Which of the following ketone will NOT give enamine on treatment with secondary amines? [where t-Bu is $$-C(CH_3)_3$$]

Explanation: Enamine formation requires removal of an $$\mathrm{\alpha}$$-hydrogen from the carbon adjacent to the carbonyl group in the final dehydration step.

Therefore, a ketone must contain at least one $$\mathrm{\alpha}$$-hydrogen to form an enamine.

In di-$$\mathrm{tert}$$-butyl ketone, the $$\mathrm{\alpha}$$-carbon is bonded to three methyl groups and the carbonyl carbon, $$\mathrm{-C(CH_3)_3}$$.

Thus, the $$\mathrm{\alpha}$$-carbon contains no hydrogen atoms.

Because no $$\mathrm{\alpha}$$-hydrogen is available, formation of the required $$\mathrm{C=C}$$ bond is impossible.

Hence, di-$$\mathrm{tert}$$-butyl ketone cannot form an enamine.

Ketones such as diethyl ketone and cyclohexanone possess $$\mathrm{\alpha}$$-hydrogens and therefore readily form enamines.

Correct Option: $$\mathrm{(B)}$$