First report on the kinetics of the uncatalyzed esterification of cellulose under homogeneous reaction conditions: a rationale for the effect of carboxylic acid anhydride chain-length on the degree of biopolymer substitution

摘要: The kinetics of the homogeneous acylation microcrystalline cellulose, MCC, with carboxylic acid anhydrides different acyl chain-length (Nc; ethanoic to hexanoic) in LiCl/N,N-dimethylacetamide have been studied by conductivity measurements from 65 85 °C. We employed cyclohexylmethanol, CHM, and trans-1,2-cyclohexanediol, CHD, as model compounds for hydroxyl groups anhydroglucose unit cellulose. ratios rate constants primary (CHM; Prim-OH) secondary (CHD; Sec-OH) employed, after correction, order split overall reaction MCC into contributions discrete OH groups. For compounds, we found that k(Prim-OH)/k(Sec-OH) > 1, akin reactions cellulose under heterogeneous conditions; this ratio increases a function increasing Nc. overall, partial decrease ethanoic- butanoic-anhydride then increase pentanoic- hexanoic anhydride, due subtle changes in- compensations enthalpy entropy activation.