bluuebunny/crossref_metadata_2025 huggingface dataset:
Selective detection of multiplets via double quantum coherence: A 19F NMR study of perfluorodecalin
Authors: Fung B. M.
Published: May 2005

Commercially obtained perfluorodecalin (octadecafluorodecahydronaphthalene) contains a mixture of cis‐ and trans‐isomers, the 19F NMR signals of which overlap. The spectrum can be simplified and assignments can be made by using techniques based on double quantum coherence. The INADEQUATE method eliminates peaks due to the cis‐isomer, and the DOUBTFUL method selectively detects two quartets of the trans‐isomer.
Use of concentration‐dependent relaxation rates for carbon‐13 chemical shift assignment of symmetric tetraalkylammonium salts in acetonitrile
Authors: Dando Neal R. , Gold Harvey S. , Dyboski Cecil
Published: May 2005

The assignment of 13C chemical shifts of several symmetric tetraalkylammonium salts in acetonitrile is based on alkyl chain carbon spin–lattice relaxation rates (T1−1), and on concentration‐dependent changes in these rates.
17O NMR study of isomeric 2‐R‐2‐oxo‐1,3,2‐dioxaphosphorinanes
Authors: Bock Paul L. , Mosbo John A. , Redmon John L.
Published: May 2005

Oxygen‐17 NMR spectra were obtained from the four pairs of isomeric 2‐R‐2‐oxo‐1,3,2‐dioxaphosphorinanes, where R=OMe (2), NMe2 (3), H (4) or Me (5). The isomerism has been previously shown to be configurational at phosphorus, with one isomer of each pair having an equatorial phosphoryl oxygen (a isomer), and the other an axial orientation for phosphoryl oxygen (b isomer). Only data for the phosphoryl oxygen are reported. Substitution of OMe or NMe2 for H or Me produced upfield shifts of 27.9‐41.8 ppm. In all cases, the chemical shifts of the a isomers were upfield of the b analogs, with differences of 7.9, 18.0, 20.3 and 8.6 ppm for 2—5, respectively. The absolute values of 1J(31P17O) were 5–9 Hz larger for the a isomers.
Nitrogen‐15 NMR studies of 1,4‐benzodiazepines: 2—The triazolobenzodiazepines
Authors: Scahill Terrence A. , Smith Stanford L.
Published: May 2005

Nitrogen‐15 NMR data for a series of 21 triazolobenzodiazepines are presented, including 15N chemical shifts and substituent effects. The line assignments made by correlation to other model compounds were confirmed by a shift reagent and protonation study. A Yb(dpm)3 study on alprazolam showed that the molar shifts of the four nitrogens ranged from 35 to 150 ppm.
Conformational preference of substituted naphthalenes: 1—Aldehyde derivatives of naphthalene
Authors: Salman Salman R.
Published: May 2005

Long‐range proton‐proton coupling constants between the aldehyde proton and the ring protons were used to deduce the conformational preference of 1‐naphthaldehyde, 2‐naphthaldehyde, 2‐hydroxy‐1‐naphthaldehyde, 2‐methoxy‐1‐naphthaldehyde and 1‐bromo‐2‐naphthaldehyde. Molecular orbital calculations at the CNDO/2 and INDO level were used to calculate the stability and the long‐range proton‐proton couplings of different conformers of 1‐ and 2‐naphthaldehyde. The Z conformer was found to be more stable in 1‐naphthaldehyde and the E conformer was more stable in 2‐naphthaldehyde.
1H and 13C NMR studies of binuclear lanthanide(III):—silver(I) shift or relaxation reagents: Competition between several bonding sites in olefinic, aromatic and heteroaromatic compounds
Authors: Audit M. , Demerseman P. , Goasdoue N. , Platzer N.
Published: May 2005

The relative abilities of weak Lewis bases to complex binuclear lanthanide(III)—silver(I) reagents were checked by inter‐ or intra‐ molecular competitions. Preferential complexation at one particular site was shown to be determined mainly by the occurrence of well localized π electrons, by the relief of strain effects or by the lack of steric hindrance. In benzofuran and methoxybenzene derivatives oxygen never interacts directly with the silver reagent and plays a role mainly through electronic effects. Unlike oxygen, sulphur in benzo[b]thiophene is the preferred site of complexation with the silver reagent. On complexation with binuclear shift reagents (lanthanide = Eu, Pr, Yb) the 1H NMR shifts were shown to result from several mechanisms. Better insight into the precise location of the reagent is obtained in 13C NMR by the use of the binuclear relaxation reagent Ag(tfa)‐Gd(fod)3.
High resolution mass spectrometry in molecular studies. Part XVII. Evidence for ring contractions in molecular ions: The fragmentation of N‐acetylmorpholine
Authors: Tesarek J. M. , Richter W. J. , Burlingame A. L.
Published: May 2005

In comparing N‐acetylmorpholine to closely related systems, two major differences in fragmentation are observed. M‐15 and M‐43 fragments, although quite common to such systems, are unusual with respect to their genesis. Formation of the M‐15 fragment by loss of C‐3 instead of the anticipitated loss of C‐2 or C‐8 is evident from shifts in the spectra of deuterated analogs. The M‐43 species arises from total loss of the N‐acyl substituent rather than the usual two‐step loss of ketene plus a ring hydrogen. These data are presented in support of mechanistic rationale involving radical induced ring contraction to a common intermediate molecular ion. Techniques of high resolution mass spectrometry and isotope labeling have been employed to substantiate certain mechanistic details.
The metastable spectra of cis‐ and trans‐butenes
Authors: Daly N. R. , McCormick A. , Powell R. E.
Published: May 2005

A new type of ion detector has been developed that can be made to operate in two ways. It can detect all ions, or it can be made to detect only those within a preselected energy range. Its use on a mass spectrometer to examine the metastable spectra of cis‐ and trans‐butenes is described.
Massenspektrometrische Strukturanalyse organischer Verbindungen. Eine Einfiihrung. Von Gerhard Spiteller. Verlag Chemie, Weinheim Bergstraße, 1966. 355 Seiten mit 91 Abbildungen und 2 Tabellen. Ganzleinen DM 44.00
Authors: Budzikiewicz H.
Published: May 2005

This book has been written with the intention of enabling the organic chemist to endeavor to interpret his own mass spectra and to decide whether mass spectrometry would be useful for his specific problems. Besides a description of experimental techniques the main body of the oeuvre consists of a thorough discussion of fragmentation processes triggered by various structural elements, followed by selected examples from miscellaneous classes of natural products. Of special value is a chapter on structure elucidation of unknown compounds. Each section also offers an ample list of literature references. The present book can be highly recommended as an introduction to organic mass spectrometry, yet it will prove useful also for those advanced in this art.
The primary fragmentation step of isoxazole upon electron impact. A correlation with photochemistry
Authors: Nakata Hisao , Sakurai Hiroshi , Yoshizumi Hideo , Tatematsu Akira
Published: May 2005

Three isomeric compounds, I, II and III, were prepared and their mass spectra recorded. Comparisons of the spectra showed that the fragmentation of I proceeds only by way of II, and that II itself is transformed in part to III upon electron impact. It is suggested that selective ionization of each one of the two isolated functional groups in II may afford two isomeric radical ions, IIa and IIb. A possible interrelation to the photochemistry of these compounds is also discussed.
Zur Massenspektrometrie von Metallkomplexen. Metallkomplexe von Corrinen und synthetischen Vorstufen
Authors: Seibl J.
Published: May 2005

A variety of metal‐complexes with Corrin‐type macrocyclic ligands and synthetic precursors thereof are investigated by mass spectrometry. Analytical results are obtained from thermal reactions in the inlet system and from electron‐impact‐induced fragmentations. The former yield information concerning identity of small ligands in octahedral Co(III)‐complexes, of anions in complex‐salts and the possibility of thermal cyclisation of open ligands, the latter provide molecular weights, a means of type analysis and theoretically interesting modes of fragmentation. An unprecedented subsequent loss of up to seven methyl‐groups is observed. Different fragmentation‐mechanisms and the possible influence of metal‐valency‐changes and even‐ or odd‐electron‐ion‐features are discussed. Some of the metals like Zn and Na seem to be able to form different types of metal‐ligand‐bonds.
Einfluss funktioneller Gruppen auf die Massenspektren von 17β‐Hydroxysteroiden
Authors: Spiteller‐Friedmann Margot , Spiteller Gerhard
Published: May 2005

AM Beispiel des 17β‐Hydroxy‐5α‐androstans wird der unterschiedliche Einfluß funktioneller Gruppen auf die Bruchstückbildung von Steroiden studiert.

Im 17β‐Hydroxy‐5α‐androstan wird durch die Hydroxylgruppe lediglich die in Steroiden vorhandene eigung zur Spaltung der C‐13/C‐17 Bindung unter Ausbildung eines positiven Ladungszentrums an C‐13 vertärkt. Dieser Einfluß der Hydroxylgruppe überwiegt aber nur, solange Substituenten fehlen, die zur Ionisation einen geringeren Energieaufwand benötigen, als zur Ionisation der C‐13/C‐17 Bindung erforderlich ist. Bereits bei Vorhandensein einer Doppelbindung kann sich das Spaltbild stark wandeln.

Wenn sich aber in Stellung 17 noch eine zusätzliche Alkygruppe befindet, so erfolgt die Ionisation mit hoher Wahrscheinlichkeit durch Abspaltung eines Elektrons vom Hydroxylsauerstoff in Stellung 17. Es treten daher andere Hauptabbaureaktionen ein als in Molekülionen, die das Ladungszentrum am C‐13 haben. In solchen Verbindungen ist selbst der dominierende Einfluß eines konjugierten Systems auf die Bruchstückbildung weitgehend eingeschränkt. Bei Verätherung der Hydroxylgruppe wird dieser Effekt potenziert.

Im Zuge dieser UNtersuchungen wurden einige bisher noch nicht bekannte, für die Anwesenheit bestimmter Strukturelemente im Steroidskelett typische Abbaureaktionen aufgefunden, die ebenfalls kurz diskutiert werden.
Mass spectrometry in structural and stereochemical problems—CLVIII electron impact promoted fragmentation of triphenylmethyl ethers
Authors: Sheikh M. Younus , Duffield A. M. , Djerassi Carl
Published: May 2005

The triphenylmethyl (trityl) moiety is frequently used for the protection of alcohols but the mass spectra of such trityl ethers have hitherto escaped scrutiny. It has now been found that triphenylmethyl derivatives of primary alcohols yield abundant molecular ions which permit the determination of the isotopic purity of the parent alcohol. Upon electron impact the triphenyl‐methyl entity directs the fragmentation of trityl ethers as demonstrated by a detailed study of n‐pentyl trityl ether and its deuterated analogs. Ions formed by migration of phenyl groups were observed in the mass spectra of the trityl ethers investigated as well as in the spectrum of triphenyl‐methane itself.
Zum Mechanismus massenspektrometrischer Fragmentierungsreaktionen.—I Methoxygruppenwanderungen in den Massenspektren der Methyläther von linearen und verzweigten aliphatischen Polyalkoholen
Authors: Grützmacher Hans‐Friedrich , Winkler Johann
Published: May 2005

Die Bildung von 1,1‐Dimethoxyalky‐umlagerungsionen in den Massenspektren der Metyläther von linearen Diolen, 1,2,3‐Triolen und Derivaten der verzweigten Polyole Pentaglycerin und Pentaerythrit wird mit Hilfe von Markierungen mit Deuterium und Massefeinbestimmungen untersucht. Methoxygruppenwanderungen treten in den Massenspektren der Dioldimethyläther nicht oder nur in sehr geringem Ausmaß auf. Die Massenspektren der 1,2,3‐Trioltrimethyläther besizen aber charakteristische Peaks der umlagerungsionen +CH(OCH3)2 und +CR(OCH3)2. Diese Ionen entstehen durch eine 1,3‐Wanderung einer Methoxygruppe, wahrscheinlich bei einem einstufigen Zerfall der Molekül‐Ionen unter Bildung von Methyl‐alkenyl‐äther und H‐Atom bzw. Alkylradikal als neutrale Fragmente. Gorße Peaks der Umlagerungsionen +CH(OCH3)2 werden in den Massenspektren von Verbindungen des Typs
magnified image
gefunde. Bei diesen Verbindungen wandert eine Methoxygruppe beim weiteren Zerfall von Radikal‐Ionen, die durch Abspaltung von HY aus den Molekül‐Ionen entstehen. Wanderungen von Hydroxy‐ und Acetoxy‐Gruppen werden ebenfalls beobachtet, aber keine Wanderung von Cl‐Atomen.
Zur Weiteren Kenntnis des Chlorophylls und des Hämins—XIX. Zur McLafferty‐Umlagerung in gerad‐ und in Ungeradelektronischen Systemen
Authors: Budzikiewicz H. , Haar F. G. V. D.
Published: May 2005

Es wird gezeigt, daß in Porphin‐Derivaten die McLafferty‐Umlagerung bevorzugt in geradelektronischen Systemen abläuft. und zwar mit großer relative Häufigkeit ausgehend von M2+, jedoch weniger begünstigt in Ionen, die durch Radikalabspaltung entstanden sind. Von dieser Beobachtung ausgehend wird ein allgemeines Schema für die McLafferty‐Umlagerung vorgeschlagen.
Amino‐acid sequence study in peptides by mass spectometry‐II. Investigation of pentadeuterobenzoyl‐peptide methyl esters
Authors: Kamerling J. P. , Heerma W. , Penders Th. J. , Vliegenthart J. F. G.
Published: May 2005

The utility of benzoyl and pentadeuterobenzoyl derivatives of peptide methyl esters for mass spectrometric analysis was investigated. The mass spectra of the glu‐his and the val‐tyr‐pro derivatives are discussed. Treatment of the peptide methyl esters with the mixed benzoic‐ethyl‐carbonic anhydride did in some cases lead to benzoyl derivatives as well as to ethoxycarbonyl derivatives.
Bildung ionischer NO‐ und NO2‐Komplexe von aromaten in der Gasphase
Authors: Schulz W. , Drost H. , Klotz H.‐D.
Published: May 2005

Es wurde versucht, die bei der Nitrierung von Aromaten entstehenden NO+‐bzw. NO2+‐Intermediärkomplexe durch Ion‐Molekül Reaktionen in der Gasphase zu erzeugen. Die utersuchungen erfolgten am Benzol. Pyridin und Toluol mit NO+, NO2+ sowie CH3NO2+ und CH2ONO2+ als ‘Nitrierungs’‐Ionen. Es ließen sich sowohl aromatische NO+‐Komplexe anchweisen mit wechselndem reaktionsquerschnitt. Die ermittelten unteren Grenzen der Bindungsenergien von 16 kcal/Mol für den NO+‐Komplex und 29 kcal/Mol für den NO2+‐Komplex legen es nahe, die nachgewiesenen Komplexe asl σ‐Komplexe anzusehe, was als weiterer Hinweis für Analogie von elektrophilen Substitutionsreaktionen und Ion‐Molekül‐Reaktionen gewertet wird.
Fragmentations in the mass spectra of 2‐oxo‐3‐indolyl derivatives
Authors: Ballantine J. A. , Fenwick R. G. , Alam M.
Published: May 2005

The mass spectra of a series of isatin, oxindole and 2‐oxo‐3‐indolyl derivatives have been investigated using high resolution and deuterium labelling techniques. The fragmentations involve the sequential loss of a number of neutral molecules and the results show that the concept of charge localisation can be applied with success to explain the fragmentation processes even in these polyheteroatom species.
Energetics of the electron‐impact fragmentation of alkoxybenzenes and alkylthiobenzenes
Authors: Gillis R. G. , Long G. J. , Moritz A. G. , Occolowitz J. L.
Published: May 2005

Using energetic considerations, ketonic structures are postulated for the [Molefin]+ fragments derived from alkoxybenzenes, alkylthiobenzenes and 9‐ethoxyanthracene. Experimentally determined heats of formation for the tautomeric molecular ions derived from anthrone and 9‐anthrol differ by 37 Kcal. mole−1.
Mass spectra of branched long‐chain aliphatic alcohols
Authors: Dolejš L. , Beran P. , Hradec J.
Published: May 2005

The mass‐spectral behaviour of long‐chain aliphatic primary alcohols of the normal, iso‐and anteiso‐series have been discussed. The mass‐spectral fragmentation of individual alcoholic types have been found to be structurally specific. The mass spectra of some deuterio derivatives have shown, however, the complicated nature of the fragmentation processes.
Bond‐forming reactions occurring in azines upon electron impact
Authors: Cooks R. G. , Tam S. W.
Published: May 2005

Skeletal rearrangement processes of the general type \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm ABC}^{\mathop {\rm + }\limits_{\rm .} } {\rm } \to {\rm AC}^{\mathop {\rm + }\limits_{\rm .} } {\rm + B} $\end{document} in which HCN is eliminated and also bond‐forming reactions involving intramolecular aromatic substitution occur in aromatic azines upon electron impact. In addition, hydrogen rearrangements can lead to abundant benzonitrile and benzalimine molecular ions and their substituted analogues. The abundant [M1] ions are predominantly formed by loss of the methine hydrogen preceded by complete scrambling of the aromatic and methine hydrogens. The similarities between the processes occurring in azines and those in anils, both in their normal bond cleavages and in some bond‐forming reactions are emphasized.
Gas chromatographic—mass spectrometric studies of long chain hydroxy acids.—III.1 The mass spectra of the methyl esters trimethylsilyl ethers of aliphatic hydroxy acids. A facile method of double bond location
Authors: Eglinton G. , Hunneman D. H. , McCormick A.
Published: May 2005

Trimethylsilylation has proved to be extremely useful in the gas chromatography and the mass spectrometry of hydroxy acid methyl esters. The characteristic mass spectral fragmentation patterns have shown these derivatives to be superior in some respects to others for structural elucidation; in particular, hydroxylation followed by trimethylsilylation provides a useful method of double bond location in unsaturated fatty acid esters.

A preliminary presentation of this method has been given by G. Eglinton at the Lecture etting in Combined Gas Chromatography—Mass Spectrometry at the school of Pharmacy, London, August 9, 1967. It has come to the authors' attention that this method simultaneously developed by Dr. P. Capella, Institute di Industria Agrarie, University of Bologna, Italy1c (P. Capella and C. M. Zorzut, Anal. Chem. 41, 1458 (1968).)
Mass spectrometry of steroid systems.—XX The application of the ionization efficiency curves to some stereochemical problems
Authors: Sadovskaya V. L. , Zaretskii V. I. , Wulfson N. S. , Sizoy V. F.
Published: May 2005

The dependence of the cleavage of some cis/trans‐isomers in the terpenoid and steroid series on the energy of the ionizing electrons have been studied.
Mass spectra of substituted thioglycollic acids and esters. Skeletal rearrangement upon electron‐impact
Authors: Bowie J. H. , Madsen J. Ø. , Lawesson S.‐O. , Cooks R. G.
Published: May 2005

The mass spectra of thioglycollic acids and esters are reported and discussed. The spectra of compounds of the type X·CH(Y)·S·CH2·COOR(X > Y) contain skeletal rearrangement fragments with the composition R·Y·C2H3SO+. Ions produced by simple cleavage processes may be usefully correlated with structure.
Field ionization mass spectrometry of carbohydrates
Authors: Krone H. , Beckey H. D.
Published: May 2005

It is shown that FI mass spectra can serve to elucidate some structural features and determine the molecular weights of mono‐ and oligosaccharides.
High resolution mass spectrometry—III: Loss of water from a nitro compound under electron‐impact
Authors: Lord G. H. , Millard B. J.
Published: May 2005

Deuterium labelling has been utilised to elucidate the mechanism by which a molecule of water is eliminated from a heterocyclic nitro compound under electron‐impact.
Fragmentation of organic compounds on electron‐impact—VI. Dideuteriooctanes
Authors: Weinberg D. S. , Scoggins M. W.
Published: May 2005

Eleven isomeric octenes were converted to the corresponding dideuterio derivatives and the mass spectra recorded. The cracking patterns of the various dideuterioctanes are unique and the distribution of peaks representing the higher molecular weight ions can be predicted using a simple fragmentation model. The application of this technique to the determination of the position of the double bond in olefins of known carbon skeleton is discussed.
Mass spectrometry in structural and stereochemical problems—CLXXI: Factors governing the preferential loss of small vs. Large radicals in the α‐fission of aliphatic amines
Authors: Brown C. A. , Duffield A. M. , Djerassi Carl
Published: May 2005

A study of the α‐cleavage processes of aliphatic amines (using RLCH2N(R)CH2Rs and RLCH(NR)Rs

RL represents the larger Rs the smaller alkyl group throughout this paper and both, unless indicated to the contrary, have similar degrees of lsubstitution on the α‐carbon atom.

as typical substrates) at several ionizing voltages indicates that the loss ratio of large and small alkyl radicals, [M  RL]/[M  Rs], decreases with ionizing voltage. This ratio, greater than 1·0 at 70 eV, may become less than unity at low voltage (15 eV, 10 eV) in some cases. Comparison of similarly structured compounds with nitrogen or oxygen as the heteroatom suggests that the effects of ionizing voltage are lessened when the fragment is of greater stability (e.g. amine vs. ether or imine vs. ketone). The effects of lowering the ionizing voltage became much less pronounced as the alkyl groups become larger or similar in size.
Mass spectrometry in structural and stereochemical problems—CLXXIV:1 Electron‐impact induced fragmentation of some aryl‐ and alkylsulfonylthioureas
Authors: Duffield A. M. , Djerassi Carl , Neidlein R. , Heukelbach E.
Published: May 2005

The mass spectra of five aryl (I to V) and four alkylsulfonylthioureas (VI toIX) have been recorded and mechanistic rationalizations are suggested for their principal fragmentation processes. The aryl analogs exhibited peaks in their mass spectra corresponding to skeletal rearrangements with elimination of SO2 from their molecular ions but this fragmentation was absent in those alkylsulfonylthioureas (VI to IX) examined.
Mass spectra of some quinoline hydroxamic acids and related compounds
Authors: Coutts R. T. , Hindmarsh K. W.
Published: May 2005

The mass spectra of some 3‐ and 4‐substituted quinoline hydroxamic acids and related compounds have been interpreted, and proposed fragmentations substantiated by means of deuterium‐labeling and accurate mass determinations. All compounds examined gave abundant molecular ions; most showed strong [M  16]+ ions and weak [M  17]+ ions. The expulsion of CO and HCN molecules and H and HCO radicals were common subsequent decompositions. The spectrum of 4‐hydroxy‐2‐methylquinazoline‐3‐oxide (VII) was unique and showed that nitric oxide was expelled from the molecular ion.
Mass spectra of indazolones and pyrazolones—II: 5‐pyrazolones
Authors: Desmarchelier J. M. , Johns R. B.
Published: May 2005

The mass spectral fragmentations of 3‐methyl‐5‐pyrazolone (I), 3‐methyl‐5‐pyrazolone‐1‐d1 (II), 3‐methyl‐5‐pyrazolone‐1,4,4‐d3 (III), 1‐acetyl‐3‐methyl‐5‐pyrazolone (IV), 3‐methyl‐5‐ethoxy‐pyrazole (V), 3,4‐dimethyl‐5‐pyrazolone (VI), 1,3‐dimethyl‐5‐pyrazolone (VII), 1‐acetyl‐5‐acetoxy‐3,4‐dimethylpyrazole (VIII), 1,2,3‐trimethyl‐5‐pyrazolone (IX), 3,4,4‐trimethyl‐5‐pyrazolone (X), 3,4,4‐trimethyl‐5‐pyrazolone‐1‐d1 (XI), 3‐phenyl‐5‐pyrazolone (XII), 2‐acetyl‐3‐phenyl‐5‐pyrazolone (XIII) and 5‐acetoxy‐3‐phenylpyrazole (XIV) are reported. Comparison is made between the mass spectra of 5‐pyrazolones and 3‐indazolones. As for the latter compounds initial loss of ·N2R is preferred to loss of ·CHO, and is followed by loss of CO. The [M  1]ions are intense in the C‐methyl substituted pyrazolones, and unlike the 3‐indazolones, the pyrazolones do not show any significant loss of HCN from these ions. The mass spectra distinguish between certain isomeric 5‐pyrazolones.
The structure of [YC6H5O]+· ions in the spectra of aryl alkyl ethers
Authors: McLafferty F. W. , Schiff L. J.
Published: May 2005

The [YC6H5O]+· ions from YC6H4OC2H5 appear to correspond in structure to the molecular ions of the analogous substituted phenols, [YC6H4OH]+·.
Evidence for ring expansion and rearrangement of alkyl 9,10‐anthraquinones in the mass spectrometer
Authors: Hall L. W. , Oliver R. W. A.
Published: May 2005

The mass spectra of four alkyl substituted 9,10‐anthraquinones are presented and discussed together with evidence in favour of a new fragmentation pattern for these derivatives.
Studies in organic mass spectrometry—VI. The fragmentation of enol derivatives of acyclic β‐diketones
Authors: Vandewalle M. , Schamp N. , Francque M.
Published: May 2005

The mass spectra of enol derivatives of β‐diketones, such as enol ethers and enaminies are discussed. Their behaviour under electron‐impact is in accordance with the fragmentation we suggested for an acyclic β‐diketone in the enol form.

Rearrangement of the enol functional group is observed in the spectra. This process is a general one, as it show not only migration of oxygen and nitrogen in the enol ethers and enamines, but also migeration of sulphur and chlorine in the thio‐ether and in 4‐chloro‐3‐pentene‐2‐one.

Enol derivatives are suitable compounds for determining the branching of alkyl chains in β‐diketones.
High resolution mass spectrometry—V: Cyclic esters of aliphatic α‐hydroxy acids
Authors: Goulden J. D. S. , Millard B. J.
Published: May 2005

The main fragmentation sequences of glycollide and its homologues are initiated by fission of a COO bond, leading to the formation of fragment ions of low, m/e, such as [R1CO]+ and [CR1R2CCO]+. When a hydrogen atom is present on a ring carbon atom, 1,3 hydrogen migration occurs to produce [CHR2OH]+. In case where a ring carbon atom carries an alkylchain ⩾ C2H5, a McLafferty rearrangement occurs with the adjacent carbonyl group. When both ring carbon atoms are dimethyl substituted, a 1,4 hydrogen migration must be invoked to account for the observed fragmentation sequence.
A mass‐spectral study of exo‐ and endo‐2‐norbornyl bromide and exo and endo‐8‐bromobicyclo[3.2.1]octane by photoionization
Authors: DeJongh D. C. , Shrader S. R. , Isakson R. G. , LeBel N. A. , Beynon J. H.
Published: May 2005

The photoionization, as well as the electron‐impact, mass spectra of exo‐and endo‐norbornyl bromide and of exo‐and endo‐8‐bromobicyclo[3.2.1]octane show that exo‐Br loss is more facile than endo‐Br loss in formation of C7H11⊕ and C8H13⊕, respectively. The relative intensity values are compared with solvolysis data from the same systems.
Terpenoids—CXXXVII: Fragmentation of constunolide and its derivatives under electron‐impact
Authors: Sathe R. N. , Kulkarni G. H. , Kelkar G. R. , Das K. G.
Published: May 2005

An attempt has been made to correlate the fragmentation modes and structure of costunolide and some lactones derived from it, containing a ten‐membered carbocyclic system. The possible origins for the major fragments have been determined, using high resolution mass spectrometry and deuterium labelling.
The mass spectra of sydnones
Authors: Goudie R. S. , Preston P. N. , Palmer M. H.
Published: May 2005

The mass spectra of thirty sydnoes have been interpreted; the types investigated include 3‐aryl, 3‐alkyl‐, substituted 3‐alkylsydnones; and bis sydnones. A characteristic fragmentation mode involves initial loss of NO and CO from the molecular ion, but peaks corresponding to alkylcarbonium ions dominate the spectra of 3‐alkylsydnones; a cyclic mechanism is suggested for weak transitions involving loss of sydnone neutral molecule from the molecular ion. A mechanism is proposed for loss of chlorine radical from the molecular ion of 3‐(2,4‐dichlorophenethyl)sydnone. An unusual feature in the mass spectrum of trimethylenebis sydnone is rationalised on the basis of a precursor 1,2,3‐oxadiazole ion. The effect of substituents in the aryl ring on the fragmentation of 3‐arylsydnones is discussed.
Electron‐impact induced fragmentation of some natural products containing bis‐2,2‐dimethylchromene and bis‐2,2‐dimethylchroman ring systems
Authors: Duffield A. M.
Published: May 2005

Derivatives of eriostoic and eriostemoic acids (II and III) and their tetrahydro analogs (VI and IX) which contain the bis‐2,2‐dimethylchromene and the bis‐2,2‐dimethylchroman ring systems respectively, fragment subsequent to electron‐impact in characteristic fashion. The former yield mass spectra dominated by the loss of a methyl radical from their molecular ions while the latter exhibit preferential fragmentation of the heterocyclic ring system. In particular the hydrogen transfer process accompanying elemination of C4H7 from the parent ion of bis‐2,2‐dimethylchromans was investigated by deuterium labeling studies. Fragment ions containing the bis‐2,2‐dimethylchroman ring undergo further fragmentation by the loss of C4H8 rather than C4H7. An unusual elimination of CH5 (accompanied by the appropriate metastable ion) from the molecular ions of the 3,5‐dinitrobenzoate esters (XIV and XV) was observed in their mass spectra.
The mass spectra of 2‐alkyl N‐methyl pyrrolidines
Authors: Osman S. , Dooley C. J. , Foglia T.
Published: May 2005

The mass spectra of a series of 2‐alkyl N‐methyl pyrrolidines have been examined and fragments which may be pyrrole type structures are apparent. These ions are most prominent in the spectra of the long chain alkyl derivatives.
The mass spectra of some 1,3,2‐oxazaborolidines
Authors: Brooks C. J. W. , Middleditch B. S. , Anthony G. M.
Published: May 2005

Low resolution mass spectra of a series of alkylphenyl‐1,3,2‐oxazaborolidines are reported. The characteristic fragmentations are shown to be an aid to the elucidation of the substituents in the 1,3,2‐oxazaborolidine ring by means of a ‘substituent shift’ technique.
Kinetic studies in mass spectrometry—V: Evaluation of wide range electron energy kinetics and metastable ion relative abundance techniques, and the structures of [XC6H4CH2]+ ions generated from substituted benzyl phenyl ethers and toluenes
Authors: Brown Peter
Published: May 2005

The problem of ion structure and energy is discussed briefly and attention directed to the existence of two types of structural information. Studies of ion formation reactions bear on the initial structure of the ion, whereas decomposition reactions relate to the ion at a later time, after structural rearrangement has had chance to occur. The desirability of conducting both types of investigation concurrently is emphasized. Of the available experimental methods at this time, kinetic measurements for formation studies and metastablel ion relative abundances for decomposition studies have been utilized, although other techniques may eventually prove preferable in the future. The [M – Y] reaction of a series of substituted benzyl substrates XC6H4CH2Y, where Y = OC6H5 and H, has been examined, and the present results are compared with previous work on ion structure and energy in this area, with the aim of evaluating the potential of the newer techniques.
Mass spectrometric determination of the configuration of the 4‐substituted 1,2‐dimethyl‐4‐hydroxydecahydroquinolines
Authors: Zaikin V. G. , Wulfson N. S. , Zaretskii V. I. , Bakaev A. A. , Akhrem A. A. , Ukhova L. I. , Uskova N. F.
Published: May 2005

The mass spectra of a number of the epimeric 1,2‐dimethyl‐4‐alkyl‐4‐hydroxydecahydroquinolines (alkyl: CCH, CHCH2, C2H5 and COCH3) have been studied. The configuration at C‐2 and C‐4 in these molecules is proposed on the basis of the data obtained. Some aspects of the fragmentation pathways under electron‐impact are discussed.
Organic ions in the gas phase—XXIII: Loss of CH3 from polymethylbenzenes
Authors: Meyerson Seymour , Fields E. K.
Published: May 2005

The mass spectra of a series of deuteriated polymethylbenzenes confirm and extend the model derived from labeled p‐xylenes for the loss of a methyl radical under electron impact. A methyl group flanked by two methyls undergoes no exchange before being lost. But one adjacent to an unsubstituted position appears to exchange with the o‐hydrogen atom via a methyl‐methylene‐methyl cycle. At least in p‐xylene, reformation of the methyl group may well be concerted with its loss. A similarly concerted coupling of CH2 and H and loss of the resultant methyl group could account for an apparent inconsistency between the mass spectra of methyl alkyl and phenyl alkyl ketones.
Trimethylphosphine and trimethylamine: Rearrangements common to their mass spectra
Authors: Gillis R. G. , Long G. J.
Published: May 2005

Metastable ions confirm the rearrangement of the [M  H]+ ion from trimethylphosphine and trimethylamine to give [C3H5]+. Two‐carbon fragments are seen but their origin is indeterminate. Extensive loss of H2 occurs, confirmed by metastable ions, but not of CH2.
Kinetic studies in mass spectrometry—VI: The [M  CH3] reaction in substituted ethylbenzenes
Authors: Brown Peter
Published: May 2005

The [M] → [M  CH3] reaction in a series of m‐ and p‐X substituted ethylbenzenes has been studied by wide range electron energy kinetics and metastable ion characteristics techniques. By this approach, qualitative measures of activation evergy differences between [XC6H4CH2]+ ions derived from m‐ and p‐X isomer substrates have been secured, for both their formation and further decomposition. These evergy differences are consistent with (but do not prove) ion structures that have been suggested by previous work in this area, involving the use of isotope labeling, and ionization and appearance potential methods.
The mass spectra of some chlorinated aromatic pesticidal compounds
Authors: Sphon J. A. , Damico J. N.
Published: May 2005

Mass spectral studies of some chlorinated aromatic pesticidal compounds are reported. The compounds studied include substituted diphenyl derivatives of methane, ethene and methanol.

The diphenylmethanes are characterized by a relatively intense peak at m/e 165. Comparison of their low voltage spectra with 9‐dichloromethylfluorene indicates that this ion has a fluorenyl ion structure.

The structure of the base peak (m/e 246) of the diphenylethenes was investigated by comparing competitive metastable transitions with 9‐dichloromethylenefluorene and utilizing defocusing metastables. Additional studies of model compounds suggest that the m/e 246 ion is very complex and is probably comprised of a number of structures.

The mass spectra of the diphenylmethanols are significantly different from the other two groups. The hydroxyl group markedly affects the fragmentation process for these compounds; the characteristic peak is presumably the chlorobenzoyl ion and is probably precursor for other fragment ions.

Mass spectral correlations of pesticidal compounds of similar structure are needed to obtain enough background to facilitate interpretation of the mass spectra of their metabolites. Furthermore, such studies make feasible the identification of characteristic product ions formed by rearrangement processes during ionization of organic molecules in the gas phase. This information can be a nucleus for correlating the other significant mass spectral data of an unknown compound. Intensive studies of carbamates,1 organophosphorus2 and bridged polycyclic chlorinated pesticidal3 compounds were invaluable in identifying metabolites of the aforementioned pesticides.4,5,6 The compounds in this
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Work are chlorinated aromatic pesticidal compounds which consist of a diphenylemthane, a diphenylethylene, or a diphenylmethanol structure. The compounds p,ṕ‐DDE were briefly discussed by Jorg, Houriet and Spiteller.7 The compounds examined are listed in Table 1.

Treatment of data. The mass spectra of the pesticides are presented as bar graphs in Figs 1 to 12
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It a metastable peak is observed, the metastable transition is indicated by m* on the figures and also by (m*) when confirmed or identified using the defocusing technique.8 Since the relative abundances of the metastable peaks for these compounds are very small (<0.1%) on special effort was made to establish their presence unless they wre pertinent.
Mass spectrometry in cardenolide chemistry—I
Authors: Blessington B. , Morton I. M.
Published: May 2005

The mass spectrum of penta acetyl gitoxin is reported and discussed. This cardenolide derivative has recently been the subject of extensive metabolic study. Fragmentation processes are described which account for all of the major ions. High resolution measurements, metastable peaks and mass shifts, for the propionyl derivative, are reported to establish the validity of these proposals. A brief indication of the potential value of this technique, when combined with deuteroacetylation, to metabolic studies in this field is given, along with comments on the spectra of related compounds.
Some aspects of the mass spectra of triptycene and tri‐ and diphenylmethanes
Authors: Meyerson Seymour
Published: May 2005

Mass spectra of isotope‐labeled triptycenes, triphenylmethanes and diphenylmethanes rule out the bulk of postulated decomposition mechanisms and fragment‐ion structures. The formation of [M  H]+ and [M  2H]2+ from triptycene, of [M  H]+, [M  CH3]+ and [M  CH4]+ from triphenylmethane, and of [M  H]2+ and [M  2H]2+‐as well as the previously reported [M  H]+ and [M  CH3]+‐from diphenylmethane all seem to be preceded or accompanied by complete loss of position identity of the α and ring hydrogens in the original molecules. A statistical preference for loss of α hydrogens is found in the process leading to [M  2H]+ and [M  H]2+ from triptycene, as in the formation of [M  H]2+ from toluene.
The β‐cleavage reaction in ethers
Authors: Bernasek Steven L. , Cooks R. Graham
Published: May 2005

β‐Cleavage in n‐butyl ethyl ether occurs neither by simple bond fission with oxiranium ion formation nor by a mechanism analogous to the γ‐cleavage reaction in carbonyl compounds, but instead it involves skeletal rearrangement within the butyl chain.
Mass spectra of tetrahydroprotoberberine methines
Authors: Dolejš L. , Slavík J.
Published: May 2005

Mass spectra of the styrene type methines of tetrahydroberberrubine, tetrahydrothalifendine, tetrahydroberberine and 1‐methoxycanadine exhibit structurally characteristic fragmentation patterns.
Effects of halo substituents on electron‐impact induced fragmentation of cyclopropanes
Authors: Deem M. L. , Roboz J.
Published: May 2005

Bromine, fluorine and/or chlorine atoms on one cyclopropyl ring jointly influence the dominant primary modes of electron‐impact induced fragmentation. Decomposition ions include CBrX, C2HQ2X and C3HQ2X2, where × is an halogen atom and Q is from the group of an halogen atom, an hydrogen atom and a methyl group. For none of the compounds studied was formation of an ionic CBrX the dominant primary process. Gem‐dibromo‐gem‐dihalocyclopropanes preferentially eliminated dibromo divalent carbon and formed decomposition products of gem‐dihalogenated C2HQ2X′s. In cases where more stable allyl ions were formed, fragmentation was through C3HQ2X2.

Upon electron‐impact, the ions CF, CHF2 and CF3 were produced in abundances directly related to the fluorine content of their cyclopropyl precursors.

When fragmentation patterns for internally generated radical ions of the composition C2HQ2X were compared with patterns obtained by direct introduction of the same fluoroolefins into a mass spectrometer, incomplete correspondence was found. Variation in the mode of decomposition can be a consequence of differences in the energy levels of the olefin fragmented.

Addition of two hydrogen atoms from water to quinones and to s‐tetrazines is well established in the literature. Reaction of an additional cyclic series, polyhalocyclopropanes, with water prior to electron‐impact is suggested.
A new mass spectrometric method for determining the degree of labeling with heavy isotopes: The study of deuterated toluenes
Authors: Beynon J. H. , Corn J. E. , Baitinger W. E. , Amy J. W. , Benkeser R. A.
Published: May 2005

A new method of general applicability for determining the percentage deuterium labeling in organic compounds is described. It uses the heights of ‘metastable peaks’ in the mass spectrum to determine the relative amounts of deuterated and undeuterated species. The method is illustrated by describing the analysis of mixtures of toluene‐o‐d1 and toluene, of toluene α‐d1 and toluene, and of toluene‐2,6‐d2, toluene‐o‐d1 and toluene.
High resolution mass spectrometric studies of some bicyclic γ‐lactones
Authors: Chen Paul H. , Kuhn William F. , Will Fritz , Ikeda Robert M.
Published: May 2005

The mass spectra of three bicyclic γ‐lactones have been studied, and the fragmentation pathways have been proposed with the aid of accurate mass measurements and metastable transitions. An unusually low [M  CH3] ion and the presence of an abundant [M  C5H9] ion in the mass spectrum of dihydroactinidiolide were interpreted as a possible rearrangement involving a methyl migration. The eliminations of methyl radical, carbon monoxide and ketene are important processes in many cases.
Gas chromatography‐mass spectrometry of some boroxines
Authors: Brooks C. J. W. , Harvey D. J. , Middleditch B. S.
Published: May 2005

Mass spectra of triphenylboroxine, tricyclohexylboroxine, tri‐t‐butylboroxine and tri‐n‐butylboroxine are reported and discussed.
Mass spectrometry of aralkyl compounds with a functional group—IX: Hydrogen scrambling in the molecular ion of hydrocinnamaldehyde
Authors: Venema A. , Nibbering N. M. M. , De Boer Th. J.
Published: May 2005

The molecular ion of hydrocinnamaldehyde (C6H5CH2CH2CHO) chiefly loses fragments C2H2O and C3H4O. Mass spectra of specifically deuterated analogues show that in the loss of C2H2O an α‐hydrogen atom (with respect to the aldehyde group) is transferred to the aromatic part. A shift of the aldehydic hydrogen to one of the ortho positions of the phenyl ring and loss of C2H2O by a McLafferty rearrangement is not observed.

In the loss of C3H4O also an α‐hydrogen atom migrates to the aromatic part. Both reactions appear to occur with an extensive randomization of all hydrogen atoms in the molecular ion.
Four‐centred rearrangements in the mass spectra of aliphatic ethers
Authors: Tsang C. W. , Harrison A. G.
Published: May 2005

The [CH3OCHCH3]+ ions observed in the mass spectra of ethers of formula CH3OCH (CH3)R(R = H or alkyl) undergo two rearrangement fragmentation reactions to form [C2H5]+ and [CH2OH]+. The scope of the rearrangements has been investigated and it is shown that enlargement of the alkyl group on either side of the ether linkage leads to alternative fragmentation routes. From a study of metastable intensities it is concluded that the fragmentations probably occur directly from the [CH3OCHCH3]+ structure through four centred rearrangements rather than through the intermediacy of the [C2H5OCH2]+ ion.
The mass spectra of succinimides, hydantoins, oxazolidinediones and other medicinal anti‐epileptic agents
Authors: Locock R. A. , Coutts R. T.
Published: May 2005

The mass spectra of the following common anti‐epileptic agents; phensuximide, methsuximide, ethosuximide, ethotoin, mephenytoin, diphenylhydantoin, trimethadione, paramethadione, primidone and phenacemide, have been recorded and interpreted. In addition the mass spectra of succinimide, α‐phenylsuccinimide and the N‐deuterated derivative of ethotoin were studied. The investigated compounds fragment in an interesting manner and give rise to stable ions by which means they are readily identified. The most diagnostic fragmentation in the majority of the spectra was the expulsion of a (CO)2NR fragment from the molecular ion.
Alcaloïdes Steroïdiques—CII: La Fragmentation des Diamines Stéroïdiques et de Leurs Dérivés en Spectrométrie de Masse
Authors: Longevialle Pierre , Diatta Luc
Published: May 2005

L'étude, en spectrométrie de massem des stéroïdes proteurs de deux groupements azotés dans des positions éloignées fait apparaítre un nouveau type de fragmentation débutant par une interaction de ces deux groupements. Le phénoméne est décrit dans le cas des diamines et de certains dérivés (imines, amides).
High resolution mass spectrometry of trimethylamine
Authors: Hvistendahl Georg , Undheim Kjell
Published: May 2005

High resolution shows that the four principal fragment peaks of trimethylamine are singlets. Close studies of the metastable transitions in the spectrum have established the origin of almost all fragment peaks.
Rearrangement ions—I: Mass spectrum of thionylaniline‐1‐13C
Authors: Siegel Alan S.
Published: May 2005

Recent publications1,2 concerning the mechanism for the electron‐impact induced loss of carbon monoxide from the molecular ion of thionylaniline have led to an examination of thionylaniline‐1‐13C. The results show that the C‐1 carbon atom is not lost in this process, but only suggest the loss of the C‐2 carbon atom.
Mass spectra of alkylferrocenes and biferrocenyls
Authors: Spilners Ilgvars J. , Larson John G.
Published: May 2005

Mass spectra of alkylferrocenes and biferrocenyls have molecular ion peaks which are also base peaks. The predominant fragment ions are formed by beta‐cleavage of the alkyl group. Gamma‐and alpha‐cleavages are the only other significant modes of alkyl side‐chain fragmentation. The cleavage of the alkyl group is often accompanied or followed by the cleavage of either one or both of the cyclopentadienyl‐iron bonds. Weak m/e 121 ([C5H5]+) mass peaks are found in the spectra of 1,1′‐dialkyl‐ and 1,1′‐disilyl‐ferrocenes. Therefore, the m/e 121 peak may not be used as a sensitive criterion to determine the presence of unsubstituted cyclopentadienyl rings. The relative intensity of the peak may, however, serve as an indicator.

Expansion of the cyclopentadienyl ring to six‐ and seven‐carbon rings in the fragmentation of alkylferrocenes, diethylbiferrocenyl and deuterated ethylferrocenes is indicated. The spectra of benzylferrocene and benzylferrocene‐alpha‐d2 do not show a beta‐cleavage but suggest a pentalene ring formation. Methyl and phenyl groups in the beta‐position of substituted ferrocenes were found to migrate to the iron atom.
Electron‐impact studies—LIV: The formation of [C13H9]+ in the mass spectra of benzyl phenyl ketoxime and 2,3‐diphenyl‐2‐H‐azirine
Authors: Simons B. K. , Nussey B. , Bowie J. H.
Published: May 2005

The formation of m/e 165 in the spectrum of benzyl phenyl ketoxime involves the intermediacy of a rearranged 2,3‐diphenyl‐2‐H‐azirine radical ion. 2H and 13C labelling of the ketoxime together with 2H labelling of the azirine has allowed certain proposals to be made concerning the complex processes producing m/e 165 in both spectra. The mode of formation of m/e 167 in the spectrum of benzyl phenyl ketoxime has also been studied.
Electron‐impact studies—LV: Skeletal rearrangement and hydrogen scrambling processes in the positive and negative‐ion mass spectra of phenyl derivatives of elements of group IV and V
Authors: Bowie J. H. , Nussey B.
Published: May 2005

The mass spectra of many triphenyl/tetraphenyl derivatives of the Group IV and V elements exhibit the processes [M+˙  C12H10] and/or [M+˙  C6H5·  C12H10]. These fragmentations are not preceded by hydrogen scrambling between all the phenyl rings. Hydrogen scrambling does occur in certain fragment ions prior to fragmentation in both the positive and negative‐ion spectra. The process [M+˙  C12H10] occurs in the negative‐ion mass spectrum of tetraphenylsilane.
Metastable ion fragmentation processes in n‐alkanes
Authors: Goldberg P. , Hopkinson J. A. , Mathias A. , Williams A. E.
Published: May 2005

The n‐alkanes, propane to heptane, have been studied in a modified MS‐9 mass spectrometer under conditions that enabled the daughter ions, resulting from metastable fragmentation processes occurring in the first field free region, to be observed with high sensitivity. The precursor ions in these fragmentations have been identified unambiguously and a general fragmentation scheme for the n‐alkanes is proposed. The mass spectrometer incorporated a variable width monitor slit and narrow settings of this slit improved the energy resolution so that fine structure could be observed in some of the ‘metastable peaks’. The implications of this fine structure are discussed.
The mass spectra of N‐phenylphosphoramidate esters
Authors: McMurray W. J. , Lipsky S. R. , Zioudrou C. , Schmir G. L.
Published: May 2005

The mass spectra of diethyl and diphenyl N‐phenylphosphoramidate are reported. Their electron‐impact behavior is similiar to that observed for the corresponding phosphate esters. High resolution mass measurements are used to confirm the elemental composition of all the peaks in the spectra. Some interesting rearrangement fragments are observed in the spectrum of the diphenyl N‐phenylphosphoramidate ester.