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Chemistry Question on Organic Chemistry- Some Basic Principles and Techniques

CH3−CH2−CH=CH2+HBr CH_3 - CH_2 - CH = CH_2 + HBr →ROOR(peroside)(X)Major+(Y)Minor \xrightarrow{ROOR\text{(peroside)}} \underset{\text{Major}}{(X)} + \underset{\text{Minor}}{(Y)} XX and YY respectively are

A

BrCH2−CH2−CH=CH2BrCH_2 - CH_2 - CH = CH_2 and C2H5−CHBr−CH3C_2H_5 - CHBr - CH_3

B

C2H5−CH2−CH2BrC_2H_5 - CH_2 - CH_2Br and Br−CH2−CH2−CH=CH2Br - CH_2 - CH_2 - CH =CH_2

C

C2H5−CH2−CH2BrC_2H_5 - CH_2 - CH_2Br and C2H5−CHBr−CH3C_2H_5 - CHBr - CH_3

D

C2H5CHBr−CH3C_2H_5CHBr - CH_3 and C2H5−CH2−CH2BrC_2H_5 - CH_2 - CH_2Br

Answer

C2H5−CH2−CH2BrC_2H_5 - CH_2 - CH_2Br and C2H5−CHBr−CH3C_2H_5 - CHBr - CH_3

Explanation

Solution

CH3−CH2−CH=CH2+HBr→ (peroxide) ROORCH _{3}- CH _{2}- CH = CH _{2}+ HBr \xrightarrow[{\text { (peroxide) }}]{ ROOR } CH3−CH2−CH2−CH2Br(Major)+CH3CH2−CHBr−CH3(Minor) \underset{\text{(Major)}}{CH _{3}- CH _{2}- CH _{2}- CH _{2} Br }+ \underset{\text{(Minor)}}{CH_3CH_2 - CHBr - CH_3} The main responsible factor here is organic peroxide which dissociates butene into free radicals and modifies the electrophilic addition to free radical addition which passes through free radicals as their intermediates. i.e. ROOR⟶2RO∙R O O R \longrightarrow 2 R O^{\bullet} RO∙+HBr⟶R−OH+Br∙R O^{\bullet}+ HBr \longrightarrow R- OH + Br ^{\bullet} Now, more stable free radical attacks H−BrH - Br molecule to form anti-Markownikoff product. The modified case of HBrHBr in presence of peroxide is called kharasck effect and considered as an example of anti Markounikoff off addition.