To understand the properties of R enantiomers, we must analyze the statements provided:
- a) It has a plus rotation. This statement is not universally true. While many R enantiomers do exhibit a positive optical rotation, this is not a strict rule for all chiral molecules, as the sign of rotation depends on the specific compound.
- b) It has a rotation. This statement can be considered true, as all chiral molecules, including R enantiomers, exhibit optical activity, meaning they will rotate plane-polarized light.
- c) It is a mirror image of the S enantiomer. This statement is always true. By definition, R and S enantiomers are non-superimposable mirror images of each other.
Based on this analysis, the correct answer is 4 (b and c), since statements b and c hold true for R enantiomers, whereas statement a does not always apply.