Effect of the carbon atom coordination on the thermoactivated motion of the carbon-bonded trichloromethyl group

The reorientational motion of the trichloromethyl group depending on the environment of the carbon atom is considered based on the chlorine-35 nuclear quadrupole resonance (NQR) data. The study is performed for CCl₃ groups bonded to tri- and tetracoordinated carbon atoms in the crystalline compounds CCl₃CCl=NR (R = CH₂C₆H₅ and CCl₃CCl₃) and CCl₃CXClN=CClC₆H₄NO_2-n (X = H and Cl).₃₅Cl NQR studies of thermoactivated motion in 70 solid trichloromethyl-containing compounds are summarized. The ranges of activation energies of CCl₃ reorientations at tri- and tetracoordinated carbon atoms were determined to be 10-50 and 30-90 kJ/mole, respectively, the activation energy being markedly greater in the latter case. CCl₃ reorientations may be completely frozen by the bulky substituents which may be present along with CCl₃ in the tetracoordinated carbon bonds. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 4, pp. 737-746, July-August, 2000     

p-Fluorphenyl group as an indicator of charge on the carbon atom in aromatic compounds

A linear equation is presented for determining, from the chemical shift of¹⁹F in a p-fluorophenyl group, the effective charge of that CH fragment of the original aromatic molecule the carbon atom of which is bonded to the fluorophenyl indicator group. It has been shown that for a cyclic aromatic 6-electron system determination of the effective charges of the CH fragments by quantum-chemical calculations and the evaluation of this charge from the¹⁹F chemical shift of the corresponding p-fluorophenyl substituents lead to coincident results.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2219–2222, October, 1989.The authors are grateful to N. P. Gambaryan for fruitful discussions.     

Conversion of the carboxyl group to the corresponding trichloromethyl group in the quinoline series

Various substituted quinaldinic acids were treated with phosphorus pentachloride in an excess of thionyl chloride. Carboxyl groups of quinaldinic acid, 6-methyl-, 6-chloro-, 4-phenyl- and 4-(p-chlorophenyl)quinaldinic acids and benzo[f]quinoline-3-carboxylic acid were converted to the trichloromethyl group, while those of 8-methyl-, 4-(3,4-dichlorophenyl)-, 4-(p-nitrophenyl)-quinaldinic acids and benzo[h]quinoline-2-carboxylic acid were not. The difference is discussed on the basis of the effects of the basicity of ring nitrogen and steric factors.     

Quantum-chemical analysis of the nucleophilic substitution of the bromine atom by the cyano group at the sp-hybridized carbon atom in the methylbromoacetylene molecule

This paper reports on our quantum-chemical analysis of the nucleophilic substitution of the bromine atom by the cyano group in the reaction of methylbromoacetylene with copper cyanide. According to calculations, the reaction can form a four-membered ring containing a copper atom.     

Catalytic properties of the thermoactivated schungite rock

A high catalytic activity of the thermoactivated schungite rock was demonstrated for reactions of CO oxidation, neutralization of CO + NO _x mixtures (model exhaust gas), oxidation of o-xylene, and oxidative dehydrogenation of ethylbenzene to styrene.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1555–1560, August, 2004.     

Fast atom bombardment mass spectrometry of coordination compounds

It is shown that fast atom bombardment mass spectrometry is well suited for the study of coordination compounds.     

Reorientation of CCl3 group in tricoordinated carbon atom (According to NQR data)

A. M. Gor'kii Perm' State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 31, No. 4, pp. 41–44, July–August, 1990.     

Effect of end group chemistry on surface molecular motion of monodisperse polystyrene films

The surface molecular motion of monodisperse polystyrene (PS) with various chain end groups was investigated on the basis of temperature‐dependent scanning viscoelasticity microscope (TDSVM). The surface glass transition temperatures, T_g^ss for the proton‐terminated PS (PS‐H) films with number‐average molecular weight, M_n of 4.9k–1,450k measured by TDSVM measurement were smaller than those for the bulk one, with corresponding M_ns, and the T_g^ss for M_n smaller than ca. 50k were lower than room temperature (293 K). In the case of M_n = ca. 50k, the T_g^ss for the α,ω‐diamino‐terminated PS (α,ω‐PS(NH₂)₂) and α,ω‐dicarboxy‐terminated PS (α,ω‐PS(COOH)₂) films were higher than that of the PS‐H film. On the other hand, the T_g^s for the α,ω‐perfluoroalkylsilyl‐terminated PS (α,ω‐PS(SiC₂C^F₆)₂) film with the same M_n was much lower than those for the PS films with all other chain ends. The change of T_g^s for the PS film with various chain end groups can be explained in terms of the depth distribution of chain end groups at the surface region.     

Coherent and diffusional motion of a chemisorbed atom

Experiments indicate that there are two extreme types of motion of an atom on a solid surface. One is characterized by an average velocity and has a mean square displacement proportion to the square of the time (we call this coherent). The other (called purely diffusional) is characterized by a diffusion coefficient and has a mean square displacement proportional to time. We present a simple stochastic model to explain the microscopic origin of these two extreme types of motion. In the case in which both types of motion coexist, the motion becomes diffusional for times longer than an intrinsic time depending on the intensity of the thermal fluctuations of the atom—lattice coupling.     

Electrophilic substitution of thetert-butyl-NNO-azoxy group by the bromine atom

The electrophilic substitution of thetert-butyl-NNO-azoxy group by the bromine atom was observed for the first time when 6-bromo-2,4-bis(tert-butyl-NNO-azoxy)-5-chloro-1,3-phenylenediamine was treated with bromine in AcOH. The structural factors promoting this reaction are discussed. The direction of the replacement was confirmed by PM3 calculations of the heats of formation of intermediate cationic σ-adducts. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2131–2134, November, 1999.     

Polydentate coordination of the thallium atom in complexes with chiral amidinylcyclopentadienyl ligands

The chiral thallium amidinium cyclopentadiene-N-ylide complexes [C₅(CO₂Me)₄{ArNC(Ar")NAr}]Tl were synthesized and structurally characterized by X-ray diffraction analysis and NMR spectroscopy. In these complexes, an unusual mode of coordination of the thallium atom was found, viz., the thallium atom is coordinated by both the side-chain nitrogen atom (N—Tl, 2.833(6) ) and the system of the cyclopentadienyl ring (Tl—Cp, 2.887(4) ⁵-bonding).