HOMOGENEOUS ACETALIZATION OF CELLULOSE IN LITHIUM-CHLORIDE AND DIMETHYLACETAMIDE

Cellulose acetal derivatives were prepared by treating regenerated cellulose with various acetals in LiCl/dimethylacetamide (DMAc). Their IR and NMR spectra as well as gas chromatograms of their hydrolyzates proved that they have hemi-acetal structures. The degree of benzacetalization increased with an increase in catalyst, acetal and cellulose concentrations, and reached a maximum at 50-60-degrees-C of reaction temperature. Benzacetalization under reduced pressure gave the maximum degree of substitution, 2.1. The acetalization of cellulose is a reversible bimolecular reaction and its equilibrium constant is about 0.001-0.023. The heat of reaction and the activation energy of the forward and back reactions were 12.1, 18.5 and 7.8 kcal/mol, respectively. The equilibrium degree of acetalization with various alkylacetals increased in the electron-releasing order of alkyl group. Cellulose acetals with a low degree of substitution were soluble in cold water as well as in dimethyl sulfoxide.