When pure (L) lactic acid is esterified by racemic-2 butanol then what is the nature of the stereoisomers so obtained i.e. whether they are diastereomers or enantiomers.
The reaction doesn't change the stereo configuration for either reactant, so we can assume that the product is enantiomerically pure with respect to the carbon attached to the hydroxyl group (in orange below), and a racemic mixture with respect to the tertiary carbon (in blue).
Since there are multiple stereocenters, you can either have both the same (same molecule), both different (enantiomers), or have some different and some the same (diastereomer). The products would be diastereomers. In particular they would be epimers, which differ in only one stereocenter.