Effect of phenyl moiety on the formation of radicals and radical cations of thioamides in n-butyl chloride: a pulse radiolysis study

Abstract

The formation of radical cations and radicals of thioamides (R)$\mathbf{(NH_{2})}$ CS, where R represents $\hbox {CH}_{3}$ in thioacetamide (TA) and $\hbox {C}_{6}\hbox {H}_{5}$ in thiobenzamide (TBA) in n-butyl chloride has been studied using pulse radiolysis technique. The radical cations of TA and TBA are observed in n-butyl chloride, and on their subsequent deprotonation, respective radicals are generated. In this study on thioamide solutions in n-butyl chloride, the transient species formed at $1.2\,\upmu \hbox {s}$ after the electron pulse exhibiting absorption maxima in 400 nm region are attributed to their radical cations. In the presence of 0.1 M ethanol ($\hbox {C}_{2}\hbox {H}_{5}\hbox {OH}$), a radical cation scavenger, the absorbance values at corresponding peaks are reduced substantially, revealing the formation of their respective radical cations. Moreover, at a later time, the generation of radical species takes place through deprotonation of radical cations and also through direct reactions during electron pulse irradiation. The mechanisms for the formation of radical cations and radicals of these two thioamides under pulse radiolysis have been revisited in butyl chloride medium wherein the charge transfer reactions are more prominent. Results of quantum chemical calculation support the mechanistic explanation and provide information on the reactivity of parent molecules, and the charge distribution on radical cations and radicals species of thioamides.

Graphical Abstract