Question

d – lactic acid and l – lactic acid are:
A.Optical isomers
B.Enantiomers
C.Functional isomers
D.Both A and B

Answer 1

Hint:
Looking at the question we can observe that it is clear that they are two forms of lactic acid . There is a difference in the arrangement in space so of course it is the stereoisomer. Further it is part of optical isomerism as it is clear that there is a difference in the space arrangement and they are non superimposable.

Complete step by step answer:
We will firstly talk about isomers . Isomers are two or more compounds which generally have the same molecular formula but they have different arrangements. So as we have discussed that they have different arrangements so it can then further be classified based on these arrangements.
As we are discussing about the different types of isomers then we come across two types that are :
Structural isomers and stereoisomers
Structural isomers have the same chemical formula but different arrangement due to which different structures are obtained whereas in stereoisomers the molecular formula is the same but there is a difference in arrangement in space .
Talking about the question it is clear that they are two forms of lactic acid . there is a difference in the arrangement in space so of course it is the stereoisomer.
But now the question arises which stereoisomer do it display. So talking about that we found that in the question it is given two symbols to mark the difference between the two. These symbols are d and l . So from this we found that “d” denotes dextrorotatory and “ l” denotes levorotatory. Further these two are the subpart of optical isomerism .in common language the compounds which do not show mirror image are under optical isomers. Further talking about the dextro and levo rotation we conclude that it classified because of their direction of rotation. When they rotate along the right then they are dextrorotatory and when they rotate towards left then they are levorotatory.
When two two forms are distinguished depending upon the direction they rotate is called enantiomers. Further it is a sub part of optical isomerism.
Hence, option B is correct.

Note: Optical isomers which do not superimpose their mirror images are called chiral and these chiral compounds can be further classified as two enantiomers.