Inducing chirality ex nihilo by an electric field

Abstract

Ab initio calculations show that an external electric field can induce chirality in achiral molecules, depending on the orientation of the molecule with respect to the field. Thus, for prochiral molecules such as glycine and CH2ClF, a field oriented along one of the C–H bonds will induce chirality by rendering the two hydrogen atoms nonequivalent. In the case of ethylene, methane, and CCl4, optical activity will be gained only when the positioning of the molecules with respect to the field will render the four substituents nonequivalent. Of the molecules studied, the strongest effect was obtained for glycine and the weakest for methane. Differences were also observed in the effect of reversing the direction of the field. In addition, for glycine, a very strong dependence was obtained for the optical rotation on the wavelength between 200 and 225 nm.