JEE Main · 2026 · 21 Jan 2026 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

The Etard reaction oxidises toluene to benzaldehyde with chromyl chloride in carbon disulphide, so it goes with ${\mathrm{CrO}}_2{\mathrm{Cl}}_2$, ${\mathrm{CS}}_2$. Rosenmund reduction turns an acyl chloride into an aldehyde over a poisoned palladium catalyst, pairing with ${\mathrm{H}}_2$, Pd-${\mathrm{BaSO}}_4$. The Gatterman-Koch reaction formylates benzene using carbon monoxide and hydrogen chloride with anhydrous aluminium chloride, pairing with CO, HCl, anhyd. ${\mathrm{AlCl}}_3$. The Stephen reaction reduces a nitrile through an aldimine to an aldehyde using stannous chloride and hydrochloric acid, pairing with ${\mathrm{SnCl}}_2$, HCl. Thus Etard matches ${\mathrm{CrO}}_2{\mathrm{Cl}}_2$/${\mathrm{CS}}_2$, Rosenmund matches ${\mathrm{H}}_2$/Pd-${\mathrm{BaSO}}_4$, Gatterman-Koch matches CO/HCl/${\mathrm{AlCl}}_3$, and Stephen matches ${\mathrm{SnCl}}_2$/HCl.