Aldehydes and ketones react with ammonia derivatives in weakly acidic/strongly acidic medium.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Reactants**: Aldehydes and ketones are carbonyl compounds that contain a carbonyl group (C=O). Ammonia derivatives include compounds like ammonia (NH₃), primary amines (RNH₂), and secondary amines (R₂NH).

2. **Nature of the Reaction**: Aldehydes and ketones undergo nucleophilic addition reactions with ammonia derivatives. The nitrogen atom in ammonia derivatives acts as a nucleophile and attacks the electrophilic carbon atom in the carbonyl group.

3. **Effect of Medium on the Reaction**: The medium in which the reaction occurs can significantly influence the reactivity of the nucleophile (ammonia derivative). In a strongly acidic medium, the nucleophilic nature of the ammonia derivatives is diminished due to protonation of the nitrogen atom. This makes it less likely to attack the carbonyl carbon.

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