Thermalanalysis of Thione Compounds.IV. Thermal Behaviours of Phenyl Thiourea,N,N’-Diphenylthiourea, Hp-Methoxyphenyl)-2-Thiourea,1-(3,4-Diclorophenyl)-2-Thiourea and 1-Methallyl-3-Methyl Thi0urea

Domenico De Marcoa; Remo Buccib; Antonino Giannettoa

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Thermalanalysis of Thione Compounds.IV. Thermal Behaviours of Phenyl Thiourea,N,N’-Diphenylthiourea, Hp-Methoxyphenyl)-2-Thiourea,1-(3,4-Diclorophenyl)-2-Thiourea and 1-Methallyl-3-Methyl Thi0urea

Domenico De Marcoa¹*, Remo Buccib² and Antonino Giannettoa²

¹Department of Inorganic, Analytical and Physical Chemistry, University of Messina, Salita Sperone 31 CP 30,98166 S. Agata (Messina) (Italy)

²Department of Chemistry, University "La Sapienza" Piazzale A. Moro 5,00185 ROMA (Italy)

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ABSTRACT:

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).

KEYWORDS:

Thiourea derivatives; Thermal behaviour; Enthalpy-Entropy relationship