question_answer

The well known compounds, \[(+)\,-\]lactic acid and \[(-)\,-\] lactic acid, have the same molecular formula, \[{{C}_{3}}{{H}_{6}}{{O}_{3}}.\]The correct relationship between them is

A)  constitutional isomerism

B)  geometrical isomerism

C)  identicalness

D)  optical isomerism

Correct Answer: D

Solution :

  Both are optical isomers because they rotate the plane of polarised light in opposite directions.