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CH2(OH)

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Originally appearing in Volume V26, Page 35 of the 1911 Encyclopedia Britannica.
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CH2(OH) + - - - See also:COH = l-gulose. When xylose is combined with hydrocyanic See also:acid and the See also:cyanide is hydrolysed, together with l-gulonic acid, a second isomeric acid, 1-idonic acid, is produced, which on reduction yields the hexaldose 1-idose. When l-gulonic acid is heated with See also:pyridine, it is converted into l-idonic acid, and See also:vice versa; and d-gulonic acid may in a similar manner be converted into d-idonic acid, from which it is possible to prepare d-idose. It follows from the manner in which 1-idose is produced that its configuration is CH2(OH)+--+COH. The remaining aldohexoses discovered by See also:Fischer are derived from d-galactose from See also:milk-See also:sugar. When oxidized this aldohexose is first converted into the monobasic galactonic acid, and then into dibasic mucic acid; the latter is optically inactive, so that its configuration must be one of those given in the See also:sixth and seventh columns of the table. On reduction it yields an inactive mixture of galactonic acids, some molecules being attacked at one 'end, as it were, and an equal number of others at the other. On reducing the lactone prepared from the inactive acid an inactive galactose is obtained from which l-galactose may be separated by See also:fermentation. Lastly, when d-galactonic acid is heated with pyridine, it is converted into talonic acid, which is reducible to talose, an isomeride I.earing to galactose the same relation that mannose bears to See also:glucose. I t can be shown that d-galactose is CH2(OH) + — + — COH, and hence d-talose is CH2(OH)+—++ COH. The configurations of the penta- and tetra-aldoses have been determined by similar arguments; and those of the ketoses can be deduced from the aldoses. Disaccharoses.

The disaccharoses have the See also:

formula C12H22011 and are characterized by yielding under suitable conditions two molecules of a hexose : C12HnOn+See also:H2O=See also:C6H,208+C,H,206. The hexoses so obtained are not necessarily identical: thus See also:cane sugar yields d-glucose and d-See also:fructose (invert sugar); milk sugar and melibiose give d-glucose and d-galactose, whilst maltose yields only glucose. Chemically they appear to be See also:ether anhydrides of the hexoses, the See also:union being effected by the aldehyde or See also:alcohol See also:groups, and in consequence they are related to the See also:ethers of glucose and other hexoses, i.e. to the alkyl glucosides. Cane sugar has no reducing See also:power and does not See also:form an See also:hydrazone or osazone; the other varieties, however, reduce See also:Fehling's See also:solution and form hydrazones and osazones, behaving as aldoses, i.e. as containing the See also:group •CH(OH)•CHO. The relation of the disaccharoses to the a- and (3-glucosides was established by E. F. See also:Armstrong (Journ. Chem. See also:Soc., 1903, 85, 1305), who showed that cane sugar and maltose were a-glucosides, and raffinose an a-See also:glucoside of melibiose. These and other considerations have led to the proposal of an alkylen See also:oxide formula for glucose, first proposed by Tollens; this view, which has been mainly See also:developed by Armstrong and Fischer, has attained See also:general See also:acceptance (see GLUCOSE and GLUCOseDE). Fischer has proposed formulae for the important disaccharoses, and in See also:conjunction with Armstrong devised a method for determining how the See also:molecule was built up, by forming the osone of the sugar and hydrolysing, whereupon the hexosone obtained indicates the aldose See also:part of the molecule. Lactose is thus found to be glucosido-galactose and melibiose a galactosido-glucose.

Several disaccharoses have been synthesized. By acting with hydrochloric acid on glucose Fischer obtained isomaltose, a disaccharose very similar, to maltose but differing in being amorphous and unfermentable by yeast. Also Marchlewski (in 1899) synthesized cane sugar from See also:

potassium fructosate and acetochloroglucose; and after Fischer discovered that acetochlorohexoses readily resulted from the interaction of the hexose penta-acetates and liquid See also:hydrogen chloride, several others have been obtained. Cane sugar, saccharose or saccharobiose, is the most important sugar; its manufacture is treated below. When slowly crystallized it forms large See also:monoclinic prisms which are readily soluble in See also:water but difficultly soluble in alcohol. It melts at 160°, and on cooling solidifies to a glassy See also:mass, which on See also:standing gradually becomesopaque and crystalline. When heated to about 200° it yields a See also:brown amorphous substance, named caramel, used in colouring liquors, &c. Concentrated sulphuric acid gives a See also:black carbonaceous mass; boiling nitric acid oxidizes it to d-saccharic, tartaric and oxalic acids; and when heated to 16o° with acetic anhydride an octa-acetyl ester is produced. Like glucose it gives saccharates with See also:lime, baryta and strontia. Milk sugar, lactose, lactobiose, C12H22011, found in the milk of mammals, in the amniotic liquid of cows, and as a pathological secretion, is prepared by evaporating whey and purifying the sugar which separates by See also:crystallization. It forms hard See also:white rhombic prisms (with 1H20), which become anhydrous at 14o° and melt with decomposition at 205°. It reduces ammoniacal See also:silver solutions in the See also:cold, and alkaline See also:copper solutions on boiling.

Its aqueous solution has a faiht sweet See also:

taste, and is dextro-rotatory, the rotation of a fresh solution being about twice that of an old one. It is difficultly fermented by yeast, but readily by the lactic acid bacillus. It is oxidized by nitric acid to d-saccharic and mucic acids; and acetic anhydride gives an octa-acetate. Maltose, See also:malt-sugar, maltobiose, C12H22Ou, is formed, together with See also:dextrine, by the See also:action of malt diastase on See also:starch, and as an intermediate product in the decomposition of starch by sulphuric acid, and of glycogen by ferments. It forms hard crystalline crusts (with 1H20) made up of hard white needles. Less important disaccharoses are: Trehalose or mycose, C12H22011.2H20, found in various See also:fungi, e.g. See also:Boletus edulis, in the See also:Oriental Trehala and in See also:ergot of See also:rye; melibiose, C12H220n, formed, with fructose, on hydrolysing the trisaccharose melitose (or raffinose), C,8H82018.5H2O, which occurs in Australian See also:manna and in the See also:molasses of sugar manufacture; touranose, C12H220n, formed with d-glucose and galactose on hydrolysing another trisaccharose, melizitose, C,8HnO1e•2H2O, which occurs in Pinus larix and in See also:Persian manna; and agavose, C,2H22011, found in the stalks of See also:Agave americana.

End of Article: CH2(OH)

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