Which of the following are Enantiomers -

Ans. is 'a' i.e., D-glucose and L-glucose D and L isomersThis type of isomerism depends on the orientation of H and OH group around the assymetric carbon atom just adjacent to terminal primary alcohol (penultimate carbon atom), e.g., carbon atom number 5 in glucose determines whether the sugar belongs to D or L isomer.When OH group on this carbon atom is on the right, it belongs to D-series, when it is on left, it is the member of L-series.D and L isomers are mirror images of each other.These two forms are called enantiomers of each other. Thus, D-glucose and L-glucose are enantiomers of each other.Similarly D-mannose and L-mannose, and D-galactose and L galactose are enantiomers.All propeies of the two members of an enantiomeric pairs (D-or L-series) are identical, they have same boiling point and melting point and the same solubility but they exhibit different optical activity