Abstract: | 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. |