Formation of negative ions by interaction of electrons with heterocyclic compounds

Curves are derived for the effective yield of negative ions from the interaction of electrons with thiophene, 2-methylthiophene, 2-propylthiophene, 3-methylthiophene, 3-propylthiophene, furan, and selenophene. It is found that there are two quasi-stationary states of the molecular negative ions having lifetimes of about 10^–14 and 4 · 10^–15 sec. The cross sections for formation of these states are estimated, and also the cross sections for resonant elastic scattering of electrons. The states are shown to be related to excited states of the molecule. It is found that alkyl substitution has the following effects on resonant electron capture: a) reduces the probability of ring breakage and b) reduces the energy levels of the quasi-stationary state. Some aspects of dissociative ionization are discussed.     

Resonance electron capture by substituted cyclopropane molecules

Conclusions The fragmentation of substituted cyclopropanes under the conditions of dissociative electron capture is accompanied by the opening of the cyclopropane ring and is determined by the nature of the functional group. The increase in the number of electron-acceptor substituents noticeably stabilizes the molecular negative ions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2473–2478, November, 1987.     

Reaction of conjugated dienes with trimethyldeuterosilane

Conclusions A study was made of the reaction of butadiene, isoprene, and 3-methyl-1,4,6-heptatriene with trimethyldeuterosilane, and the location of the deuterium atom in the alkenylsilane molecule was established on the basis of the¹H and¹³C NMR spectral data, and also the mass-spectral data for dissociative electron capture. A scheme was proposed for the hydrosilylation process.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 204–208, January, 1977.     

Mass spectra of the negative ions of some steroids

It has been shown that the main directions of the fragmentation of the molecular negative ions are connected with the formation of systems of conjugated bonds and the delocalization of the negative charge over a π-system of electrons. The mass spectrometry of the negative ions formed by the dissociative capture of electrons (DCE) is promising for the study of the molecules of steroid compounds.     

Negative-ion mass spectra of heteroorganic compounds of group IV

Conclusions The dissociative resonance capture of electrons by the molecules of heteroorganic compounds of group IV was studied. It was shown that a new resonance state is observed with the introduction of a vinyl substituent. The nonadditive increase in the relative cross section for the formation of the negative ion with increase in the number of vinyl substituents is due to the stabilization of the molecule negative ion by * -* interaction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 566–571, March, 1986.     

Positive- and negative-ion mass spectra of racemic diptocarpamine and its sulfide precursor

Features of the fragmentation on electron impact and resonance electron capture of racemic diptocarpamine (I), its sulfide precursor (II), and N-decyl-N-isopropylurea have been determined which consist in a predominance of simple bond cleavages over the rearrangement processes involving the elimination of S(O)NH-containing neutral fragments that are typical for diptocarpidine. The elementary compositions of the characteristic lines in the EI mass spectra were established by measuring accurate values of the mass numbers of the ions. An estimate of the efficacy of the spatial interaction of the heteroatomic groupings separated by carbon chains in the and M^– ions of compounds (I) and (II) has been made. On the basis of the REC mass spectra it has been concluded that the molecules of compounds (I) and (II) exist in twisted or folded conformations.Institute of Chemistry, Bashkir Scientific Center, Urals Branch, Academy of Sciences of the USSR, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 80–86, January–February, 1989.