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

Answer: (D)

D $>$ C $>$ B $>$ A

Answer 2

The rate of dehydrohalogenation (elimination) depends on the ability of the halide ion to act as a leaving group. Iodide (I$^-$) is the best leaving group, followed by bromide (Br$^-$), chloride (Cl$^-$), and fluoride (F$^-$).
Therefore, the correct order of reactivity is: $R-I > R-Br > R-Cl > R-F$.