The electrophilie which attacks in Friedel-Craft acylation is

Options

A. `R-overset(O)overset(||)underset(o+)C`
B. `R-overset(overset(o+)O)overset(||)C`
C. `R-overset(overset(-)O)overset(|)underset(+)C-overset(-)O`
D. `overset(o+)SO_(2)overset(-)OH`

Answer

To solve the question regarding the electrophile that attacks in Friedel-Craft acylation, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Friedel-Craft Acylation**:
Friedel-Craft acylation is a type of electrophilic aromatic substitution reaction where an acyl group (RCO) is introduced into an aromatic ring. This reaction typically uses an acyl chloride (RCOCl) and a Lewis acid catalyst, such as AlCl3.

2. **Identifying the Reactants**:
The main reactants in Friedel-Craft acylation are:
- An aromatic compound (e.g., benzene)
- An acyl chloride (RCOCl)
- A Lewis acid (e.g., AlCl3)

3. **Role of the Lewis Acid**:
The Lewis acid (AlCl3) is crucial because it activates the acyl chloride. AlCl3 is electron-deficient and can accept electron pairs. It coordinates with the chlorine atom in the acyl chloride, facilitating the formation of a more reactive electrophile.

4. **Formation of the Electrophile**:
When AlCl3 coordinates with RCOCl, the chlorine atom, which has a lone pair of electrons, forms a bond with AlCl3. As a result, the bond between the carbonyl carbon (C=O) and chlorine becomes polarized. The chlorine atom, being electronegative, cannot stabilize the positive charge that develops on the carbonyl carbon, leading to the cleavage of the C-Cl bond.

5. **Identifying the Electrophile**:
The resulting species after the cleavage is a positively charged acylium ion (R-C^+=O), which is the actual electrophile that attacks the aromatic ring. Thus, the electrophile in Friedel-Craft acylation is the acylium ion (R-C^+=O).

6. **Conclusion**:
Therefore, the electrophile that attacks in Friedel-Craft acylation is the acylium ion (R-C^+=O).

### Final Answer:
The electrophile which attacks in Friedel-Craft acylation is the acylium ion (R-C^+=O).

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