Synthesis and Thermal Decomposition of Some Bis(2-thenoyl) Peroxides^1,2

Abstract

A new series of symmetrical 5,5'-disubstituted bl(2-thenoyl) peroxides was prepared, with the substituents chloro, bromo, methyl, t-butyl, and nitro groups. The unsymmetrical bmethylbis( Zthenoyl) peroxide and two new 4,4'-disubstituted bis-(2-thenoyl) peroxides, the 4,4'-dimethyl and 4,4'-dibromo compounds were also prepared. The thermal decomposition products of bis(2thenoyl) peroxides in carbon tetrachloride are 2-thenoic acid (20 mole per cent), carbon dioxide (20 mole per cent), and a polymeric material (46 per cent by weight of initial peroxide). In the presence of the free radical scavenger 3,4dichlorostyrene, a polymer was isolated which contained 2.95% sulfur. The rates of spontaneous thermal decomposition of the thenoyl peroxides in carbon tetrachloride were determined by conducting their decompositions in the presence of the efficient free radical scavenger, 3,4dichlorostyrene. In all cases studied, with the exception of bis( 5-nitro-2-thenoyl) peroxide, the decomposition rates followed strict first-order kinetics. In the absence of a free radical scavenger the rate of decomposition of bis(2-thenoyl) peroxide is much greater. The rate constants (75') show that electron-donating substituents on the thiophene rings accelerate the rate of decomposition, while electron-withdrawing substituents have the opposite effect. The Hammett equation was found applicable to the spontaneous decomposition of the substituted bis (2-thenoy1)peroxides.

A new series of unsymmetrical acyl peroxides

“…The only unsymmetrical peroxy compound reported before the present work i s 5-methyl-bis-(2-thenoyl) peroxide (6).…”

Synthesis and thermal decomposition of series of acyl peroxides

“…While alkyl chlorides were not isolated from reaction of the alcohols with the generated hydrochloric acid, they presumably were formed to some extent. Procedures involving reaction of sodium alkoxides with the tetiachloroterephthaloyl chloride (8) and direct reaction of the dichloride with hydroxy compounds in the presence of pyridine were also found to be viable, especially with phenolic compounds. However, in other experiments, to be described at a later date, we found attempted reaction of a tertiary…”

“…Up to roughly 10 years ago dibenzoyl peroxide and several of its derivatives have been the only acyl peroxides which have been studied in detail, especially in relation to their rates of decomposition. Earlier work (1) in these laboratories and at Michigan State University had been limited to symmetrical thenoyl peroxides (7,8), but more recently a few unsymmetrical peroxides of the thiophene series containing also the benzoyl group were studied by Gruen et al (2). The present paper is concerned with the study of the influence of various ring systems (both heterocylic and carbocylic) on the decomposition rates of acyl peroxides of the general formulation:…”