Issue 14, 2021

Ambient l-lactic acid crystal polymorphism

Abstract

Only one crystalline phase of the metabolite, L-lactic acid (LLA), has been described since its isolation from sour milk as long ago as 1780. Herein, we report the structures of two new crystalline polymorphs of LLA obtained from supercooled melts and characterized by X-ray diffraction and micro-Raman spectroscopy, as well as their transformations from one phase to another. None of the three crystal structures are consistent with the aggregate geometries of LLA in cold matrices, in solution, or those predicted by quantum chemical computations. The latter aggregates feature typical cyclic carboxylic acid dimers not represented in any of the crystal structures. These differences underscore the difficulty of reasoning solid state structure from associations in other media.

Graphical abstract: Ambient l-lactic acid crystal polymorphism

Supplementary files

Article information

Article type
Communication
Submitted
27 févr. 2021
Accepted
23 mars 2021
First published
23 mars 2021

CrystEngComm, 2021,23, 2644-2647

Author version available

Ambient L-lactic acid crystal polymorphism

J. Yang, C. T. Hu, E. Reiter and B. Kahr, CrystEngComm, 2021, 23, 2644 DOI: 10.1039/D1CE00285F

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