Which of the following reactions will produce benzene ?

Options

A.
B.
C.
D.

Answer

To determine which of the given reactions will produce benzene, we will analyze each reaction step by step.

### Step 1: Analyze Reaction A (Phenol + Zinc)
- **Reaction**: Phenol (C6H5OH) reacts with zinc (Zn).
- **Mechanism**: When phenol is heated with zinc, a distillation reaction occurs. The hydroxyl group (-OH) in phenol is removed as water, and the remaining carbon structure forms benzene (C6H6).
- **Conclusion**: This reaction produces benzene.

### Step 2: Analyze Reaction B (Acetylene + Iron or Cobalt)
- **Reaction**: 3 molecules of acetylene (C2H2) react in the presence of iron (Fe) or cobalt (Co) as a catalyst.
- **Mechanism**: Under heating conditions, the triple bonds in acetylene can undergo coupling reactions. The pi electrons from the triple bonds rearrange, leading to the formation of benzene.
- **Conclusion**: This reaction also produces benzene.

### Step 3: Analyze Reaction C (Nitro-benzene + HCl)
- **Reaction**: Nitro-benzene (C6H5NO2) reacts with HCl.
- **Mechanism**: This reaction involves the reduction of the nitro group (-NO2) to an amine group (-NH2), resulting in aniline (C6H5NH2).
- **Conclusion**: This reaction does not produce benzene; it produces aniline instead.

### Step 4: Analyze Reaction D (Benzene-diazonium chloride + H3PO2)
- **Reaction**: Benzene-diazonium chloride reacts with phosphorous acid (H3PO2).
- **Mechanism**: The diazonium group (-N2+) is replaced by a hydrogen atom, resulting in the formation of benzene and nitrogen gas (N2) is released.
- **Conclusion**: This reaction produces benzene.

### Summary of Results:
- **Reactions that produce benzene**: A, B, and D.
- **Reaction that does not produce benzene**: C.

### Final Answer:
The reactions that will produce benzene are A, B, and D.

---