Nuclear Magnetic Resonance Spectra of Some Simple Epoxides

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Abstract
High resolution NMR spectra of four epoxides have been observed at 40 Mcps and analyzed. These epoxides are of the type[Complex chemical formula]where R is a phenyl group (styrene oxide), a cyanide group (glycidonitrile), an acetyl group (1,2‐epoxy‐3‐butanone), and a carboxyl group (glycidic acid). For each molecule the spin‐spin coupling constants and nuclear magnetic screening parameters for the A, B, and Cprotons were derived from the experimentally determined energy levels. The method for obtaining numerical values for the energy levels from the spectra is described fully. ABK and AA′K approximations as well as an iterative ABC method of solution are described and illustrated. Corresponding coupling constants are found to be about the same in all four molecules with JAB =5.8±0.5 cps, JAC =2.2±0.5 cps and JBC =4.6±0.5 cps. However, the variations from molecule to molecule are considerably greater than the estimated precision of ±0.05 cps. The ABX approximation is shown to be inadequate either for the precise determination of the constants or for the calculation of relative intensities. As compared with the iterated ABC solution, the ABK or AA′K approximation leads to good values for the constants and adequately describes the relative intensities.