The process of separation of a racemic mixture into $d$ and $l$ enantiomers is called .............

Which of the following pairs of compounds are not positional isomers?

The correct statement$(s)$ about the compound given below is(are):
$A$. The compound is optically active
$B$. The compound possesses centre of symmetry
$C$. The compound possesses plane of symmetry
$D$. The compound possesses axis of symmetry

The number of stereoisomers formed in a reaction of $(\pm) Ph(C=O)C(OH)(CN)Ph$ with $HCN$ is $..........$

If a carbon atom is attached to $-H, -OH, -COOH$ and $-OCO^{-}C_2H_5$ groups,the number of chiral $C$ atoms in the molecule is:

Among the structures shown below,which has the lowest potential energy?