Question

Reactivity order of halides for dehydrohalogenation is :-

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

Answer 1

The Correct Option is B

 To determine the reactivity order of halides for dehydrohalogenation, we need to understand the factors influencing the process. Dehydrohalogenation is an elimination reaction that involves the removal of a halogen (X) and a hydrogen (H) from adjacent carbon atoms in alkyl halides, resulting in the formation of alkenes. The reactivity of halides depends mainly on the bond strength between the carbon and the halogen atom and the stability of the resulting alkene.

The order of bond strength between carbon and halogen in alkyl halides generally follows:

• \(C-F\) (Strongest)
• \(C-Cl\)
• \(C-Br\)
• \(C-I\) (Weakest)

In dehydrohalogenation reactions, weaker C-X bonds lead to faster and easier elimination. Therefore, the order of reactivity for dehydrohalogenation is the reverse of the bond strength order. Hence, iodides, with the weakest bond to carbon, will react the fastest, and fluorides, with the strongest bond, will react the slowest.

Halide	Reactivity Order
\(R-I\)	Most reactive
\(R-Br\)	Second most reactive
\(R-Cl\)	Less reactive
\(R-F\)	Least reactive

Based on this reasoning, the correct order of reactivity for dehydrohalogenation is:

• \(R-I \gt R-Br \gt R-Cl \gt R-F\)

Therefore, the correct answer is:

\(R-I \gt R-Br \gt R-Cl \gt R-F\)