Adsorption and Catalytic Decomposition of 4-Nitrobenzenesulphonylmethylcarbamate by Smectite

Paolo Fusi1, Giuseppe Gabriele Ristori2 and Marco Franci2
1 Istituto di Chimica Agraria e Forestale, Università di Firenze, Piazzale delle Cascine 28, Florence, Italy.
2 Centro di Studio per i Colloidi del Suolo, C.N.R., Firenze, Piazzale delle Cascine 28, Florence, Italy.

Abstract: Adsorption and catalytic decomposition of 4-nitrobenzenesulphonylmethylcarbamate (herbicide Nisulam) on Upton, Wyoming, bentonite saturated with different cations was studied using thin-layer chromatography and infrared spectroscopy. Nisulam is adsorbed at room temperature by coordination through the NO2 group to the exchange cation regardless of the cation's nature. On moderate heating (75°–90°C) this molecule decomposes to 4-nitrobenzenesulphonamide whereas a similar compound (herbicide Asulam) containing the NH2 functional group instead of NO2 is adsorbed by protonation at room temperature and decomposes into different products. For cations having a high polarizing power, a coordination bond between the Asulam molecule's C=O group and the exchange cation is established, and the molecule decomposes to sulphanilic and carbamic acid. In contrast, for cations having a low polarizing power there is no coordination, and the molecule decomposes mainly into sulphanilamide. Nisulam's coordination to the exchange cation through the NO2 group instead of C=O is ascribed to inductive and conjugation effects, typical of the nitro group.

Key Words: Adsorption • Asulam • Bentonite • Decomposition • Herbicide • Nisulam

Clays and Clay Minerals; August 1982 v. 30; no. 4; p. 306-310; DOI: 10.1346/CCMN.1982.0300409
© 1982, The Clay Minerals Society
Clay Minerals Society (www.clays.org)