Question

Match List-I (herbicide class) with List-II (herbicide group)

List-I	List-II
(A) Weak base herbicide	(I) Sulfonyl ureas
(B) Strong base herbicide	(II) Triazines
(C) Weak acid herbicide	(III) Dintroanilines
(D) Non-ionic herbicide	(IV) Bipyridilliums

Choose the correct answer from the options given below

• (A) - (II), (B) - (IV), (C) - (I), (D) - (III)
• (A) - (IV), (B) - (I), (C) - (II), (D) - (III)
• (A) - (II), (B) - (I), (C) - (IV), (D) - (III)
• (A) - (III), (B) - (IV), (C) - (I), (D) - (II)

Hint:

To remember this:
- Bipyridiliums (Paraquat) are always strong divalent cations (strong bases).
- Sulfonylureas are weak acids.
Matching these two highly characteristic groups immediately identifies the correct option.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Herbicides can be classified based on their ionic charge and chemical properties in solution. This classification (acidic, basic, or non-ionic) is important because it dictates soil adsorption, mobility, and absorption through plant cell membranes.

Step 2: Detailed Explanation:
Let us analyze and pair each herbicide class with its corresponding chemical group:

(A). Weak base herbicide: Triazine herbicides (such as atrazine and simazine) are weakly basic. They can accept protons in highly acidic environments, which increases their adsorption to soil organic matter and clay minerals at low pH. Thus, (A) matches with (II).

(B). Strong base herbicide: Bipyridilium herbicides (such as paraquat and diquat) exist as strong, permanently charged divalent cations in aqueous solution. Because of this strong positive charge, they adsorb rapidly and tightly to negatively charged soil clay minerals. Thus, (B) matches with (IV).

(C). Weak acid herbicide: Sulfonylurea herbicides (such as chlorsulfuron and sulfosulfuron) contain an acidic sulfonylurea bridge that can readily donate a proton, making them weakly acidic. Under alkaline soil conditions, they deprotonate to form anions, which are highly mobile and less adsorbed by soil. Thus, (C) matches with (I).

(D). Non-ionic herbicide: Dinitroaniline herbicides (such as pendimethalin and trifluralin) do not possess any acidic or basic functional groups that can ionize. They remain as neutral, non-ionic molecules in soil solution and are highly lipophilic. Thus, (D) matches with (III).
Combining these matches gives: (A) - (II), (B) - (IV), (C) - (I), (D) - (III).

Step 2: Final Answer:
The correct option is (A).