JEE Main levelSingle correct optionDifficulty 2 of 3st065
Assertion (A): a compound with n stereocentres always has exactly 2n stereoisomers.
Reason (R): each stereocentre can have either the R or the S configuration.
ABoth A and R are true and R is the correct explanation of A
BBoth A and R are true but R is not the correct explanation of A
CA is true but R is false
DA is false but R is true
Answer: D
Each centre can indeed be R or S, so R is true and gives an upper limit of 2n. The limit is reached only when the molecule has no symmetry; for example 2,3-dibromobutane has 3 stereoisomers, not 4. Therefore A is false and R is true.