A piece of research carried out by the EHU’s Spectroscopy Group and the Biofisika Institute (CSIC/EHU) and published in the Journal of the American Chemical Society has analysed the stepwise hydration of prolinol, a molecule widely used as a catalyst and as a building block in chemical synthesis. The study shows that just a few water molecules are capable of completely changing the preferred structure of prolinol.
Physical Chemistry applies the principles and concepts of physics to understand the basics of chemistry and explain how and why transformations of matter take place on a molecular level. One of the branches of this field focusses on understanding how molecules change in the course of a chemical reaction or process.
Understanding the interactions of chiral molecules with water is crucial, given the central role that water plays in chemical and biological processes. Chiral molecules are those that, despite comprising the same atoms, cannot be superimposed on their mirror image in a way similar to what happens with right and left hands or a pair of shoes.
In this context, the Spectroscopy Group of the University of the Basque Country / Euskal Herriko Unibertsitatea (EHU) and the Biofisika Institute (CSIC/EHU), led by Emilio J. Cocinero, investigated the interactions of prolinol (a chiral catalyst and auxiliary widely used in asymmetric synthesis) with one, two and three water molecules. The study is part of the group’s line of research focusing on the structural analysis of relevant molecules using high-resolution spectroscopic techniques, and has recently been highlighted by the Spanish Biophysical Society (SBE).
The results show directly that water does not act exclusively as a passive ‘medium’, but that it fulfils an active role in the conformation adopted by the molecules.
Prolinol is a small, but highly representative molecule. It is widely used as a catalyst and as a building block in chemical synthesis; moreover, it has two key functional groups (an alcohol and an amine) that interact strongly with water. This makes it an ideal model for studying how water competes with the internal bonds of the molecule and can force structural changes. What is more, its flexible structure allows the effects induced by hydration to be clearly observed. “By adding water step by step, we can see that prolinol adopts conformations that under normal conditions would be ‘unfavourable’. The water acts as a true conformational switch,” added the researcher Emilio J. Cocinero.
The study is also underpinned by an experimental approach that combines ultra-high-resolution rotational spectroscopy with theoretical calculations and studies in solution by means of NMR and simulations. This combination makes it possible to connect in great detail what happens when only a few water molecules interact with prolinol with the actual behaviour of the molecule in solution.
