Question

With a mixture of conc. \[HN{O_3}\] and conc. \[{H_2}S{O_4}\] anisole gives ______________.
A.Ortho nitro anisole
B.Para nitro anisole
C.Ortho and para nitro anisole
D.Meta nitro anisole

Answer 1

Hint:The attachment of an electrophile ortho or para to anisole leads to a more stable complex because of resonance involving the electron donating substituent. On the other hand, meta-attack does not permit any resonance stabilization or interaction and order of the distribution of final products in the reaction is Para > ortho >> meta.

Complete answer:
All of the ortho, para-directing substituents are either alkyl groups or groups that have unshared electron pairs on atoms directly attached to the benzene ring. Although other types of ortho, para-directing groups are known, the principles on which ortho, para-directing effects are based can be understood by considering electrophilic substitution reactions of benzene derivatives containing these types of substituents.
Anisole which is also known as methoxybenzene is an electron-rich arene that will react with nitric acid
(\[HN{O_3}\]) in the presence of sulphuric acid (\[{H_2}S{O_4}\]) in an electrophilic aromatic substitution.

When anisole is nitrated with a mixture of conc. \[HN{O_3}\]​ and conc. \[{H_2}S{O_4}\]​ (nitrating mixture), anisole gives ortho nitro anisole (minor product) and para nitro anisole (major product). Methoxy group (\[ - OC{H_3}\]​ group) is activating an ortho para directing group. The reaction is shown below:

Note:
When we see the reaction of a general electrophile \[{E^ + }\] with anisole (methoxybenzene). We notice that the atom that is directly attached to the benzene ring i.e., the oxygen of the methoxy group has unshared electron pairs. Reaction of \[{E^ + }\] at the para position of anisole gives a carbocation intermediate. Nitration is used to add nitrogen to a benzene ring, which can be used further in substitution reactions and as sulfonation is a reversible reaction, it can also be used in further substitution reactions in the form of a directing blocking group because it can be easily removed.