0
$\begingroup$

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.

I studied the mechanism of esterification but I didn't find anything regarding the stereo isomerism that can affect the formation of the product.Any ideas.Thanks.enter image description here

$\endgroup$
6
  • $\begingroup$ You can start by identifying all stereocenters in reactants and products. You should assume the reactants are racemic so you will get all combinations in the product. $\endgroup$ – Zhe Dec 15 '16 at 19:04
  • $\begingroup$ @Zhe in the question it is given that a racemic mixture of 2 butanol is used as the reactant but I do not get how it might affect the resulting stoichiometry of the product.thanks. $\endgroup$ – Pink Dec 15 '16 at 19:29
  • $\begingroup$ @aniline You are correct, esterification will not affect the stereocenters. So keeping in mind that the stereocenters are preserved, what products result? $\endgroup$ – ron Dec 15 '16 at 19:52
  • 2
    $\begingroup$ @ron Yes that would mean that L configuration would remain unchanged and two products with different configuration on other chiral carbon would result in diastereomers. $\endgroup$ – Pink Dec 15 '16 at 20:03
  • $\begingroup$ @aniline Nice going! $\endgroup$ – ron Dec 15 '16 at 20:04
4
$\begingroup$

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).

Mathematica graphics

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.

$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.