Knowledge Bank

The spacing of the doublet in the proton resonance spectrum of this compound was measured over the temperature range of $-70$ to $+90\circ C$. In principle, the coupling constants of the rotational isomers and their energy difference can be evaluated from the observed changes in spacing. Within the limits of the experimental error it was possible to determine only ranges of values for these parameters. However, it can be definitely concluded that the trans coupling constant is about a magnitude greater than the gauche constant, provided the gauche form is the more stable as indicated by the temperature dependence of the vibrational spectrum.