The kinetics of oxidation of benzaldehyde. I

Abstract
For the study of the mechanism of oxidation of hydrocarbons and other organic compounds it is desirable to find systems suitable for kinetic study in which the mechanism of peroxide formation is not complicated by autocatalysis. The oxidation of benzaldehyde in benzene solution in the absence of light has been examined from this point of view. It was found that in the absence of catalysts and inhibitors consistently reproducible rates of oxidation are to be obtained only with special precautions in the preparation and handling of the materials. For a short period after the beginning of the reaction, the amount of peroxide in the solution corresponds closely to the oxygen taken up. There is no sign of autocatalysis. The reaction, on the contrary, is self-inhibiting. The rate of oxidation is extremely sensitive to the presence of inhibitors, the effect of 10~e mole /?-naphthol/mole solution being easily detected. The reaction is catalyzed by dibenzoyl peroxide according to the relationship ρ = ρ u + k [ Bz 2 O 2 ]1/2 , P and pu being the initial rates in the presence and absence of dibenzoyl peroxide respectively and k a constant. Two conclusions are drawn from this result: (i) in the peroxide catalyzed reaction the chains are terminated by mutual interaction and (ii) the mechanism of the uncatalyzed dark reaction involves different chain carriers from those of the catalyzed reaction. In the presence of dibenzoyl peroxide both reactions take place simultaneously but independently. The oxidation is also catalyzed, though in a rather more complicated manner, by Pyrex glass.