Which of the following hydrogen halides is the most difficult to add to the double bond of alkenes ?

Options

A. `HI`
B. `HBr`
C. `HCl`
D. `HF`

Answer

D

Explanation

During addition, hydrogen halide provides a proton `(H^(+))` as an electrophile. Thus, the order of reactively is related to the order of acid strength:
`HI gt HBr gt HCl gt HF`
`HI` being the most acidic is the most reactive. Moreover, `I^(-)` is the strongest nucleophile while `F^(-)` is the weakest nucleophile.