Yu. L. Frolov

Structure and Properties of 2,2-Dibromovinyl Trifluoromethyl Ketone

It was established by IR spectroscopy and quantum-chemical calculations along nonempirical DFT method in B3LYP version with the basis set 6-311 G(d,p) that 2,2-dibromovinyl trifluoromethyl ketone consisted of a mixture of s-cis planar conformer and s-trans-form deviating from a plane by 13°, whereas the s-cis-form is more energetically stable than the s-trans one (ΔE -5.07 kcal mol-1). Also in 2,2-dibromovinyl methyl ketone the planar s-cis conformer is more stable. Chlorine-containing analogs, 2,2-dichlorovinyl trifluoromethyl ketone and 2,2-dichlorovinyl methyl ketone, are more stable in the planar s-trans-conformation. Charge distribution and polarization in the dibromovinyl ketones are analogous to those in dichlorovinyl ketones in agreement with the established reactivity of dibromovinyl trifluoromethyl ketone. By reaction of 2,2-dibromovinyl trifluoromethyl ketone with 2,4-dinitrophenyl-, alkylhydrazines, N,N-dimethylhydrazine, N,N-, N,O-, N,S-binucleophiles were respectively obtained hydrazone, derivatives of pyrazole, imidazole, oxazole, and 1,3-thiazine containing a trifluoromethyl group.

The fine difference in electronic structure of heteroatoms in methyl vinyl ether and sulfide

Abstract Quantum chemical calculations carried out in D95++(d,p) basis set at B3LYP level of density functional theory were obtained for methyl vinyl ether and methyl vinyl sulfide to compare the electronic structure of heteroatom lone pairs. The molecules were observed in the framework of Baders theory ‘Atoms in Molecules’. Essential differences in electronic structure of oxygen and sulfur atoms are observed. An asymmetry of sulfur atom is supposed.

Regioselectivity of the hydrolysis of 2-(1-alkoxyvinyl)-substituted imidazolidines, 1,3-thiazolidines, and 1,3-oxazolidines

Abstract2-(1-Alkoxyvinyl)-1,3-thiazolidines reacted with H2O or D2O in the presence of 105 mol % of p-toluenesulfonic acid or trifluoroacetic acid (20°C, 1 h) to give 2-acetyl-1,3-thiazolidine in quantitative yield. 2-(1-Alkoxyvinyl)-3,5-diphenylimidazolidines underwent hydrolysis in the presence of 20 mol % of an acid (20°C, 24 h) at the vinyloxy group with high regioselectivity yielding 2-acetylimidazolidines. Hydrolysis of 2-(1-alkoxyvinyl)-3-phenyl-1,3-oxazolidines in the presence of 10 mol % of p-toluenesulfonic acid (20°C, 5 days) takes two pathways, one of which involves the endocyclic C-O bond with ring opening and the other involves the vinyloxy group to produce 2-acetyl-3-phenyl-1,3-oxazolidine. Unlike phenyl-substituted 1,3-thiazolidines and imidazolidines, hydrolysis of their 3-methyl- and 3,5-dimethyl-substituted analogs in acid medium occurs mainly via ring opening. The observed hydrolysis pathways were interpreted in terms of B3PW91/6-311G(d,p) quantum-chemical calculations.

Intramolecular Thiiranocyclobutane-Open Chain Isomerization of 3,3'-Dithioxo Sulfide Derivatives: A Quantum-Chemical Study

The thermodynamic stability and structural and electronic characteristics of thiabicyclic structures, expected products of photochemical isomerization of bis(3-thioxo-1-phenylpropenyl), bis(3-thioxo-1-propenyl), and bis(5,5-dimethyl-3-thioxocyclohex-1-enyl) sulfides, were evaluated by quantum-chemical calculations. The energy in the thiabicyclic structures is accumulated owing to formation of metastable highly strained fused systems. The heats of dark isomerization of thiabicyclic structures into acyclic ones range from 50 to 250 kJ mol-1. The activation energy of thermal transformations into acyclic isomers are 90-310 kJ mol-1. Higher thermal effects and lower activation energies are obtained when the polarity of the medium is taken into account. The calculation results show that this class of compounds is promising for solar energy conversion.

Conformations of methoxy(hydroxy)-substituted benzenes and benzaldehydes in the gas phase

The electronic structure ofo-methoxy(hydroxy)-substituted benzenes has been investigated by the combined use of photoelectron spectroscopy and molecular orbital calculations by means of the semi-empirical AM1 method. Absorption bands in the PE spectra have been assigned, the dependence of someπ-orbital energies on the molecular conformation has been found, and the estimation of the mean torsion angle of the OCH3-group with the plane of the benzene ring has been carried out. The results obtained show that the gas-phase conformations of the heavy-atom framework of guaiacol and vanillin molecules are planar. For veratrole and veratraldehyde, nonplanar conformations with mean torsion angles ϕ ≈ 80° and 55°, respectively, have been observed.

Quantum-Chemical Study of Interactions between the Hydroxonium Cation and the Monomethyl Mercury Cation in Aqueous Media

AbstractThe potential surface of the reaction between the polyhydrated monomethyl mercury cation and the hydroxonium cation is considered. An n

Ab initio Calculations of the Internal Rotation Barrier in the Dimethylacetylene Molecule

S_{N^2 }

Conformational Structure of Molecules with Weakly Hindered Internal Rotation

n type reaction, resulting in solvate-separated products (mercury dication and methane molecule), was found to be thermodynamically probable. The thermal balance of the reaction is 132.3 kJ/mole. The activation energy of the limiting stage of the process is 56.7 kJ/mole.