While the use of additives to control the crystallization of polymorphs is well known, similar methodology to promote the crystallization of a metastable conglomerate over a stable racemic compound in enantiomeric systems has not been reported. Here we demonstrate this phenomenon in the case of 2-chloromandelic acid.
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http://dx.doi.org/10.1039/c1cc16173c | DOI Listing |
Mol Pharm
February 2024
Univ Rouen Normandie, Normandie Univ, SMS, UR 3233, F-76000 Rouen, France.
The solid-state landscape of proxyphylline (PXL), a chiral derivative of theophylline crystallizing as a racemic compound, was extensively investigated by means of thermal analyses and diffraction techniques. This study revealed the presence of five distinct polymorphic forms that were characterized: two polymorphs of the racemic mixture and three polymorphs of the pure enantiomer. The nature of each solid phase was confirmed by combining the different analytical techniques, revealing the presence of a thermodynamically stable racemic compound, RI (= 134 °C), in equilibrium with the stable enantiopure crystal form, EI ( = 148.
View Article and Find Full Text PDFACS Catal
May 2023
Functional Nanomaterials Group and Catalysis Research Center, Department of Chemistry, School of Natural Sciences, Technical University of Munich, 85748 Garching, Germany.
The metastability of supported metal nanoparticles limits their application in heterogeneous catalysis at elevated temperatures due to their tendency to sinter. One strategy to overcome these thermodynamic limits on reducible oxide supports is encapsulation via strong metal-support interaction (SMSI). While annealing-induced encapsulation is a well-explored phenomenon for extended nanoparticles, it is as yet unknown whether the same mechanisms hold for subnanometer clusters, where concomitant sintering and alloying might play a significant role.
View Article and Find Full Text PDFCryst Growth Des
February 2022
Department of Chemical and Biomolecular Engineering, School of Energy Science and Engineering, Vidyasirimedhi Institute of Science and Technology, Rayong 21210, Thailand.
The stereoisomeric system of -2-phenylglycinamide (PGA) and --acetyl tryptophan (NAT) is significant in the application of chiral resolution because it has been shown that this system can be used for enantioseparation of PGA and/or NAT using a novel deracemization route of the conglomerate salt formed. However, it was also found that the conglomerate salt eventually converted into different crystal forms that limited the time available for the separation. Herein, we try to understand the phase conversion occurring in this system using DSC, PXRD, and SC-XRD.
View Article and Find Full Text PDFPhys Chem Chem Phys
November 2021
Normandie Univ, UNIROUEN, INSA Rouen, CNRS, GPM, 76000 Rouen, France.
The present work aims at addressing the issue of molecular handedness in glassy and liquid states and its impact on heterogeneous equilibrium. For this purpose, we evaluated the glass forming ability (GFA), crystallization propensity, molecular mobility and hydrogen bonding structure of a chiral conglomerate forming system, -acetyl-α-methylbenzylamine (Nac-MBA), at various enantiomeric excesses (ees) using experimental and computational techniques. We revealed that the rich relaxational landscape (Debye (D), α, β and ϒ) and the temperature dependence of the time scale of each process were insensitive to chirality.
View Article and Find Full Text PDFCryst Growth Des
September 2019
Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106 Magdeburg, Germany.
Preferential crystallization (PC) is a powerful method to separate the enantiomers of chiral molecules that crystallize as conglomerates. The kinetically controlled separation method works in a typically narrow metastable zone. Currently, there are no simple models available that allow estimating the productivity of PC and, thus, the comparison with rivalling resolution techniques.
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