(a) Glucose reacts with HI to form n-hexane indicating that the six carbons are linked in a straight chain.
(b) Glucose reacts with acetic anhydride to form glucose pentaacetate on acetylation. This reaction confirms that five −OH groups are present in glucose and that too on different carbon atoms, otherwise the resulting pentaacetate would be highly unstable.
(c) It reacts with hydrogen cyanide to form cyanohydrin and with hydroxylamine to form an oxime.
The reactions clearly indicate the presence of a carbonyl group in glucose.
