Question

What will be the decreasing order of electrophilic nitration of the following compounds?

• A. S > R > P > Q
• B. R > S > P > Q
• C. R > P > S > Q
• D. P > S > R > Q

Answer 1

The correct option is C R > P > S > Q

Among the given compounds only 'R' has electron donating group whereas in others, electron withdrawing groups are present. So, in structure R, maximum electron density on the ring is present and so it reacts with the fastest rate with an electrophile.
In structure P, $Cl$ has both -I effect and +M effect. Due to its electron withdrawing nature it is less reactive than (R) with an electrophile but more reactive than (Q) and (S).
Comparing (Q) and (S), structure (S) has electron donating group ($C_2{H}_5$) along with an electron withdrawing group ($N{O}_2$) which makes it more reactive than Q. If $C_2{H}_5$ is not there, then this order reverses for Q and S.
$N{O}_2$ is more deactivating than $S{O}_{3}H$, which is more deactivating than $Cl$.
Hence, the correct option is (c).