JEE Main · 2026 · 08 Apr 2026 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

Benzene with carbon monoxide and hydrogen chloride over cuprous chloride undergoes the Gattermann\u2013Koch reaction to give benzaldehyde, so $x={\mathrm{C}}_6{\mathrm{H}}_5\mathrm{CHO}$. Benzene with ethanoyl chloride and anhydrous $\mathrm{AlC}{\mathrm{l}}_3$ undergoes Friedel\u2013Crafts acylation to give acetophenone, so $y={\mathrm{C}}_6{\mathrm{H}}_5\mathrm{COC}{\mathrm{H}}_3$. Heating these together with alkali brings about a Claisen\u2013Schmidt (cross-aldol) condensation to give chalcone, ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{CH}=\mathrm{CHCO}{\mathrm{C}}_6{\mathrm{H}}_5$, as $z$. This molecule has two benzene rings contributing $6+6=12\pi$ electrons, one $\mathrm{C}=\mathrm{C}$ contributing $2$ and one $\mathrm{C}=\mathrm{O}$ contributing $2$, a total of $16\pi$ electrons.