Question

In the addition of HBr to propene in the absence of a peroxide, the first step involves the addition of :

• A. H${}^{+}$
• B. Br${}^{-}$
• C. H${}^{\cdot }$
• D. Br${}^{\cdot }$

Answer 1

The correct option is A H${}^{+}$

When no peroxide is added, the first step in the addition of HBr to propene involves addtion of $H^{+}$ ion to form carbocation intermediate. The second step is the addition of bromide ion.
$C{H}_2=CHC{H}_3+H^{+}\to C{H}_{3}C{H}^{+}C{H}_3$
$C{H}_{3}C{H}^{+}C{H}_3+B{r}^{-}\to C{H}_{3}CHBrC{H}_3$