Question

The decreasing order of reactivity of meta-nitrobromobenzene (I), $2,4,6$-trinitrobromobenzene (II), para-nitrobromobenzene (III), and $2,4$-dinitrobromobenzene (IV) Towards $H{O}^{-}$ ions is:

• A. I $>$ II $>$ III $>$ IV
• B. II $>$ IV $>$ III $>$ I
• C. IV $>$ II $>$ III $>$ I
• D. II $>$ IV $>$ I $>$ III

Answer 1

The correct option is A I $>$ II $>$ III $>$ IV

The decreasing order of reactivity of m- nitro bromobenzene (i) 2,4,6 -tri-nitrobromobenzene (ii) para- nitrobromobenzene (iii) and 2, 4 - dinitrobromobenzene (iv) towards $O{H}^{-}$ ions is $I>II>III>IV$.
Nitro would create regions of high positive charge in ortho and para position with respect to the nitro group.
In P- nitro bromobenzene Br is in para position with respect to the nitro group hence the positive charge would be created only in the ortho position as para position is blocked . Also in meta nitrobromobenzene there would be regions of positive in both ortho and para positions w.r.t to the nitro group.