Solution:
In electrophilic aromatic substitution reactions, an electrophile replaces a hydrogen atom in an aromatic ring. The position where the new substituent attaches (ortho, meta, or para) depends on the nature of the substituents already present on the ring.
Meta Directors:
Substituents that direct incoming electrophiles to the meta position relative to themselves are called meta directors. These groups typically withdraw electrons through resonance or induction, making the ortho and para positions less reactive toward electrophiles.
Common Meta Directors:
- Nitro group (-NO2)
- Carboxyl group (-COOH)
- Cyano group (-CN)
- Sulfonic acid group (-SO3H)
Application to the Question:
The highest yield of a meta product in electrophilic substitution will occur with an aromatic compound already having a strong meta-directing group. For example:
- Nitrobenzene (C6H5NO2):
- The nitro group is a strong electron-withdrawing group.
- It directs electrophilic substitution to the meta position, leading to the highest yield of meta products.
