JEE Main · 2026 · 06 Apr 2026 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

Prolonged heating of glucose with HI reduces the whole chain to $n$-hexane, which on passing over ${\mathrm{V}}_2{\mathrm{O}}_5$ at high temperature and pressure aromatises to benzene. Friedel$-$Crafts acylation of benzene with benzoyl chloride and anhydrous $\mathrm{AlC}{\mathrm{l}}_3$ then gives benzophenone, $({\mathrm{C}}_6{\mathrm{H}}_5{)}_2\mathrm{C}=\mathrm{O}$. In benzophenone the two rings supply six $\pi$ bonds and the carbonyl one $\pi$ bond, that is seven $\pi$ bonds carrying 14 electrons, while the carbonyl oxygen carries two lone pairs, 4 electrons. The total number of electrons in the $\pi$ bonds and lone pairs is 18.