Bromination of cellulose with tribromoimidazole, triphenylphosphine and imidazole under homogeneous conditions in LiBr-dimethylacetamide

Abstract

The bromination of microcrystalline cellulose with tribromoimidazole, triphenylphosphine and imidazole was studied under homogeneous conditions in LiBr- N,N-dimethylacetamide. Bromodeoxycellulose samples having ds values up to 1.6 were obtained at high molecular ratios of bromination reagents to the repeating unit of cellulose (5 or higher). Recoveries of high ds samples were below 50%. 3,6-Dibromo-3,6-dideoxyglucose units were present in the samples having high ds values together with 3,6-dibromo-3,6-dideoxyallose and 6-bromo-6-deoxyglucose units. The dibromoglucose units were formed from dibromoallose units by a nucleophilic substitution of bromine atoms at C-3 with bromide ions present in the system.