Chiroptical properties of lactones. Part III. Electronic rotatory strengths of the n→π* transition in αβ-unsaturated γ-lactone systems
- 1 January 1976
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 14,p. 1674-1677
- https://doi.org/10.1039/p29760001674
Abstract
The chiroptical properties associated with the n→π* transition of dissymmetric αβ-unsaturated γ-lactone systems are calculated and relationships between the chiroptical observables and the stereochemical and electronic structural features of these systems are examined. The calculations are based on the INDO-MO model for the electronic structure of the molecular systems and excited states are constructed in the virtual orbital-configuration interaction approximation. The lowest-energy singlet-singlet transition is calculated to be of the n→π* type for each of the αβ-unsaturated γ-lactone structures examined. The n orbital in this transition is found to be somewhat localized on the carbonyl oxygen atom of the OC–O moiety, whereas the π* orbital is delocalized over the CC and O–C–O fragments. Oscillator strengths, rotatory strengths, and dissymmetry factors are calculated for the n→π* transition in a number of exo-ene and endo-ene αβ-unsaturated γ-lactone systems. The signs and magnitudes of the calculated rotatory strengths are related to specific structural features in these systems.Keywords
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