190 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



PROPERTIES AND REACTIONS OF THE MONO- 

 SACCHARIDES. 



The properties and reactions of the monosaccharides are very 

 similar, the differences between the individual members being only in 

 certain peculiarities. The reactions of glucose may be taken as typical 

 of the reactions of all monosaccharides. 



A. GLUCOSE. 



(1) Formation of Esters. 



Glucose is converted by acids, acid anhydrides and acid chlorides 

 into esters. 



Pentabenzoyl glucose is precipitated when a solution of glucose 

 is shaken with benzoyl chloride and excess of sodium hydroxide: 

 C 6 H 7 0(OH) 8 + 5C 6 H 5 . CO . Cl = C 6 H 7 O(O . OC . C 6 H,) 5 + 5 HC1. 



(2) Formation of Compounds with Metallic Hydroxides. 



Glucose forms compounds with metallic hydroxides which are analagous 

 to the alkoxides. 



(a) If copper sulphate and sodium hydroxide be added to a solution of 

 glucose in the proportions of 



C 6 H 12 O 6 : sCuSO 4 . sH 2 O : uNaOH, 



the glucose is precipitated almost completely from solutions as a voluminous 

 blue compound. 



(b) On adding basic lead acetate and caustic soda, or ammonia, to a 

 solution of glucose in the proportions of 



the glucose is precipitated completely as an insoluble white compound. 



i he precipitation is not complete unless these quantities are nearly pro- 

 portional. Glucose is most conveniently removed from solution by this means. 



(3) Reduction. 



When glucose is reduced with sodium amalgam it is converted into the 

 hexahydric alcohol, sorbitol. 



(4) Oxidation. 



When oxidised by bromine water glucose is converted into gluconic acid ; 

 when oxidised by nitric acid it is converted into saccharic acid. 



(5) Action of Alkali. Glucose is acted upon by sodium hydroxide 

 at 37. The rotation of the solution diminishes and its acidity in- 

 creases. It passes over into fructose and mannose. Carbonates have 

 a slighter action and ammonia of the same concentration is almost 

 without action. 



Moores Test. On boiling a solution of glucose with sodium 

 hydroxide it turns yellow, then dark brown, and smells of caramel. The 

 smell becomes more distinct on acidifying the solution with dilute 

 sulphuric acid and its colour becomes lighter. Lactic acid and other 

 acids are formed. 



