Question

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : $\dot{C}H_3$ behave as nucleophiles.
Reason (R) : Odd electron species where unpaired electron is accommodated in a low energy SOMO also behave as nucleophiles.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

To quickly determine radical character: Radicals adjacent to electron-donating groups (e.g., alkyl, ether oxygens) have raised SOMO levels and are nucleophilic. Radicals adjacent to electron-withdrawing groups (e.g., carbonyls, halogens, nitriles) have lowered SOMO levels and are electrophilic.

Answer 1

The Correct Option is C

Step 1: Concept:
The question relies on Frontier Molecular Orbital (FMO) theory to explain the reactivity of free radicals, specifically focusing on whether the methyl radical ($\dot{C}H_3$) acts as a nucleophile or an electrophile, and how the energy level of the Singly Occupied Molecular Orbital (SOMO) dictates this behavior.

Step 2: Key Formula or Approach:
In radical chemistry, FMO theory states that radical reactivity is governed by interactions between the SOMO of the radical and either the HOMO or LUMO of the reacting partner:
- A radical with a High-Energy SOMO acts as an electron donor (nucleophile), preferring to interact with the LUMO of an electrophilic molecule. Alkyl radicals typically fall into this category due to electron-donating hyperconjugative effects.
- A radical with a Low-Energy SOMO acts as an electron acceptor (electrophile), preferring to interact with the HOMO of a nucleophilic molecule. Radicals with electron-withdrawing groups (like halogens or carbonyls) fall into this category.

Step 3: Step-by-step Explanation:

• Evaluating Assertion (A): The methyl radical ($\dot{C}H_3$) is an alkyl radical. While it lacks the electron-donating hyperconjugation of larger alkyl radicals (like tert-butyl), simple alkyl radicals generally behave as weak to moderate nucleophiles in their addition reactions to alkenes (they prefer to attack electron-deficient, electrophilic double bonds). Therefore, the assertion that they behave as nucleophiles is generally considered correct in organic chemistry.

• Evaluating Reason (R): Reason (R) states that an odd electron species with a low energy SOMO behaves as a nucleophile. This fundamentally contradicts FMO theory. A low-energy SOMO means the orbital is highly electronegative and wants to accept an electron, rendering the radical an electrophile. It is a high energy SOMO that makes a radical a nucleophile (ready to donate its electron). Thus, the statement in Reason (R) is scientifically incorrect.

Step 4: Final Answer:
Because (A) is correct and (R) is conceptually incorrect, the answer is option (C).