bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mass spectrometry of volatile derivatives—III: N‐aryl trifluoracetamides
Authors: Saxby M. J. 
Published: May 2005

AbstractThe effects of substituents on the fragmentation of N‐aryl trifluoracetamides has been investigated. The base peak in all ring‐monosubstituted derivatives is the molecular ion. Other important ions arise by loss of CF3 and COCF3 from the molecular ion, and the latter daughter ion fragments further, by loss of the aromatic substituent and by expulsion of small neutral molecules. The effects of substituents on the intensity of these ions is discussed. 1‐Phenylethyl trifluoracetamide exhibits a base peak which is the molecular ion, wheras the corresponding 2‐phenyl derivative has a molecular ion of very low intensity.
Mass spectra of π‐cyclopentadienyl‐diene cobalt complexes
Authors: Yasufuku Katsutoshi , Yamazaki Hiroshi 
Published: May 2005

AbstractMany reports on the mass spectra of organotransition‐metal complexes have appeared in recent years,1 whilst there have only been a few reports on the mass spectra of transition metal olefin complexes, some metal carbonyl olefin complexes234 and π‐cyclooctenyl‐π‐cyclooctadienyl cobalt.5 Recently fragmentation paths of π‐cyclopentadienyl‐cyclooctadiene rhodium were elucidated by King.6 The present authors found metastable ions in the mass spectra of π‐cyclopentadienyl‐diene cobalt complexes as well as in the mass spectra of π‐cyclopentadienyl‐diene rhodium complexes.7.In the present paper the authors wish to report the mass spectra of several π‐cyclopentadienyl diene cobalt complexes.
Metastable transitions in the mass spectra of fluoro‐ethylenes
Authors: Jennings K. R. 
Published: May 2005

AbstractMetastable transitions in the mass spectra of six fluoroethylenes are reported. In several cases in which HF is the neutral species lost, 0.4 to 0.7 eV of kinetic energy is liberated. In two fragmentations, it is shown that the kinetic energy release is only about half the minimum energy of activation of the back reaction calculated from thermochemical data. Evidence is presented to support the view that in some cases at least, fragmentation occurs from two or more electronic states of the molecular ion.
Positive‐ion fragmentation mechanisms of some organophosphorus esters
Authors: Pritchard J. G. 
Published: May 2005

AbstractThe mass spectra of the dimethyl and diethyl esters of phosphonic, phosphorochloridic and phosphorochloridothioic acid have been obtained, and the main paths of decomposition of their positiveions have been compared. Losses of formaldehyde occur from positive ions of all the methyl esters. Losses of C2H3˙ radicals occur consistently from the positive ions of the ethyl esters, but diethyl phosphorochloridothioate differs in showing a principal decomposition path involving initial loss of acetaldehyde. Other details are discussed.
The mass spectra of s‐triazines
Authors: Preston P. N. , Steedman W. , Palmer M. H. , Mackenzie S. M. , Stevens M. F. G. 
Published: May 2005

AbstractThe mass spectra of twenty‐one s‐triazines have been interpreted. An unusual feature noted in the spectra of some of the compounds is transfer of a hydrogen atom of a side chain to a nitrogen atom of the s‐triazine ring; two such shifts are suggested as a rationale for the unusual loss of nitrogen from a hydrazide derivative. The fragmentation of triamino‐ and some diamino‐ derivatives indicates that imino tautomers play a significant role. The spectra of aryldiamino s‐triazines suggest that the site of a substituent in the aryl ring is important in some cases in directing the decomposition; some transitions have been rationalised on the basis of the juxtaposition of the substituent in relation to a nitrogen atom of the heterocyclic ring.
Ortho effects–I: Fragmentation mechanisms in some ortho‐substituted nitroarenes
Authors: Benoit F. , Holmes J. L. 
Published: May 2005

AbstractThe mass spectra of o‐nitrobenzoic acid, o‐nitroanisole, o‐nitrosobenzoic acid, o‐nitrobenzamide, o‐nitrobenzyl alcohol and o‐nitrosobenzaldehyde have been studied. Fragmentation mechanisms are proposed for the above compounds; their elucidation was aided by isotopic labeling with D and O18. Two ‘ortho‐effects’ are discussed; one involving H atom transfer between substituents and the other migration of an atom or group to a charge carrying vacant ortho position. The importance of nitro to nitrite conversion in molecular and fragment ions is discussed.
Zum mechanismus Massenspektrometrischer Fragmentierungsreaktionen–III: Stereospezifische Reaktionen in den Massenspektren der Methyläther cyclischer Polyalkohole
Authors: Winkler Johann , Grützmacher Hans‐Friedrich 
Published: May 2005

AbstractEin Vergleich der Massenspektren von Stereoisomeren der Polymethoxycycloalkane läßt eine deutliche Abhängigikeit von der Geometrie der Molekül‐Ionen erkennen. Die Größe des stereochemischen Effekts wird beeinflußt von der cyclischen Molekü‐Ionen. Wegen energetisch günstiger Ringspaltungen wird der Effekt durch vicinale Methoxysubstituenten aufgehoben, durch Methylsubstituenten benachbart zu Methoxygruppen vermindert.Die wichtigsten steeochemisch kontrollierten Fragmentierungen sind Elilminierung einer Methoxygruppe als Methanol‐ oder Formaldehydmolekül aus den Molekü‐Ionen. Durch Untersuchung spezifisch mit Deuterium markierter Di‐ und Tri‐methoxycyclohexane wird gezeigt, daß beide Reaktionen mit der Übertragung eines leicht abspaltbaren H‐Atoms von einem Carbinol‐C‐Atom an das O‐Atom einer Methoxygruppen beginnen. Der Eintritt beider energetisch günstiger Reaktionen hängt davon ab, ob in den möglichen Konformationen der Molekül‐Ionen eine hinreichende räumliche Annäherung der beteiligten H‐ und O‐Atome möglich ist.Die Stereochemische Kontrolle der Fragmentierung von 1,3‐Dimethoxycyclopentan mit dem wenig beweglichen Fünfring ist gering, die der Fragmentierung von Di‐methoxycycloheptanen mit dem flexiblen Siebenring ist von vergleichbarer Größe wie der sterische Effekt in den Massenspektren von Cyclohexanderivaten.
Mass spectra of organometallic compounds–XII: Tetraphenylcyclobutadiene derivatives
Authors: King R. B. , Efraty A. 
Published: May 2005

AbstractThe mass spectra of the tetraphenylcyclobutadiene complexes (C6H5)4C4Fe(CO)3, C5H5CoC4(C6H5)4 and C9H7CoC4(C4H5)4 are reported. Evidence is presented for the loss of the tetraphenylcyclobutadiene ring by a two‐step sequence involving successive losses of two (C6H5)2C2 fragments. Significant differences are observed in the fragmentations of the monopositive and dipositive molecular ions of C9H7CoC4(C6H5)4.
Mass spectrometric studies–VI: Aziridines
Authors: Porter Q. N. , Spear R. J. 
Published: May 2005

AbstractThe mass spectra of C‐alkylaziridines show that generally β‐cleavage is the most important fragmentation, although α‐cleavages also occur as do γ‐, and δ‐ and ϵ‐cleavages in appropriate examples. A surprising rearrangement of the β‐cleavage ions has been explained as the result of a four‐centre cyclization followed by fragmentation. Other decompositions occur via transannular cleavages with and without hydrogen transfer. α‐Cleavage appears to be the most important fragmentation of N‐alkylaziridines. N‐Phenylaziridine shows very marked 1,2‐phenyl‐migration before fragmentation.
Electron‐impact fragmentation of N‐substituted 2‐aminobenzoxazoles and 2‐aminobenzothiazoles
Authors: Ogura H. , Sugimoto S. , Itoh T. 
Published: May 2005

AbstractThe mass spectra of twenty‐eight N‐substituted 2‐aminobenzoxazoles and 2‐aminobenzothiazoles have been recorded and the identity of various ions in the mass spectra have been established by high resolution measurement. The molecular compound of series, benzoxazole, undergoes loss of hydrogen cyanide and carbon monoxide from the molecular ion as the most important decomposition pathways. The mass spectra of N‐substituted benzothiazoles showed a similar fragmentation as that of N‐substituted benzoxazoles.
Mass spectrometry of kaurene derivatives—I. The mass spectra of some (−)‐kauran‐16‐ols
Authors: Kalinovsky A. I. , Serebryakov E. P. , Zolotarev B. M. , Simolin A. V. , Kucherov V. F. , Chizhov O. S. 
Published: May 2005

AbstractThe mass spectra of nine compounds belonging to the group of (−)‐kauran‐16‐ols are reported. These compounds differ either by stereochemistry at C16 (I, II) or by the nature of the substituent at C4 (III to VIII). In all cases the most characteristic ions correspond to a process in which ring D is split off and lost as a C3H6O fragment. The nature of the substituent R1 at C4 can be deduced from such typical ions as [M  R1]+ or [M  R1  H2O]+. Kauranols epimeric at C16 show little difference in their mass spectra; the assignment of configuration at this centre may be reliable only when the spectra of both epimers are compared.
Mass spectra of 1‐phenylflavazole derivatives of monosaccharides
Authors: Dolejš L. , Veisová Z. , Farkaš J. 
Published: May 2005

Abstract1‐Phenylflavazole derivatives of monosaccharides show structurally characteristic and easily interpretable mass spectral fragmentation processes. The position of the deoxy or methoxy grouping may be conveniently localized.
Chemical ionization mass spectrometry of complex molecules—VI: Peptides
Authors: Kiryushkin A. A. , Fales H. M. , Axenrod T. , Gilbert E. J. , Milne G. W. A. 
Published: May 2005

AbstractThe chemical ionization mass spectra of a series of simple peptides containing six or fewer amino acids have been studied. Using methane as the reactant gas we found cleavage of the peptide bond occurs in two ways, yielding either the acyl carbonium ion or the complementary ammonium ion. The observation of both types of fragments permits the determination of the amino acid sequence of the peptide. The ammonium ions provide an additional sequence determining route compared to that available from electron‐impact spectra. ‘Sequence‐determing ions,’ especially the quasimolecular ion at m/e [M+1] are usually more intense than in the electron‐impact mass spectra.
Mass spectral fragmentation studies in monomeric and dimeric coumarins
Authors: Kutney James P. , Engendorf Guenter , Inaba Tadanou , Dreyer David L. 
Published: May 2005

AbstractA study on the behavior of a large number of monomeric and dimeric coumarins in the mass spectrometer is reported and discussed. The results illustrate that the observed characteristic fragmentation patterns are of considerable utility in the application of mass spectrometry to structure elucidation in this series.
Mass spectrometry of hop compounds—III. Mass spectra of substituted 1,3‐cyclopentanediones derived from hop constituents
Authors: Shaw S. J. , Shannon P. V. R. , Collins E. 
Published: May 2005

AbstractThe mass spectra of isohumulones (IV, V), tetrahydroisocohumulones (VI, VII), tetrahydroisohumulones (VIII) neohydroisocohumulones (XI, XII) cohumulinic acid (III), lupuloxinic acid (XV), humulinone (XIV) and related compounds are described. Ions which appear to be diagnostic for particular structures are discussed.
Field desorption mass spectrometry with high temperature activated emitters
Authors: Schulten H. R. , Beckey H. D. 
Published: May 2005

AbstractThe use of emitters which have been activated at high temperature in Field Ionization and Field Desorption mass spectrometry offers some important advantages over the usual emitter type activated at room‐temperature. Higher thermal stability of the microneedles is achieved and the emitters are extremely resistant to chemical attack. It becomes possible to induce a thermal fragmentation of solid compounds adsorbed on the emitter surface between room‐temperature and approximately 2000°C. The field anodes may be re‐used many times without loss of quality. The problem of mass references is solved in Field Ionization/Field Desorption‐Mass Spectrometry when high temperature emitters are used. The Field Ionization mass spectra of perfluorokerosene (PFK) and perfluorotributylamine display peaks in the mass range between m/e 50 to 800, with a resolution of up to 30000 (10% valley definition). A short description of a rapid and easy activation to produce high temperature microneedles is given.The following abbreviations are used throughout this paper:—

HT
High Temperature

RT
Room‐Temperature

BAT
Best Anode Temperature

HR
High Resolution

MS
Mass Spectrometry/Spectrum/Spectra

EI
Electron Impact

FI
Field Ionization

CI
Chemical Ionization

FD
Field Desorption
Mass spectra and pyrolysis of some oxymethylene‐linked perfluoroaromatic compounds
Authors: Cotter J. L. 
Published: May 2005

AbstractThe mass spectra of four oxymethylene‐linked perfluoroaromatic compounds are reported and discussed. Proposed ion structures are substantiated by precise mass measurement. The principal fragmentation pathways involving scission of oxygen to methylene bonds are supported by appropriate metastable peaks.Parallels between the electron‐impact and thermal behaviour of two of these compounds are noted.
Chemical ionization mass spectra of amino acids and derivatives. Occurrence and fragmentation of ion‐molecule reaction products
Authors: Leclercq P. A. , Desiderio D. M. 
Published: May 2005

AbstractThe Chemical ionization mass spectra of free amino acids, their amides, methyl esters and Na‐acetyl derivatgives, using methane as reagent gas, are presented, The occurrence and fragmentation of ion‐molecules reaction products are discussed. A preference for a head to tail, configuration of the association complex [2M + 1]+ is postulated to esplain promienent fragmentation pathways of this complex. Interesting fragmentation pathways have been found with onithine, arginine and citrulline.
Mass spectrometric studies—II: Mass spectrometric studies of maleimides and benzaldazine adducts. Identification of solid mixtues
Authors: Tam S. W. 
Published: May 2005

AbstractIt has been found by mass spectrometric studies that the so‐called ‘1:1‐adduct’ formed by N‐( nbutyl)maleimide and benzaldazine, is in fact a solid mixture of one part bis‐imide L and one part benzaldazine. Bis‐imide L is one of the three stereoisomeric products obtained by the addition of two mole of N‐( n‐butyl)malemide and one mole of benzaldazine. The three stereoisomeric bis‐imides gave identical mass spectra. Mass spectra of bis‐imide M and bis‐imide M‐ d2 are discussed, and confirm the proposed structures of perhydroprazolo‐pyrazole derivatives for these 1:2‐adducts.
The fragmentation of ortho‐methoxyphenyl‐2‐propanone oximes and related compounds–further examples of an ortho‐effect
Authors: Coutts R. T. , Malicky J. L. 
Published: May 2005

AbstractAn [M  31]+ ion was a prominent fragment in the mass spectra of three ortho‐methoxy‐phenyl‐2‐propanone oximes and is shown to be due to the expulsion of a methoxyl radical from the molecular ion as a result of an ortho‐effect. In contrast, an [M  31]+ ion was absent from the spectra of a structurally related ketone and a hydroxylamine, and was not observed in the spectra of meta‐ and para‐methoxyphenyl‐2‐propanone oximes.
Etude en Spectrometrie de Masse d'une Serie d'Anhydride du Type Acetoxy‐3 Bicyclo[2.2.2]octene‐2 Dicarboxylique‐5,6
Authors: Cassan J. , Geribaldi S. , Torri G. , Azzaro M. 
Published: May 2005

AbstractUne série d'anhydrides du type acétoxy‐3 bicyclo[2.2.2]octéne‐2 dicarboxylique‐5,6 ne différant que par des substituants hydrocarbonés, a été étudiée en spectrométrie de masse é I'aide de la haute résolution. Les spectres de cette série sont complexes et ne différent que par la présence de certains pics et par des intensités relatives variables. Par des mécanismes classiques, nous avons pu expliquer la presque totalité des pics. Nous nous sommes appuyés sur les mécanismes observés dans une série analogue1,2 de bicyclo‐[2.2.2]octéne‐2 étudiée par Cimarusti et Wolinsky. On retrouve le méme schéma directeur quels que soient les substituants et les positions relatives de ceux‐ci.
Mass spectrometry of stable free radicals—II: pyrrolidine nitroxides
Authors: Davies A. P. , Morrison A. , Barratt M. D. 
Published: May 2005

Abstract3‐Substituted‐2,2,5,5‐tetramethylpyrrolidine nitroxides are stable free radicals used extensively in the synthesis of ‘spin labels’. The high resolution mass spectra of these nitroxides substituted with CH2OH, OH, NH2 and o have been recorded on magnetic tape and the elemental compositions of the ions calculated by computer. Ionisation by electron bombardment(70eV), gives rise to an even‐electron molecular ion species. [M+1]+. ions are observed in the spectra of all compounds examined, except in the case of the 3‐carbonyl compound, 2,2,5,5‐tetramethylpyrrolid‐3‐one‐1‐oxyl. Loss of a methyl radical from these ions leads to the appearance of ions at [M ‐14]+. The predominant fragmentation for those compounds in which the substituents can supply electrons to the ring, is the sequential elimination of isobutene, nitric oxide and a hydrogen radical. In the case of the 3‐hydroxy compound, these ions account for 23 percent of the total ion current.2,2,5,5‐Tetramethylpyrrolid‐3‐one‐1‐oxyl, which bears an electron‐withdrawing substituent gives rise to a fragmentation pattern somewhat different from those of the other compounds. The main features are the absence of a peak at [M + 1]+˙ and the general phenomenon of fewer peaks but with higher intensities.
Electron‐impact‐induced fragmentation of some diterpenoid acetals
Authors: Cambie R. C. , Preston A. F. , Woodgate P. D. 
Published: May 2005

AbstractStudy of the low and high‐resolution mass spectra of a series of diterpenoid acetals, including both positional isomers and stereoisomers, has permitted the proposal of some characteristic fragmentation pathways leading to analytically distinctive peaks. The mass spectrum was particularly informative in the assignment of structure to an unexpected rearrangement product (V).
Mass spectrometry in structural and stereochemical problems‐CCXXIX: Electron‐impact‐induced fragmentation of boric acid esters
Authors: Hammerum Steen , Djerassi Carl 
Published: May 2005

AbstractThe mass spectral decompositions of cyclic and acyclic borates have been examined. Straight chain trialkyl borates fragment by CO cleavage reactions accompanied by transfer of one or two hydrogen atoms, whereas tri‐(sec‐alkyl) borates primarily undergo α‐cleavage reactions. Both types of cleavage are observed in the fragmentation of cyclic borates. BO bonds are not broken in the formation of most major fragment ions. The fragmentations of borates are compared with those of phenylboronates with special emphasis on the rearrangements leading to hydrocarbon ions in the spectra of the latter.
Metastable peaks in a mass spectrum measured automatically under high resolution fast scan conditions
Authors: Carrick Alan , Paisley H. M. 
Published: May 2005

AbstractThree metastable peaks have been automatically recorded in the fast scan high resolution mass spectrum of 2‐hydroxy‐4‐octoxybenzophenone. Values for released kinetic energy in the transitions m/e 326 to 325 and m/e 214 to 213 agree with the results obtained by conventional means.
Massenspektrometrie von Silylpyrazolen—I: Isomere Trimethylsilylpyrazole
Authors: Birkofer L. , Franz M. , Schmidtberg G. 
Published: May 2005

AbstractDurch Vergleich der Massenspektren von isomeren Mono‐, Bis‐ und Tris(trimethylsily)pyrazolenDie Trimethylsilyl‐Gruppe (CH3)3Si‐wird im folgenden mit TMS bezeichnet.
lassen sich charakteristische Einflüsse der verschiedenen TMS‐Gruppen ableiten. Eine N‐TMS‐Gruppe liefert bei N‐TMS‐pyrazol ein Ion m/e 72 und führt bei mehrfach silylierten Pyrazolen zur Abspaltung eines neutralen Fragmentes C3H8Si. Eine 4‐TMS‐Gruppe zeichnet sich durch bevorzugte Fragmentierung und somit durch eine geringe Molpeak‐Intensität (c.5%Σ40) aus. Eine intensive HCN‐Eliminierung aus dem [M  CH3˙]+‐Ion zeigt bei N‐silylierten Pyrazolen, die keine 4‐TMS‐Gruppe besitzen, ein unsubstituiertes C‐3‐Atom an. Für nicht N‐silylierte unsymmetrisch substituierte Pyrazole ist eine Aussage über das vorherrschende Tautomere nach silylierung mit eine N‐Trimethylsilylacetamid möglich.
The mass spectra of 1,6‐dibromo‐1,6‐dideoxyhexitols
Authors: Jarman M. , Tamás J. 
Published: May 2005

AbstractThe mass spectra of 1,6‐dibromo‐1,6‐dideoxy‐D‐mannitol and its O‐deuterated analogue were rationalised in terms of the number and location of the bromine and hydroxy substituents on the carbon chain.
The mass spectrometry of four acyl derivatives of 2,2′‐difurylmethane
Authors: Ferretti Aldo , Flanagan Vincent P. , Ruth John M. 
Published: May 2005

AbstractLow resolution mass spectra and high resolution data for selected important peaks are presented and discussed for the following compounds: [(5‐acetyl‐2‐furyl)‐(2′‐furyl)]methane (I), [(5‐acetyl‐2‐furyl)‐(5′‐methyl‐2′‐furyl)]methane (II), [(5‐formyl‐2‐furyl)‐(2′‐furyl)]methane (III) and [(5‐formyl‐2‐furyl)‐(5′‐methyl‐2′‐furyl)]methane (IV). The fragmentation of II has been clarified by examining the mass spectrum of its d3‐acetyl analog; the fragmentation of III and IV by examining the spectra of their carbonyl 13C‐labeled analogs.
Mass spectrometry of pyrylium salts. Free radical evaporation
Authors: Hvistendahl Georg , Györösi Peter , Undheim Kjell 
Published: May 2005

AbstractFrom ionisation potential measurements it is shown that 2,4,6‐triphenylpyrylium and thiopyrylium cations are thermally reduced in the mass spectrometer to the corresponding free radicals during evaporation of the bromides, iodides and fluoroborates. For the fluoroborates minor amounts of a fluoride adduct were also present. Perchlorate salts led to oxidation. The gaseous species from 2,6‐diphenyl‐4‐methylpyrylium iodide consists of the anhydro base and hydrogen iodide.
The mass spectrometry of 1,3,4‐thiadiazolines
Authors: Wolkoff Peder , Hammerum Steen 
Published: May 2005

AbstractThe mass spectra of di‐, tri‐ and tetraaryl substituted 1,3,4‐thiadiazolines have been examined. They are characterized by thiadiazolium ions, formed by elimination of a C‐5 substituent, by ions formed through elimination of C6H5S˙ radicals arising by transannular phenyl migration and by ions generated via elimination of thiocarbonyl neutrals in retro‐1,3‐dipolar cycloaddition reactions. The influence of the stability of the dipolarophile on the latter reaction is discussed and the fragmentation reactions of thiadiazolines and oxadiazolines are compared.
Chemical ionization mass spectrometry. i‐Butane reactant gas modified by ethanolamine or ethylenediamine
Authors: Bowen D. V. , Field F. H. 
Published: May 2005

Abstract1,2‐Diaminoethane and 2‐aminoethanol‐1 were added to the isobutane plasma of a chemical ionization mass spectrometer. The resulting reactant gas mixture did not react with additives containing a single oxygen functional group. Addition reactions were observed with some additives containing multiple oxygen functions. Additives containing nitrogen functions were protonated by the reactant mixture. The relative proportion of protonation to addition depended on the ability of the additive to chelate the reactant ion and on the basicity of the additive. This use of 1,2‐diaminoethane and 2‐aminoethanol‐1 provides a convenient method of varying the reactivity of the plasma in a chemical ionization source.