question_answer 87)

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

Answer:

                  Refer to the structure (I) of glucose given on page 14/6. The -OH group present on the terminal carbon atom (i.e., ) is called the I" hydroxyl group while all the four remaining OH groups present on and 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  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.