The Rzepa research group is a member of the synthesis section in the department of Chemistry, Faculty of Natural Sciences. The group is interested in molecules, and in particular modelling their shapes, properties and reactions. The example currently showcased below involves modelling the key transition state in the catalytic polymerisation of lactide to polylactide, a new generation of bio-sustainable polymer not dependent on oil. This particular Magnesium-based catalyst produces heterotactic polymer, where the configuration of the lactide units alternates in the polymer chain, in the manner RR, SS, RR, SS, etc. Understanding why this happens was achieved using quantitative modelling, derived from accurate quantum mechanical (density functional) calculations of the reaction mechanism.
A second theme has been the exploration of a fundamentally new form of aromaticity which has the property of chirality (dissymetry). These helical aromatics derive from Mobius topologies, and our work has extended the categorisation of such systems from single half twist, to double (lemniscular) systems, and even higher up to six half twists. We have reviewed the area and introduced a new topological metric of aromaticity based on writhe.