Mass spectra of some furanosesquiterpenes

Some of the fragmentation modes operating in a few furanosesquiterpenes have been established from accurate mass measurements and metastable data.     

Mass spectra of some silylaryladamantanes

Conclusions The molecular weight and the number and nature of the substituents, and also their position, can be determined from the mass spectra of silylaryladamantanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 707–708, March, 1982.     

Mass spectra of some diazadiamides

Electron impact mass spectra at nominally low electron energies are reported for a series of diazadiamides. Diazadiamides are of interest because of their use as ligands in transition metal complexes.     

Mass spectra of some thionocarbamates

The mass spectra of a number O-alkylthionocarbamates with two, one or no alkyl substituents on the nitrogen atom are presented and discussed. The main primary fragmentation pathways are McLafferty rearrangements, including the double so-called protonated McLafferty rearrangement. Generally, rearrangement products give charge delocalized ions, which release hydroxyl or sulphydryl radicals and water or hydrogen sulphide, to produce stable fragments. It has been found that the position of alkyl moieties may be deduced on the basis of mass spectral fragmentation patterns.     

Mass spectra of some steroidal diols

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.     

Mass spectra of some oxadiazole derivatives

The mass spectra of some substituted oxadiazoles have been determined and analysed with the aid of high resolution mass spectrometry. Some characteristic and major differences between their spectra have been noted, and possible rationalizations have been advanced. The main fragmentation patterns of the 1,3,4-oxadiazole derivatives have been interpreted in terms of diazirine intermediates. Specific skeletal rearrangement processes have been observed in the spectra of the 1,3,4- and 1,2,4-oxadiazoles, and possible mechanisms are proposed.     

Mass spectra of some 1,2,4-thiadiazoles

Substituted 1,2,4-thiadiazoles were found to undergo fragmentation by loss of RCN from the molecular ion with both 3- and 5-substituents being involved to some extent. This was followed by loss of sulfur to yield a nitrilium ion. With 5-hydrazino substituents, hydrogen transfer was observed from the substituent to a ring nitrogen atom.     

Mass spectra of some substituted imidazoles

Comparison of fragmentation pathways and high resolution measurements has revealed that the molecular ions of 1-(2-hydroxy-2-phenylethyl)imidazoles undergo elimination of benzaldehyde. The parent ions of trans-1-styrylimidazoles also cyclise in a manner similar to their photochemical reactivity. A rearrangement involving OH or OMe transfer between the trans-1-styryl and 5-acid or 5-methyl ester group of an imidazole is also described.     

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.     

Mass spectra of some alkyl isoxazoles

The mass spectra of several compounds obtained during the process of Stork's isoxazole synthesis9 as well as the related isoxazoles have been investigated. The fragmentations of simple alkyl isoxazoles are nicely formulated via azirine intermediates. A striking difference between the spectra of isoxazoles and those of methylfurans as to the relative abundance of [M — l] peaks is noteworthy. The very low abundance of these peaks in the former reflects the unique character of isoxazole nucleus due to the preferential cleavage of N? O linkage rather than a benzylic C? H bond rupture. If an alkyl substituent is present at 4-position in 3,5-dimethylisoxazoles, strong peaks at m/e 110, 68 and 43 are common in their spectra. The analyses of metastable transitions and high resolution measurements have demonstrated that the formation of these ions can be interpreted by a mechanism involving the cleavage of N? O linkage.     

Mass spectra of some 2,6-di-tert-butyl-p-methylenequinones

Conclusions The mass spectra of a number of 2,6-di-tert-butyl-p-methylenequinones are described and some of the process for their fragmentation are explained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1892–1894, August, 1977.     

Mass spectra of some neopentylphosphorus derivatives

The fragmentation patterns and major metastable ions of the mass spectra of the neopentyl-phosphorus derivatives [(CH₃)₃CCH₂]₃P, [(CH₃)₃CCH₂]₂P(O)H, [(CH₃)₃CCH₂]_nPX_3-n (n = 1 and 2; X = H, Cl, C₆H₅ and CH = CH₂), [(CH₃)₃CCH₂]₃PS, [(CH₃)₃CCH₂]_nP(S)R_3-n (n = 1 and 2; R = C₆H₅ and CH = CH₂), [(CH₃)₃ CCH₂]₂PCH₂CH₂P[CH₂C(CH₃)₃]₂, ([CH₃)₃CCH₂]₂PCH₂PCH₂-CH₂P(H)C₆H₅ and [(CH₃)₃CCH₂]₂PCH₂CH₂P(S)(CH₃)₂ are described. Fragmentation of a neopentyl group by elimination of either C₄H₈ or CH₃ is very favourable when the neopentyl group is bonded to either a tricoordinate or tetracoordinate phosphorus atom. In neopentylphosphines with two or three neopentyl groups, stepwise elimination of C₄H₈ from all of the neopentyl groups occurs very readily. The resulting [(CH₃)_nPX]^+._3-n ions are often the most intense ions in the mass spectra.     

Mass spectra of some N-amino compounds

N-amino compounds on electron-impact commonly lose NH from the molecular ion, and frequently lose N, NH₂ and NH₃. This behaviour contrasts with C-amino compounds which mainly lose HCN and H₂CN. The mass spectra of eight N-amino compounds are recorded and discussed, together with some data from literature sources.