Why is it necessary to control the pH during the reaction of aldehydes and ketones with ammonia derivatives?

Explanation

The addition of ammonia derivative `(NH_(2)-G)` to aldehydes and ketones and ketones is done in weakly acidic medium (`p_(H)` about `3*5`). In case the medium is strongly acidic (`p_(H)` close to `1`), then the ammonia derivative will the also protonated and will not be able to act as a nuclephile.