A solution of ( + )-1-chloro-1-phenylethane in t toluene racemises slowly in the presence of a small amount of `SbCl_(5)` due to the formation of

Options

A. a carbene
B. a carbocation
C. a free radical
D. a carbanion.

Explanation

To solve the problem, we need to understand the process of racemization and the role of the reagent SbCl5 in the reaction involving (+)-1-chloro-1-phenylethane.

### Step-by-Step Solution:

1. **Identify the Compound**: The compound in question is (+)-1-chloro-1-phenylethane. This compound is chiral due to the presence of a carbon atom bonded to four different groups (a chlorine atom, a phenyl group, and two ethyl groups).

2. **Understand Racemization**: Racemization is the process of converting an optically active compound into a racemic mixture, which contains equal amounts of both enantiomers. In this case, (+)-1-chloro-1-phenylethane can be converted into its enantiomer (-)-1-chloro-1-phenylethane.

3. **Role of SbCl5**: Antimony pentachloride (SbCl5) is a strong Lewis acid. When added to the solution, it can coordinate with the chlorine atom of the chiral compound, leading to the formation of a more reactive carbocation intermediate.

4. **Formation of Carbocation**: The coordination of SbCl5 with the chlorine atom results in the cleavage of the C-Cl bond, generating a carbocation. This carbocation is planar and can be attacked from either side by a nucleophile, leading to the formation of both enantiomers.

5. **Racemization Process**: As the carbocation can be attacked from either side, the original (+)-1-chloro-1-phenylethane can convert to both (+) and (-) forms, thus leading to racemization. The process is slow, indicating that the reaction is not highly favorable but can occur over time.

6. **Conclusion**: Therefore, the solution of (+)-1-chloro-1-phenylethane in toluene racemizes slowly in the presence of a small amount of SbCl5 due to the formation of a carbocation intermediate.

### Final Answer:
A solution of (+)-1-chloro-1-phenylethane in toluene racemizes slowly in the presence of a small amount of SbCl5 due to the formation of a carbocation intermediate.

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