In which of the following reactions does the amine behaves as an acid?

Options

A. `(C_(2) H_(5) )_(2) NH+ H_(2) PtCI_(6)`
B. `CH_(3) NH_(2) + H_(2) O`
C. `("Me"_(2) CH)_(2) NH + n - C_(4) H_(9) Li`
D. `(C_(2) H_(5) )_(3) overset(..)(N) + BF_(3)`

Answer

To determine in which of the following reactions an amine behaves as an acid, we need to analyze the given options and understand the behavior of amines in the presence of other substances.

### Step-by-Step Solution:

1. **Understanding Acid-Base Behavior**:
- An acid is a substance that can donate a proton (H⁺) or accept an electron pair, while a base is a substance that can accept a proton or donate an electron pair.
- Amines generally act as bases due to the presence of a lone pair of electrons on the nitrogen atom, which can be donated.

2. **Analyzing Each Option**:
- **Option A**: Amine + Chloro-pitalinic acid
- Chloro-pitalinic acid is already an acid. The amine will act as a base here because it can donate its lone pair to the acid.
- **Conclusion**: Amine does not behave as an acid.

- **Option B**: Amine + Water
- Water can act as a stronger acid than amines. In this reaction, the amine will again act as a base, accepting a proton from water.
- **Conclusion**: Amine does not behave as an acid.

- **Option C**: Amine + n-Butyl lithium
- n-Butyl lithium is a strong base. In this case, the amine will behave as a weaker base compared to n-butyl lithium, which means it can act as an acid by donating a proton to the stronger base.
- **Conclusion**: Amine behaves as an acid.

- **Option D**: Amine + BF₃
- BF₃ is an electron-deficient species and acts as a Lewis acid. The amine can donate its lone pair to BF₃, thus behaving as a base in this reaction.
- **Conclusion**: Amine does not behave as an acid.

3. **Final Conclusion**:
- The only reaction in which the amine behaves as an acid is **Option C** (Amine + n-Butyl lithium).