V. I. Kadentsev

Studies on substitution of nitro groups in 1,3,5-trinitrobenzene with NH-azoles

Conditions were found under which NH-azoles (benzotriazole and its derivatives, 1,2,3- and 1,2,4-triazoles, pyrazole and its derivatives) replace one nitro group in 1,3,5-trinitrobenzene (TNB) to form the corresponding N-(3,5-dinitrophenyl)azoles in the presence of inorganic bases in aprotic dipolar solvents. The reaction pathway was found to depend on the structure of the starting azole. The benzotriazolyl and 1,2,4-triazolyl fragments activate the replacement of the meta-nitro group to virtually the same extent as the nitro group in TNB, which made it possible to successively replace all three nitro groups in TNB.

Peculiarities of interaction of H+, Me3C+, and Me3Si+ ions with multifunctional molecules in the gas phase

Peculiarities of interaction of H+, Me3C+, and Me3Si+ ions with functional groups of molecules in the gas phase have been studied. Proton tends to form chelates with virtually all of the functional groups studied, whereas Me3Si+ ions exhibit no capacity for chelation. Using isomeric xylenes as examples it was shown that Me3Si+ ions (unlike Me3C+ ions) experience virtually no steric hindrance when they react with nucleophilic centers. Effects of functional groups present in molecules of nitriles on the generation of [M+Me3C]+ adducts in the gas phase and the Ritter reaction in solution were estimated.

Interaction of trimethylsilyl ions with nitrates of the estrane series in the gas phase

The interaction of trimethylsilyl ions with nitrates of the estrane series affords the adducts [M + SiMe3]+, whose fragmentation proceeds through the elimination of the functional groups either along with the trimethylsilyl residue, or in the form of molecules containing no SiMe3.

Tetramethylsilane as reagent gas: mass spectra of nitrocarboxylic acid esters and nitroalcohols

Nitrocarboxylic acid esters and nitroalcohols react with trimethylsilyl cation in the gas phase under conditions of chemical ionization to form stable [M+SiMe3]+ ions. The pathways of their fragmentation were established and characteristic distinctions in the mass spectra caused by mutual arrangement of functional groups were found.

Specific features of the interaction of methyl ethers of methyl (methyl-α-D-galactopyranoside)uronate with trimethylsilyl ions in the gas phase

Specific features of the interaction between trimethylsilyl ions and methyl (methyl-α-d-galactopyranoside)uronate and its methyl ethers were revealed. It was shown that a hydrogen atom is generated when the trimethylsilyl ion is located at hydroxyl group. This atom migrates over the methoxy and hydroxyl groups toward the glycoside methoxy group, resulting in the formation of [Me+SiMe3−MeOH]+ ions.

Interaction of the trimethylsilyl cation with molecules of aliphatic nitro compounds in the gas phase

Interaction of mononitroalkanes with the trimethylsilyl cation in the gas phase under chemical ionization (CI) conditions results in the formation of [M+SiMe3]+ ions, which are more stable than the corresponding protonated molecular ions. In the case of 2-nitro-2-methylpropane and 2-nitropentane, fragmentation of the [M+SiMe3]+ ions occurs with the formation of C4H9+ and C5H11+ carbocations, respectively. In the case of 1,1-dinitroethane and 1-halo-1,1-dinitroethane, fragmentation of the [M+SiMe3]+ ions occurs with splitting off of a NO2. radical or an XNO2 molecule (X=H, F, or Cl).

Specific features of the behavior of ?- and ?-glycosylfluoride tetraacetates during chemical ionization in isobutane and tetramethylsilane

Reactions of α- and β-glycosylfluoride tetraacetates with trimethylsilicenium ion in the gas phase during chemical ionization have been studied. The [M+SiMe3]+ ions formed from the glycosylfluorides are more stable than the corresponding [M+H]+ ions. The cleavage of the weakest glycosidic bond leading to the generation of glycosidic ions is not dominant for the trimethylsilylated ions, as it has been observed in the corresponding protolytic reactions. The ratio of the intensities of the [M+SiMe3]+ and [M−F]+ ions characterizes the probability of the initial localization of the trimethylsilyl ion at the glycosidic center; the equatorial orientation of fluorine at C(1) makes it possible for the electrophile to bond with this substituent. Generation of the glycosidic ions is rather weakly affected by increasing temperature, whereas [M-AcO]+ formation is significantly intensified.

Reactivity of functional groups toward H+ and SiMe3+ ions

No correlation was observed between the gas-phase basicities of various functional groups toward H+ and SiMe3+ ions. Differences in the reactivity of functional groups studied toward SiMe3+ ions are smaller than those in the reactivity toward protons.

Reactivity of molecules with nitrogen-containing functional groups toward H + and SiMe3 + ions

The equilibrium constants of trimethylsilyl cation transfer reactions differ from those of proton transfer reactions by many orders of magnitude. The basicity of MeCN (1), MeNO2 (2), and Et2NH (3) in the gas phase decreases in the series3≫1>2, whereas the affinity of the same compounds for trimethylsilyl cation decreases in the series1≫3≈2. Semiempirical quantum-chemical MNDO calculations indicate that the formation of MeCN·SiMe3+ ions is thermodynamically more favorable than that of MeNH2·SiMe3+ ions.

Gas-phase reactions of 2,2-dihalocyclopropyl-N-nitroamines under electron impact and under chemical-ionization conditions

Conclusions1.In the electron-impact mass spectra of 2,2-dihalocyclopropyl-N-nitroamines, molecular ion peaks are absent, and the fragmentation of the latter leads to the formation of fragments [M -NO2]+, [M -X]+ (X=halogen), [M -N02 -X]+., [M -NO2 -X -H]+,as well as [C3H3X2]+, [C3H2X]+, and [C2H2X]+.2.A nitroamine group attached to the dihalocyclopropane ring increases the ring stability to the action of acids, while primary and secondary fragmentations of the protonated molecular ions are accompanied by a preferential elimination of particles (NO2, X), which do not include the proton of the reagant gas.