Benzyne Mechanism

Question

Elimination-addition (benzyne) mechanism is favored by treatment of chlorobenzene with:

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1. **Dow's Process Mechanism**: Chlorobenzene does not undergo nucleophilic substitution under normal conditions due to partial double bond character.
2. **Extreme Conditions**: Under high pressure and temperature ($623K$ and $300$ atm) with $NaOH$, reaction occurs.
3. **Benzyne Formation**: A very strong base ($OH^-$ or $NH_2^-$) abstracts an ortho-hydrogen, following which the halide leaves, creating a triple bond within the benzene ring (**Benzyne intermediate**).
4. **Attack**: The nucleophile then attacks the benzyne to restore the aromatic system.
5. **Requirement**: This pathway requires **high energy (molten/fused alkali)** to overcome the aromatic stability barrier.

Benzyne Mechanism

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