Reactions of chiral molecules in the presence of a time-non-invariant enantiomorphous influence: a new kinetic principle based on the breakdown of microscopic reversibility
✍ Scribed by L.D. Barron
- Publisher
- Elsevier Science
- Year
- 1987
- Tongue
- English
- Weight
- 702 KB
- Volume
- 135
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
It is suggested that conventional kinetic principles do not apply to processes involving chiral molecules in the presence of a time-non-invariant enantiomorphous influence on account of the breakdown of microscopic reversibility and hence of detailed balancing. This implies different rate constants for enantiomeric processes, and absolute asymmetric synthesis in a reaction under kinetic control. Since the chiral enantiomers are isoenergetic in the presence of the influence, the enantiomeric excess will disappear if the reaction has been allowed to reach true thermodynamic equilibrium. A chemical quadrangle is used to show how the kinetic and thermodynamic requirements can be reconciled. A general analysis is given which parallels that for particle-antiparticle processes in the presence of Cp violation, and similarly depends on unitarity, rather than microscopic reversibility, for the validity of the underlying thermodynamic principles. A simple example is considered involving the conrotatory ring closure of a substituted butadiene to produce a chiral cyclobutene.