hexahydric acyclic alcohols, HOCH2(CHOH)4-CH2OH; colorless crystalline substances with a sweet taste. Readily soluble in water and alcohol; insoluble in ether. The hexitols contain four asymmetric carbon atoms and exist as ten stereoisomers that may be obtained by reduction of hexoses. Hexitols are easily esterified; oxidation leads to hexoses and sugar acids. Some hexitols (D-mannitol, D-sorbitol, dulcitol, and D-iditol) are encountered in nature.
D-mannitol (I). Melting point, 166°C; boiling point, 276°-280° C/133.322 newtons per sq m (that is, 1 mm Hg); specific rotation [α]
= -0.244° (water). It is found in the solidified sap of the Transcaucasian ash (so-called manna), as well as in marine algae, fungi, olives, and other plants. In industry, D-mannitol is produced from marine brown algae or catalytic hydrogenation of saccharose. It is the starting material in the production of surface-active agents, drying oils, resins, and lacquer and is also used in the foodstuffs and pharmaceutical industries and in perfume manufacture.
D-sorbitol (II). Melting point, 110°-111°C (anhydrous); [α] = − 1.73° (water); it is found in large quantities in algae, mountain ash, and other plants. D-sorbitol is obtained by catalytic or electrolytic reduction of D-glucose.
D-sorbitol is a major intermediate product in the production of ascorbic acid; it is also used as a substitute for sugar for persons suffering from sugar diabetes.
Dulcitol. Melting point, 188.5° C. Found in marine algae and in yeast. It can be produced synthetically by reduction of D-galactose by sodium amalgam. Dulcitol is a component of mediums used in bacteriological studies.
D-iditol. Melting point, 73° C. Found in the berries of the mountain ash together with sorbitol.
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