Question

Which of the following reactions are not feasible?

• A. I & IV only
• B. II & III only
• C. II & IV only
• D. I & III only

Hint:

Reaction Feasibility. Check if the reagent type matches the substrate reactivity:

• Friedel–Crafts alkylation: Requires carbocation stability.
• KOH reactions: Form alkynes from dihalides, not single halides.

Answer 1

The Correct Option is D

Reactions I and III are not feasible due to their mechanism or reagent incompatibility.

• I: Alkene formation by reaction with HCl is incorrect without rearrangement or suitable mechanism.
• III: Terminal alkyne formation from this substrate using KOH is mechanistically impossible.
• II and IV are feasible with the given reagents (Friedel-Crafts and oxidation respectively).

Answer 2

Step 1: Analyze Reaction I
Reaction I suggests alkene formation by reaction with HCl. However, without rearrangement or a suitable mechanism, this reaction is not feasible.

Step 2: Analyze Reaction III
Reaction III proposes terminal alkyne formation using KOH. This is mechanistically impossible for the given substrate because KOH cannot induce the required elimination or substitution to form a terminal alkyne.

Step 3: Analyze Reaction II
Reaction II involves Friedel-Crafts reaction which is a feasible electrophilic aromatic substitution when suitable reagents are used.

Step 4: Analyze Reaction IV
Reaction IV is an oxidation reaction which is feasible with the given substrate and reagents.

Step 5: Conclusion
Only Reactions II and IV are feasible, while I and III are not due to mechanism or reagent incompatibility.