The kinetics of disproportionation–combination reactions between the s-butoxy-radical and nitric oxide, and of the pyrolysis of the O–O bond in di-s-butyl peroxide in the gas phase

Abstract

A study of the reactions of the s-butoxy-radical, produced by pyrolysis of di-s-butyl peroxide, with nitric oxide in the gas phase at 100–140°: Bu^sO·+ NO ⇀ HNO + EtCOMe (2); Bu^sO·+ NO ⇀ Bu^sONO (3) shows that the disproportionation–combination ratio, k₂/k₃, is 0·25–0·27 and temperature-independent, with k₂=A₂∼ 1·3 × 10¹⁰ mole^–1 cm.³ sec.^–1. Determination of the rate of depletion of the peroxide by product analysis shows that fission of the O–O bond is first-order, with k₁= 1·8 × 10¹⁵ exp(–36,400/)RT sec.^–1, from which it can be shown that the rate constant k_–1(assumed temperature-independent) for recombination of the s-butoxy-radical is 8·5 × 10¹¹ mole^–1 cm.³ sec.^–1. From E₁ and the calculated value of ΔH_t° for the peroxide, the heat of formation of the s-butoxy-radical is found to be –17·5 kcal. mole^–1.