Question

In the presence of peroxide, hydrogen chloride and hydrogen iodide do not give anti-Markovnikov's addition to alkenes because:

• A. Both are highly ionic
• B. One is oxidising and the other is reducing
• C. One of the step is endothermic in both the cases
• D. All the steps are exothermic in both cases.

Answer 1

The correct option is C One of the step is endothermic in both the cases

HI and HCl do not do this for energetic reasons.

The addition of Cl and I radicals to alkanes in an anti-Markovnikov fashion is an endothermic reaction and therefore counterproductive.

Without the presence of peroxide, all hydrogen halides will add according to the Markovnikov rule.