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Crystal structure prediction and thermodynamic modelling of chiral molecules

Hylton, Rebecca Kathryn; (2018) Crystal structure prediction and thermodynamic modelling of chiral molecules. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

This thesis explores the potential of computed crystal energy landscapes as an aid in the rational design of chiral separation processes. Crystal structure prediction (CSP) methods have been used to explore the crystal energy landscapes of prototypical chiral systems and the corresponding lattice energies and properties are used to help explore the thermodynamics of these systems. The crystal energy landscape of two very different chiral systems is explored. The small, but very flexible 3-chloromandelic acid molecule which can form strong hydrogen bonding motifs, and the rigid lactide molecule where the crystal structures are dominated by weak van der Waals forces. These crystal energy landscapes highlight the complexity of chiral molecules, particularly the enantiopure structures which tend to be high Z’. These systems demonstrate that the factors which influences the kinetics of crystallisation and growth are not yet adequately understood. The accuracy of CSP methods was explored through the CCDC Blind Test on the supposedly rigid, pseudo-chiral structure XXII ([1,4]dithiino[2,3-c]isothiazole-3,5,6-tricarbonitrile). The crystal structure was successfully predicted within the submitted structures at a comparable rank to much more sophisticated prediction methods by other groups. This suggests that the CSP methods used in my research can give reliable results. The sublimation cycle is an approach which can be used to support the rational design of chiral separation process by crystallisation. Lattice energy calculations and k = 0 phonon calculations were performed for the 3-chloromandelic acid, lactide and naproxen experimental structures. These results have been used in conjunction with experimental methods, performed by experimentalists at the MPI, Magdeburg, to explore the sublimation cycle. The methods proposed show promise for aiding chiral separation process design.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Crystal structure prediction and thermodynamic modelling of chiral molecules
Event: UCL
Open access status: An open access version is available from UCL Discovery
Language: English
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
URI: https://discovery.ucl.ac.uk/id/eprint/10040863
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