Organoboron antioxidants: Part 1—Boric acid derivatives as primary antioxidants

Abstract

Organoboron compounds, particularly boric acid esters and arylboronic acid derivatives, are known to be good antioxidants. In this paper, the inhibiting activities of various boron compounds are compared with those of phenolic antioxidants and phosphites. Whereas in the autoxidation of polypropylene, aryl borates give rise to approximately the same induction periods as the constituent phenols, aryl phenylboronates are, to some extent, considerably better. For the calculation of kinetic data, particularly the rate constants ( k 7) of the reaction with peroxyl radicals and the stoichiometric factor ( f), investigations into the inhibiting activity of boron compounds in the initiated oxidation of cumene at low temperatures are used. The rate constant k 7 of aryl phenylboronates is approximately ten times greater than that for structurally analogous phosphites, whereas aryl borates can be regarded as ‘depots’ for phenols.