Search for Electron-Transfer Decomposition and the Production of Electronically Excited State Species in the Thermolysis of p-(Dimethylamino)phenyl-Substituted Dialkyl Peroxides

Article abstract of DOI:10.1021/jo00144a022

Kinetic, product, and chemiluminescence (CL) studies were made with 1-<4-(dimethylamino)phenyl>ethyl tert-butyl peroxide (1), 2-<4-(dimethylamino)phenyl>propyl tert-butyl peroxide (2), and 1-phenylethyl tert-butyl peroxide (3).Activation parameters for 1 in chlorobenzene are as follows: E_a = 36.2 +/- 0.6 kcal/mol, log A = 15.45 +/- 0.32, ΔH(excit) = 35.4 +/- 0.6 kcal/mol, ΔS(excit) = 9.66 + 1.35 eu.These activation parameters are within the range expected for simple peroxide bond homolysis.The small rate acceleration by the p-dimethylamino group (k₁/k₃ = 2.07 at 129 deg C) is reasonable, again for the simple peroxide bond homolysis.Product studies with 1 and 2 in comparison to 3, indicate that the dimethylamino group serves as a good hydrogen atom donor.This was further substantiated by the thermolysis of 3 in the presence of N,N-dimethylaniline and 2,6-di-tert-butyl-p-cresol.CL was observed in the thermolysis of 1 and 2 in aerated o-dichlorobenzene solutions at 140 deg C.The CL quantum yield decreased significantly when solutions of 1 and 3 were purged with nitrogen or argon.No CL was observed in the thermolysis of 3, but CL was observed when N,N-dimethylaniline was added to the aerated solution.These results suggest that the CL from 1 and 2 is due primarily or entirely to autoxidation processes involving the dimethylamino group and not to electron-transfer processes involving this group and the peroxide bond.