Question

hydrazones of aldehydes and ketones are not prepared in highly acidic medium.

Answer 1

In highly acidic medium , the NH2NH2 group of hydrazine gets protonatedNH2−NH2+H+⟶NH3−NH2NH2−NH2+H+⟶NH3−NH2because of strong I-effect of the NH3NH3 group ,the lone pair of electrons on the −NH2−NH2 group of protonated hydrazine is not available for nucleophilic attack on the C=OC=O and hence hydrazone formation does not occur .

Answer 2

Hydrazones of aldehydes and ketones are not prepared in highly acidic medium. In highly acidic medium the protonation of hydrazine (H2N = NH2) decreases its nucleophilic character. Thus, hydrozones of aldehyde and ketones are not prepared in highly acidic medium.