Discuss the methods of preparing alkyl halides from hydrocarbon compounds.

(N/A) Free radical halogenation of alkanes: Free radical chlorination of alkanes in the presence of $Cl_2$ and $h\nu$ or heat,and bromination in the presence of $Br_2$ and $h\nu$ or heat,results in a mixture of mono- and poly-halogenated compounds. It is difficult to separate these components in pure form. Therefore,this method is not suitable for preparing a single alkyl halide.
$(b)$ Alkyl halides from alkenes:
$(i)$ Hydrohalogenation of alkenes: Addition of hydrogen halides ($HCl$,$HBr$,or $HI$) to alkenes leads to the formation of alkyl halides via electrophilic addition. If two addition products are possible,the major product is formed according to Markovnikov's rule. For example:
$CH_3CH=CH_2 + HI \rightarrow CH_3CHICH_3 \text{ (major)} + CH_3CH_2CH_2I \text{ (minor)}$
$(ii)$ Addition of halogens $(X_2)$ to alkenes: Addition of bromine $(Br_2)$ dissolved in $CCl_4$ to an alkene results in the formation of vicinal dibromides. The reddish-brown color of $Br_2$ in $CCl_4$ disappears as the colorless dibromide is formed,which serves as a laboratory test for unsaturation (double bond).