Question

The reactivity order of halides for dehydrohalogenation is 

(a) R-F > R-CI > R-Br > R-I 

(b) R-I > R-Br > R-CI > R-F 

(c) R-I > R-CI > R-Br > R-F 

(d) R-F > R-I > R-Br > R-CI

Answer 1

(b) R-I > R-Br > R-CI > R-F 

Reactivity order of halides for dehydrohalogenation is R - I > R - Br > R - Cl > R - F. Alkyl iodides are most reactive and alkyl fluorides are least reactive. Iodide ion is a good leaving group, as the negative charge is on a larger atom and is dispersed. Also, C - I bond is weaker than C - F bond.