Question

Among the following, total number of meta directing functional groups is (Integer based) \(−OCH_3​, −NO_2​, −CN, −CH_3​, −NHCOCH_3​, −COR, −OH, −COOH, −Cl\).

Answer 1

Correct Answer: 4

In organic chemistry, functional groups can influence the reactivity of a benzene ring as ortho/para or meta directors based on their electron-withdrawing or electron-donating effects. Meta directing groups generally withdraw electrons from the ring. Let's identify the meta directing groups among the given options: 

1. −OCH3: This is an electron-donating group due to the strong +M (mesomeric) effect of the lone pair on oxygen, making it an ortho/para director.
2. −NO2: This is a strongly electron-withdrawing group by resonance and inductive effects, making it a meta director.
3. −CN: The cyano group is electron-withdrawing due to the presence of a highly electronegative nitrogen atom; hence, it is a meta director.
4. −CH3: This is a weakly electron-donating group via hyperconjugation, making it an ortho/para director.
5. −NHCOCH3: The amide linkage has resonance stabilization that donates electrons, making it an ortho/para director.
6. −COR: This carbonyl functional group is electron-withdrawing due to the resonance and inductive effect, rendering it a meta director.
7. −OH: Similar to methoxy, it is a strong electron-donating group due to the +M effect and thus an ortho/para director.
8. −COOH: The carboxyl group is electron-withdrawing by resonance and induction, making it a meta director.
9. −Cl: Though chlorine is electronegative, it is ortho/para directing because of its ability to donate electrons via resonance.

Thus, the meta directing groups are: −NO2, −CN, −COR, and −COOH.

Counting these, there are 4 meta directing groups.

Answer 2

The meta-directing functional groups are those that are electron-withdrawing, which include:

\(-NO_2, -C \equiv N, -COR, -COOH\)