True and false chirality, CP violation, and the breakdown of microscopic reversibility in chiral molecular and elementary particle processes

Abstract

The concept of chirality is extended to cover systems that exhibit enantiomorphism on account of motion. This is achieved by applying time reversal in addition to space inversion and leads to a more precise definition of a chiral system. Although spatial enantiomorphism is sufficient to guarantee chirality in a stationary system such as a finite helix, enantiomorphous systems are not necessarily chiral when motion is involved, which leads to the concept of true and false chirality associated with time‐invariant and time‐noninvariant enantiomorphism, respectively. Only a truly chiral influence can induce an enantiomeric excess in a reaction that has reached true thermodynamic equilibrium (i.e., when all possible interconversion pathways have equilibrated); however, false chirality can suffice in a reaction under kinetic control due to a breakdown of microscopic reversibility analogous to that observed in particle‐antiparticle processes involving the neutral K‐meason as a result of CP violation, with the apparently contradictory kinetic and thermodynamic aspects being reconciled by an appeal to unitarity. This reveals that CP violation is analogous to chemical catalysis since it affects the rates of certain particle‐antiparticle interconversion pathways without affecting the initial and final particle energies and hence the equilibrium thermodynamics. Consideration of falsely chiral influences, including the ‘ratchet effect’ arising from the associated breakdown in microscopic reversibility, greatly enlarges the range of possible chiral advantage factors in prebiotic chemical processes if far from equilibrium.