the combined form. It is present in sweet fruits and honey. Ripe grapes also contain glucose in large amounts. It is prepared as follows: .
From sucrose (Cane sugar) : If sucrose is boiled with dilute HCl or H SO in alcoholic solution, glucose and fructose are obtained in equal amounts. Preparation of Glucose . . .
Glucose + C H O H O C H O + C H O + → Sucrose Glucose Fructose . From starch : Commercially glucose is obtained by hydrolysis of starch by boiling it with dilute H SO at K under pressure. + n 393K; - atm (C H O ) + nH O nC H O → Starch or cellulose Glucose Glucose is an aldohexose and is also known as dextrose. It is the monomer of many of the larger carbohydrates, namely starch, cellulose.
It is probably the most abundant organic compound on earth. It was assigned the structure given below on the basis of the following evidences: . Its molecular formula was found to be C H O . .
On prolonged heating with HI, it forms n-hexane, suggesting that all the six carbon atoms are linked in a straight chain. . Glucose reacts with hydroxylamine to form an oxime and adds a molecule of hydrogen cyanide to give cyanohydrin. These reactions confirm the presence of a carbonyl group (>C = O) in glucose.
. Glucose gets oxidised to six carbon carboxylic acid (gluconic acid) on reaction with a mild oxidising agent like bromine water. This indicates that the carbonyl group is present as an aldehydic group. CHO (CH ) (CH ) CH OH CH OH Br water Gluconic acid .
Acetylation of glucose with acetic anhydride gives glucose pentaacetate which confirms the presence of five –OH groups. Since it exists as a stable compound, five –OH groups should be attached to different carbon atoms. Structure of Glucose CHO (CH ) CH OH Glucose . On