JEE Main · 2005 · 08 May 2005 · Offline · Aldehydes Ketones and Carboxylic Acids

A ketone reacting with an amine can stop at different products depending on the amine. Cyclohexanone with dimethylamine, a secondary amine, cannot form an imine, because an imine needs the $\mathrm{N}-\mathrm{H}$ of a primary amine to finish as the $\mathrm{C}=\mathrm{N}$. Instead, after the nitrogen adds and water is driven off, a proton leaves the $\alpha$-carbon, placing the double bond between carbon and carbon next to the nitrogen. That $\mathrm{C}=\mathrm{C}-\mathrm{N}$ product, formed with continuous removal of water, is an enamine.