Addition HBr to propene yields 2-bromopropane, while in the presence of benzoyl peroxide, the same reaction yields 1-bromopropane. Explain and give mechanism.

Explanation

`to` Addition of HBr to prpene yield 2- Bromopropene. Here the reaction mechanism is electrophillic additon mechinism .
`to` Additon of Hbrtopropene ispresence ofbenzoyl peroxide the reaction proceeds through free radical mecanism.
`CH _(3) - CH - CH _(2) + HBr to CH _(3) - underset( Br) underset(|) (CH)- CH _(3)`(2-Electrphilic additon mechanism: (Ionic Mechanism)
Step (i): Formation of carbonium ion mechanism)
Stet (i) : Formation of carbonium ion

`HBr to H ^(+) + Br ^(o+)`
`CH_(3) - CH = CH + H ^(+) to underset( " Less stable") ( CH _(3) - CH _(2) -) overset(o+) ( CH _(2))+ underset("More stable") ( CH _(2) - overset(o+)(CH) - CH _(3)`
Step (ii): Stable carbonium ion is attacked by `Br ^(o+)`

b) `CH _(3) - CH = CH _(2) + HBr overset ( "Peroxide") to underset( "1- bromo propane ") ( CH - CH _(2) - CH _(2) Br )`
Free radical mechanism:
i) `C _(3) H _(5) + HBr to C _(6) H _(6) + overset(o+ ) (Br)`

iii) `CH _(3) - CH - CH _(2) Br + HBr to underset(" Major product") ( CH _(3) - CH _(2) - CH _(2) Br + Br)`