Question

The group added on to the benzene ring(-CH=CH-CH=O) should be an electron withdrawing group, yet the sources I found online suggest an ortho-/para- product rather than the expected meta product. Is there an explanation for this and preferably a mechanism for the reaction?

Answer 1

The ortho-/para- products are favored over the meta product when adding an electron withdrawing group to the benzene ring due to steric hindrance. The mechanism involves the formation of an arenium ion intermediate.

Step-by-step explanation:

The addition of the group (-CH=CH-CH=O) to the benzene ring does indeed make it an electron withdrawing group. However, the ortho-/para- products are favored over the meta product due to steric hindrance. The ortho and para positions are less hindered and more accessible compared to the meta position.

The mechanism for the reaction involves the formation of an arenium ion intermediate. The electron withdrawing group stabilizes the positive charge on the ring, making it easier for the nucleophile to attack. This results in the formation of the ortho or para product.