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].

Analysis of the electron impact mass spectra, collision-induced dissociation spectra, and high-resolution mass spectrometry data of N-[2-(cyclopent-1-en-1-yl)phenyl]arylamides and isomeric 2-arylspiro[3,1-benzoxazine-4,1'-cyclopentanes] indicated that only a small portion of the molecular ions of the arylamides undergo cyclization to give the corresponding substituted 3,1-benzoxazines prior fragmentation. The donor-acceptor properties of the benzene ring substituents affect the efficiency of cyclization of the molecular ions.

The arrangement of N-[2-(cyclopent-1-en-1-yl)phenyl]benzamide to give 2-phenylarylspiro[3,1-benz-oxazine-4,1'-cyclopentane] was carried out in the presence of DCl. Analysis of the electron impact mass spectra of this benzoxazine and its deuterated analogs showed initial formation of a monodeuterated product. The contributions of polydeuterated benzoxazines increase as the reaction progresses.

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.

Measurements of mass-spectromical characteristics of molecular ions and precise values of mass numbers of all significant ion peaks in electron ionization mass-spectra of 3-brom-(4-nitroethyliden)-hydrazino-(1-tiethanil-3)-1,2,4-triazol (1) and its 1-oxo(2) and 1,1-dioxo(3) derivatives are carried out. Properties of the highest occupied molecular orbitals are shown to influence significantly on the analyzed compounds mass-spectra generation processes. The increase of sulphur atom oxidation degree leads to ione electron pair disappearance and sulphur containing fragments contribution reduction.

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.

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.