Evidence Regarding Relative Activations and Accessibilities of Cellulosic Hydroxyl Groups

Abstract

The courses of the reversible reactions of methyl vinyl sulfone with hydroxyl groups at C-2, C-3, and C-6 of the D-glu copyranosyl units of a decrystallized cotton cellulose and a fibrous crystalline cotton cellulose have been investigated. Rate constants for reactions at the three types of hydroxyl groups of decrystallized cellulose have been estimated. The ratios of k2:k3:k6at 18° and 70°C, respectively, were found to be 0.50:0.18:1.00 and 0.28:0.11:1.00. The relative thermal activations of hydroxyl groups at C-2, C-3, and C-6 in these reactions appear to be 0.58:0.65:1.00. From data on the relative reactions in the fibrous cotton cellulose and in the decrystallized cotton cellulose, we obtained an Indica tion and an estimation of the relative accessibilities of the individual types of hydroxyl groups in the fibrous cellulose. As a result of short reaction periods (30 min), the relative accessibilities of the hydroxyl groups at C-2, C-3, and C-6 in fibrous cellulose are about 1.5:1.5:1.0 in dimethyl sulfoxide and about 1.1:0.6: 1.0 in water.