Problem Set 4 – Electrophilic aromatic substitution

1. The nitration of N,N-dimethylaniline, C₆H₅N(CH₃)₂, in 85% H₂SO₄ gives 45% m-nitro product and 38% p-nitro product.

a. What is the species actually undergoing nitration to give the meta product?

b. How is it formed?

c. What is its relative reactivity to that of benzene?

d. Why does this species under go meta substitution?

2. The nitroso group, -N=O, is ortho-para directing but deactivating. Explain in terms of resonance and inductive effects.

3. Hexachlorophene, a substance used in the manufacture of germicidal soaps, is prepared by reaction of 2,4,5-trichlorophenol with formaldehyde in concentrated sulfuric acid. Propose a mechanism.

4. Propose a synthesis of 2-bromo-4-nitrotoluene from benzene.

5. Two alcohols, “A” and “B”, have the same molecular formula C₉H₁₀O and react with sulfuric acid to give the same hydrocarbon “C”. Compound “A” is optically active and compound “B” is not. Catalytic hydrogenation of “C” gives a hydrocarbon “D”, C₉H₁₀, which gives two and only two products when nitrated once with HNO₃/H₂SO₄. Give the structures of “A”, “B”, “C”, and “D”.

6. Propose a mechanism for the following reaction: