JEE Main 2026 — Aldehydes and Ketones Question with Solution

Benzene reacts with $CO$ and $HCl$ in the presence of $CuCl$ to give benzaldehyde ($x$) via the Gattermann-Koch reaction.

Benzene reacts with ethanoyl chloride ($C{H}_{3}COCl$) in the presence of anhydrous $AlC{l}_3$ to give acetophenone ($y$) via Friedel-Crafts acylation.

Heating benzaldehyde ($x$) and acetophenone ($y$) in the presence of alkali results in a crossed aldol condensation to form benzalacetophenone ($z$).

$C_6{H}_{5}CHO+C{H}_{3}CO{C}_6{H}_5\stackrel{O{H}^{-},\Delta }{\to }{C}_6{H}_5-CH=CH-CO-C_6{H}_5+H_{2}O$

The structure of $z$ ($C_6{H}_5-CH=CH-CO-C_6{H}_5$) contains two phenyl rings ($6$ $\pi$ bonds), one $C=C$ double bond ($1$ $\pi$ bond), and one $C=O$ double bond ($1$ $\pi$ bond).

Total number of $\pi$ bonds = $6+1+1=8$

Total number of $\pi$ electrons = $8\times 2=16$

Answer: $16$