Direct Conversion of Alginate Oligo- and Polysaccharides into Biodegradable and Non-Ecotoxic Anionic Furanic Surfactants—An Experimental and Mechanistic Study

A series of novel anionic furanic surfactants characterized by the presence of a couple of lipophilic chains acetal-linked to a sodium 2-furoate head group, are prepared by the conversion of oligo-alginates or alginate to butyl 5-(dibutoxymethyl)-2-furoate, followed by the introduction of fatty alkyl chains containing 7 to 18 carbon atoms and the release of the carboxylate function. A plausible mechanism for the unexpected formation of butyl 5-(dibutoxymethyl)-2-furoate is proposed through a study based on both experimental results and density functional calculations. One-pot processes involving hydrolysis, butanolysis, dehydration, transesterification, transacetalization, and saponification reactions, are successfully developed to provide furan-type surfactants under conditions that respect the principles of green chemistry. The surface activities of these products in a pure form or as a mixture are evaluated and quite low values of superficial tensions (<25 mN m(-1)) and foaming properties are obtained depending on the alkyl chain length. In addition, a readily biodegradability and an absence of aquatic ecotoxicity are shown for a surfactant composition based on sodium 5-(dioctyloxymethyl)-2-furoate.