We located "hidden" S-character chirality in formally achiral glycine using a vectorbased interpretation of the total electronic charge density distribution. We induced the formation of stereoisomers in glycine by the application of an electric field. Control of chirality was indicated from the proportionate response to a non-structurally distorting electric field. The bond-flexing was determined to be a measure of bond strain, which could be a factor of three lower or higher, depending on the direction of the electric field, than in the absence of the electric field. The bond-anharmonicity was found to be approximately independent of the electric field. We also compared the formally achiral glycine with the chiral molecules alanine and lactic acid, quantifying the preferences for the S and R stereoisomers. The proportional response of the chiral discrimination to the magnitude and direction of the applied electric field indicated use of the chirality discrimination as a molecular similarity measure.
The association between molecular chirality and helical characteristics known as the chirality-helicity equivalence is determined for the first time by quantifying a chirality-helicity measure consistent with photoexcitation circular dichroism experiments. This is demonstrated using a formally achiral S N 2 reaction and a chiral S N 2 reaction. Both the achiral and chiral S N 2 reactions possess significant values of the chirality-helicity measure and display a Walden inversion, i. e. an inversion of the chirality between the reactant and product. We also track the chirality-helicity measure along the reaction path and discover the presence of chirality at the transition state and two intermediate structures for both reactions. We demonstrate the need for the chirality-helicity measure to differentiate between steric effects due to eclipsed conformations and chiral behaviors in formally achiral species. We explain the significance of this work for asymmetric synthetic reactions including the intermediate structures where the Cahn-Ingold-Prelog (CIP) rules cannot be used.
The effect of a directional electric‐field on the bonding of the undoped and sulfur doped diarylethene (DTE) switch molecule is investigated using next generation QTAIM (NG‐QTAIM). We introduce chemical bonding concepts in the form of the least and most preferred directions of charge density accumulation relative to a bond‐path, namely the precessions K and K′ that are demonstrated to be much more responsive to the electric‐field than the Laplacian ∇2ρ(rb). A concept of bond fatigue is presented in terms of the tendency for a bond‐path to rupture that provides directional versions of familiar bonding QTAIM concepts. Examples of fatigue resistance and fatigue are included where the applied electric‐field reduces and increases the tendency toward bond‐path rupture respectively. A brief discussion is undertaken of applications of the precessions K and K′ including switches, ring opening reactions and molecular rotary motors in the presence of fields that cause a redistribution of ρ(r).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.