Some Quantitative Tests of Intermolecular Bonding Between Aromatic Sulphonates and Simple Carbohydrates in Water, and its Relation to Cellulose Dyeing 1

Abstract

The method of continuous variations, using refractometry, shows that complexes form between sucrose in aqueous solution and non-azo aromatic sulfonates, but not between either sucrose or methyl-β-D-glucopyranoside (used as models of cellulose) and sulfonated azo dyes. Yoshida's method has been applied to determine thermodynamic parameters Entropy values of comllex formation are high, especially for the complex between sucrose and a sulfonated anthra quinone dye—probably indicating that the complexes form by face-to-face association of the molecules. It is suggested that a new type of π-bond is formed in which the π-electrons are attrated simultaneously by protons on the closely adjacent carhohydrate hydroxy-groups. This bond is not prevented by the water of solvation as are normal hydrogen bonds. The azo group appears to reduce the π-electron density in the aromatic nuclei and so prevents the bond forming The result supports the hypothesis that neither hydrogen bonds nor any form of π-bonds directly bind dyes to cellulose and is consistent with other recent work in pointing to a purely aggregation effect as the operative factor in cellulose dyeing.