Nitration of Toluene Toluene reacts 25 times faster than benzene. The methyl group is an activating group. The product mix contains mostly ortho and para substituted molecules. CH3 CH. CH. HNO3 H2SO NO O,N NO2 toluene o-nitrotoluene m-nitrotoluene p-nitrotoluene (60%) (4%) (36%) => Chapter 17 11
Chapter 17 11 Nitration of Toluene • Toluene reacts 25 times faster than benzene. The methyl group is an activating group. • The product mix contains mostly ortho and para substituted molecules. =>
Sigma Complex Ortho attack CH CH CH H NO, NO NO NO H 3(favorable) Intermediate Para attack is more CH3 CH stable if nitration H NO H NO, H NO. occurs at 3(favorable) 2 Meta attack the ortho CH3 CH CH CH or para position. NO. NO H H => NO 2 2 Copyright2005 Pearson Prentice Hall,Inc Chapter 17 12
Chapter 17 12 Sigma Complex Intermediate is more stable if nitration occurs at the ortho or para position. =>
Energy Diagram H benzene meta CH3 ortho,para H CH NO2 CH3 H K3jaua CH; NO2 NO2 ++N02 > reaction coordinate- 13 Copyright 2005 Pearson Prentice Hall,Inc
Chapter 17 13 Energy Diagram =>
Activating,O-,P- Directing Substituents Alkyl groups stabilize the sigma complex by induction,donating electron density through the sigma bond. 。 Substituents with a lone pair of electrons stabilize the sigma complex by resonance. CH; OCH3 -NO2 -NO2 H Chapter 17 14
Chapter 17 14 Activating, O-, PDirecting Substituents • Alkyl groups stabilize the sigma complex by induction, donating electron density through the sigma bond. • Substituents with a lone pair of electrons stabilize the sigma complex by resonance. OCH3 H NO2 + OCH3 H NO2 + =>
Substitution on Anisole Ortho attack :OCH OCH +OCH3 :OCH, :OCH, H NO NO NO especially stable Meta attack :OCH :OCH :OCH :OCH NO H NO Moe日 Para attack :OCH, OCH :OCH +OCH; :OCH3 M H NO, H NO, NO > especially stable 15 Copyright2005 Pearson Prentice Hall.Inc
Chapter 17 15 Substitution on Anisole =>