Electrophilic Addition

The reactivity of alkenes towards HBr addition depends on the stability of the carbocation intermediate formed during the reaction:

$%5Ctext%7B-%20MeOCH%3DCH%7D_2$ (III) forms a resonance-stabilized carbocation due to the electron-donating methoxy group, making it the most reactive.
$%5Ctext%7B-%20CH%7D_3%5Ctext%7B-CH%3DCH%7D_2$ (I) forms a secondary carbocation, which is moderately stable.
$%5Ctext%7B-%20CF%7D_3%5Ctext%7B-CH%3DCH%7D_2$ (II) forms a destabilized carbocation due to the electron-withdrawing CF₃ group.
$%5Ctext%7B-%20CH%7D_3%20-%20%5Coverset%7B%5Ctext%7BO%7D%7D%7B%5Coverset%7B%7C%7C%7D%7B%5Ctext%7BC%7D%7D%7D%20-%20%5Ctext%7BCH%3DCH%7D_2$ (IV) forms a sterically hindered carbocation, making it the least reactive.

Thus, the order of reactivity is III>I>II>IV.

Chapter Questions
1 MCQs