Birch reduction is done in the presence of

Options

A. Palladium supported over charcoal
B. `Na-liq. NH_3`
C. `H_2 - Nickel`
D. Alc. KOH

Answer

**Step-by-Step Solution:**

1. **Understanding Birch Reduction**: Birch reduction is a chemical reaction that involves the reduction of aromatic compounds to form non-aromatic compounds, typically using sodium (Na) in liquid ammonia (NH3).

2. **Identifying the Correct Reagents**: The question asks for the reagents used in Birch reduction. The common reagents known for this reaction are sodium metal and liquid ammonia.

3. **Analyzing the Options**: The options provided are:
- (a) Palladium supported over charcoal
- (b) Na + liquid ammonia
- (c) S2 in presence of nickel
- (d) Alcoholic KOH

Among these, option (b) Na + liquid ammonia is the only combination that is known to facilitate Birch reduction.

4. **Mechanism Overview**: Birch reduction involves the formation of radical anions through the donation of an electron from sodium to the aromatic compound. This is followed by protonation from ammonia, leading to the formation of a non-aromatic compound.

5. **Conclusion**: Based on the analysis, Birch reduction is specifically done in the presence of sodium and liquid ammonia, making option (b) the correct answer.

**Final Answer**: Birch reduction is done in the presence of Na + liquid ammonia.

---