bluuebunny/crossref_metadata_2025 huggingface dataset:
The electron‐impact induced loss of water from meconine and related derivatives
Authors: King Bonnie M. , Evans D. A. , Biemann K.
Published: May 2005

The mass spectrum of meconine (I), a constituent of raw opium, exhibits several anomalous features (e.g. pronounced loss of H2O from the molecular ion) which are not readily explicable in terms of simple fragmentation processes. The study of the low resolution mass spectrum of meconine and its derivatives in conjunction with deuterium labeling experiments has indicated a highly specific fragmentation mechanism in which both hydrogen atoms eliminated as H2O originate from the methoxy function ortho to the lactone carbonyl group in meconine.
Mass spectrometric study of 1‐chloro‐2‐nitrosocycloalkanes, dimers in gaseous phase
Authors: Tou James C. , Chang Kuo Yuan
Published: May 2005

The electron‐impact mass spectra and the field ionization mass spectra of 1‐chloro‐2‐nitrosocyclohexane and 1‐chloro‐2‐nitrosocyclopetane are presented and discussed. The two compounds investigated exist in dimeric form in the gaseous phase.
Mass spectrometry in structural and stereochemical problems–CXCIII: On the combined hydroxyl and water loss in nitrophenylhydrazones
Authors: Liedtke Raymond J. , Duffield A. M. , Djerassi Carl
Published: May 2005

The mass spectrum of valeraldehyde o‐nitrophenylhydrazone displays only a low intensity peak (3% relative abundance) corresponding to the loss of 35 mass units from its molecular ion contrary to data previously published. Mention is also made of the fragmentation of 5‐nonanone 2,4‐dinitrophenylhydrazone in view of a recent challenge to a published rationalization for the electron impact promoted fragmentation for this compound.
Mass spectrometry of isomeric methyl phenylpentanoates and methyl phenylnonanoates
Authors: Ansell M. F. , Whitfield G. F.
Published: May 2005

The mass spectra of methyl 3‐, 4‐ and 5‐phenyl pentanoates, and all the straight‐chain methyl phenylnonanoates have been recorded. The major fragmentation patterns have been discussed; when the phenyl group is non‐terminal, cleavage was observed at the branching position. It is shown that a mixture of methyl 3‐, 4‐ and 5‐phenylpentanoates may be analysed both qualitatively and quantitatively by mass spectrometry; in a methyl phenylnonanoate mixture a similar analysis is possible with the exception of the 8‐ and 9‐phenyl isomers.
The expulsion of formic acid and methyl formate during the fragmentation of 3‐phenylpropionic acid derivatives under electron‐impact
Authors: Ballantine J. A. , Curtis R. F.
Published: May 2005

Examination of the mass spectra of several 3‐arylpropionic acids and methyl esters showed that one of the major fragmentation processes corresponded to the expulsion of a molecule of formic acid or methyl formate directly from the molecular ion.
Loss of carbon dioxide in the mass spectra of some partially fluorinated β‐diketonato iron chelates
Authors: Clobes A. L. , Morris M. L. , Koob R. D.
Published: May 2005

Evidence suggesting elimination of carbon dioxide as a decomposition path for tris(1‐phenyl‐4,4,4‐trifluoro‐1,3‐butandionato) iron (III) [Fe(btac)3] and tris (1‐thienyl‐4,4,4‐trifluoro‐1,3, butandionato) iron (III) [Fe(ttac)3] is presented and discussed. A mechanism is proposed for this reaction. Other examples of CO2 elimination are observed for substituted phenyl Fe(btac)3, tris(1‐cyclopropyl‐4,4,4‐trifluoro‐1,3‐butandionato) iron (III) and Co(III) (btac)3.
Studies of selenides of thiophene and furan series—V: Mass spectra of some thiophene, furan and selenophene derivatives
Authors: Chizhov O. S. , Zolotarev B. M. , Sukiasian A. N. , Litvinov V. P. , Gol'dfarb Ya. L.
Published: May 2005

Mass spectra of some selenides, sulphides and ethers of furan, thiophene and selenophene series are described. A new fragmentation reaction, consisting in splitting off alkyl, insertion of heteroatom in the cycle and loss of one of heteroatoms as CX, is discussed in detail.
Rearrangement ions—II: Mass spectra of the C‐13 labeled 2‐methyl‐2‐hydroxy‐propanes and 2‐methyl‐2‐aminopropanes
Authors: Siegel A. S.
Published: May 2005

The mass spectra of 2‐methyl‐2‐hydroxypropane (I) and 2‐methyl‐2‐aminopropane (II) exhibit fragment ions which suggest skeletal rearrangement processes. The C‐13 analogs of I and II, labeled in the 1‐ and 2‐positions, were prepared in order to determine the most probable mechanistic pathways for fragmentation. Label retentions in major fragment ions indicate that I and II decompose into common fragments through structurally similar intermediates.
The mass spectra of carboxylic acids–II: Fragmentation mechanisms in the homologous series HOOC(CH2)nCOOH
Authors: Holmes J. L. , St. Jean T.
Published: May 2005

The mass spectra of the homologous series of acids HOOC(CH2)nCOOH from n = 0 to 12 have been studied together with certain deuterium labeled members. The fragmentation mechanisms of the lower homologues are discussed in some detail. The loss of one or two molecules of water from the molecular ions was shown to proceed most favorably via a 6‐centred intermediate involving the methylene group β‐ to a carboxyl function. It was observed that the ease of carboxyl‐carboxyl interaction promoting CO2 elimination from the molecular ion could be simply correlated with n and thus serves as a structure‐identifying feature.
A cyclization reaction in the electron‐impact induced fragmentation of some N‐propargylic oxoquinazolines and anilines
Authors: Bogentoft Conny
Published: May 2005

Evidence for an acetylenic rearrangement, involving the ring‐closure of ions containing the N‐propargylaniline substructure to the corresponding quinoline ions, has been obtained in a study of the electron‐impact induced fragmentation of 1,4‐dihydro‐4‐oxo‐2‐phenyl‐1‐propargylquinazoline (I) and 1,2,3,4‐tetrahydro‐2‐oxo‐3‐phenyl‐1‐propargylquinazoline (II). The N‐propargylaniline moiety is formed from compounds I and II through the RDA process. N‐Methyl‐N‐propargylaniline (III), which was examined as a model compound, was also found to undergo this rearrangement but N‐methyl‐N‐propargyl‐2,6‐xylidine (IV), on the other hand, exhibits a quite different fragmentation pattern due to its blocking methyl groups, which prevent the rearrangement. Exact mass measurement and specific deuterium labelling were used to establish the fragmentation routes.
The mass spectra of some copper(II) complexes related to anti‐carcinogens
Authors: Warren Larry E. , Bursey Maurice M. , Hatfield William E.
Published: May 2005

Fragmentations of the molecular ions of three α‐diketone‐bis(thiosemicarbazone) complexes of copper (II) are tabulated and rationalized.
Mass spectrometry in structural and stereochemical problems—CC A study of the fragmentation processes of some pyrilium salts
Authors: Duffield A. M. , Djerassi Carl , Balaban Alexandru T.
Published: May 2005

The principal mode of fragmentation, at both 70 and 15 eV, of pyrilium iodides (I to V) which are substituted by at least one methyl group is the elimination of hydrogen iodide from the non‐detectable molecular ion. In contrast the mass spectrum (Fig. 6) of 2,4,6‐triphenyl pyrilium iodide (VI) shows its dominant fragmentation to be due to the loss of an iodine atom from the molecular ion. The mass spectra (for example Figs. 6 and 7) of 2,4,6‐triphenyl pyrilium iodide, bromide and tetrafluoroborate (VI, VII and VIII) are virtually identical except for the peaks corresponding to a molecule of iodine (m/e 254), hydrogen iodide (m/e 128) and iodine (m/e 127) in the mass spectrum (Fig. 6) of the iodide. Other fragmentation routes common to these pyrilium salts are described.
Studies on the syntheses of azole derivatives—V: The mass spectra of 1,2,4‐triazoles and oxadiazoles (studies on the syntheses of heterocyclic compounds—CCCLXXIV)
Authors: Kametani Tetsuji , Hirata Shoji , Shibuya Shiroshi , Shio Masahisa
Published: May 2005

The electron‐impact induced fragmentation of twenty 3‐alkyl‐1‐phenyl‐Δ2‐1,2,4‐triazolin‐5‐ones, three 1‐phenyl‐1,2,4‐triazolin‐3,5‐diones and ten 2‐alkyl‐4‐phenyloxadiazolin‐5‐ones has been studied by conventional mass spectrometry. The major cleavages take place in the 1‐phenyl‐Δ2‐1,2,4‐triazolin‐5‐one nucleus, producing three major fragment ions. 4‐Phenyloxadiazolin‐5‐ones exhibit a similar fragmentation pattern to 1‐phenyl‐Δ2‐1,2,4‐triazolin‐5‐ones. Furthermore, several additional fragmentation processes are observed in the case of specific 1,2,4‐triasolines.
Ion kinetic energy spectroscopy
Authors: Chait E. M. , Askew W. B.
Published: May 2005

Preliminary results indicate the value of ion kinetic energy (1KE) spectra in adding a new dimension to structural information obtained by mass spectrometry. These spectra are especially useful in the distinction of some isomer pairs. Energy spectra provide a summary of gaseous ion chemistry occurring as metastable transitions in the first‐field free‐drift region of the double‐focusing (Mattauch‐Herzog geometry) mass spectrometer and are produced by scanning the electrostatic sector voltage while recording the ions transmitted by the sector with the beam monitor electrometer.
Negative and positive mass spectra of some substituted trinitromethanes
Authors: Larkins John T. , Nicholson Jesse M. , Saalfeld Fred E.
Published: May 2005

The negative and positive ion mass spectra of a series of substituted trinitroalkanes (nitroform, tetranitro methane, methyl, fluoro, chloro, bromo and iodo‐trinitro methane) have been measured with an Aatlas CH‐4 Mass Spectrometer, under varying electron energies from 70 over the total range at which ions are produced. The modes of decomposition of the compounds are presented. A few metastable transitions are observable in the negative ion spectra, but only at high electron energies (ion pair region) and are very low in intensity. the negative and positive ion clastograms of these polynitro compounds showed little parent‐daughter ion correlation. Finally, the negative ions formed appear to contain excess amounts of kinetic energy even at low electron energies; as a retult there is a great deal of overlap in the various mechanisms for the formation of negative ions.
Mass spectra of bis‐π‐allylic‐palladium halides
Authors: Lammens H. , Sartori G.
Published: May 2005

The mass spectral fragmentation of (π‐allyl‐PdCl)2, (π‐methallyl‐PdCl)2, (π‐crotyl‐PdCl)2 and (π‐allyl‐PdBr)2, (π‐methallyl‐PdBr)2, (π‐crotyl‐PdBr)2 are described and discussed.

It is shown that the breakdown of these complexes after ionization depends on the nature of the groups attached to the metal.
Mass spectra of some steroidal acetals
Authors: Waight E. S. , Herz J. E. , Santoyo Yolanda
Published: May 2005

Some steroidal methoxymethyl ethers exhibit intense molecular ions upon electron‐impact.
Studies in organic mass spectrometry—II
Authors: Ikeda M. , Tsujimoto N. , Tamura Y.
Published: May 2005

The mass spectra of various N‐aryliminopyridinium and isoquinolinium betaines have been recorded. The most prominent fragmentation process of these compounds is N‐N bond cleavage with the charge retention on both the pyridine and aryl fragments. An ortho‐effect has been observed in the mass spectrum of N‐o‐nitrophenyliminopyridinium betaine (IXa).
Energy and substituent effects on the mass spectra of substituted benzophenones
Authors: Einolf Noel , Munson Burnaby
Published: May 2005

For two competing decompositions of the same molecular ion to give products [A1+] and [A2+], the ratio [A1+]/[A2+], is equal to the ratio of rate constants for the formation of the stable ions. Thr ratios, [Y C7H4O+]/[C7H5O+], were determined for several benzophenones for electron energies from 15 to 70 eV. Plots of log [Y C7H4O+]/[C7H5O+] vs.[ω+] gave good straight lines at all energies. Similar correlations have been reported for log [Y C7H6+]/[C7H7+] from substituted diphenyl ethanes and are also true for substituted acetophenones, log [YøCO+]/[CH3CO+]. A few charge exchange data were obtained which showed the same general trend as the electron‐impact data and emphasize the contribution of low energy ions in the 70 eV mass spectra. Relatively poor correlations were obtained for the [Y C6H4+] and [C6H5+] ions that are formed by both one‐step and two‐step decompositions.
Oberflächenreaktionen bei der Feldionisierung von Aldehyden und Nitrilen
Authors: Migahed M. D. , Beckey H. D.
Published: May 2005

Oberflächenreaktionen von Aldehyden und Nitrilen bei hoher elektrischer Feldstärke wurden rnassenspektrometrisch untersucht. Einige allgemeine Erscheinungen werden für den Fall von Oberflächenreaktionen von Crotonaldehyd aufgezeigt. Die Feldionisations Massenspektren (FI) polarer Substanzen hängen stark davon ab, ob die organischen Mikronadeln auf dem FI‐Emitter eine dichte oder eine poröse Struktur hahen. Protonentransfer‐Reaktionen werden mit den meisten polaren Substanzen beobachtet. Sie können reduziert werden, wenn die Emitteroberfläche mit einer stark adsorbierten Substanz bedeckt wird, die nicht mit der polaren Substanz reagiert. Die ursprünglich dichte Struktur der Mikronadel kann sich zu einer porösen Struktur wandeln. Die FI‐Massenspektren polarer Substanzen können sich dann im Laufe der Zeit wegen Kapillarkondensation oder der Bildung von Multischichten drastisch verändern.

Die Erhöhung der Emittertemperatur verringert die Intensität der Fragment‐ und dimeren Ionen der polaren Substanzen, die Multischichten auf der Emitteroberfläche bilden. Thermische Desorption der Multischichten verringert die Anzahl der in ihnen vorkommenden Reaktionen. Selbst bei hohen Temperaturen (750° C) ist die Reduzierung von Fragmentintensitäten infolge des Abbaus der Multischichten ausgeprägter als diezunahmevon Fragmentintensitäten infolge thermischer Bindungsbrüche, vorausgesetzt daß das C, N, O‐Gerüst der Moleküle entweder aus starken Bindungen, wie konjugierten Doppelbindungen zusammengesetzt ist, oder da13 es eine zyklische Striktur hat.

Es wird gezeigt, daß die FI‐Massenspektren der Benzonitrile wesentlich einfacher sind als die einiger aliphatischer Nitrile, und daß die Mechanismen der Feldpolyrnerisation in beiden Fällen verschieden sind.
Carbon‐nitrogen bond cleavage provoked by hydrogen rearrangement: The fragmentation of N‐acetylpyrrolidine and homologues
Authors: Richter W. J. , Tesarek J. M. , Burlingame A. L.
Published: May 2005

Carbon‐nitrogen bond cleavage provoked by hydrogen rearrangement in molecular ions is reflected in several prominent features of the fragmentation of acylated cyclic amines, notably N‐acetylpyrrolidine. Contrary to the behavior of the free amine, the positional origin of the atoms involved in the ejection of ethylene from the molecular ion of the acetyl derivative reveals participation of an α‐carbon atom, i.e. a carbon atom directly attached to nitrogen. Abstraction of hydrogen from the α‐position of the ring moiety by the acyl substituent is proposed as initiating the over‐all process. The analogous behavior of systems incorporating larger rings or extended acyl substituents (N‐acetylpiperidine, N‐acetylhexamethyleneimine, N‐propionylpyrrolidine and N‐n‐butyrylpyrrolidine) lends support to the general applicability of this mechanistic rationale.
Mass fragmentation and structure of siphonaxanthin, siphonein and derivatives
Authors: Strain H. H. , Svec W. A. , Aitzetmüller K. , Cope B. T. , Harkness A. L. , Katz J. J.
Published: May 2005

High resolution mass spectrometry has been employed to establish the structural formulae of the unique carotenoid pigment siphonaxanthin, its natural ester, siphonein and several derivatives. Siphonaxanthin exhibits a fragmentation reaction that is unusual among carotenoid pigments, namely, the elimination of carbon dioxide, observed as [M ‐ CO2] and [M ‐ (CO2 + H2O)]. This reaction involves the migration of an oxygen atom. Siphonaxanthol, a partially hydrogenated siphonaxanthin, exhibits a similar reaction involving the elimination of carbon monoxide and formaldehyde. From the fragmentation of derivatives of siphonaxanthin, such as the triacetate, the dimethyl ether and siphonaxanthol, and also from the fragmentation of related pigments, such as loroxanthin and fucoxanthin, the unique structural units responsible for the elimination of the carbon dioxide and carbon monoxide have been identified.
Vapor phase bimolecular reactions of alkyl siliconium and other metal ions in mass spectrometry
Authors: Harvey D. J. , Horning M. G. , Vouros Paul
Published: May 2005

The vapor phase reactions of various metal alkyl and alkoxy ions are discussed. Ions produced from suitable precursors can react with neutral molecules which contain an electronegative site. It appears that ions containing a positively charged silicon, tin, germanium or mercury center are more reactive than corresponding carbonium ions.
The mass spectrum of 1:12, 2:3, 4:5, 6:7, 8:9, 10:11‐hexabenzocoronene
Authors: Reed R. I. , Tennent A.
Published: May 2005

The mass‐spectra of 1:12, 2:3, 4:5, 6:7, 8:9, 10:11‐hexabenzocoronene and the isomer 1:2, 3:4, 5:6, 7:8, 9:10, 11:12‐hexabenzocoronene have been examined. The former is typically that of an aromatic conjugated hydrocarbon and is sparse, the latter is more intense. It is conjectured that the former may be found in interstellar space.
Mass spectra of partially fluorinated β‐diketonato complexes of Al(III), Cr(III), Fe(III) and Co(III)
Authors: Clobes A. L. , Morris M. L. , Koob R. D.
Published: May 2005

The mass spectra of the Al(III), Cr(III), Fe(III) and Co(III) complexes of the anions of hexafluoroacetylacetone (hfac) trifluoroacetylacetone (ttac), benzoyltrifluoroacetone (btac) and thenoyltrifluoroacetone (ttac) have been determined and are discussed here. Emphasis is placed on discerning which of the observed reactions may properly be attributed to the influence of the metal in the complex and those which may be thought of as arising from the nature of the ligand. The most important influence of the coordinated metal is related to its ability to be reduced2; however, the presence of the metal serves to prohibit or facilitate certain rearrangement reactions relative to the free protonated ligand. Since essentially all fragmentation occurs within or by loss of a ligand, the nature of the ligand determines the nature of the observed fragments. Where intramolecular com‐petition of fragment types is possible (tfac, btac and ttac complexes), the most probable fragment of a given class, odd electron or even electron, is easily determined. The most commonly eliminated fragments are CF3and CF2. Certain metastable peaks are associated with consecutive decomposition in the field free region. Such a phenomenon appears to be common for molecules of the type studied here.
A study of the fragmentation of caprolactam and its methyl derivatives under electron‐impact
Authors: Mitera J. , Kubelka V.
Published: May 2005

A study of the low and high‐resolution mass spectra of caprolactam (I), 1‐methylcaprolactam (II), 3‐methylcaprolactam (III), 4‐methylcaprolactam (IV), 5‐methylcaprolactam (V), 6‐methylcaprolactam (VI), 7‐methylcaprolactam (VII) and deuterium labelled compounds has facilitated the proposal of some principal fragmentation mechanisms of ionized molecules of these compounds.

The base peaks in the spectra of all compounds studied (except 3‐methylcaprolactam) are the ions m/e 30 and m/e 44 respectively formed through the cleavage of the C6–C7 bond and the C2–N bond with simultaneous transfer of a hydrogen atom.

It has been proved that the fragmentation of molecular ions leading to ions with the structure of cyclopentanone 2‐methylcyclopentanone and 3‐methylcyclopentanone respectively (according to the position of methyl group) is the general feature of the fragmentation of caprolactam and its methyl derivatives.
The characteristics of oxime ethers upon electron‐impact
Authors: Graham Cooks R. , Varvoglis A. G.
Published: May 2005

The O‐methyl ethers of aromatic and aliphatic aldoximes and ketoximes are characterized by hydrogen and skeletal rearrangements involving four‐membered cyclic transition states. In the aliphatic compounds, four‐centered rearrangement sometimes yields the species with the higher ionization potential, in contradiction of Audier's rule. The n‐propyl oxime ethers show a novel skeletal rearrangement involving CH2O elimination. The [M—H]+ process in the aromatic aldoxime ethers and an [M—Cl]+ process in an o‐chloro derivative involve atom elimination by intramolecular aromatic substitution. Aromatic aldoxime ethers and the isomeric nitrones behave completely differently upon electron‐impact.
Rearrangement in the mass spectrometer via a 3,3,1‐bicyclic reaction path
Authors: Breuer S. W. , Gladstone W. A. F. , Hirst P. A.
Published: May 2005

The fragmentation of some azoacylals showed a 3,3,1 bicyclic rearrangement which could be demonstrated by a deuterium labelling study.
The loss of CO and HCN in the fragmentation of isatin and the methyl isatins
Authors: Butcher M.
Published: May 2005

3‐13C‐Isatin has been shown to eliminate the 2‐carbonyl group as the initial fragment, followed predominantly by loss of HCN. In 4‐, 5‐and 6‐methyl‐isatin the loss of the second carbonyl group competes evenly with HCN loss, whilst the 7‐methyl isomer fragments almost exclusively by successive loss of two molecules of CO from the molecular ion.
Properties and reactions of 1,3‐oxathianes—II: Mass spectra of 1,3‐oxathiane and its alkyl derivatives
Authors: Pihlaja Kalevi , Pasanen Paavo
Published: May 2005

The mass spectral fragmentation patterns of 1,3‐oxathiane and several of its alkyl derivatives have been recorded. Of the nine possible modes of ring cleavage yielding fragments containing two to four atoms, only six modes were actually observed and, moreover, two of them clearly predominated. The modes of fragmentation of 1,3‐oxathianes differ from those of 1,3‐dioxanes, but resemble closely those observed for 1,3‐oxathiolanes when the different ring sizes are taken into account.
Electron‐impact studies—LXIV: Negative‐ion mass spectrometry of functional groups. Nitroaniline derivatives
Authors: Bowie J. H. , Blumenthal T. , Walsh I.
Published: May 2005

The various fragmentations of the o‐nitrobenzanilide molecular anion have been studied by labelling procedures and substituent effects. The loss of HO· from the molecular anion is a specific proximity effect, involving the oxygen of the nitro group and the hydrogen of the amide moiety. The losses of NO· from variously substituted nitrobenzenes are considered in depth and it is suggested that the nitro→ nitrite rearrangement is a radical reaction. Negative‐ion mass spectrometry may be used for the structure determination of sulphonamides and nitrophenylhydrazones.
Massenspektrometrie und ihre anwendun auf strukturelle und stereochemische Probleme—CCVI: Beobachtungen bei der Fragmentierung Olefinischer Kohlenwasserstoffe
Authors: Mayer Klaus K. , Djerassi Carl
Published: May 2005

Bei Olefinen der allgemeinen Struktur I, II und III erleidet das unter Elektronenbeschuss erzeugte Molekülion neben der als Hauptreaktion ablaufenden McLafferty‐Umlagerung auch bei milden Anregungsbedingungen eine vor der Fragmentierung eintretende Isomerisierung.

Es wurde versucht, Herkunft und Entstehungsweg eines sowohl beim Abbau des Molekülions als auch des McLafferty‐Ions gebildeten gemeinsamen Bruchstückes mit Hilfe von 13C‐ und D‐Markierung zu klären.

Der Einfluss einer Verzweigungstelle in γ‐, ω‐ oder ϵ‐Position zur Doppelbindung bei Olefinen vom Typ I auf deren Verhalten im Massenspektrometer wurde untersucht.
General aspects of the mass spectra of some benzyloxyalkyl substituted purine and pyrimidine nucleoside analogues; A demonstration of the concept of charge localization
Authors: Grose W. F. A. , Eggelte T. A. , Nibbering N. M. M.
Published: May 2005

The molecular ions of the title compounds appear to lose a molecule of benzaldehyde or a benzyl radical. The first reaction is followed by the elimination of a second molecule of benzaldehyde, the second reaction by either the expulsion of a molecule of benzaldehyde or a molecule of benzylalcohol. These degradations can be readily explained by assuming charge localization in the purine or pyrimidine part of the molecular ions. For the successive loss of a benzyl radical and of a molecule of benzaldehyde from the molecular ions, however, charge localization at one of the ether oxygen atoms may also be responsible to some extent, as demonstrated by the mass spectrum of 1,3‐dibenzyloxy‐2‐ethylpropane.
Fluorinated carbohydrates—X: The mass spectra of acetylated deoxyfluoro‐D‐glucitols
Authors: Adamson J. , Barford A. D. , Bessell E. M. , Foster A. B. , Jarman M. , Westwood J. H.
Published: May 2005

The deoxyfluoro‐D‐glucopyranoses with the fluorine substituent severally at positions 6, 4, 3 and 2 were converted into the corresponding deoxyfluoro‐D‐glucitol pentaacetates (I to IV) and their 1‐deuterated analogues (V to VIII). The mass spectra of these derivatives were rationalised in terms of the position of the fluorine substituent on the carbon chain.
Collection de fragments organiques a l'aide d'un separateur d'isotopes
Authors: Lageot Claude
Published: May 2005

Après modification, nous avons pu déposer une quantité pondérable de matière organique sur le collecteur d'un séparateur d'isotopes.
Spectrometrie de masse, problemes de structure et de stereochimie—CCVII Fragmentations des Ethers Insatures
Authors: Morizur Jean‐Pierre , Djerassi Carl
Published: May 2005

En liaison avec I'accumulation de données pour I'interprétation automatique des spectres de masse des composés organiques le comportement des éthers insaturés est examiné. Trois groupes ont été étudiés: allylique, allylique substitué et éthers possédant 2 ou 3 groupes méthylènes entre la double liaison et I'atome d'oxygène. Un total de 36 composés dont 11 dérivés deutériés ont été préparés et leurs principales voies de dégradation rationalisées. I1 est montré que les éthers allyliques s'isomérisent aprés l'ionisation en éthers vinyliques, alors qu'aucune migration de la double liaison soit avant soit après l'impact électronique n'est observée entre les éthers allyliques, homoallyliques et ceux ayant 3 groupes méthylènes entre la double liaison et I'atome d'oxygène. Quand la chaîne saturée a au moins sept atomes de carbone les éthers allyliques expulsent une molécule d'alcool saturé [R' + C3H6OH] faisant intervenir un quadruple transfert d'hydrogène avant la fragmentation.
Feldionen‐Massenspektren von Kohlenhydraten
Authors: Krone H. , Beckey H. D.
Published: May 2005

Mit Hilfe der Feldionisation wurde die Massenanalyse von Mono‐ und Oligosacchariden durchgeführt. Die FI‐Spektren

FI wird als Abkürzung für Feldionisation und ES für Elektronenstoß‐Ionisation benutzt.

unsubstituierter Monosaccharide zeigtren zwar alle einen intensiven Peak auf der MZ [M + 1], eignen sich aber wegen der thermischen Labilität nur schlecht für Strukturanalysen. Im Hinblick auf Oligosaccharide ist eine Permethylierung für die Aufnahme von FI‐Massenspektren vorteilhaft. Permethylierte Disaccharide, die über C‐1—C‐4 bzw. über C‐1—C‐6 verknüpft sind, zeigten charakteristische Unterschiede in den Fragment‐Ionenintensitäten. Dagegen lassen sich aus dem FI‐Spektrum der permethylierten Raffinose nicht alle Verknüpfungsarten entnehmen. Für zukünftige Untersuchungen thermisch labiler Substanzen eignet sich die Felddesorptionsmethode besser als die Methode der Probenverdampfung aus einem Ofen mit anschließender Feldionisation.
Modification of a double focusing mass spectrometer for the observation of metastable ions decaying in two field‐free regions
Authors: Hills L. P. , Futrell J. H.
Published: May 2005

The occurrence of ‘metastable’ ions formed in the ion source as one species decays to a lower mass ion prior to mass analysis provides direct evidence for dissociation mechanisms in organic mass spectra. Both unimolecular and collision‐induced decay processes provide useful information on available dissociation pathways, ion structures, and energetics. In double‐focusing mass spectrom‐eters the existence of two field‐free regions presents a convenient vehicle for studying these processes and for obtaining kinetic information on consecutive metastables through simple modification in circuitry and operating conditions. These modifications are described and the method is used to demonstrate consecutive metastable decay processes in acetyl acetone, 1‐butene, toluene and alumin‐um hexafluoroacetylacetonate. Drift tube pressure studies showed that, within experimental error, consecutive metastables observed in acetyl acetone and 1‐butene were collision‐induced, while toluene and the aluminum chelate both exhibit two‐step unimolecular decays.
Oligosaccharide sequencing by means of mass spectrometry—I: N‐phenylosotriazole acetates
Authors: Chizhov O. S. , Kochetkov N. K. , Malysheva N. N. , Shiyonok A. I. , Chashchin V. L.
Published: May 2005

Fragmentation of the acetates of the N‐phenylosotriazoles of some mono‐, di, tri‐, tetra‐ and pentasaccharides under electron‐impact (EI) has been studied. The mass spectra of these derivatives can be used for determination of the sequence of monosaccharide units in oligosaccharides (oligosaccharide sequencing), of molecular weight, of the location of the position of the interglycosidic bond in disaccharides and of the position of the methyl group in partially methylated monosaccharides.
Electron‐impact and molecular dissociation—XX: Some studies on the indolosteranes
Authors: Harvey D. J. , Laurie W. A. , Reed R. I.
Published: May 2005

The mass spectra of a series of indolosteranes have been obtained in order to investigate whether or not such a method may prove a diagnostic tool in determining structure. While differences are revealed they are sometimes too slight for this purpose. An interesting observation made here is that in the fragmentation pattern those ions which contain the indole grouping usually predominate.
The chemistry of hexahydro‐1,2,4,5‐tetrazines—II: Mass spectra of 1,4‐dialkylhexahydro‐1,2,4,5‐tetrazines and 1,4‐dialkyl‐2,5‐diacylhexahydro‐1,2,4,5‐tetrazines
Authors: Hammerum Steen , Møller Jørgen
Published: May 2005

The mass spectra of twenty‐eight 1,4‐dialkylhexahydro‐1,2,4,5‐tetrazines and 1,4‐dialkyl‐2,5‐diacylhexahydro‐1,2,4,5‐tetrazines (1) have been recorded and interpreted with the aid of deu‐terium labelling, high resolution measurements, and the metastable defocusing technique. The principal fragmentations involve initial scission of ring bonds, particularly C‐N bonds, leading to characteristic ions of mass M/2 and M/2± 1, and to 2,3‐diaza‐1,3‐butadienyl ions (II). In the spectra of acylated compounds, acyl migration occurs within the molecular ion. The elimination of formaldehyde from the principal fragment ion is discussed.
Electron‐impact induced rearrangements of substituted biphenyls
Authors: Safe S.
Published: May 2005

The electron‐impact induced rearrangements of halobiphenyls show substituent equilibration in the molecular ion for the chloro, bromo and iodo isomers. The above halo compounds as well as the fluoro, methyl and methoxybiphenyls all show considerable H/D randomization in the molecular ion or some subsequent decomposition ion.
Mass spectra of macrolide antibiotics. The utility of the N‐oxide derivatives in enhancing fragmentation of the non‐sugar portion of basic antibiotics
Authors: Mitscher L. A. , Foltz R. L. , Levenberg M. I.
Published: May 2005

Fragmentation of macrolide antibiotics containing amino sugar moieties in the mass spectrometer provides limited structural information because amino sugar fragmentation dominates the spectrum. Formation of the N‐oxide derivative suppresses these processes and allows the non‐sugar portion to make a more substantial contribution to the spectrum. The N‐oxide may be formed in situ.
Spectrographie de masse en série du bornane—II: Amino‐bornanols et dérivés
Authors: Daniel Alfred , Pavia Andrè Armand
Published: May 2005

Les auteurs ont étudié les spectres de masse d'un grand nombre d'amino‐bornanols et dérivés et leurs oxazolidines. Une étude comparative des fragments obtenus selon la position de l'amine montre que la rupture entre les carbones 2 et 3 porteurs des substituants reste primordiale aussi bien pour les amino‐2 que pour les amino ‐3 bornanols.

L'étude des spectres des oxazolidines et des amino‐alcools, montre que, si dans les premiers la charge semble être également répartie entre les deux hétéroatomes, N et 0, il n'en est pas ainsi dans les amino‐alcools ou l'azote porte préférentiellement la charge.

Enfin, si la spectrographie de masse ne semble pas d'une grande utilité pour l'etude de la stéréoisomérie, elle se révèle un moyen de choix pour préciser l'isomérie deposition dans ce type de composé.
Mass spectrometric investigation of bimolecular compounds
Authors: Heunisch George W. , Keen Gary W.
Published: May 2005

Two points involving molecular structure have been investigated using mass spectrometry. First, mass spectra have been obtained that indicate a rapid means for differentiating bimolecular compounds from other structural isomers. Second, the mass spectrometric method has been used to evaluate bonding within bimolecular compounds. Quinone compounds have been reacted with dhydroxybenzene compounds to produce quinhydrone products, and upon mass spectrometric analysis, the quinhydrones decompose to regenerate derivatives of the starting materials. Evaluation of the decomposition products suggests that the hydroxyl hydrogens are involved in a resonance structure, and while in symmetrical quinhydrones, the hydroxyl hydrogens are probably associated equally with each reactant, unsymmetrical quinhydrones generate an unbalanced electronic distribution that eliminates the complete equivalency of the hydrogens.
Mass spectrometric studies on platinum (II) complexes
Authors: Chan T. H. , Wong E.
Published: May 2005

Several platinum(I1) complexes were subjected to mass spectrometric investigation. The major fragmentation pathways for dichloro‐bis(phosphine) platinum(II) were elucidated to be: (i) successive loss of hydrogen chloride or chlorine depending on the structure of the phosphine, (ii) cleavage of P–R bond with the loss of R group, (iii) the presence of [R1R2R3P—Cl]+ in the mass spectra and (iv) fragmentation of the free phosphine.
Factors determining relative ionic abundances in competing fragmentation reactions
Authors: Harrison A. G. , Finney C. D. , Sherk J. A.
Published: May 2005

For the competing fragmentation reactions [la] and [Ib], it is shown that the relative abundances of [R1]+
magnified image
and [R1]+ are determined by the relative values of the ionization potentials of the corresponding free radicals R1. and R2. In most cases the appearance potentials of [R]+ from RH follow the trends shown by the radical ionization potentials with the result that the appearance potentials can be used to correlate relative ionic abundances. The potential usefulness of relative abundances to estimate radical ionization potentials is illustrated.
Mass spectra and thermochemistry of methyl phenanthrenes. A contribution to the analogy between mass spectral and thermal fragmentation reactions
Authors: Dougherty Ralph C. , Bertorello Héctor E. , de Bertorello M. Martínez
Published: May 2005

The mass spectra of both nonhindered and sterically hindered methyl phenanthrene derivatives follow the patterns established for other alkyl aromatics. The ‘unimolecular’ thermochemistry of these systems parallels the mass spectral fragmentation in a qualitatively predictable way. Generally the major thermochemical products correspond to one of the five most intense fragment ions, and the importance of products which correspond to ions with high appearance potentials increases with increasing temperature of the thermolysis system. On the basis of this empiricism we have outlined a tentative procedure for anticipating the results of thermolysis experiments based on mass spectral data. The use of appearance potential differences to estimate steric strain energies in the compounds studied did not give satisfactory results.
The mass spectra of isomeric hydrocarbons—I: Norbornene and nortricyclene; The mechanisms and energetics of their fragmentations
Authors: Holmes J. L. , McGillivray D.
Published: May 2005

The mass spectra of norbornene, nortricyclene and deuterium labeled derivatives thereof have been studied. The appearance potentials of the ions [C7H10]+·, [C7H9]+, [C6H7]+ and [C5H6]+· have been determined for both compounds and heats of formation of the hydrocarbons have been estimated. Detailed fragmentation schemes are proposed for the molecular ions and it is concluded that they dissociate by essentially different mechanisms which do not involve common intermediates. The structures and energy contents of the primary fragment ions are discussed in detail by comparing energetics, labeling experiments and metastable ion abundances.
Charge exchange spectra of simple ketones
Authors: Turk Jonathan , Shapiro Robert H.
Published: May 2005

Charge exchange spectra of three simple 2‐ketones are reported. Comparison of charge exchange data with low voltage electron‐impact spectra provides information on the nature of the electron‐impact energy distribution. The existence of high energy molecular ions which do not decompose in the mass spectral time scale led us to postulate that isolated states or photon emission reactions are operative in the present system.
Loss of CH2O and H2O by stepwise mechanisms in mass spectrometry
Authors: Lacey M. J. , Macdonald C. G. , Shannon J. S.
Published: May 2005

Experimental evidence demonstrating reversible hydrogen transfer between specific positions in the molecular ions of anisole and o‐toluic acid suggests stepwise mechanisms for the loss of CH2O and H2O, respectively. Added support for a stepwise mechanism for the loss of CH2O is found in the mass spectra of pyridine and quinoline analogues.
Carbon skeletal rearrangements in 2‐phenylthiophene and 2,5‐diphenylthiophene under conditions of electron‐impact
Authors: Weringa W. D. , Sinnige H. J. M. , Janssen Matthijs J.
Published: May 2005

The mass spectra of 13C‐labelled 2‐phenylthiophenes and 2,5‐diphenylthiophenes were studied. The label distributions for the [HCS]+, [C2H2S]+·, [C8H6]+·, [C9H7]+ and [C7H5]S+ ions from 2‐phenylthiophene and the [HCS]+, [C9H7]+, [C7H5S]+·, and [C15H11]+ ions from 2,5‐diphenylthiophene were interpreted in terms of both carbon skeletal rearrangements in the thiophene ring and migration of the phenyl substituent. The degree of carbon scrambling in the thiophene ring appeared to be almost independent of the electron beam energy. The formation of some of the fragment ions studied seems to be so fast that no carbon scrambling could be detected at all; in neither case was complete scrambling of the carbon atoms of the thiophene ring observed.
Heterocyclic studies—XXV: Mass spectra of some 4‐trifluoromethylpteridine derivatives
Authors: Clark Jim , Yates F. S.
Published: May 2005

Mass spectra of 4‐trifluoromethylpteridine and nine of its derivatives are recorded. Electron impact induced fragmentations of 4‐trifluoromethylpteridine and its 2‐chloro‐, 7‐methyl‐ and 6, 7‐dimethyl‐derivatives resemble those of pteridine and simple methylpteridines except that loss of a trifluoromethyl radical usually intervenes at some stage. Fragmentation of 4‐trifluoromethyl‐pteridine derivatives with an amino, substituted‐amino, alkoxy or alkylthio group in the 2‐position fragment by a variety of mechanisms. Accurate mass measurements and deuterium labelling were used to help elucidate some fragmentation pathways.
Mass spectra of staphylomycin S components and of related cyclodepsipeptide antibiotics
Authors: Compernolle F. , Vanderhaeghe H. , Janssen G.
Published: May 2005

The electron‐impact induced fragmentation of staphylomycin S (I) and related cyclodepsipeptides (II to V) is mainly initiated by elimination of an azomethin molecule (RCHNR′), i.e. 1,2‐dehydro‐4‐oxopiperidine for I and II, 1,2‐dehydro‐4‐hydroxy‐piperidine for III and IV, and an unknown hydroxy‐1,2‐dehydro‐4‐oxopiperidine for VI. Cyclic imino acids, e.g. a pipecolic acid derivative for I to IV and 4‐hydroxyproline for etamycin (IX) preferentially trigger this reaction. Clearcut evidence for the amino acid sequence is given by the mass spectra of the linear peptides obtained from I, V and IX by alkaline hydrolysis of the lactone function and esterification of the carboxy group.
A comparative study of the mass spectra of stilbene and fluorene
Authors: Güsten H. , Klasinc L. , Marsel J. , Milivojević D.
Published: May 2005

A comparative study of metastable peaks formed in the first field free region during the fragmentation of stilbene and fluorene indicates that [M — 1] ion of fluorene and the [M — 15] ion of stilbene have a common [C13H9]+ (m/e 165) ion to only 75%. Demethylation of the stilbene cation leads to some extent to a more reactive [C13H9]+ species with a different structure.
The electron‐impact‐induced fragmentation of some methylated histamines
Authors: Dawborne J. S.
Published: May 2005

The mass spectra of twelve mono‐, di‐ and tri‐methyl substituted histamines are reported and discussed. It is shown that the position(s) of substitution may be deduced from a study of the fragmentation pattern, relative intensity and metastable ions allowing unambiguous identification of structure.
Massenspektroskopische Fragmentierungsreaktionen—II: Ein den ‘Ortho‐Effekt’ vortäuschender Zerfall von Diphenylmethanderivaten
Authors: Budzikiewicz H. , Rullkötter J. , Schiebel H. M.
Published: May 2005

Es ist i.a. nicht möglich, zwischen Diphenylmethan‐Derivaten (und analogen Verbindungen), die in o‐Stellung zur CH2‐Brücke substituiert sind, und inren m‐ und P‐Isomeren nur auf Grund des ‘ortho‐Effektes’ zu unterscheiden. Eine Erklärung für dieses scheinbar anomale Verhalten wird gegeben.
Studies in chemical ionization mass spectrometry: Aryl Ketones
Authors: Michnowicz J. , Munson B.
Published: May 2005

The CI mass spectra of aryl ketones, πCOR, were studied and found to give primarily [M + 29]+, [M + 1]+, [M − 1]+, [πCO]+ and [RCO]+ ions. The major change in the spectra with increasing length of the aliphatic side chain was an increase in the [M − 1]+/[M + 1]+ ratio. Increasing sample size was reflected primarily in the formation of [2M + 1]+ ions and a decrease in [M + 1]+ ions. Small amounts of water in the reactant gas reduced the extent of fragmentation action.
The mass spectra of some naturally‐occurring 3,4‐dialkoxy furocoumarins and their nor‐derivatives
Authors: MacLeod J. K. , Nakayama M.
Published: May 2005

The mass spectral fragmentations of several naturally‐occurring 3,4‐dialkoxy furocoumarins from the Halfordia species and their nor‐derivatives have been studied using deuterium labelling and metastable analysis. Halfordin (I), isohalfordin (VI) and halkendin (X) show a common major breakdown pathway involving initial loss of a methyl radical from the 3‐methoxy group followed by expulsion of CO, then loss of C2H3O, the latter fragment containing the methyl group from the 4‐position.
Electron impact studies—LXVII. The mass spectra of alkyl‐1,3‐dithianes
Authors: Bowie J. H. , White P. Y.
Published: May 2005

The mass spectra of 1,3‐dithiane, 2‐methyl‐ and 2,2‐dimethyl‐1,3‐dithiane have been studied by 2H labelling and metastable defocusing. The various molecular ions eliminate S2H. to produce the ions [C4H7]+, [C5H9]+ and [C6H11]+ respectively, each of which scramble the hydrogens either before or accompanying further decomposition. Other processes are complex, but parallel those already reported for 2‐aryl‐1,3‐dithianes.
Electron‐impact and thermal fragmentation patterns of some cyclic fluoroethers
Authors: Cotter J. L.
Published: May 2005

The mass spectra of cyclic fluoroethers of the general formula magnified image (n = 1 to 4) are reported and discussed. Although these spectra show many similar features, those for which n = 3 and 4 contain intense peaks at m/e 63 which are only of relatively low intensity in the spectra of the other two.

A similarity between the electron‐impact and thermal fragmentation patterns of these compounds is noted.
GLC—MS studies of sulphonamides
Authors: Blessington B.
Published: May 2005

Peralkylation of a series of sulphonamides, including clinically important diuretics, is described. G.l.c. analysis, and g.l.c.‐m.s. characterisation of the products is detailed.
Ionization and dissociation of some perfluoroalkylene‐linked silanes and cyclic siloxanes under electron‐impact
Authors: Cotter J. L.
Published: May 2005

The mass spectra of two silanes and two cyclic siloxanes of the general formulae HSi(CH3)2‐C6H4(CF2)nC6H4(CH3)2SiH and magnified image (n = 2 and 3) are reported and discussed. Although some major differences are apparent between the spectra of the two silanes, the fragmentation patterns of the cyclic siloxanes are largely identical.
Heterocyclic studies—XXVIII Mass spectra of some 5‐trifluoromethylpyrimido‐(5,4‐e)as‐triazines
Authors: Clark Jim
Published: May 2005

Fragmentation of 7‐substituted 5‐trifluoromethylpyrimido(5,4‐e)as‐triazines is dominated by consecutive losses of N2 and HCN from the triazine ring. Deuterium labelling, accurate mass measurements and spectral changes with substitution patterns confirm the fragmentation pathways.

Comparison of the spectra with those of corresponding pteridines indicates that the 1,2,4‐triazine ring fragments much more readily than the pyrazine ring.
Electron‐impact‐induced ion fragmentation of polyfunctional N‐cyclohexylcarbamates
Authors: Schildcrout Steven M. , Gebelein Charles G.
Published: May 2005

Mass spectra at 70, 15 and 10 eV are reported for methyl N‐cyclohexylcarbamate, methyl N‐trans‐2‐iodocyclohexylcarbamate, allyl N‐cyclohexylcarbamate and allyl N‐trans‐2‐iodocyclo‐hexylcarbamate. Principal modes of ion fragmentation including hydrogen and skeletal rearrangements are discussed in terms of individual functional groups and their interaction, and are consistent in many cases with mechanisms previously proposed for other compounds. The effects of the iodo and the allyl groups, when present, predominate in the spectra. The application of McLafferty's ‘active site’ concept to these polyfunctional compounds is found to be useful.
Thermally and electron‐impact‐induced rearrangements of dimethylthioncarbamates in gaseous phase
Authors: Tou James C. , Rodia R. M.
Published: May 2005

The thermally and electron‐impact‐induced rearrangements of the dimethylthioncarbamates to the dimethylthiolcarbamates are discussed. Owing to the competition with the ion fragmentation reactions in the mass spectrometric time, < 10−6 seconds, the extent of the mass spectrometrically observed ion isomerization cannot be predicted from that of the thermal induced one. In the ion fragmentations of the non‐rearranged molecular ions, it was found that the relative abundance of the ion (CH3)2NCO⊕ to the total ionization is larger than that of the ion (CH3)2NCS⊕. This is believed to be attributable to the differences in the dissociation energies of the CS bond and the CO bond and in the stabilities of the two ions.
Mass spectrometric determination of the configuration of 2‐methyl‐and 1,2‐dimethyl‐4‐vinyl‐ethinyl(n‐butyl)‐4‐hydroxyperhydroquinolines
Authors: Wulfson N. S. , Bakaev A. A. , Zaikin V. G. , Akhrem A. A. , Ukhova L. I. , Marochkin A. P. , Bludova G. V.
Published: May 2005

The configuration at C‐2 and C‐4 in the molecules of 2‐methyl‐ and 1,2‐dimethyl‐4‐vinylethinyl(n‐butyl)‐4‐hydroxyperhydroquinolines was determined by mass spectrometry. The principal conclusions concerning the stereochemistry were made on the basis of differences in the values of the I[M−15]+/I[M]+·, I[M−17]+/I[M]+·, I[M−43]+/I[M]+· and I[M−57]+/I[M]+· ratios in the mass spectra of the epimeric vinylethinylic alcohols, and of the I[M−15]+/I[M]+· and I[M−15]+/I[M]+· ratios in the case of the n‐butylic alcohols.
Mass spectra of some steroidal diols
Authors: Wyllie S. G.
Published: May 2005

The mass spectral fragmentations of a number of steroidal 3,5‐ and 4,5‐diols and some derivatives have been examined using high resolution mass spectrometry and deuterium labelling. Although the 3,5‐ and 4,5‐diols have very similar mass spectra those of the derived ketols are quite characteristic. A pathway for the formation of the important m/e 332 ion in the mass spectrum of cholestan‐4β,5α‐diol has been postulated.