Homogeneous acetalization of cellulose in lithium chloride and dimethylacetamide

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Abstract
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°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.