Question

why is meta nitroaniline obtain as major product on direct nitration of aniline​

Answer 1

Answer:

Nitration generally carried out in acidic medium( nitric acid +sulphuric acid) so aniline being a weak base get protonated and get converted to anilinium ion which cause strong -I effect.

Due to this -I effect ring overall get deactivated but Ortho position being the nearest get highly deactivated. Now remains meta and para also deactivated to a lesser extent due to their distance as you must know inductive effect becomes weak along with distance.

Obviously meta will be more deactivated than para so the maximum nitration occur at para position and it is the major product so almost equal to meta next major as inductive effect is not position specific as mesomeric effect.

So in nutshell the +M effect of amino group is destroyed in acidic media and replaced by -I effect.

Answer 2

Nitrating mixture is mixture of conc.HNO₃ and conc. H₂SO₄.

When aniline is reacted with nitrating mixture,mixture of ortho,meta and para nitro anilines are obtained.

HNO₃ and conc. H₂SO₄. When aniline is reacted with nitrating mixture,mixture of ortho,meta and para nitro anilines are obtained. ... Hence aniline reacts with nitrating mixture to form considerable amount of meta nitroaniline also,alongwith o-nitroanilne and p-niteoaniline.