Question

The set of meta directing functional groups from the following sets is:

• A. –CN, –NH$_2$, –NHR, –OCH$_3$
• B. –NO$_2$, –NH$_2$, –COOH, –COOR
• C. –NO$_2$, –CHO, –SO$_3$H, –COR
• D. –CN, –CHO, –NHCOCH$_3$, –COOR

Answer 1

Answer: (C)

–NO$_2$, –CHO, –SO$_3$H, –COR

Answer 2

Meta directing groups are typically electron-withdrawing groups (EWGs) that deactivate the benzene ring and direct incoming electrophiles to the meta position relative to themselves. This is due to their ability to withdraw electron density from the ortho and para positions, making these positions less reactive to electrophilic substitution reactions.
Explanation of Each Functional Group Set
Option (1): Groups like --NH$_2$, --NHR, and --OCH$_3$ are electron-donating and act as ortho/para directors, not meta directors.
Option (2): While --NO$_2$ and --COOH are meta directing, --NH$_2$ is an electron-donating group and acts as an ortho/para director.
Option (3): Groups --NO$_2$, --CHO, --SO$_3$H, and --COR are strong electron-withdrawing groups and are known meta directors.
Option (4): --NHCOCH$_3$ and --COOR are electron-withdrawing groups but are less effective meta directors compared to the strong meta directing groups in Option (3).
Conclusion: The correct set of meta directing functional groups is --NO$_2$, --CHO, --SO$_3$H, --COR.