Interaction of trifluoroacetic acid with cellulose and related compounds

The reaction of cellulose, cellobiose, and their acetyl derivatives with trifluoroacetic acid has been studied by the method of infrared spectrophotometry. Changes in optical density were measured at 25°C. as a function of time. Band assignments are adequate for the present study, although some uncertainties exist, especially in the 8 to 10 μ region. Trifluoroacetic acid effects the solution of cellulose by an initial process of swelling, rupture of hydrogen bonds, and micellar dispersion of the cellulose structure. Esterification takes place, possibly by a mechanism involving the formation of an intermediate addition compound. Cellobiose reacts in a similar manner. Partially acetylated cellulose is subject to further esterification by trifluoroacetic acid under similar conditions. The results suggest a more rapid rate of esterification of primary than of secondary hydroxyls.