Which of the following compounds will give racemic mixture on nucleophilic substitution by OH- ion?

(i)
(ii)
(iii)

  
1.  (iii) 
2.  (i), (ii) and (iii)     
3.  (ii) and (iii)     
4.  (i) and (iii) 

A mixture containing two enantiomers in equalimolar amount have zero optical

rotation, as the rotation due to one isomer is cancelled by the rotation due to other

isomer. Such a mixture is known as racemic mixture. All those compounds which

follow sN2 mechanism during nucleophilic substitution reaction form racernic mixture.

Order of reactivity of alkyl halides.towards SN1.

and reactions as follows:

Tertiary halide; secondary halide; primary hatide; CH3X.

For SN1 reaction.

Thus, CH2CHBr
               |
            C2H5 contains a chiral carbon and gives a racemic product.

Hence, option (a) is correct.