1
Increasing order of electrophilic substitution for following compounds [figure]
- IV < I < II < III
- III < II < I < IV
- I < IV < III < II
- II < III < I < IV
Answer
(1) IV < I < II < III
Solution
As per NCERT, electron-donating groups activate the benzene ring towards electrophilic substitution and electron-withdrawing groups deactivate it.
III (-OCH3): strong +R effect ⇒ most activated.
II (-CH3): +I effect and hyperconjugation ⇒ activated, but less than -OCH3.
I (benzene): reference.
IV (-CF3): strong −I effect of three F atoms ⇒ deactivated, least reactive.
∴ Increasing order: IV < I < II < III
Answer: (1)
AIPMT 2000