Which of the following pair make fastest coupling reaction in acidic medium ?
a) C6H5OH , C6H4(N2Cl)(NH2)
b) C6H5NH2 , C6H4(N2Cl)(NO2)
c) C6H5OH , C6H4(N2Cl)(NO2)
d) C6H5OCH3 , C6H4(N2Cl)(NH2)
Please explain 

Dear Student,

Coupling reaction is an electrophilic substitution reaction. The diazomium group behaves as a weak electrophile and thus couples with highly activated aromatic ring. 
In acidic condition, coupling with aromatic amines is more fast while in basic condition phenols are more reactive. 
Therefore, the aromatic compound will be aniline here. Now, -NO2 will deactivate the ring making diazomium salt more electrophilic while -NH2 will make it less electrophilic. Therefore, the pair undergoing coupling reaction fast will be b.

  • 36
What are you looking for?