Benzene reacts with CH3COCl and anhydrous AlCl3 to give A, and A is nitrated with a HNO3/H2SO4 mixture to give B, 1-(3-nitrophenyl)ethanone, molecular formula C8H7NO3. Calculate the degree of unsaturation (number of rings plus pi bonds, counting the nitro group as one) of B (nearest integer).

JEE Main levelNumerical answerDifficulty 2 of 3si209

Benzene reacts with $CH X_{3} COCl$ and anhydrous $AlCl X_{3}$ to give A, and A is nitrated with a $HNO X_{3} / H X_{2} SO X_{4}$ mixture to give B, 1-(3-nitrophenyl)ethanone, molecular formula $C X_{8} H X_{7} NO X_{3}$ . Calculate the degree of unsaturation (number of rings plus pi bonds, counting the nitro group as one) of B (nearest integer).

Numerical answer type, tolerance 0.5.

For

C X_{c} H X_{h} N X_{n} O X_{o}

, degree of unsaturation =

\frac{2 c + 2 + n - h}{2} = \frac{16 + 2 + 1 - 7}{2} = 6

. This matches the benzene ring (4), the C=O (1) and the nitro group (1).