Phenylhydrazines. Structure and basicity

The main properties of phenylhydrazines are governed by the p-character of the unshared electron pair of the nitrogen of imino group changing in keeping with sp ³ → sp ²-regibridization of its atomic orbitals under the steric and electronic (-I effect of amino group) effect of substituents.     

Kinetics of the transfer of the dimethyl-carbamoyl group from N- and O-acylonium salts to azines and their N-oxides

The rate constants and activation energies were determined for a series of reactions involving the transfer of a dimethylcarbamoyl group from the N,N-dimethylcarbamoylonium salts of a series of nitrogen heterocycles and their N-oxides to nucleophiles (azines and their N-oxides) in acetonitrile. The measured values were compared with the structural, reaction, and equilibrium characteristics. L. M. Litvinenko Institute of Physical Organic Chemistry and Coal Chemistry, National Academy of Sciences of Ukraine, Donetsk. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 143–148, May–June, 1997.     

Effect of structure on the kinetics of the nucleophilic substitution of acylonium ions

A study was carried out on 67 reactions involving transfer of acyl groups from the corresponding N-, O-acylonium salts to pyridine N-oxides, highly basic pyridines, and N-methylimidazole in acetonitrile solution. PM3 calculations were carried out for the ionization potentials of the nucleophiles and electron affinities of the N-, O-acylonium cations. A multiparameter correlation was obtained predicting the rate of acyl group transfer. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 34, No. 2, pp. 96–102, March–April, 1998.     

Acetyl transfer from N-acetyloxypyridinium cations to 4-(4′-N,N-dimethylaminostyryl)-pyridine N-oxide and 4-dimethylaminopyridine

Kinetic data are given for the transfer of the acetyl group from the N-acetyloxypyridinium cations of tetraphenylborate salts to 4-(4′-N,N-dimethylaminostyryl)pyridine N-oxide and 4-dimethylaminopyridine in acetonitrile solution. Structural factors were found to affect the rate constants and activation parameters. Correlation equations are given relating the acetyl transfer rate constants with pK_BH+ values of the leaving group and frequencies of the carbonyl vibrations of the salts. Translated from Teoreticheskaya i éksperimental’naya Khimiya, No. 2, pp. 75–77, March–April, 1997.     

Correlation of IR parameters with reactivity characteristics for the hydrazides of carboxylic acids

Measurements have been made of the frequencies of the N-H and C=O stretching modes in dilute solution in CCl₄ for 23 aliphatic and aromatic substituted hydrazides of carboxylic acids. These are compared with the (⁰) Taft constants. Measurements have also been made of the basicity constants at 25 in water and the rate constants for reaction with phenyl isocyanate at 25. Correlation equations are derived for the transfer of electronic effects across the -CONH-bridge. It is found that the sign of the reaction constant in the correlation of with ⁰ reverses on passing from aromatic amines to amides via the hydrazides of carboxylic acids.We are indebted to L. M. Litvinenko and A. F. Popov for a discussion of the results.     

Reaction of Acetyl and Benzoyl Chlorides with Pyridines and Pyridine N-Oxides

The rate of formation of N- and O-acetyl and benzoyl salts of pyridines and pyridine N-oxides in acetonitrile and methylene chloride and equilibria therein were studied. The process occurs in one step following the SN2 mechanism with a small degree of bond rupture in the transition state.     

Influence of temperature gradients on the composition of crystallization products of ammonium chloroplatinum(IV) and chlorohodium(III) complex salts

The influence of temperature gradients on the particle size and component composition of solid phases in heterogeneous systems of ammonium chloroplatinum(IV) and chlorhodium(III) complex salts was studied. A Benard cell was implemented as applied to not only homogeneous but also heterogeneous systems. Two contributions to the cocrystallization of rhodium with platinum are distinguishable and kinetically resolved: the formation of nonequilibrium solid solutions by ammonium chlorometalates and equilibrium Ostwald ripening. The elucidation of both factors helps in finding crystallization parameters for minimizing the rhodium contamination of platinum in refining practice.     

Composite film coatings prepared by cationic polymerization of epoxy-polysiloxane systems

Cationic polymerization of dicyclohexylpropane diglycidyl ether in the presence of boron trifluoride was studied with the aim to prepare hybrid coatings.