Question

Total diastereomeric and enantiomeric pairs possible from respectively are:-
$C{H}_3-\underset{Cl}{\underset{|}{C}}H-\underset{Br}{\underset{|}{C}}H-C{H}_3$

• A. $2,2$
• B. $2,4$
• C. $2,3$
• D. $4,2$

Answer 1

The correct option is D $4,2$

There are two optically active only two configuration for one chiral atom i.e R,S. So, total possible configurations are

R R

R S

S R

S S

Enantiomers are mirror images of each others. So there are two pairs possible

(1) [(R,R), (S,S)]

(2) [(R,S), (S,R)]

Diastereomers are not mirror image so there are 4 pairs possible

(1) [(R,R), (R,S)]

(2) [(R,R), (S,R)]

(3) [(S,S), (R,S)]

(4) [(S,S), (S,R)]

So answer is (4,2).