SolutionsDirecting Effects

1. Energy diagrams

Give a real example of the nitration of a monosubstituted benzene for each of the qualitative energy diagrams. Take the energy profile of the nitration of benzene as reference.

Four qualitative energy diagrams for the nitration of a monosubstituted benzene X–C₆H₅ (ortho, meta and para pathways), compared with that of the nitration of benzene

Energy diagram of the nitration of phenol

Phenol. Pathways below that of benzene: activating. Ortho and para pathways of lowest energy: ortho-para director.

Energy diagram of the nitration of chlorobenzene

Chlorobenzene. Pathways above that of benzene: deactivating. Ortho and para pathways of lowest energy: ortho-para director.

Energy diagram of the nitration of trifluoromethylbenzene

Trifluoromethylbenzene. Pathways above that of benzene: deactivating. Meta pathway of lowest energy: meta director.

Energy diagram of the nitration of benzoic acid

Benzoic acid. Pathways above that of benzene: deactivating. Meta pathway of lowest energy: meta director; the para pathway is inaccessible.

2. Activating or deactivating?

Classify these groups as activating or deactivating and as ortho-para or meta directors: –OCH₃, –CHO, –Br, –CH₂CH₃, –SO₃H, –NHCOCH₃, –CN.

Group	Effect	Orientation
–OCH₃	strongly activating	ortho-para
–NHCOCH₃	moderately activating	ortho-para
–CH₂CH₃	weakly activating	ortho-para
–Br	weakly deactivating	ortho-para
–CHO	deactivating	meta
–CN	strongly deactivating	meta
–SO₃H	strongly deactivating	meta

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