Sucrose

SUCROSE (cane sugar), a disaccharide that upon hydrolysis gives d-glucose and d-fructose [a-1 (1,5) glucosido-β-2 (2,6) fructoside]; the residues of monosaccharides are connected in it by a diglycosidic bond (see Disaccharides), consequently it does not possess reducing properties and does not react with phenylhydrazine; upon acetylation and methylation it reveals 8 free hydroxyl groups. S. rotates to the right [α]_D=66.5°; under the influence of the enzyme sucrase or acids S. is hydrolyzed, and the resulting mixture of glucose and fructose rotates to the left (see Inversion). S. exists in two allotropic modifications A and B. A is obtained upon crystallization from water and alcohol, melts at 184-185°; B-from methyl alcohol, melts at 170-171°. Form A is more stable than B, which slowly on air transforms into form A; commercial sugar is probably a mixture of both forms (melts at 160°). S. crystallizes in the form of large monoclinic crystals, very soluble in water (100 parts of water at 12° dissolve 199 parts of sugar, at 45°-245 parts), difficult in alcohol (in 100 cm³ of 97% alcohol at 14° 0.4 g of S. dissolves). When heated above the melting point S., losing water, caramelizes; depending on the degree of heating and duration various products are formed: isosaccharosan (a substance of bitter taste, according to Pictet - an isomer of S.), caramelan, caramelen. Sucrose was first synthesized in 1928 by Pictet and Vogel; however to this day this synthesis has not been reproduced by any other researchers. Pictet also described isomers of S. obtained synthetically by him: isomer D, consisting of residues of d-glucose and β-fructose in the β-form, isomer C, which reduces Fehling's solution. S. is extremely widespread in the plant world; it is contained in the stems of sugar cane (14-26%) and sugar maple, in the tubers of sugar beet (14-20%), carrots, in the trunks of some palms, maples, etc., is also found together with glucose in sweet fruits. When acted upon by yeast S. undergoes fermentation after being split by sucrase. S. has great nutritional significance, as it is a good glycogen-former; in the intestine it is normally absorbed only after hydrolysis by sucrase and only when consumed in large quantities is it absorbed unchanged and can be found in the blood and urine (see Glycosuria). Upon parenteral administration almost all of S. is excreted in the urine. It is found in urine in infantile cholera.

m. karyisha.