QuestionOrganic / ipso substitution
Which one of the following reactions is NOT an example of ipso-substitution?
- (a) o-Chloronitrobenzene → o-nitrophenol (Na₂CO₃, H₂O, 135 °C)
- (b) 2,4-Dinitrophenyl phenyl sulfone + piperidine → N-(2,4-dinitrophenyl)piperidine
- (c) o-Bromoanisole + NaNH₂/liq. NH₃ → m-anisidine
- (d) Picryl chloride → picric acid (Na₂CO₃, H₂O, 35 °C)
Answer: (c)
Ipso = the nucleophile enters the carbon that carried the leaving group. (a), (b), (d) are SNAr at that carbon. (c) goes via benzyne: NH₂ enters the adjacent carbon (cine substitution) → NOT ipso → (c).