Optimization of the synthesis of N-alkyl and N,N-dialkyl thioureas from waste water containing ammonium thiocyanate

Abstract

The optimized methods for N-alkyl and N,N-dialkyl substituted thioureas synthesis starting from ammonium thiocyanates, waste water constituent from the production of tetramethylthiuram monosulfide (TMTS), and alkyl amine, are presented in this work. Therefore, thioureas synthesis was developed in two ways: Method I - reaction of the thiocyanate and alkylamine in the presence of hydrochloric acid; Method II - reaction of the thiocyanate with benzoyl chloride following by amine addition in the first step, and base hydrolysis in the second step. The structure of the synthesized compounds was confirmed by IR, 1H and 13C NMR and MS instrumental methods, and purity was determined by high-performance liquid chromatography method. It is shown that the proposed methods offer a high degree of conversion and purity of product, absence of by-products and technological applicability at industrial scale. Considering importance of the tetramethylthiuram disulfide (TMTD) and TMTS as vulcanization accelerators as well as thiourea as the pharmacologically active compounds, it can be said that application of the optimized methods of thiourea synthesis will provide significant improvement in sustainable development and implementation of eco-friendly production technology. The described, environmentally benign process of thioureas synthesis, represent a suitable option to existing methods.