How will you distinguish `1^(@) and 2^(@)` hydroxyl groups present in glucose? Explain with reactions

Explanation

Glucose molecule contains five hydroxyl groups attached to five different carbon atoms (`C_(2), C_(3), C_(4), C_(5) and C_(6)` in the open chain structure). The hydroxyl group attached to the terminal carbon (i.e., `C_(6)`) is the `1^(@)`-hydroxyl group. while all other are `2^(@)`-hydroxyl groups. Carbon atoms attached to `1^(@)-`hydroxyl group are easily oxidised to form `-COOH` group, but C-atoms attached to `2^(@)`-hydroxyl groups undergo oxidation only under drastic conditions causing break-down of the molecule. Thus, glucose is oxidised by `HNO_(3)` to give a dicarboxylic acid, saccharic acid, containing the same number of C-atoms. In this case, one `-COOH` is obtained by the oxidation of `-CHO` group, while the other is obtained by the oxidation of the terminal `-CH_(2)OH` group. For the reaction.