Predict the product (B) in the following sequence of reactions:
Ethylbenzene `underset(Delta)overset(KMnO_(4)-KOH)to A overset(H_(3)O^(+))toB`

Options

A. benzaldehyde
B. benzophenone
C. benzene
D. acetophenone

Explanation

To predict the product (B) in the given sequence of reactions, we start with ethylbenzene and follow the steps outlined in the problem.

### Step-by-Step Solution:

1. **Identify the starting compound**: The starting compound is ethylbenzene, which has the chemical structure \( C_6H_5CH_2CH_3 \).

2. **First reaction with KMnO4 in basic medium**:
- Ethylbenzene undergoes oxidation when treated with potassium permanganate (KMnO4) in a basic medium (KOH).
- KMnO4 is a strong oxidizing agent and will oxidize the side chain (the ethyl group) of ethylbenzene.
- The oxidation of the ethyl group leads to the formation of benzoate ion (the deprotonated form of benzoic acid). The reaction can be summarized as:
\[ C_6H_5CH_2CH_3 \xrightarrow{KMnO_4, KOH} C_6H_5COO^{-} \]
- Here, the ethyl group is converted to a carboxylate ion (benzoate ion).

3. **Second reaction with H3O+**:
- The next step involves the addition of \( H_3O^+ \) (hydronium ion), which will protonate the benzoate ion formed in the previous step.
- This protonation converts the benzoate ion into benzoic acid:
\[ C_6H_5COO^{-} + H_3O^{+} \rightarrow C_6H_5COOH \]
- Therefore, the final product (B) is benzoic acid.

### Final Answer:
The product (B) is **benzoic acid** (\( C_6H_5COOH \)).