combined form it is present in sucrose, starch, cellulose etc., Preparation of glucose . When sucrose ( cane sugar ) is boiled with dilute H SO in alcoholic solution, it undergoes hydrolysis and give glucose and fructose. C H O + H O C H O + C H O H + Sucrose Glucose Fructose CHO CH CH OH n ALDOSE n= , , , H C CH CH OH n KETOSE n= , , , , Figure . Structure of aldoses and ketoses XII XII - - - - .
Glucose is produced commercially by the hydrolysis of starch with dilute HCl at high temperature under pressure. (C H O ) n + n H O n C H O H + Starch Glucose - atm 393K Structure of Glucose Glucose is an aldohexose. It is optically active with four asymmetric carbons. Its solution is dextrorotatory and hence it is also called as dextrose.
The proposed structure of glucose is shown in the figure . which was derived based on the following evidences. . Elemental analysis and molecular weight determination show that the molecular formula of glucose is C H O .
. On reduction with concentrated HI and red phosphorus at 373K, glucose gives a mixture of n hexane and –iodohexane indicating that the six carbon atoms are bonded linearly. Glucose n-hexane Major product -iodohexane Minor product CH — CH — CH + CH — CH — CH — CH HI / P K