The γ‐butyrolactone ring puckering

The 60 and 100 MHz 1H NMR spectra of γ‐butyrolactone were analysed in detail. The best set of coupling values (Hz ± 0.03) is 3J  ABc = 7.86, 3J  ABt = 6.27, 3J  BCc = 9.52, 3J  BCt = 6.86, 4J  ACc + 4J  ACt = −0.18, 2JA − 2JB = 3.89 and 2JB − 2JC = 4.86 (A, B and C refer to α, β and γ protons, with respect to the ring oxygen, and c and t mean the same and opposite side of the ring, respectively). The 3J values support the conclusion that the molecule is interconverting between two equivalent conformations of near envelope type with the β‐carbon out of the mean plane defined by the fragment COCOC.

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