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The methoxide anion (produced from methyl nitrite) reacts with neutral ketones (M) to form non-decomposing(M-H+)- ions. The (M-H+)- ions are ambident species and they undergo a number of ion-molecule reactions, including (i) characteristic reactions through the carbanion centre with methyl nitrite, and (ii) for acetone, the formation of an [M +(M- H+)]- ion. In several cases peaks due to collision-stabilized (M+MeO-) ions are observed (e.g. MeO-/acetone), but they are not detected for the majority of cases studied.

The trimethylsilyl cation forms 1 : 1 adducts with both 2,2- dimethylpropan-1-ol and 1-methoxy-2,2-dimethylpropane, with both adducts eliminating C5H10 by (at least) two mechanisms. One mechanism involves a 1,2-hydride transfer from the carbon α to oxygen to the oxygen acceptor site; the other a 1,4-transfer from a γ-carbon substituent.

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Carbon and hydrogen scrambling occurs either prior to, or during, the decompositions of the ions C9H9+, CllH13+, and C12H15+ in the first field-free region of the mass spectrometer. The ions may be produced from various substrates, and the decompositions of CllH13+ may be interpreted in terms of a decomposing ion in which some, but not all, of the C-H bonds have broken and reformed. The ions C9H9+ and C10H11+ may be produced by complex hydrogen rearrangement in the side-chain of particular bromo-and hydroxy-alkylcyclooctatetraene derivatives.

The mass spectra of the monomethyl and monophenyl derivatives of 1,2,4-triazoline-5-thione are reported and discussed. The fragmentation patterns of these compounds are complex, and the investigation was aided by 2H, 15N, and 15N-2H labelling, metastable defocusing, and high-resolution studies.

The negative-ion mass spectra of 3- and 4-nitrophthalic anhydride contain a series of rearrangement ions. One of these, an M-CO2 ion, is mainly produced by loss of CO from the anhydride unit together with an oxygen of the nitro group.

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The three nitrophenyltrifluoroacetamides are readily differentiated by negative-ion mass spectrometry. Many unusual fragmentations are noted in these spectra and certain of these have been substantiated by labelling and defocusing studies.

The root-bark of two Coelospermum species is rich in colouring matter now shown to be a mixture of anthraquinones. In C. reticulatum they occur mostly in the free state. The principal constituent is a new natural anthraquinone, coelulatin, which has been identified as 1,3,8-trihydroxy-2-hydroxpethylanthraquinone Small amounts of rubiadin and lucidin have also been isolated. In C. paniculatum the anthraquinones occur mostly as glycosides which have been hydrolysed to a mixture of rubiadin, rubiadin-1-methyl ether, and lucidin. Nordamnacanthal is present in the free state, together with damnacanthol (isolated as the cyclic dimethyl ketal) and another new pigment which appears to be a dimethyl ether of coelulatin. Both plants apparently contain asperuloside but this could not be isolated.

Whole roots of Morinda citrifolia yielded nordamnacanthal (1.7%), morindone (0.5%), rubiadin, and rubiadin-1-methyl ether as the principal pigments. Damnacanthol was isolated as a new derivative, which is probably an artifact, and another minor component is believed to be soranjidiol (1,6-dihydroxy-2-methylanthraquinone). Rubiadin and rubiadin-1-methyl ether have also been isolated from a small sample of the root bark of M. jasminoides.

The mass spectra of anils with ortho-alkoxyl substituents in the aromatic ring derived from the aldehyde contain pronounced peaks prod- uced by C=N bond cleavage accompanied by one and/or two hydrogen transfers to the nitrogen-containing fragment. Deuterium-labelling studies show that the hydrogen atoms involved are those attached to the α-carbon (α to oxygen) of the alkoxyl group. The extent of the hydrogen rearrangements may be altered by the addition of further substituents to the aromatic rings.

The mass spectra of S-alkyl-β-thiopropionic acids contain skeletal- rearrangement ions which arise by hydroxyl migration to a carbonium-ion centre followed by elimination of a neutral molecule (e.g. ketene or formaldehyde). In contrast, those of methyl S-alkyl-β-thiopropionates contain peaks which are formed by methoxyl migration to sulphur, followed by loss of ketene.

The mass spectra of substituted isoxazoles are reported and discussed. The spectra of isoxazoles are strikingly different from those of oxazoles because the initial fragmentations of isoxazoles involve N-O bond fission. Specific skeletal-rearrangement processes are observed in many spectra, and it is proposed that they proceed through azirine and oxazole intermediates. Certain fragmentations have been studied by deuterium labelling. The hydrogens attached to an isoxazole ring do not randomize with the hydrogens of the methyl and phenyl substituents.

Aryl hydroxamic acid derivatives fragment in a diagnostic manner upon electron impact. A hydroxamic acid containing both styryl and benzyl substituents undergoes skeletal-rearrangement of the type ABC → AC+B. The mass spectra of the O- and N-acetyl derivatives of O- benzylhydroxamic acids are indistinguishable. M-CO2 fragments are again observed in the mass spectra of several substituted phthalimides.

The negative-ion mass spectra of thioglycollic esters and S- alkylthioglycollic acids exhibit ions produced by simple cleavage and/or cleavage with hydrogen rearrangement. Similar spectra of arylsulphinylamines show pronounced molecular ions together with simple cleavage fragments. No skeletal-rearrangement fragments are present in the negative-ion spectra, in marked contrast with those observed in the corresponding positive-ion spectra.

The negative-ion mass spectra of aromatic azoxy compounds, nitrones, and N-oxides exhibit pronounced molecular ions and simple fragmentation processes. No skeletal-rearrangement fragments are produced upon electron impact, in marked contrast to those exhibited in the positive-ion spectra of these compounds.

Skeletal-rearrangement fragments are observed in the mass spectra of all anils derived from aromatic aldehydes. The rearrangement processes have been studied by high-resolution mass spectrometry and in certain cases by deuterium labelling. All processes are of the general type [ABC]+ → [AC]+ +B.

Solvent shifts [ΔC6H6 = δCCk4 ? δCCl4 p.p.m.] are recorded for a number of acyclic and cyclic α-diketones. Benzene produces upfield shifts of methyl and methylene resonances in the spectra of saturated acyclic and cyclic α-diketones. The shift of the α-methylene resonance of acyclic a-diketones may be related to the length (and bulk) of the side-chain. The formation of a 1 : 1 complex is proposed, and variable temperature studies (in toluene-ds) have allowed calculation of thermodynamic parameters for an acyclic and a cyclic compound. The dependence of solvent shifts on the position of methyl and hydrogen substituents of aromatic α-diketones has been demonstrated.

No abstract available.

The mass spectra of a series of a-diketones are reported and discussed. Fragmentation patterns have been substantiated by exact mass measurements, metastable ions, and in two cases, by deuterium labelling studies. The McLafferty rearrangement is not observed in the spectra of aliphatic α-diketones; fragmentation proceeds by α-cleavage. The fragmentation modes of those cyclic α-diketones studied depend largely on the ring size. Molecular ions are observed in all spectra.

The mass spectra of a series of benzo[c]cinnoline derivatives are reported and discussed. The spectra are useful for analytical purposes, as all compounds give pronounced molecular ions, and the fragmentation processes generally occur without skeletal-rearrangement. Many benzo[c]cinnolines which are substituted in the 4-position may be differentiated from other isomers by the presence of "proximity- effects" in their mass spectra.

The mass spectra of 11 quercetagetin derivatives are reported and discussed. The spectra are generally simple and amenable to analysis. 4 number of fragmentation processes have been substantiated by exact mass measurements, appropriate metastable ions, and deuterium labelling.

The mass spectra of some 2-cyclohexen-1-ones, tetralones, and indanones have been investigated. The characteristic fragmentation processes, substantiated by appropriate metastable peaks, exact mass measurements, and in some cases by deuterium labelling studies, greatly facilitate the determination of both the type of system and the position of substituents on that system.

Fragmentations of the amide group are not generally observed from molecular anions produced by the capture of slow electrons. Enhancement of the internal energy of the molecular anions by collision excitation allows the detection of the fragmentations of the substituent in the field-free regions of the mass spectrometer. Fragmentation of the amide group occurs α to either the carbonyl or amino functions.

The reaction between 2,3-diphenyl-2H-azirine and phenyldiazomethane produces the stable 1-azido-1,2,3-triphenylprop-1-ene in good yield. The structure is confirmed by an alternative synthesis which indicates that the double bond has the E-configuration.

A device is described which allows the measurement of ?doubly charged ion? mass spectra on the m/e 300 mass range of an Hitachi Perkin-Elmer RMU7 mass spectrometer. The unit gives a sensitivity enhancement 110 times that described in previous papers, and has been used to study hydrogen-scrambling and metastable processes which occur in the ?doubly charged ion? spectra of a range of simple benzenoid derivatives.

The loss of a phenyl radical from the molecular ion of 2,4,6- triphenylpyridine is a slow process which occurs mainly from the 2- position with a minimum of scrambling of the pyridine carbon atoms or migration of the phenyl groups. The spectra of 2H, 13C, and F labelled derivatives demonstrate that no phenyl/pyridine carbon scrambling occurs during this process, that fluorine scrambling does not occur between the phenyl residues, but that considerable hydrogen scrambling precedes or accompanies fragmentation. The loss of HCN from the [M- Ph.]+ ion of 2,4,6-triphenylpyridine occurs in a specific manner, showing that the original pyridine carbon atoms retain their positional identity during this elimination.

The technique of Beynon1,2 has been used to determine the ?doubly charged ion? mass spectra of a series of benzoic acid derivatives. A general feature of all spectra is the presence of pronounced M-CO species. The losses of carbon monoxide from the doubly charged molecular ions of m- amino- and m-hydroxy-benzoic acids originate mainly from the carboxyl groups, whereas the predominant loss from benzoic acid involves the aryl ring system. The spectra of anthranilates and salicylates contain peaks produced by characteristic proximity effects.

No Abstract Available

A study of the abundances of certain metastable peaks formed by the de- composition of ions in the first and second field-free regions of a double-focusing mass spectrometer has shown that the M-1 ions (m/e 165) in the mass spectra of fluorene and phenalene have different structures. Correlations based on these structures have been obtained for C13H9+ species formed from different systems.

The mass spectra of acyl phosphoranes exhibit peaks which arise by P-O bond formation. The problem of thermal against electron impact rearrangement is considered and the rearrangements have been studied by deuterium labelling. The formation of the fluorenyl cation (m/e 165) has also been investigated.

The mass spectra of substituted pyridazines, phthalazines, and related compounds are reported and discussed. Molecular ions are a prominent feature of all the spectra, and fragmentation modes may be usefully correlated with both the type of heterocycle and its substitution pattern. Fragmentation patterns have been substantiated by extensive high resolution studies and appropriate metastable ions.

The mass spectra of a series of [18]annulene derivatives are reported and discussed. The majority of fragmentation modes exhibited in these spectra are produced by well-defined skeletal reorganization. In the case of one compound, all the observed fragmentations occur as the result of skeletal rearrangement processes. This appears to be the first reported example of such a phenomenon.

The mass spectra of 37 imidazoles are reported and discussed. The spectra exhibit pronounced molecular ions and characteristic fragmentation patterns. The fragmentation modes have been substantiated by deuterium labelling, exact mass measurements, and appropriate metastable ions. Skeletal rearrangement fragments are rare in these spectra; consequently mass spectrometry is useful for structure elucidation of imidazoles.

The mass spectra of 15 aromatic azoxy compounds are reported and discussed. The spectra exhibit pronounced molecular ions, and fragmentation modes which are produced by both simple cleavage and complex skeletal reorganization processes.

The mass spectra of a series of alkaloids of the spermatheridine group, together with those of their alkoxy derivatives, are reported and discussed. The characteristic fragmentation processes, substantiated by appropriate metastable peaks, exact mass measurements, and in some cases by deuterium labelling, facilitate the location of substituents in the tetracyclic system. A structure for moschatoline is deduced from a consideration of the mass spectra of its derivatives.

The mass spectra of 34 acridones have been determined and interpreted with the aid of both high-resolution measurements and deuterium labelling studies. The spectra contain pronounced molecular ions and are free of skeletal rearrangement fragments. The fragmentation patterns are dependent on the nature and position of substituents, and therefore mass spectrometry can be a useful aid to structure determination in this class of naturally occurring compounds.

The mass spectra of representative series of simple alkyl acetoacetates, alkyl acetothioacetates, and some unsaturated esters derived from unsaturated alcohols or phenols are reported and discussed. The fragmentation schemes have been established by high resolution measurements, appropriate metastable ions, and by deuterium and 18O labelling. Many of the spectra show significant skeletal rearrangement fragments arising from either loss of carbon monoxide or carbon dioxide.

Maesopsin, C15H12O6, (obtained from the heartwood of Maesopsis eminii, Rhamnaceae) on fusion with alkali forms a yellow product, C15H10O5, which on methylation forms two methyl ethers. Structures for these products are suggested from a consideration of their N.M.R. and mass spectra, which afford confirmation of the original work.