JEE Chemistry 2024 Question with Solution

Given: The groups are –OCH$_{3}$, –NO$_{2}$, –CN, –CH$_{3}$, –NHCOCH$_{3}$, –COR, –OH, –COOH, and –Cl.

Find: The total number of meta-directing functional groups.

Meta-directing groups are generally electron-withdrawing groups. From the given list:

1. –OCH$_{3}$ is electron-donating, so it is ortho/para directing.
2. –NO$_{2}$ is strongly electron-withdrawing, so it is meta directing.
3. –CN is electron-withdrawing, so it is meta directing.
4. –CH$_{3}$ is electron-donating, so it is ortho/para directing.
5. –NHCOCH$_{3}$ donates by resonance, so it is ortho/para directing.
6. –COR is electron-withdrawing, so it is meta directing.
7. –OH is electron-donating, so it is ortho/para directing.
8. –COOH is electron-withdrawing, so it is meta directing.
9. –Cl is deactivating but ortho/para directing due to resonance donation.

Thus, the meta-directing groups are –NO$_{2}$, –CN, –COR, and –COOH.

Therefore, the total number of meta-directing functional groups is $4$.

Given: A list of substituents on a benzene ring.

Find: How many are meta directors.

A quick rule is that most strongly electron-withdrawing groups are meta directing, while groups that donate by resonance are usually ortho/para directing.

Using this pattern:

• –NO$_{2}$, –CN, –COR, and –COOH are electron-withdrawing.
• –OCH$_{3}$, –NHCOCH$_{3}$, and –OH donate by resonance.
• –CH$_{3}$ is weakly donating by hyperconjugation.
• –Cl is an exception: deactivating, but still ortho/para directing.

So the count of meta-directing groups is $4$.