Nucleophilic Aromatic Substitution. Benzyne

In a commercially important synthesis, aqueous sodium hydroxide reacts with chlorobenzene to give phenol. [Pg.197]

The addition-elimination mechanism involves two intermediates, a chlorophenyl anion and benzyne. A simple displacement mechanism can be ruled out because reaetion of ort/io-chlorotoluene gives not only ort/io-methylphenol but also meto-methylphenol. [Pg.197]

Examine the geometry of methylbenzyne. Measure carbon-earbon distances. Which 7C bonds are deloealized and whieh are localized Is there really a triple bond (Compare bond distance to triple bond in hexa-l,5-dien-3-yne and to partial double bonds in benzene). Are you able to draw a single Lewis structure whieh adequately represents the geometry of the molecule [Pg.197]

Hydration of methylbenzyne is believed to require nucleophilie attack by hydroxide. Examine the lowest-unoccupied molecular orbital (LUMO) of methylbenzyne. How many sites are there for nucleophilic attack Does hydroxide attaek in the plane of the ring, or perpendicular to the ring plane Explain. [Pg.197]

LUMO of methylbenzyne reveals likely site of nucleophilic attack. [Pg.197]

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