Chemistry of peroxyacyl nitrates I. Thermal decomposition in cyclohexane solution; effect of added nitric oxide and of nitrogen dioxide

Abstract

AbstractThe peroxyacyl nitrates 1b and 1c, in cyclohexane solution (0.01 − 0.1 M, 25‐60°C) decompose smoothly, displaying first‐order kinetics. Added nitrogen dioxide lowers the rate (approx. 3 x) but added nitric oxide results in a (7‐fold) rate enhancement, independent of the NO concentration. Under the latter circumstances the Arrhenius parameters for 1b are: log A/s−1 = 15.3, Ea = 26.7 kcal.mole−1.Products from 1b include CO2 (>85%), RNO2, RONO, ROH and corresponding derivatives from solvent cyclohexane. 1b does not produce caproic acid, but m‐chlorobenzoic acid together with chlorobenzene (RH), are prominent products from the thermolysis of 1c.These features are interpreted via a homolytic mechanism involving primary steps [1] and [2]. With added NO, step [1] is rate‐determining, whereas with added NO2 decomposition occurs via reaction [2].The relevance of radical pair (cage) processes is outlined.Attack on solvent occurs by transient free‐radical intermediates (e.g. R*, RO*) and by nitrogen dioxide.The effect of other additives (such as dihydroanthracene, resulting in RCO3H as isolable product) is in accord with this mechanism.Thermochemical‐kinetic features are discussed.