PYROLYSIS OF DIMETHYL PEROXIDE

By using isobutane (t-BuH) as a radical trapit has been possible to study the initial step in the decomposition of dimethyl peroxide (DMP) over the temperature range of 110–140°C in a static system. For low concentrations of DMP (2.5 × 10−5−10−4M) and high pressures of t−BuH (∼0.9 atm) the first-order homogeneous rate of formation of methanol (MeOH) is a direct measure of reaction (1): . For complete decomposition of DMP in t-BuH, virtually all of the DMP is converted to MeOH. Thus DMP is a clean thermal source of Me. In the decomposition of pure DMP complications arise due to the H-abstraction reactions of Me from DMP and the product CH2O. The rate constant for reaction (1) is given by k1 = 1015.5−37.0/θ sec−1, very similar to other dialkyl peroxides. The thermochemistry leads to the result D(MeOOMe) = 37.6 ± 0.2 kcal/mole and /H(Me) = 3.8 ± 0.2 kcal/mole. It is concluded that D(ROOR) and D(ROH) are unaffected by the nature of R. From ΔS and A1, k2 is calculated to be 1010.3±0.5M−1· sec−1: . For complete reaction, trace amounts of t-BuOMe lead to the result k2 ∼ 109M−1 ·sec−1: products. From the relationship k6 = 2(k2k5a)1/2 and with k5a = 108.4M−1 · sec−1, we arrive at the result k6 = 109.7M−1 · sec−1: .