++is usually the base peak in the spectrum and its main fragmentation involves loss of C2H2, in sharp contrast wit the [M]+˙ ion which always loses HCN. Measurement of the Kinetic energy released in chargeseparation reactions can yield useful structural information. Result strongly support the concept of charge‐localization on nitrogen atoms. Extensive scrambiling prior to nfragmentatiom was observed in all isomeric compoounds studied.
The mass spectrum and fragmentation mechanism of exo‐ and endo‐ norborneol
Authors: Holmes J. L. , McGillivray D. 
Published: May 2005

AbstractThe mass spectra of exo ‐and endo‐norborneol and a number of deuterium labelled and‐logues have been studied in detail. The two alcohols have common fragentation pathways, the major routes of which can be related to specific rearrangements of the molecular ion. The loss of water from the molecular ion consists of two processes, one involving and one4 not involving the hydroxyl hydrogen atom. The limitions of the labelloing experiements are discussed.
The fragmentation of some alkyl thio‐phosphate esters by electron‐impact
Authors: Santoro E. 
Published: May 2005

AbstractThe mass spectra of the following compounds have been studied:

equation image

and the fragmentation pathways established with the aid of accurate mass measurements, metastable transition and appearance potential determination. The mass spectra show that the sulphur‐containing compounds (II to IV) give a stronger molecular ion that that of compound I. A further significant difference is the low intensity, in the mass spectra of II to IV, of the fragments relative to the processes that occur in I, probably because the electron removed upon ionisation belongs to the sulpher atom in compounds II to IV and to the oxygen in compound I. The isomeric compounds, (III and IV) show quite different mass spectra, The radicals containing only Phosphorus and oxygen have an ionisation potential close to 9 eV and the presence of sulphur considerably lowes this value. The measured ionisation potentials of compounds I to IV are respectively, 10·70, 9·55, 9·20 and 9·00eV. The heats of formation of compounds II and III have been estimated as −176 and −118 Kcal mole−1, respectively.
The mass spectra of the pyrethrins and related compounds
Authors: Pattenden G. , Crombie L. , Hemesley P. 
Published: May 2005

AbstractThe mass spectra of the natural pyrethrins, allethrin, the chrysanthemic acid, and the rethrolonyl and rethronyl portions of the insecticidal esters are presented, and their main fragmentation pathways are discussed.
Variantes de mycosides caracterisees par des residus glycosidiques substitues par des chaines acyles–I: Spectres de masse des mycosides G′ et A′ peracetyles
Authors: Gastambide‐Odier Mireille 
Published: May 2005

AbstractLes spectres de masse des mycosides G′ et A′ peracétylés sont caractérisés par des ions oxoniums réarrangés correspondant à des désoxysucres substitués qui auraient perdu une chaǐne acyle par fragmentation dans le spectrographe de masse.Le constituant glycosidique majeur du mycoside G′ est un désoxysucre avec une chaǐne acyle et un groupement méthyle. Le mycoside A′ contient des désoxysucre avec une chaǐne acyle et 0, 1 ou 2 méthyles. I1 existe ausi des désoxysucres sans chaǐne acyle mais avec un (G′, A′) ou deux (A′) méthyles.Les spectres de masse indiquent que les chaǐnes acyles pourraient ětre du type mycolique: I1 existe des pics qui pourraient correspondre à une coupure des deux cǒtés de la ramification méthyle magnified image et le fragment CH+˙CC22H45, trouvé dans le spectre du mycoside G′ paracétylé, est caractéristique de la chaǐne raifiée. Les pics les plus élevés (m/e 1072 et 1100) du spectre du mycoside A′ paracétylé correspondraient à une chaǐne mycolique, après l'élimination d'une molécule d'acide acétique, d'une molécule de méthanol et perte d'un H (l) ou l'élimination d'une molécule d'acide acétique et perte d'un H (m).Les měmes spectres permettent de preéciser la nature et l'abondance des acides mycocérosiques qui estérifent les aglycones et confirment aussi la structure de ces aglycones qui a été établie antérieurément par dégradation et par spectrométric de masse. La mycoside G′ est caractérisé par des acides mycocérosiques en C27 et C24 et le mycoside A′ par des acides mycocérosiques en C29, C32, C30 et C27 qui sont classés par ordre d'importance décroissante.
High resolution field desorption mass spectrometry—I: Nucleosides and nucleotides
Authors: Schulten H. R. , Beckey H. D. 
Published: May 2005

AbstractThe first complete high resolution (HR) field desorption (FD) mass spectra (MS) are presented and constitute a helpful tool in the structure elucidation of biologically significant compounds. This is especially relevant for the determination of the molecular weight of substances with very low volatilities which suffer from thermal decomposition when evaporated into the ion source. An additional advantage is the very small sample consumption (in the submicrogram range).Further improvements in the ion production method are the introduction of high temperature activated emitters and a specially designed micromanipulator for optimal adjustment of the field anodes. These enabled values of mass resolution between 15000 and 25000 (10% valley definition) to be achieved when vacuum evaporated Ag Br plates were used for photographic recording.
Massenspektrometrische Untersuchung aromatischer Halogenide der Summenformel C9H11Cl: Mechanismus der Äthylen‐Abspaltung aus dem Ion [M  Cl]+˙
Authors: Köppel Claus , Schwarz Helmut , Bohlmann Ferdinand 
Published: May 2005

AbstractDurch die Untersuchung 2H‐ und 13C‐markierter isomerer C9H11Cl‐Verbindungen wird gezeigt, dass das [M  C]+‐Ion bevozugt über alkylsubstituierte Tropylium‐Ionen unter C2H4‐Abspaltung in das Ion [C7H7]+ übergeht. Phenylierte Cyclopropan‐Kationen haben, wenn überhaupt, nur einen geringen Anteil an diesem Fragmentierungsvorgang.
Intramolecular transfer reactions induced by electron‐impact. Transsulfonations and transmethylations in polymethylene glycol dimethanesulfonates
Authors: Pomonis J. George , Nelson D. R. 
Published: May 2005

AbstractThe dimethanesulfonate esters of polymethylene glycols undergo three types of double‐group transfer reactions as a result of electron‐impact mass spectrometry: 1. Transfer of a hydrogen and one methanesulfonate group to the second methanesulfonate with cleavage to yield a protonated methanesulfonic acid anhydride. 2. Transfer of two hydrogens to a methanesulfonate group with cleavage to yield a protonated methanesulfonic acid. 3. Transfer of a hydrogen and a methyl group to the second methanesulfonate with cleavage to yield a protonated methyl methanesulfonate. Bicyclic transition states are proposed for these reactions.