Question

Which of the following substitution of benzene is ortho-para in electrophilic substitution and ortho-para in nucleophilic substitution.
A. $-N{{O}_{2}}$
B. $-NO$
C. $-S{{O}_{3}}H$
D. $-S{{O}_{2}}Me$

Answer 1

The molecules which behave as a strong electron withdrawing group react with nucleophile in this case it will be benzene on ortho-para position to get the substitution products. Strong electron withdrawing groups get attracted towards the ortho-para position because they have high electron density.

Complete step by step solution:
From your chemistry lessons you have learned about the electrophilic and nucleophilic substitution reaction. Electrophilic substitution reaction is a type of reaction in which a functional group is removed by an electrophile and here in the question in electrophilic substitution benzene ring will behave as a nucleophile so it can attract the electrophile towards itself. Nucleophilic substitution reaction is a type of reaction in which it is attacked by a nucleophile and in this case the benzene ring will behave as an electrophile or positively charged group. In this question the group which is ortho–para directing in electrophilic substitution and nucleophilic substitution of benzene is nitro $(-N{{O}_{2}})$group. Here the nitro group behaves as a strong electron withdrawing group. Being a strong electron withdrawing group nitro group reacts with nucleophile at ortho and para position to give substitution product. As we know that the electron density is benzene ring is more at ortho and para position so, the strong electron withdrawing group such as nitro $(-N{{O}_{2}})$ group gets attracted towards ortho and para position in both electrophilic and nucleophilic substitution. Therefore the nitro group is the one which is ortho-para directing in benzene substitution for both the electrophilic and nucleophilic substitution.

Thus the correct option will be (A).

Note: Electrophiles are the neutral or positively charged species which are attracted towards the electron and they are also known as electron acceptor or electron receiving group. Nucleophiles are a chemical species which have negative charge on them and act as electron donors because they donate electron pairs of one pi bond or electrons. They have an extra electron with them in the form of a lone pair or pi bond.