The free‐radical reaction of tri‐n‐butyltin hydride with peroxides

Rate constants for the tri‐n‐butyltin radical (Sn ·) induced decomposition of a number of peroxides have been measured in benzene at 10°C. The values range from ∼100 M−1 sec−1 for di‐t‐butyl peroxide to 2.6 × 107 M−1 sec−1 for di‐t‐butyl diperoxyisophthalate. The majority of the peroxides, including diethyl peroxide, diacetyl peroxide, and t‐butyl peracetate, have rate constants of ∼105 M−1 sec−1. It is shown that di‐n‐alkyl disulfides are ten times as reactive toward Sn · as di‐n‐alkyl peroxides, although the exothermicities of these reactions are ∼15 and ∼39 kcal/mole, respectively. The enhanced reactivity of the disulfides is attributed to the easier formation of an intermediate or transition state with 9 electrons around sulfur, compared with an analogous species with 9 electrons around oxygen. The following bond strengths (kcal/mole) have been estimated: D[SnOR] = 77; D[SnH] = 82; D[SnSR] = 83; and D[SnOC(O)R] = 86, where R = alkyl. Rate constants for reaction of Sn · with some benzyl esters have also been measured. It has been found that t‐butoxy radicals can add to benzene and abstract hydrogen from benzene at ambient temperatures.