Which is the wrong statement about oxymercuration `-` demercuration `?`

Options

A. In the first step, oxymercuration occurs, `i.e.,` water and `Hg(Oac)_(2)`, add to the double bond.
B. In the second step, demercuratio occurs, `i.e., NaBH_(4)` reduces `(HgOAc)` group to hydrogen.
C. The net reaction is the addition of water according to Markovnikov's rule.
D. Rearrangement takes place

Answer

To determine which statement about the oxymercuration-demercuration reaction is wrong, we first need to understand the mechanism of this reaction.

### Step-by-Step Solution:

1. **Understanding the Reaction**: The oxymercuration-demercuration reaction involves the addition of water across a double bond in an alkene using mercuric acetate (Hg(OAc)₂) followed by reduction with sodium borohydride (NaBH₄).

2. **Markovnikov's Rule**: This reaction follows Markovnikov's rule, meaning that when water adds across the double bond, the hydroxyl group (OH) will attach to the more substituted carbon atom, while a hydrogen atom (H) will attach to the less substituted carbon atom.

3. **Mechanism Overview**:
- The alkene reacts with mercuric acetate to form a cyclic mercurinium ion intermediate.
- Water then attacks the more substituted carbon from the backside, leading to anti-addition.
- The resulting product is a mercurial alcohol.

4. **Demercuration Step**: In the second step, sodium borohydride reduces the mercurial alcohol, replacing the HgOAc group with a hydrogen atom, thus forming the final alcohol product.

5. **Evaluating the Statements**:
- **Statement A**: "In the first step, oxymercuration occurs, that is water and HgOAc add to the double bond." - This is correct.
- **Statement B**: "In the second step, demercuration occurs, that means NaBH₄ reduces HgOAc group to hydrogen." - This is correct.
- **Statement C**: "The net reaction is the addition of water according to the Markovnikov rule." - This is correct.
- **Statement D**: "Rearrangement takes place." - This is incorrect because there is no carbocation formed in this reaction; instead, a cyclic intermediate is formed, which does not allow for rearrangement.

6. **Conclusion**: The wrong statement about the oxymercuration-demercuration reaction is **Statement D**.