CARBOHYDRATES 4! 



to the fact that the fructose molecule is more strongly levo-rotatory 

 than the glucose molecule is dextro-rotatory. The product of this 

 inversion is called invert sugar. 



Sucrose does not reduce metallic oxides in alkaline solution and forms 

 no osazone with phenylhydrazine. Prolonged boiling in the presence 

 of an acid phenylhydrazine solution will, however, hydrolyze the su- 

 crose and cause the forrnation of glucosozone and fructosozone. It 

 is not fermentable directly by yeast, but must first be inverted by the 

 enzyme sucrase (invertase or invertin) contained in the yeast. The 

 probable structure of sucrose may be represented by the following 

 formula. Note the absence of any free ketone or aldehyde group. 

 CH 2 OH CH 2 OH 



I I 



CHOH HC 



HC CHOH 



O 



CHOH 



I 

 CHOH 



O 



CHOH 



I 

 C 



C- -Q/ CH 2 OH 

 H 



Sucrose. 



EXPERIMENTS ON SUCROSE 



i-6. Repeat Solubility, Fehling's, Nylander's, Barfoed's, Phenylhydrazine 

 and Fermentation tests according to the directions given under Glucose, pages 

 21-31. 



7. Inversion of Sucrose. To 25 c.c. of sucrose solution in a beaker add 5 

 drops of concentrated H 2 SC>4 and boil one minute. Cool the solution and render 

 neutral with saturated barium hydroxide. Filter off the precipitate of barium 

 sulphate and upon the resulting fluid repeat the phenylhydrazine, Fehling, 

 Nylander's and Barfoed's reactions as given under Glucose, pp. 22, 25, 27 and 29 ; 

 and the Resorcinol-Hydrochloric Acid Reaction (Seliwanoff), as given under Fruc- 

 tose, page 35. Explain the results. 



TRISACCHARIDES, Ci 8 H 32 Oi 6 



RAFFINOSE 



This trisaccharide, also called melitose, or melitriose occurs in cotton 

 seed, Australian manna, and in the molasses from the preparation of 

 beet sugar. It is dextro-rotatory, does not reduce Fehling's solution, 

 and is only partly fermentable by yeast. 



RatEnose may be hydrolyzed by weak acids the same as the poly- 

 saccharides are hydrolyzed, the products being fructose and melibiose' 

 further hydrolysis of the melibiose yields glucose and galactose. Raffi- 



