The ratio of $\sigma$ and $\pi$ bonds in benzene is:

Calculate the sum of $\alpha$-hydrogen atoms in the given structures $(i)$ and $(ii)$:
$(i)$ $1,3$-dimethylbenzene
(ii) $1,3$-diethylbenzene
Sum $= (i) + (ii) = ?$

Which of the following has the lowest knocking property?

In the following reactions,$X$ and $Y$,respectively,are

Identify $X$ in the following reaction.

Catalytic oxidation of benzene at $500\,^oC$ in the presence of $V_2O_5$ gives ..........