Abstract

Domenico De Marcoa¹*, Remo Buccib² and Antonino Giannettoa²

Solid N-substituted derivatives of thiourea are stable on heating. Liquid thioureas decompose at temperatures > 150°C up to the complete volatilisation of the sample. N-monosubstituted derivatives decompose in two well separated steps, the first one involving the formation of thiocyanate group. N.N'-disubstituted derivatives decompose in single step. 1-(p-Methoxyphenyl)-2-thiourea and 1 -(3,4-DiClorophenyl)-2-thiourea decompose during the melting. The Enthalpy changes for melting of several substituted thioureas are linearly related to the corresponding Entropy changes (ΔfH = 2.78 + 0.311 ΔfS; Corr. Coeff. =0.985).

Thiourea derivatives; Thermal behaviour; Enthalpy-Entropy relationship

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