Which is the wrong statement ?

Options

A. In ocymercuration and demercuration reaction, alcohol is formed by markovnikov addition.
B. In hydroboration oxidation reaction, alcohol is formed by anti`-` Markovnikov addition
C. Regiospecificity of `HBO` reaction is syn.
D. Regispecificity of oxymercuration and ddemersuraction reaction is anti and rearragement occurs.

Answer

To determine which statement is wrong regarding oxymercuration and demercuration reactions and hydroboration oxidation reactions, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding Hydroboration-Oxidation Reaction**:
- Hydroboration involves the addition of BH3 to an alkene. This reaction follows a **syn addition**, meaning that both the boron and hydrogen atoms add to the same side of the double bond.
- The second step involves oxidation, where H2O2 and OH- are used, leading to the formation of an alcohol. This process follows the **anti-Markovnikov rule**, meaning that the hydroxyl group (OH) adds to the less substituted carbon of the alkene.

2. **Understanding Oxymercuration-Demercuration Reaction**:
- Oxymercuration involves the addition of mercuric acetate (Hg(OAc)2) in the presence of a nucleophile (like water or alcohol). This reaction leads to the formation of a cyclic transition state.
- The addition follows the **Markovnikov rule**, meaning that the nucleophile adds to the more substituted carbon of the alkene.

3. **Analyzing the Statements**:
- **Statement 1**: "In oxymercuration and demercuration, alcohol is formed by Markovnikov rule."
- This is **correct** because the addition of the nucleophile follows Markovnikov's rule.

- **Statement 2**: "In hydroboration oxidation reaction, alcohol is formed by anti-Markovnikov rule."
- This is **correct** as the hydroxyl group adds to the less substituted carbon.

- **Statement 3**: "Reduced reactivity of hydroboration oxidation is seen as syn addition."
- This is **correct** because hydroboration indeed follows a syn addition mechanism.

- **Statement 4**: "Regioselectivity of oxymercuration and demercuration is anti and rearrangement occurs."
- This is **wrong** because while the regioselectivity is indeed anti (following Markovnikov's rule), rearrangement does not occur due to the formation of a cyclic transition state, which prevents carbocation rearrangement.

4. **Conclusion**:
- The wrong statement is **Statement 4**.

### Final Answer:
The wrong statement is: "Regioselectivity of oxymercuration and demercuration is anti and rearrangement occurs."

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