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 CH 2 ClF, 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 CCl 4 , 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. Résumé :Des calculs ab initio montrent qu'un champ électrique externe peut induire la chiralité dans des molécules achirales selon l'orientation de la molécule par rapport au champ. Ainsi, si l'on considère des molécules prochirales comme la glycine et le CH 2 ClF, un champ orienté dans le sens de l'une des liaisons C-H induira la chiralité en rendant les deux atomes d'hydrogène non équivalents. Dans le cas de l'éthylène, le méthane et le CCl 4 , l'activité optique ne sera acquise que si le positionnement des molécules par rapport au champ peut rendre les quatre substituants non équivalents. Parmi les molécules étudiées, la glycine a permis d'obtenir l'effet le plus marqué et le méthane, l'effet le plus faible. On a aussi observé des différences en ce qui a trait aux effets d'inversion de la direction du champ. En outre, dans le cas de la glycine, une très forte corrélation a été observée quant à la rotation optique aux longueurs d'onde comprises entre 200 et 225 nm. [Traduit par la Rédaction]Mots-clés : calculs ab initio, chiralité, champ électrique.

Control of chirality, bond flexing and anharmonicity in an electric field

“…In this investigation we will seek to locate the presence of chiral character for electron density and manipulate induced chirality in glycine by varying the direction and magnitude of an applied electric ( E )‐field to create S and R stereoisomers. The application of an E ‐field will induce symmetry‐breaking changes to the length of the C–H bonds attached to the alpha carbon atom (C1) of formally achiral glycine, as previously studied by Wolk et al in achiral glycine [39], see Scheme 1.…”

Controlling Achiral and Chiral Properties with an Electric Field: A Next-Generation QTAIM Interpretation

“…Recently, we examined formally achiral glycine subjected to an E field [14] using NG-QTAIM. This work followed on from investigations performed by Wolk et al on the application of an E field to induce stereoisomers via symmetry breaking changes to the length of the C-H bonds [15]. Again, this previous study on glycine was unable to provide the mix of S σ and R σ stereoisomer contributions in U σ space for each of the S a and R a geometric stereoisomers due to the use of only a single dihedral angle to construct T σ (s).…”

Control of Chirality, Bond flexing and Anharmonicity in an Electric Field

“…The application of an E -field will induce symmetry-breaking changes to the length of the C-H bonds attached to the alpha carbon atom (C1) of formally achiral glycine, as previously studied by Wolk et al . in achiral glycine [39], see Scheme 1 . E -fields are known to alter a PES in general [40]- [46].…”