Jouko Koskikallio

Kinetics of reactions between methyl and dimethyl-aminyl radicals formed in the flash photolysis of tetramethylhydrazine, tetramethylurea and tetramethyltetrazene in the gas phase

Abstract Methyl and dimethylaminyl radicals are formed in the flash photolysis of tetramethylhydrazine, tetramethylurea and tetramethyltetrazene in the gas phase. The rate constants of radical combination and hydrogen exchange reactions between methyl and dimethylaminyl radicals were calculated with a computer integration program, using a least-squares iteration method, from the amounts of final products determined by gas chromatography. The ratio of the rate constants of the combination and hydrogen abstraction reactions between two dimethylmaminyl radicals (1.55 ± 0.2) is close to the value (1.59 ± 0.2) for the ratio of the rate constants of the respective reactions between methyl and dimethylaminyl radicals.

Investigation of the mechanism of phenanthrene photocyanation by flash photolysis in dry acetonitrile

Abstract The mechanism of photocyanation of phenanthrene was studied by flash photolysis. Two transients were observed in the presence of the cyanide anion. One decayed by second-order kinetics and the intensity of absorption of the other was linearly proportional to the square of the intensity of the exciting light. Two possible mechanisms based on the experimental results are presented for the formation and quenching of the transients.

Self-termination rate of para-substituted benzyl radicals in aqueous solutions : a time-resolved study

Abstract The self-termination rates of the benzyl radical (C 6 H 5 CH 2 ) and para-substituted benzyl radicals (XC 6 H 4 CH 2 ) were studied in aqueous solutions. The Arrhenius parameters and activation energies were determined in the temperature range 275.5–328 K. The kinetic activation energies of these radicals were close to the dynamic activation energy of the solvent, indicating that the termination rate is controlled by diffusion. The values for the rate constants (2 k t (10 9 dm 3 mol −1 s −1 )) and the activation energies ( E (kJ mol −1 )) were 5.94±0.52 and 14.69±0.61 for CH 3 OC 6 H 4 CH 2 , 4.52±0.2 and 17.65±1.16 for CH 3 7z.sbnd;C 6 H 4 CH 2 , 3.07±0.45 and 17.58±0.97 for HC 6 H 4 CH 2 , 4.13±0.81 and 19.10±1.20 for ClC 6 H 4 CH 2 and 4.17±0.44 and 14.62±0.52 for NO 2 C 6 H 4 CH 2 .