Title
Regioselectivity in the acylation of cellulose with 2-bromoisobutyryl bromide under homogeneous conditions
Authors
HONGLE WANG YINGJUAN FU ZEFENG WANG ZHIYONG SHAO and MENGHUA QIN

Received April 22, 2015
Published Volume 51 Issue 1-2 January-February
Keywords cellulose-based macroinitiator, DMAc/LiCl, homogeneous acylation, 2-bromoisobutyryl bromide, regioselectivity

Abstract
A cellulose-based macroinitiator, cellulose-BiB, was prepared homogeneously by acylation of the hydroxyl groups of cotton cellulose with 2-bromoisobutyryl bromide (BrBiB) in N,N-dimethyl acetamide/lithium chloride (DMAc/LiCl) system. The effects of the molar ratio of BrBiB/anhydroglucose unit (AGU), reaction temperature, and reaction time on the degree of substitution (DS) were investigated in detail. The investigation was focused on the reactivity of the three hydroxyl groups at different position during the partial homogeneous acylation process. The results revealed that the DS of the cellulose-BiB increased with the increase of the molar ratio of BrBiB/AGU and the reaction time. At equivalent accessibility, the homogeneous acylation favored substitution at the C6 position, showing a regioselectivity of C6-OH>>C3-OH>C2-OH for the cotton dissolving pulp. Moreover, the 2-bromoisobutyryl bromide groups could be regioselectively introduced into the AGU of cellulose by controlling the reaction time.