Acetylation of starch with vinyl acetate in imidazolium ionic liquids and characterization of acetate distribution

Starch was acetylated with vinyl acetate in different 1-butyl-3-methylimidazolium (BMIM) salts as solvent in effort to produce starches with different acetylation patterns. Overall degree of substitution was much higher for basic anions such as acetate and dicyanimide (dca) than for neutral anions such as chloride and nitrate. There was a strong preference for acetylation at the C2 position in BMIM dca while acetylation was similar for C2, C3 and C6 in BMIM OAc. Molecular weights were not changed significantly by the reaction conditions. These results suggest that ionic liquids can provide a convenient medium for the homogeneous modification of starches with some control over substitution patterns.