CHANGE IN THE REACTIVITY OF DI-TERT-BUTYL PEROXIDE DURING HOMOLYSIS WITH AN INCREASE IN THE DEGREE OF CONVERSION AND PRESSURE

It was found that the differential reactivity (k(d)') of di-tert-butyl peroxide (DTBP) in a solution of 2-methoxy- (1) and 2-ethoxytetrahydropyran (2) at 130-degrees-C and pressures p = 20 and 1000 MPa is a periodic function of the degree of conversion, arbitrarily measured by the concentration of tert-butyl alcohol (TBA) formed. The function k(d)' = F([TBA]) was calculated with the spline approximation (SA) of the experimental [TBA] as a function of the reaction time tau, giving a continuous curve of d[TBA]/dtau as a function of tau. The integral reactivity k(d) = G([TBA]) calculated with the kinetic equation for a first-order reaction for decomposition of DTBP in 1, 2, 1 + C6H6 and 2 + C6H6 in three segments of tau in the range of p = 20-1000 MPa changes differently with an increase in the degree of conversion for different p. The volume activation effects (DELTAV(p) not-equal) determined by SA of the experimental In k(d) as a function of p were calculated for close degrees of conversion, [TBA] = 0.1-0.14 M. The DELTAV(p) not-equal as a function of p obtained were compared with the similarly processed published data on decomposition of DTBP in n-heptane and dicumyl peroxide (DCP) in different aromatic solvents. The results were attributed to the effect of the type of packing of the solvent molecules surrounding the reacting molecule on the reactivity of the peroxide and not to the effect of radical recombination in the primary cage.