If meta position shows no mesomerism effect then how come -R group is meta ditective?
 

Asked by peedyojb | 24th Oct, 2017, 04:54: PM

Expert Answer:

The direction of substitution is depend on -R group which is present on benzene ring, thus there are two types of substituents 1) ortho & para directing 2) meta directing.
for example the electrophlic substitution of nitro group to the nitro benzene 
 
in above structeres the positive charge is at the ortho and para positions. therefore they are unreactive to the attacking electrophile which is also positively charged (NO2+), naturally now meta position becomes electron rich than ortho and para positions therefore in this way without showing resonance effect at meta position meta substitution takes place

Answered by Ramandeep | 25th Oct, 2017, 11:11: AM