Homogeneous acylation of eucalyptus wood at room temperature in dimethyl sulfoxide/N-methylimidazole

Succinoylation and benzoylation of ball-milled eucalyptus wood using succinic anhydride and benzoyl chloride as acylating reagent, respectively, were investigated at room temperature using dimethyl sulfoxide/N-methylimidazole (DMSO/NMI) as reaction medium without additional catalysts. The effects of the corresponding acylating reagent dosage (1–5:1 for succinoylation and 0.5–5:1 for benzoylation) and reaction time (0.35–5 h for succinoylation and 0.5–3 h for benzoylation) on the extent of acylation, measured by weight percent gain (WPG), were studied. WPG of succinoylation and benzoylation was in the range of 70.8–144.7% and 17.3–43.1%, respectively. The efficiency of acylation at room temperature significantly increased in DMSO/NMI compared with ionic liquid 1-butyl-3-methylimidazolium chloride because of the role of NMI as solvent, base and catalyst. Fourier transform infrared (FT-IR), and solid-state cross-polarization/magic-angle spinning (CP/MAS) 13C nuclear magnetic resonance (NMR) spectroscopy studies provided evidence for the occurrence of succinoylation and benzoylation reactions and the attachment of functional groups via ester bonds.

► Wood acylation in dimethyl sulfoxide/N-methylimidazole was tested at room temperature. ► The system provides higher acylation efficiency of wood than ionic liquids. ► Succinoyl and benzoyl groups was introduced into wood via ester bonds. ► Acylating reagent dosage and reaction time were examined. ► NMI acts as solvent, base and catalyst in this system.