Question

What is the order of reactivity of alkyl halides with ammonia?

• A. $R-Cl > R-Br > R-I$
• B. $R-Br > R-I > R-Cl$
• C. $R-I > R-Br > R-Cl$
• D. $R-Cl > R-I > R-Br$

Hint:

In nucleophilic substitution, the better the leaving group (lower bond strength), the higher the reactivity.

Answer 1

The Correct Option is C

Step 1: Concept
Reactivity depends on the bond strength of the $C-X$ bond.

Step 2: Analysis
- As the size of the halogen increases ($Cl < Br < I$), the $C-X$ bond length increases and bond dissociation energy decreases. - $C-I$ is the weakest bond and easiest to break.

Step 3: Conclusion
The reactivity order is $R-I > R-Br > R-Cl$.
Final Answer: (C)