Issue 28, 2018

Serendipitous isolation of a disappearing conformational polymorph of succinic acid challenges computational polymorph prediction

Abstract

A conformational polymorph (γ) of succinic acid was discovered in an attempt to purify a leucine dipeptide by cocrystallization from a methanol solution in the presence of various impurities, such as trifluoroacetic acid. The new γ-form was found to have crystallized concomitantly with the most stable β form. In light of this situation, a crystal structure prediction study was undertaken to examine the polymorph landscape. These studies reveal that the γ polymorph is thermodynamically competitive with the other observed polymorphs; having a more stable folded conformation than the planar crystalline conformation in the β form, but being stabilized less by the intermolecular interactions. Simulations and experiment show that the folded conformation is dominant in solution, but that trapping long-lived crystals of the new metastable polymorph may be challenging. Thus the γ polymorph provides a stringent test of theories for predicting which thermodynamically plausible structures may be practically important polymorphs.

Graphical abstract: Serendipitous isolation of a disappearing conformational polymorph of succinic acid challenges computational polymorph prediction

Supplementary files

Article information

Article type
Paper
Submitted
18 Dzi 2018
Accepted
30 Mud 2018
First published
30 Mud 2018

CrystEngComm, 2018,20, 3971-3977

Serendipitous isolation of a disappearing conformational polymorph of succinic acid challenges computational polymorph prediction

P. Lucaioli, E. Nauha, I. Gimondi, L. S. Price, R. Guo, L. Iuzzolino, I. Singh, M. Salvalaglio, S. L. Price and N. Blagden, CrystEngComm, 2018, 20, 3971 DOI: 10.1039/C8CE00625C

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