Methanol-Soluble Complexes of Lactose and of Other Carbohydrates

Lactose, sucrose, maltose, galactose, fructose, and many other carbohydrates and derivatives are found highly soluble in cold absolute methanol containing sufficient calcium chloride.From a highly concentrated viscous solution prepared from lactose, calcium chloride, and methanol in a molar ratio such as 1:3:24, a complex of p-lactose, calcimn chloride, and methanol in the molar ratio of 1:1:4 slowly crystallizes.After about 6 M of water are added to such a concentrated solution per mole of calcium chloride, a complex of a-lactose, calcium chloride, and water in the molar ratio 1:1:7 soon crystallizes.The equilibrium ratio of a-to ~-lactose in the concentrated solutions is about 5:3.The dilution of such a concentrated solution with methanol causes lactose to crystallize in the same anomeric ratio as exists in the solution.Within the investigated range, the logarithm of the solubility of this crystallized lactose in methanol is a linear function of the calcium chloride concentration.Complexes of calcium salts, sugars, and water were first described by Ritsert (23, 24), who prepared a crystalline product consisting of 1 M of lactose, 1 M of calcium chloride, and between 6 and 8 M of water, and who later investigated similar addition products of other sugars.Many other investigators later prepared many other complexes of sugars and hydrated salts of alkali or alkaline earth metals (1,6,7,8,12,13,20,21,25,26).The properties of the complex containing lactose, calcium chloride, and water of hydration were investigated by tIerrington (9).As alcohols, like water, are able to solvate calcium chloride (3, 4, 16, 17, 18, 19), we thought it might be of interest to investigate the analogous sugarcalcium chloride-alcohol addition products; such products had never been prepared.The compound that Dale (6) prepared by evaporating slowly a solution of mannose and caleimn chloride tetrahydrate in hot ethanol contained water rather than ethanol; it was fi-mannose-CaC12.2H20.We have found that many sugars, even anhydrous, are highly soluble in solutions of calcium chloride and anhydrous methanol.Of the various sugars used, lactose was the most thoroughly investigated. EXPERIMENTAL 5[ETHODS