Synthesis and structure of 5,5-dialkyl-3-arylamino-2-thiohydantoins

The reaction of arylhydrazides of -alkyl--chlorocarboxylic acids with thiocyanate ions gave intermediate thiocyanates which rearranged to isothiocyanates on heating and the latter cyclized to 5,5-dialkyl-3-arylamino-2-thiohydantoins.Institute of Technical Chemistry, Urals Branch, Russian Academy of Sciences, Perm' 614000. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 898–903, July, 1997.     

Alkylhydrazides and their protonated forms: Physical methods andab initio calculations

The basicity of hydrazides of the highest aliphatic carboxylic acids RC(O)NHNH₂ (R = C_nH_2n+1,n = 5-12) has been studied by potentiometric titration, and IR and¹H NMR spectroscopy.Ab initio Hartree-Fork calculations using the 6–31G^* basis set with full optimization of geometry were carried out on the simplest acy1hydrazines and their possible protonated forms. Based on these calculations, and the 1R and¹H NMR spectra, the tautomerism of alkylhydrazides and the structures of their protonated forms are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2645–2649, November, 1996.     

Characteristic features of interaction between atoms in chloro-substituted 1,4-dioxane fromab initio calculations

Ab initio calculations in a split-valence shell 6-31G(d) basis for the 2-chloro-1,4-dioxane (with axial and equatorial Cl atom) and 2,3-cis-dichloro-1,4-dioxane molecules with full optimization of their geometry were performed. The major contribution to the lowering of the NQR frequencies of the axial Cl atoms compared with the equatorial Cl atoms comes from the higher p-electron population of the former in these molecules. The populations of the orbitals for the unshared electron pairs of the axial and equatorial Cl atoms are identical in these molecules. But these orbitals are polarized differently, which also has some effect on the ratio of the NQR frequencies of these atoms. The differences in the electron populations of the axial and equatorial Cl atoms for the studied molecules are due to the asymmetry of the electron distribution in the Cl atoms geminal to them, which is responsible for the different polarization of the valence p-orbitals of the axial and equatorial Cl atoms.Institute of Technical Chemistry, Urals Branch, Russian Academy of Sciences, Perm' 614000, Russia; e-mail: chemist@mail.psu.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1485–1490, November, 1999.     

Electronic and Spatial Structure of Piperidine and Its Substituted Derivatives from the Results of ab initio Calculations

The results of non empirical quantum-chemical calculations using the RHF/6-31G(d) and MP2/6-31G(d) methods do not agree with proposals for the axial position of the H atom on the N atom in the piperidine molecule. According to RHF/6-31G(d) calculations for the N-methylpiperidine molecule and its chloro-substituted derivatives an equatorially placed methyl group is energetically more favored than an axial. The axial C-Cl and C-H bonds in these molecules are longer than the equatorial. The ³⁵ Cl NQR frequencies for the axial Cl atoms are lower than the equatorial. The ³⁵ Cl NQR frequency of the axial chlorine atom in 2-chloro-1-methylpiperidine is anomalously low. This is chiefly due to the high population density of its p σ-orbital and this is a result of the polarization of the C-Cl bond via the N atom unshared electron pair directly through the field. The effect of a similar unshared electron pair on the parameters of the C-Cl bond in the ClCH₂NH₂ molecule has been studied by the RHF/6-31(g) method for different angles of rotation of the ClCH₂ group around the C-N bond. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1044–1052, July, 2005.     

Coordination isomerism of the complex of o-methoxybenzoyl chloride with tetrachlorostannane. The results of ab initio calculations

Quantum-chemical calculations of three isomers of the o-methoxybenzoyl chloride complex with tetrachlorostannane and of their components were performed applying the RHF/3-21G* and MP2/3-21G* methods. It was found that a complex with trigonal-bipyramidal structure is formed, its formation occurred through the interaction of ester (not carbonyl) oxygen atom with tin atom. This complex eventually is transformed into the energetically more favorable cis-octahedral complex of the same composition. The tin atom in the latter complex interacts with two oxygen atoms. The reasons for the formation of energetically unfavorable complex of trigonal-bipyramidal structure is the almost equal probability of the existence of various possible forms of o-methoxybenzoyl chloride and therefore higher probability of the Sn atom to interact with the ester oxygen atom possessing a much more negative charge than the carbonyl oxygen.     

Electronic and spatial structure of five-membered oxygen-or sulfur-containing cyclic phosphorus and arsenic compounds based on quantum-chemical calculations

We have carried out nonempirical quantum-chemical calculations for five-membered heterocyclic molecules containing O or S atoms and also P or As atoms in the ring, using RHF/6-31G(d) and MP2/6-31G(d) methods with full optimization of their geometry. We have studied their electronic and spatial structure and the characteristics of the interaction between atoms in the molecules. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 629–634 April, 2006.     

Influence of the Lone Electron Pairs of the Ether Oxygen Atom on the Electron Density Distribution in α-Chloro Ethers

The axial and equatorial C-Cl bonds in cyclic -chloro ethers are polarized differently because of different orientation of the lone electron pair of oxygen relative to these bonds.     

Structural features of SnCl<Subscript>4</Subscript>–<Emphasis Type="Italic">ortho</Emphasis>-dimethoxybenzene complexes as derived from ab initio computations

Computations for the possible structures of SnCl₄–ortho-dimethoxybenzene complexes and initial components have been performed by MP2/LANL2DZ method. Computation results have been compared with experimental data of ³⁵Cl nuclear quadrupole resonance. cis-Octahedral structure of the complex through the coordination of both oxygen atoms has been confirmed. This complex differs considerably from the majority of studied tetrachlorostannane complexes of cis-octahedral structure in terms of the ratios of axial and equatorial Sn–Cl bond distances, p _σ electron density, and ³⁵Cl NQR frequencies for axial and equatorial chlorine atoms.     

<Emphasis Type="Italic">Ab Initio</Emphasis> calculations of 3-(trichlorogermyl)propanoylamide structure and nature of its Ge←O coordination bond

Calculations of 3-(trichlorogermyl)propanoylamide molecule containing a Ge←O coordination bond were performed by RHF/6-31G(d) method with full and partial geometry optimization. Its total energy 2.22 kcal mol⁻¹ is lower than that of the molecule with tetracoordinated germanium atoms. Germanium and oxygen atoms initiate the formation of a coordination Ge←O bond in this molecule and are conductors of the electron density transfer from the atoms nearest to the oxygen on the atoms of the germanium coordination polyhedron. No electron density transfer occurs from the oxygen atom to germanium. Upon decrease in the Ge...O distance the axial Ge-Cl bond is polarized much stronger than the equatorial bonds. In the crystalline state of the substance these molecules are fixed in an energetically unfavorable structure.     

Nature of the coordination bond in the GeCl4-trimethylamine complex

Quantum-chemical computations were performed for the GeCl₄ ← N(CH₃)₃ system using the MP2/6-31G(d) method with total optimization of its geometry and at different fixed Ge…N distances (from 2.0 to 4.5 Å). The coordination bond in the complex results from the involvement of different AOs of Ge and N atoms (along with other atoms in the molecule) in the formation of a number of MOs. The number of these MOs increases with decreasing Ge…N distance, thus reducing the total energy of a molecule and stabilizing it. The coordination bond and the covalent bond are of the same nature. When the distance between the components of the system is reduced, the partial negative charges of N, C, and all Cl atoms increase; the partial positive charges of Ge and H increase as well.