The proton magnetic resonance spectrum of propiolactone

Abstract

The complete analysis of the AA′BB′ spectrum of propiolactone has been performed using maximum resolution and increased r.f. power to observe all but one of the allowed transitions. The coupling constants are J_gem=–16·40 and –5·00, J_cis= 6·93, and J_trans= 4·61 c./sec. The difference between J_cis and J_trans proves conclusively that the previous spectra of this compound were deceptively simple and not magnetically equivalent A₂B₂ spectra.