Complexes of homoionic montmorillonite with thioamides: Fid-Bau Portal

Complexes of homoionic montmorillonite with thioamides

Ristori, G.G. / Fusi, P. / Franci, M.

AbstractThe adsorption and catalytic decomposition mechanisms of thioacetamide, thiobenzamide and 2,6-dichlorothiobenzamide (Chlorthiamid, used as herbicide) on Al- and Ca-montmorillonite (Upton, Wyoming) have been studied. According to the results of the infrared analysis, the 2,6-dichlorothiobenzamide is adsorbed on Al-montmorillonite by protonation of the CS roup; in contrast, with Ca-montmorillonite the molecule is adsorbed by a coordination bond to the exchangeable cation. Thiobenzamide is mainly adsorbed on Al-montmorillonite by a coordination bond between the CS group and the exchangeable cation: a small fraction of the molecule is, at the same time, decomposed to benzoic acid, NH3 and H2S. The presence of benzoic acid was confirmed by thin-layer chromatography. The same coordination bond is only observed when the molecule is adsorbed on Ca-montmorillonite. Thioacetamide, adsorbed on Al-montmorillonite, is partially decomposed to acetate ion, acetic acid, NH3 and H2S. The presence of acetic acid was confirmed by thin-layer chromatography. The remaining molecules of thioacetamide are adsorbed by coordination of the CS group to the exchangeable cation. On Ca-montmorillonite the hydrolytic decomposition to acetic acid is strongly reduced and the molecule is adsorbed by a coordination bond to the exchangeable cation.