Consider the molecule p-nitroaniline. If you assign a mathematical value of to any functional group — GOC and Organic Chemistry Basics Chemistry Question
Question
Consider the molecule p-nitroaniline. If you assign a mathematical value of $+1$ to any functional group showing a primary $+M$ effect and $-1$ to any group showing a primary $-M$ effect, what is the net algebraic sum of the mesomeric effects exerted by the two functional groups attached to the aromatic ring?
Answer: 0
💡 Solution & Explanation
The amino group ($-NH_2$) possesses a lone pair on nitrogen and donates electrons to the ring, exerting a $+M$ effect (value = $+1$). The nitro group ($-NO_2$) possesses electronegative oxygen atoms attached via multiple bonds, withdrawing electrons from the ring, exerting a $-M$ effect (value = $-1$). The sum is $+1 + (-1) = 0$.
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