The kinetics of disproportionation–combination reactions between the isopropoxyl radical and nitric oxide, and of the pyrolysis of the O–O bond in di-isopropyl peroxide

Abstract

A study of the early stages of the gas-phase pyrolysis of di-isopropyl peroxide in the presence of excess of nitric oxide at 104·6–149·3° shows that the ratio of the disproportionation reaction, forming acetone and nitroxyl, to combination, forming isopropyl nitrite, is 0·22. The disproportionation reaction has zero activation energy with A2=k2∼ 1·2 × 1010 mole–1 cm.3 sec.–1. The initial O–O bond fission in the peroxide is first-order with k1= 1·4 × 1015 exp. (–36,800/RT) sec.–1; the close agreement with liquid-phase results is probably due to the low value of the rate constant (6·6 × 1011 mole–1 cm.3 sec.–1) for the recombination of isopropoxyl radicals.