Synthesis of tosyl starch in eco-friendly media

Abstract

A green strategy for efficient tosylation of starch was demonstrated in the eco-friendly solvent NaOH–urea in the presence of surfactants. The influence of surfactant nature, surfactant amounts, and the molar ratio between p-toluenesulfonyl chloride (TsCl) and the anhydroglucose unit (AGU) on the degree of substitution (DS) was studied. The tosyl products were characterised by means of CHNS elemental analysis and spectroscopy including FTIR, ¹H-NMR and ¹³C-NMR. The results demonstrate that this methodology allows a range of degrees of substitution (DS) to be observed depending on the surfactants and prove that neutral surfactants are not necessary to obtain high DS of tosyl groups as in the case with cellulose starting materials previously reported. Subsequent nucleophilic displacement (S_N) reactions of the tosyl groups in this medium were also investigated.