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FRUCTOSE, LAEVULOSE

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Originally appearing in Volume V11, Page 253 of the 1911 Encyclopedia Britannica.
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FRUCTOSE, LAEVULOSE , or See also:FRUIT-See also:SUGAR, a See also:carbohydrate of the See also:formula CsH12O6. It is closely related to See also:ordinary d-See also:glucose, with which it occurs in many fruits, starches and also in See also:honey. It is a hydrolytic product of See also:inulin, from which it may be prepared; but it is more usual to obtain it from " invert sugar," the mixture obtained by hydrolysing See also:cane sugar with sulphuric See also:acid. Cane sugar then yields a syrupy mixture of glucose and fructose, which, having been freed from the acid and concentrated, is mixed with See also:water, cooled in See also:ice and See also:calcium hydroxide added. The fructose is precipitated as a saccharate, which is filtered, suspended in water and decomposed by See also:carbon dioxide. The liquid is filtered, the filtrate concentrated, and the See also:syrup so obtained washed with See also:cold See also:alcohol. On cooling the fructose separates. It may be obtained as a syrup, as See also:fine, silky needles, a See also:white crystalline See also:powder, or as a granular crystalline, somewhat hygroscopic See also:mass. When anhydrous it melts at about 95° C. It is readily soluble in water and in dilute alcohol, but insoluble in See also:absolute alcohol. It is sweeter than cane sugar and is more easily assimilated. It has been employed under the name diabetin as a sweetening See also:agent for diabetics, since it does not increase the sugar-content of the urine; other medicinal applications are in See also:phthisis (mixed with See also:quassia or other See also:bitter), and for See also:children suffering from See also:tuberculosis or See also:scrofula in See also:place of cane sugar or See also:milk-sugar.

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

conversion by H. Kiliani into methylbutylacetic acid. The See also: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 See also: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 See also:property), and also in its See also:power of reducing alkaline See also:copper and See also:silver solutions; this latter property is assigned to the readiness with which hydroxyl and ketone See also:groups in See also:close proximity suffer oxidation. For the structural (stereochemical) relations of fructose see SUGAR.

End of Article: FRUCTOSE, LAEVULOSE

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