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

Explanation

The `-OH` group present on the terminal carbon atom (i.e., `C_6`) is called the `1^@` hydroxyl group while all the four remaining OH groups present on `C_2,C_3,C_4 and C_5` are called `2^@` hydroxyl groups. `1^@` Hydroxyl groups are easily oxidised to give carboxylic acids but `2^@` hydroxyl groups undergo oxidation only under drastic conditions. For example , glucose on oxidation with `HN_3` gives a dicarboxylic acid, saccharic acid having the same number of carbon atoms as glucose. This indicates that glucose contains one `1^@` hydroxyl group while the remaining four are `2^@` hydroxyl groups.