¹H and ¹³C NMR studies on 3‐aryl‐5‐alkyl‐2,4‐oxazolidinediones. The magnetic non‐equivalence of isomeric nuclei

Abstract

Abstract Magnetic non‐equivalence of diastereotopically related proton and 13 C nuclei in enantiomeric and diastereomeric rotational isomers of 3‐aryl‐5‐alkyl‐2,4‐oxazolidinedlones has been investigated. Steric interactions between the aryl and the heterocyclic moieties of these compounds produce sufficient restriction to rotation about the aryl CN bond that the presence of torsional isomers may be detected at normal temperatures. Free energies of activation for rotation have been calculated. Chemical shift differences, associated with rotational isomerism, may be detected for both the proton and the 13 C nuclei on the hetero ring, but only in the 13 C spectra of the nuclei on the aryl moiety.