Henry S. Rzepa

Web sites: http://rzepa.ch.ic.ac.uk/ and http://rzepa.net/

Welcome to this on-line pot-pourri of my professional activities in chemistry. Click on the hyperlinks shown in colour on the right if you seek further information about any category.

A note about what you should see above: We are interested in molecules, their shapes, properties and reactions. The Applet above will display and animate the molecule on this page, and various others scattered throughout the documents describing our work. For the applet controls, press the right mouse button (or ctrl-click with MacOS).

    The example above shows 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 the above model, derived from accurate quantum mechanical (density functional) calculations of the reaction mechanism. This was published as: Gibson, Vernon C.; Marshall, Edward L.; Rzepa, Henry S. " A computational study on the ring-opening polymerization of lactide initiated by β-diketiminate metal alkoxides: The origin of heterotactic stereocontrol", J. Am. Chem. Soc., 2005, 127, 6048-6051. DOI: 10.1021/ja043819b. A. P. Dove, V. C. Gibson, E. L. Marshall, H. S. Rzepa, A. J. P. White and D. J. Williams, "Synthetic, Structural, Mechanistic and Computational Studies on Single-Site β-Diketiminate Tin(II) Initiators for the Polymerization of rac-Lactide", J. Am. Chem. Soc., 2006, DOI: 10.1021/ja061400a
  1. We have been exploring a new type of cyclic delocalization which leads to the phenomenon of chiral aromaticities. These manifest as figure-eight shaped or lemniscular molecules with Möbius topologies, of which new examples are being rapidly discovered. For the basic theory behind this, see S. M. Rappaport and H S. Rzepa, "Intrinsically Chiral Aromaticity. Rules Incorporating Linking Number, Twist, and Writhe for Higher-Twist Möbius Annulenes", J. Am. Chem. Soc., 2008, 130, 7613-7619. DOI: 10.1021/ja710438j

© H. S. Rzepa, 2011.