How will you distinguish $1^o$ and $2^o$ hydroxyl groups present in glucose? Explain with reactions.

(N/A) Glucose contains one primary alcoholic group $(-CH_2OH)$ and four secondary alcoholic groups $(-CHOH)$.
When glucose is oxidized with nitric acid $(HNO_3)$,it forms a dicarboxylic acid known as saccharic acid (glucaric acid).
The oxidation of the primary alcoholic group to a carboxylic acid group confirms its presence.
The reaction is as follows:
$CHO-(CHOH)_4-CH_2OH \xrightarrow{HNO_3} COOH-(CHOH)_4-COOH$ (Saccharic acid).
Similarly,gluconic acid $(COOH-(CHOH)_4-CH_2OH)$ also yields saccharic acid upon oxidation with $HNO_3$,confirming the presence of the primary alcoholic group.
The remaining four $-OH$ groups are secondary,as they do not oxidize under these conditions.