LAEVULOSE

FRUCTOSE  , or FRUIT-SUGAR, a carbohydrate of the formula CsH12O6 . It is closely related to ordinary d-glucose, with which it occurs in many fruits, starches and also in honey . It is a hydrolytic product of inulin, from which it may be prepared; but it is more usual to obtain it from " invert sugar," the mixture obtained by hydrolysing cane sugar with sulphuric acid . Cane sugar then yields a syrupy mixture of glucose and fructose, which, having been freed from the acid and concentrated, is mixed with water, cooled in ice and calcium hydroxide added . The fructose is precipitated as a saccharate, which is filtered, suspended in water and decomposed by carbon dioxide . The liquid is filtered, the filtrate concentrated, and the syrup so obtained washed with cold alcohol . On cooling the fructose separates . It may be obtained as a syrup, as fine, silky needles, a white crystalline powder, or as a granular crystalline, somewhat hygroscopic mass . When anhydrous it melts at about 95° C . It is readily soluble in water and in dilute alcohol, but insoluble in absolute alcohol . It is sweeter than cane sugar and is more easily assimilated . It has been employed under the name diabetin as a sweetening agent for diabetics, since it does not increase the sugar-content of the urine; other medicinal applications are in phthisis (mixed with quassia or other bitter), and for children suffering from tuberculosis or scrofula in place of cane sugar or milk-sugar .

Chemically, fructose is an oxyketone or ketose, its structural formula being CH2OH•(CH•OH)m.CO•CH2OH; this result followed from its

conversion by H . Kiliani into methylbutylacetic acid . The form described above is laevo-rotatory, but it is termed d-fructose, since it is related to d-glucose . Solutions exhibit mutarotation, fresh solutions having a specific rotation of -104.0°, which gradually diminishes to — 92° . It was synthesized by Emil Fischer, who found the synthetic sugar which he named a-acrose to be (d+l)-fructose, and by splitting this mixture he obtained both the d and 1 forms . Fructose resembles d-glucose in being fermentable by yeast (it is the one ketose which exhibits this property), and also in its power of reducing alkaline copper and silver solutions; this latter property is assigned to the readiness with which hydroxyl and ketone groups in close proximity suffer oxidation . For the structural (stereochemical) relations of fructose see SUGAR .