Cycloheptatriene derivatives are studied by means of resonance electron capture negative ion mass spectrometry (REC NIMS). The average lifetimes of molecular negative ions (NIs) are measured with respect to electron autodetachment. Using the Arrhenius approach, electron affinity EAa of the molecules under study is estimated, and the effective temperature of the resulting negative molecular ions is determined as a function of the electron energy. It is assumed that the dissociation of negative molecular ions in the ground electronic state is a process similar to that of the thermal degradation of molecules.

The formation of negative ions of some diterpene alkaloid molecules having conjugated πС=С and πС=О bonds in their structure by resonance electron capture has been studied. The mass spectra of these compounds are due to electron capture onto the lowest unoccupied molecular orbital (LUMO), which is π*-С=С or π*-С=О in nature. It has been found that the partial conversion of the test compound molecules into the enol form is possible on transferring into a gas phase; for this purpose, the appearance potentials of the ions (M–H)– and (M–OCH3)– have been compared with the calculated thermodynamic thresholds of their appearance in the keto and enol forms.

According to available experimental data, the formation of long-lived (∼10−5 s) negative molecular ions (NMIs) due to resonant electron capture (REC) by polyatomic molecules is observed experimentally with the proviso that their electron affinity (EA) is on the order of several tenths of electronvolt or above. Such compounds are characterized by large NMI formation cross sections. High ability to effectively capture thermal electrons correlates with their ability to capture free radicals, in particular, to act as inhibitors of radical polymerization [1]. It is likely that these compounds will exhibit antioxidant activity as well. It is therefore of interest to use the REC technique for studying antioxidant compounds, of which the bioflavonoid quercetin (QU) (1) (Fig. 1) and its derivatives are prominent representatives [2, 3].

Processes resulting in the formation of negative ions by molecules of some diterpene alkaloids via resonance electron capture have been studied. The mass spectra of these compounds have a small number of lines represented largely by intense peaks in the thermal electron energy region and are due to electron capture onto the lower unoccupied molecular orbital, which is π*-C=O or π*-Ph-C=O in character.

The processes of formation of negative ions by allylsilane molecules were studied by resonanceelectron-capture mass spectrometry, and photoelectron spectra of these compounds were obtained. It was experimentally found that the overwhelming majority of fragment negative ions are produced in the energy range ∼6–10 eV. It was shown that the resonance-electron-capture mass spectrum is almost entirely described by one or two series of intershell resonances due to excitation of an electron successively from several higher occupied orbitals to the lower unoccupied π molecular orbital.

Resonant electron capture (REC) mass spectra of phthalimide- and pyridine-2,3-dicarboimidoalkyl-α-diazoketones have been investigated. Based on calculations using the Hartree–Fock method and density functional theory with the B3LYP functional the structure of the negative ions (NIs) [M–N2]− and [M–N2–C3H3RO]− as well as the reactions leading to their formation have been proposed.

The formation of negative ions from pyrazoline and its derivatives was studied by the negative-ion and resonance-electron-capture mass spectrometry techniques. The results were compared with those of the dissociation processes of the excited-state pyrazoline molecule, and resemblance to the fragmentation processes of the molecular negative ion was revealed.

Negative ion (NI) mass-spectra of molecules of substituted cyclopropylurea have been measured. The method of resonance electron capture (REC) NI could be applied for the investigation of electron properties of substitutes cyclopropane fragment of the molecule. In mass-spectra of this compounds with electron-acceptor substitutes picks of ions, which characterize disinteration of cyclopropane ring, were registered. Surge of neutral fragment of carben R1СR2 by (M-H)ion were observed during this process. In spectra of compounds with electron-donor substitutes this process were not observed.

12-Oxo derivatives of 11-desoxolycyrrhetic acid and its derivatives were produced by oxidative transformation using ozone. Olean-3,12-dion-30-oic acid was produced for the first time by exhaustive ozonolysis of 11-desoxoglycyrrhetic acid at −60°C.

Mass spectra of phthalymidoalkyl-a-diazoketones were obtained and quantum-chemical calculations by using Hartry-Fock and density functional theory methods were carried out. The most abundant ion in negative ion mass spectrum is due to the loss of N2 molecule followed by cyclopropanone molecule abstraction [M-N2-cyclo-C3H3RO]at 0.3 eV. Herewith the loss of H-atom occures from b-position of benzene ring to one of the CO-groups of phthalymide fragment. Autodetachment lifetime of methyl esters of phthalyl aminoacids is increased by the raise of a number of methylene groups in alkyl chain. Such dependence is not observed for the phthalyl aminoacids. Metastable transitions under resonance electron capture of N-butylphthalymide molecules were revealed.

The mass spectra of negative ions of keto-stabilized sulfur ylides, obtained from amino acids were studied. Increasing of electron-donor properties of a-positioned alkyl substituent to the phthalimide moiety as well as of S-positioned substituents R3, R4 in the ylide molecule raises probability of cyclization process. The loss of bulky C3H7-fragment from keto-stabilized sulfur ylide is more favorable in comparison to CH3-group.

Processes of the formation of negative ions from aniline and its derivatives were studied by the resonance electron capture technique. The results were compared with those obtained earlier for molecules of benzene, phenol, and chlorophenols. It was concluded that the processes of formation of negative ions in aniline differ substantially from those in benzene and phenol. The triplet series of resonances beginning from the resonance at 2.6 eV is observed.

The enol forms of uracil and its derivatives were detected in the gas phase by mass spectrometry. The [M - H] − ion is produced by resonance electron capture to the lowest unoccupied molecular orbitals, the process being accompanied by the detachment of the hydrogen atom from the nitrogen atom of the diketo form (low-energy peak at 0.8 eV) and from the oxygen atom of the enol form (in the energy region of 1.4 eV). The gas phase contains ∼10 −3 % of the enol form.