On the Possibility of Chiral Symmetry Breaking in Liquid Hydrogen Peroxide.

Abstract

Molecular chirality is a key concept in chemistry with implications for the origin of life and the manufacturing of pharmaceuticals. Previous simulations of a chiral molecular model with an energetic bias toward homochiral interactions show a spontaneous symmetry-breaking transition from a supercritical racemic liquid into a subcritical liquid enriched in one of the two enantiomers. Here, we employ molecular dynamics simulations in order to test the possible existence of this phenomenon in hydrogen peroxide, the smallest chiral molecule. For this purpose, we study the fluid phase of this substance between 100 and 1500 K, and from 100 kPa to 1 GPa. We find a glass transition and we suggest that hydrogen bonds play a central role in such behavior. We also test the possibility of observing chiral symmetry breaking by performing both constant temperature and cooling simulations at multiple pressures, and we do not observe the phenomenon. An analysis of the structure of the liquid shows negligible differences between homochiral and heterochiral interactions, supporting the difficulty in observing chiral symmetry breaking. If hydrogen peroxide manifests spontaneous chiral symmetry breaking, it likely takes place significantly below room temperature and is hidden by other phenomena, such as the glass transition or crystallization. More broadly, our results, and recent experimental observations, suggest that greater molecular complexity is needed for spontaneous chiral symmetry breaking in the liquid phase to occur.