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 determine the electrophile that attacks during Friedel-Crafts acylation, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reagents**: In Friedel-Crafts acylation, the primary reagents used are an acyl chloride (for instance, acetyl chloride, CH3C(O)Cl) and a Lewis acid (commonly aluminum chloride, AlCl3).

2. **Formation of the Electrophile**: The acyl chloride reacts with the Lewis acid. The aluminum chloride (AlCl3) acts as a Lewis acid by accepting a lone pair of electrons from the chlorine atom in acetyl chloride. This interaction weakens the carbon-chlorine bond.

3. **Generation of the Electrophile**: As the bond between carbon and chlorine breaks, a positively charged acylium ion is formed. For acetyl chloride, this results in the formation of the electrophile:
\[ \text{Electrophile: } CH3C^+=O \]
This acylium ion (CH3C^+=O) is the active electrophile that will participate in the Friedel-Crafts acylation reaction.

4. **Electrophilic Attack on Benzene**: The generated electrophile (acylium ion) then attacks the benzene ring. The π electrons from the benzene ring attack the electrophile, leading to the formation of a sigma complex (an arenium ion).

5. **Deprotonation**: The sigma complex then loses a proton (H+) to restore aromaticity, resulting in the final product. For example, if we started with benzene, the product would be acetophenone (C6H5C(O)CH3).

6. **Conclusion**: The electrophile that attacks in Friedel-Crafts acylation is the acylium ion, represented as:
\[ CH3C^+=O \]

### Final Answer:
The electrophile which attacks in Friedel-Crafts acylation is the acylium ion, \( CH3C^+=O \).

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