Question

Explain why: Aniline with $B{r}_2/OH$ gives 2, 4, 6 -tribromoaniline, while PhNMe${}_2$ gives meta nitro derivative when mono nitrated with$\text{HN}{\text{O}}_{\text{3}}\text{/}{\text{H}}_{\text{2}}\text{S}{\text{O}}_{\text{4}}$

Answer 1

Here lone pair of nitrogen atom ${NH}_2$ group spread into the benzene ring and delocalisation of electron is occur. The negative charged develops of the 2,4,6 (O and P) position or the change density is higher during delocalisection. So, $-{NH}_2$ group activates the ortho and para positive gives the 2,4,6-tribromo aniline as a product.

$PhN{Me}_2$ act as a base in acidic condition and the formation of $\stackrel{\oplus }{N}H{Me}_2$ (meta directing group) which is a meta directing group.