Radicals and radical cations of thioacetamide and thiobenzamide in aqueous sulfuric acid media

Studies on the radical cations and radicals of thioacetamide [(CH3)(NH2)C=S] and thiobenzamide [(C6H5)(NH2)C=S], in aqueous sulfuric acid media of various strengths were carried out using pulse radiolysis technique. In this system, the formation time of thioacetamide/thiobenzamide radical cation was observed to be different at different acid strengths. At acid system of pH/H 0 = −3.5, the slow growth kinetics signifies a dominating reaction of SO4 •− radical with these solutes (reaction rate constants found in the range of 1–4 × 108 M−1 s−1). Two different reactions (solute molecule with •OH and SO4 •−) lead to the formation of lone intermediate species (radical cation) following immediate (fast) and delayed (slow) kinetics. By this process, the transient yield increased by 65 % (as the transients’ absorbance at 400 nm increased to 0.090 from 0.055) in the case of thiobenzamide, whereas in the case of thioacetamide, this figure was higher. The general mechanism for the formation of radical cations of these solutes during radiation chemical studies has been revisited wherein the electron transfer reactions are more favorable.