Question

According to the SAR of Chloroquine electron:

• A. Withdrawing group at 6^th position of the quinoline ring is important for the inhibition of hemozoin formation
• B. Donating group at 7^th position of the quinoline ring is important for the inhibition of hemozoin formation
• C. Donating group at 6^th position of the quinoline ring is important for the inhibition of hemozoin formation
• D. Withdrawing group at 7^th position of the quinoline ring is important for the inhibition of hemozoin formation

Answer 1

The Correct Option is D

The correct option is (D): Withdrawing group at 7^th position of the quinoline ring is important for the inhibition of hemozoin formation.

Answer 2

The question is about the structure-activity relationship rule that governs chloroquine's ability to block hemozoin formation. Let's check each combination of position and electronic effect against how chloroquine actually works.

1. Withdrawing group at 6th position: Position 6 of the quinoline ring is not the site associated with hemozoin inhibition activity in chloroquine's structure-activity relationship, so substituents placed here have little bearing on antimalarial potency.
2. Donating group at 7th position: An electron-donating substituent at position 7 would raise electron density on the quinoline ring nitrogen, which weakens the ring's ability to bind heme rather than helping hemozoin inhibition.
3. Donating group at 6th position: Like the other 6th-position option, this is not the site that matters for activity, and even if it were, a donating group would work against the electron-poor ring character needed for strong binding.
4. Withdrawing group at 7th position: Chloroquine's own 7-chloro substituent is an electron-withdrawing group at exactly this position. It lowers electron density on the ring nitrogen, favoring strong binding of the protonated ring to ferriprotoporphyrin IX, which blocks the polymerization of heme into inert hemozoin and lets toxic free heme build up inside the parasite.

Only an electron-withdrawing substituent placed at position 7 matches both the correct site and the correct electronic effect needed for potent hemozoin inhibition.

The correct answer is Withdrawing group at 7th position of the quinoline ring is important for the inhibition of hemozoin formation.