Radical cations and radicals of thiourea and its derivatives in n-butyl chloride solutions: A pulse radiolysis study

The formation of radical cations and radicals of thiourea and its derivatives such as thiosemicarbazide, diethylthiourea, phenylthiourea in n-butyl chloride solutions using pulse radiolysis technique is reported. Solute radical cations generated initially produce respective radicals on deprotonation. The yields of radicals of these compounds are reduced partly upon addition of ethanol (C2H5OH), a radical cation scavenger, which reveals the generation of solute radical is two channel processes: one through direct reaction during the electron pulse irradiation and other through deprotonation of radical cations. The thioureayl radicals and their respective radical cations are characterized with optical absorption measurements and their kinetic analyses. The spectral absorption maximum of radical cations and radicals of thiourea and its derivatives is red shifted when we move from thiourea to phenylthiourea. Results obtained on urea exhibits no defined absorption peaks for radical cations in contrast to 320 nm peak in selenourea under identical experimental conditions. Moreover, the uniqueness of S in optical spectral characteristics of radical cations and radicals of thiourea and its derivatives is observed as compared to O and Se in urea and selenourea respectively. Quantum chemical calculations support the mechanistic interpretation and endow with the charge distributions in ureayl radical and radical cations along with their respective parent molecules. The formation of radical cations and radicals of these organic compounds using pulse radiolysis is revisited in n-butyl chloride in which the charge transfer reaction is more prominent.