Question

The reactivity order of the following alkyl halides towards dehydrohalogenation:
(A) R-F
(B) R-Br
(C) R-Cl
(D) R-I
Choose the correct answer from the options given below:

• A. A $>$ B $>$ C $>$ D
• B. A $>$ C $>$ B $>$ D
• C. D $>$ B $>$ C $>$ A
• D. D $>$ C $>$ B $>$ A

Answer 1

The Correct Option is D

Dehydrohalogenation is a chemical reaction where a halogen atom (X) and a hydrogen atom (H) are removed from an alkyl halide to form an alkene. The reactivity of alkyl halides in this reaction is primarily determined by the strength of the carbon-halogen (C-X) bond. A weaker C-X bond is more easily broken, resulting in higher reactivity. The order of carbon-halogen bond strength, from strongest to weakest, is:

• C-F (strongest)
• C-Cl
• C-Br
• C-I (weakest)

Consequently, the reactivity of alkyl halides towards dehydrohalogenation follows the inverse order of bond strength, with the weakest bond exhibiting the highest reactivity:
(D) R-I > (B) R-Br > (C) R-Cl > (A) R-F
This indicates that alkyl iodides (R-I) are the most reactive, while alkyl fluorides (R-F) are the least reactive.
The correct reactivity order is: D > B > C > A