Flow ESR and Static Studies of the Decomposition of Phenyl-Substituted Ethanes

Article abstract of DOI:10.1021/j100271a022

The thermal decomposition of 1,1,2,2-tetraphenylethane (DD) was studied in high-temperature fluids by using both sealed tube and flow ESR techniques.In the sealed tube experiments its central C-C bond homolysis rate constant in tetralin solvent was 10^15.92+/-0.13 exp<-(23910+/-160)/T>s^-1 (473-550 K).Concentrations of diphenylmethyl radicals in equilibrium with DD were measured by ESR between 648 and 683 K.The equilibrium constant for the dissociation reaction was 10^6.69+/-0.66 exp<-(23770+/-1020)/T>M.Combining this expression with the dissociation rate constant for diphenylmethyl radicals of 1.5 x 10⁹M^-1s^-1 at 648 K.Bond homolysis of 1,1,2-triphenylethane (BD) was also studied in tetralin.Its rate constant was 10^16.18+/-0.11 exp<-(29080+/-150)/T>s^-1 (593-653 K).An analysis of the above data shows that the rate of BD dissociation is not strongly affected by release of steric energy.In contrast, the DD homolysis rate was increased by more than an order of magnitude through release of strain.