A theoretical and experimental study on etherification of primary alcohols with the hydroxyl groups of cellulose chain (n = 1–3) in acidic condition

Abstract

Etherification mechanism of primary alcohols R-CH2OH with the hydroxyl groups of cellulose chain (n = 1–3) in acidic condition were investigated by using density functional theory (DFT) and two-layer ONIOM approach. Geometry and energy of the reactants, products, reactant complexes, product complexes and transition state (TS) structures were optimized and calculated at the B3LYP/6–311 g(d,p) level, ONIOM (B3LYP/6–311 g(d,p):PM3MM) level, and CCSD(T)/6–311+g*//B3LYP/6–311 g(d,p) level. The computational results reveal that the etherification comply with bimolecular nucleophilic substitution (SN2) mechanism; potential energy surface (PES) of the reaction is compatible with the type of cation-molecule reaction; reactants and products can form the stable activated complexes with H+ and water, in this state H+ is occupied by both alcohol and water, or ether and water; substituent R in primary alcohol R-CH2OH (R = H, CH3, CH2CH3, CH2NHCH3, CH2OCH3, CH2N(CH3)3Cl, CH2F) affect significantly on the both energy barrier of activation step and energy barrier of H3O+ releasing step. The combination of calculational data and experimental data were applied to make findings more rigorous.