Chemical ionization mass spectrometry of some aromatic and aliphatic oximes

Aromatic and aliphatic oximes are protonated under methane or isobutane chemical ionization conditions. The structural identity of the [MH? H₂O]⁺˙ ions with nitrilium cations is established by the mass analysed ion kinetic energy method after collisional activation. The results also show the stereospecific nature of the transposition in the gas phase.     

The mass spectra of some aromatic polyketones

The behaviour of some aromatic tri- and tetraoxo compounds and of their p-substituted derivatives under electron-impact has been investigated by means of high and low resolution mass spectrometry, metastable refocusing and deuterium labelling. Some characteristic fragmentation processes observed with these compounds indicate that their molecular ions exist in the enol form. The formation of principal fragment ions is discussed.     

The mass spectrometry of some t-butyl peresters

Mass spectrometry is suggested as a method for the general characterization of mono- and di-t-butyl peresters. In many instances it is possible to measure the molecular ion, especially in the mono-t-butyl peresters. The fragmentation patterns of various t-butyl peresters are presented.     

The mass spectra of some chlorinated aromatic pesticidal compounds

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 Work are chlorinated aromatic pesticidal compounds which consist of a diphenylemthane, a diphenylethylene, or a diphenylmethanol structure. The compounds p,?-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 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.     

The long-wavelength edge of photosensitivity of aromatic azides

The absorption spectra of heteroaromatic azides from the azidopyridine-azidoazahexacene series (with the size of the aromatic system of 6–26 e) were calculated by the TD B3LYP/6–31G* method using the geometric parameters optimized by the PM3 method. A linear relationship of the long-wavelength absorption band (LWAB) on the size of the azide π system was found for the experimentally measured spectra of azidopyridine, azidoquinoline, and azidoacridine. The calculation results in conjunction with the data obtained in the previous theoretical and experimental studies predict the feasibility of synthesis of photoactive azides that exhibit the LWAB in the visible region of 580–670 nm and have a high quantum yield of photodissociation of the azido group (φ > 0.1) upon photoexcitation in this spectral region.     

Differentiation among some isomeric di- and trifunctional aromatic amines by plasma desorption mass spectrometry

Isomeric di- and trifunctional aromatic amines are easily differentiated on the basis of their plasma desorption (PD) mass spectra. Six series of aromatic amines were studied in the positive-ion mode. In each series, the differences observed in the PD mass spectra allow each isomer to be characterized. In the formation of molecular ions, these differences proceed from the competition between electron impact ionization and protonation. Several chemoselective or regioselective reactions such as hydrogenation, hydration, dimerization and some fragmentations also allow isomeric aromatic amines to be differentiated.     

Photochemistry of aromatic azides and nitrenes

Experimental and theoretical studies on the photodissociation of aromatic azides, spectral and photochemical characteristics of nitrenes, as well as the application of azides as a light-sensitive component of positive luminescent photography, are reviewed.     

Reaction of tetraphenylmethylenediphosphine with aromatic azides

Conclusions Some tetraphenylmethylenediphosphinemono- and tetraphenylmethylenediphosphinedi-(arylimines) were obtained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1159–1161, May, 1967.     

High-pressure collisional activation mass spectrometry of aromatic halides

The high-pressure collisional activation mass spectra with methane as the reagent/collision gas are reported for five aromatic halides. The major decomposition of the protonated aromatic halides is hydrogen halide elimination. The energy-resolved mass spectra and the chemical reactivities of fragment ions with the methane collision gas are used to establish dissociation pathways and structures of fragment ions. The high-pressure collisional activation mass spectra are compared with conventional collisionally induced dissociation and chemical ionization mass spectra.     

Pyrene fluorescence quenching by aromatic azides

Pyrene fluorescence quenching by phenylazide derivatives with donor and acceptor substituents has been studied by fluorescence spectroscopy and flash photolysis. The rate constants of quenching (k _q) in acetonitrile ((0.2–1.2) × 10¹⁰ l mol^?1 s^?1) are found to be close to a diffusion limit; the rate constants were somewhat higher for perfluoro-substituted arylazides. It is found that k _q does not depend on solvent polarity; the formation of the pyrene cation in the course of pyrene fluorescence quenching by tolylazide was not detected. Pyrene fluorescence quenching occurred by an energy-transfer mechanism; this is supported by the coincidence of the quantum yields of the direct and sensitized photodecomposition of tolylazide. As estimated, energy transfer in rigid media occurs at characteristic distances of about 10 Å.     

Electron impact mass spectrometry of some naphthoxypolymethylenethiopyrimidines

The electron impact induced fragmentation of a large number of 2- and 4-S-(2-naphthoxy)-polymethyienethiouracils is discussed in detail, with the aid of exact mass measurements and observation of metastable decompositions. The 2- and 4-thiopyrimidine structures can be easily distinguished by their mass spectra.     

Simple conversion of aromatic amines into azides

[reaction: see text] A straightforward and highly efficient synthesis of aromatic azides from the corresponding amines is accomplished using triflyl azide under mild conditions.     

Tandem mass spectrometry of some nitropyridylaryl sulfides

The electron impact tandem mass spectrometry of 3- and 5-nitropyridinylaryl sulfides are reported and discussed. The [M-1](+) ion is observed as the base peak for all the 5-nitropyridinylaryl sulfides, series I, whereas the 2-mercapto-3-nitrosopyridine fragment at m/z 139 represents the base peak for the 3-nitro isomers, series II, with the exception of the 3-substituted derivatives and the unsubstituted parent sulfide. The proposed fragmentation processes are substantiated by tandem mass spectrometry (MS/MS). Hammett correlation analysis of the substituent effect on the formation of fragments [RH(4)C(6)S](+), [C(6)H(4)R](+) and [M-HNO(2)](+) is discussed. Copyright 2000 John Wiley & Sons, Ltd.     

Identification of the aromatic hydroxylamine group by mass spectrometry

The mass spectra of aromatic hydroxylamines are diagnostic; [M], [M – 2], [M – 16] and, in most instances, [M – 17] ions are observed.     

Electron impact mass spectrometry of some macrocyclic tetraesters

The electron impact mass spectrometric behaviour of five recently synthesized macrocyclic tetraesters is described and discussed in detail with the aid of exact mass measurements, linked scans and collisional activation experiments. The unusual primary loss of a dehydrogenated catecholic radical leads to a very stable cation which is the precursor of the most of the fragmentation products.     

Mass spectra of some sulphonyl azides

A series of sulphonyl azides decomposed upon electron-impact with loss of azide radical. This fragmentation was in marked contrast to the photochemical behaviour of the compounds. An interesting ortho-extrusion process occurred in the mass spectrum of 2,4,6-triisopropylbenzenesulphonyl azide.     

Gas chromatography mass spectrometry of some steroidal spirolactones

Gas chromatography mass spectrometry of a number of steroidal spirolactones and their TMS ethers is reported. Open tubular column gas chromatography provides useful structural information for these compounds as shown by shifts in retention index values. The electron impact fragmentation pathways have been established for a number of the compounds. The results of the study indicate that open tubular column gas chromatography mass spectrometry will be of value in studies of the metabolism of this class of steroids in animals and man.     

Electron impact mass spectrometry of some geminal bis-sulphones

The behaviour under electron impact of six 1,1-bis(benzenesulphonyl)cyclioalkanes and of 1-phenyl-1-(benzensesulphaonyl)cyclopropane has been studied in detail with the aid of exact mass measurements, linked scans for metastable ion analysis, collisional spectroscopy and kinetic energy release measurements. The molecular ions of these compounds undergo a sulphone-sulphinate rearrangement with alkyl group migration on oxygen, in analogy with what is found for simple monosulphones and, in general, their fragmentation resembles that of mono-sulphonyl compounds. Loss of SO₂ from the molecular ion is observed for all substrates, but only in the case of 1, 1-bis(benzenesulphonyl)cyclopropane is this followed by loss of the second SO₂ unit; the first loss of SO₂ is probably accompanied by rearrangement since the fragmentation pattern of [M ? SO₂]⁺˙ ions from this compound is different than that of the isobaric molecular ions of 1-phenyl-1-(benzenesulphonyl)cyclopropane.