Chirality of Molecular Structures — Basic Principles and Their Consequences

Abstract

This article reviews the concept of molecular chirality from the standpoint of modern physics. The application of the fundamental symmetry operations of space inversion and time reversal together are shown to lead to a more precise definition of a chiral object than that usually employed. It follows that, although spatial enantiomorphism is sufficient to guarantee chirality in a stationary object, enantiomorphous systems are not necessarily chiral when motion is involved, leading to the concept of true and false chirality associated with time-invariant and time non-invariant enantiomorphism, respectively. Although only a truly chiral influence can induce absolute asymmetric synthesis in a reaction that has reached true thermodynamic equilibrium, it is shown how false chirality can suffice in a reaction under kinetic control due to a breakdown of microscopic reversibility and hence of detailed balancing. The discussion then turns to a consideration of symmetry violation and how it differs from symmetry breaking. This provides considerable insight into molecular chirality and exposes productive analogies between the quantum states of a chiral molecule and those of various elementary particles. As well as facilitating a sound understanding of the structure and properties of chiral molecules and of the factors involved in their synthesis and transformations, it is hoped that this article will encourage greater awareness of the value of concepts from modern elementary particle and condensed matter physics in theoretical chemistry.