Question

Nucleophilic addition of ammonia and its derivatives does not occur with carbonyl group in strongly acidic medium.

Hint:

In organic chemistry, "Strongly Acidic" often means a basic reagent will be neutralized and rendered unreactive.

Answer 1

Nucleophilic addition of ammonia and its derivatives does not occur with the carbonyl group in a strongly acidic medium.

Explanation:
In a strongly acidic medium, the carbonyl group (C=O) becomes protonated, forming a positively charged oxonium ion (C+–OH). This protonation increases the electrophilic character of the carbonyl carbon, making it more susceptible to nucleophilic attack. However, the protonated carbonyl group is highly unstable and does not favor nucleophilic addition reactions, especially with ammonia or its derivatives.
1. Protonation of Carbonyl Group: When the medium is strongly acidic, the carbonyl oxygen (which is highly electronegative) accepts a proton from the acid, forming a protonated carbonyl group (C+–OH). This reduces the electron density around the carbonyl carbon, making it highly electrophilic but also much less reactive toward nucleophiles like ammonia (NH₃) and its derivatives.
2. Steric Hindrance and Instability: The positive charge on the oxygen in the protonated carbonyl group creates significant steric hindrance and reduces the availability of the carbonyl carbon for nucleophilic attack. In addition, the oxonium ion formed is unstable and would rather undergo dehydration or revert to the carbonyl form, thus preventing nucleophilic addition.
Therefore, in a strongly acidic medium, nucleophilic addition by ammonia and its derivatives does not occur because the protonation of the carbonyl group makes it less susceptible to nucleophilic attack.