Image 1

The following reaction has been taken from my study material. This shows that the benzene ring is undergoing a nucleophilic aromatic substitution via benzyne mechanism (presence of a strong base like $\ce{NaNH2}$). My question is:

Why is substitution preferred at the ortho position?

The following link explains the mechanism quite well and gives an example of ortho-chlorotoluene undergoing a similar reaction. Since both proceed via the same benzyne intermediate, why is there a difference in the products formed by meta-chlorotoluene? Or is my study material wrong in saying that o-aminotoluene is a major product? Any help regarding this is appreciated!

Attaching the related reaction's image: enter image description here

  • $\begingroup$ I am not sure though but maybe the -NH2 group at ortho may stabilise more the hyperconjugative structures of the product. $\endgroup$ Aug 3, 2022 at 13:23

1 Answer 1


The Me group has no directing effect in the deprotonation so there are 2 protons (o & p) that can be removed with equal probability by the NaNH2 to give the benzyne. These give 2 possible benzynes (2 and 3 relative to Me). The nucleophile will add with equal facility to either end of either benzyne giving a mixture of 3 isomers in 1:2:1 ratio. The major isomer is the m- aminotoluene because it can arise from both of the possible benzynes.

  • $\begingroup$ Ok that makes a lot of sense. So that means that m-aminotoluene and not o-aminotoluene is the major product, which means that the first reaction is wrong. $\endgroup$ Nov 19, 2019 at 10:03

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.