Starch complexes with bismuth (III) and (V)

Studies are presented on bismuth (III) and bismuth (V) derivatives of starch. Bismuth (III) derivatives of starch were prepared by reaction of either bismuth trichloride or bismuth tri-tert-pentoxide with either granular or activated potato starch. Bismuth (V) starch derivatives were prepared by heating a solid blend of activated starch and NaBiO3 in a microwave oven. Thermal analysis (thermogravimetry-TGA, differential thermogravimetry-DTGA, and differential thermal analysis-DTA) as well as IR- and X-ray photoelectron spectroscopies showed that starch reacted with bismuth (III) alkoxide by substitution of its one alkoxide group with one hydroxyl group of the D-glucose unit. D-Glucose units bound no more than two Bi(O-akyl)(2) groups. D-Glucose units reacted with BiCl3 in benzene with the evolution of hydrochloride which hydrolysed starch to dextrins. Starch was crosslinked on heating with sodium bismuthate. Bismuthated starches were slightly less thermally stable than original starches. (C) 2003 Elsevier Science Ltd. All rights reserved.