Cellulose Studies
1948
Mehta, P.C. | Pacsu, Eugene
On the basis of their experiments, Pacsu and Hiller have shown that the classical concept of the structure of cellulose as built up from glucose anhydride residues connected by 1,4-β- glycosidic linkages is inadequate. They proposed that in cellulose there are units of about 260 glucose anhydride residues linked through 1,4-β-glycosidic bonds, these units being then con nected by hemiacetal or acetal bonds. The present experiments on the kinetics of heterogeneous hydrolysis of cellulose, in organic and inorganic acids, were conducted to test the validity of this concept. The results are: (1) an initial rapid hydrolysis down to a D.P. of about 260; k = 3.43 x 10⁻³ at 97° C, which is of a much higher order than the rate constant for hydrolysis of the 1,4-β-glycosidic bonds under similar conditions; (2) a practically complete stand still of the hydrolysis after the limiting D.P. of 260 is reached; (3) a negative value for the entropy of activation as calculated from Eyring's equation for absolute reaction rates, in con trast to the positive value obtained for the random hydrolysis of cellulose, starch, maltose, etc. Similar experiments on commercial viscose rayon showed hydrolysis to be at a uniform rate down to a D.P. of about 60, after which no appreciable change occurred.
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