What is the major product obtained by oxidation of phenylethene...

Phenylethene (styrene) has the structure $\text{C}_6\text{H}_5\text{CH}=\text{CH}_2$.

When treated with a strong oxidizing agent like $\text{KMnO}_4$ in an acidic medium (dilute $\text{H}_2\text{SO}_4$), oxidative cleavage of the carbon-carbon double bond takes place.

The terminal $=\text{CH}_2$ group is oxidized to $\text{CO}_2$ and $\text{H}_2\text{O}$.

The $\text{C}_6\text{H}_5\text{CH}=$ group is oxidized to a carboxylic acid, yielding benzoic acid ($\text{C}_6\text{H}_5\text{COOH}$).

The reaction is given by:
$\text{C}_6\text{H}_5\text{CH}=\text{CH}_2 \xrightarrow{\text{KMnO}_4, \text{H}^+} \text{C}_6\text{H}_5\text{COOH} + \text{CO}_2 + \text{H}_2\text{O}$

Thus, the major product obtained is benzoic acid.

Answer: Benzoic acid