Rapid and environmentally friendly preparation of starch esters

The effects of microwave heating and reactant composition on the iodine-catalyzed acetylation of starch by acetic anhydride were investigated. After only 2 min at 100 °C, significant amounts of acetylation occurred using small amounts of iodine (0.16–2.5 mol%). Values of degree of substitution (DS) increased as iodine/starch and acetic anhydride/starch ratios increased. Starch acetates having DS of up to 3 were prepared using 2.5 mol% iodine. Molecular weights decreased as iodine levels increased. This method of starch acetylation is attractive since no solvent is needed, reaction is rapid, energy inputs are relatively small, and the catalyst has low toxicity.