Structural Assignments of Ethylidene Acetals by NMR Spectroscopy

Abstract

Abstract The 1H and 13C NMR spectra of ethylidene derivatives of simple diols and of carbohydrates were measured to determine whether NMR parameters could be found which could be related to structure. Four NMR parameters were considered; the chemical shifts of the acetal proton and carbon, the 2JC,H value between the acetal proton and methyl carbon and the 1JC,H value of the acetal carbon. The values,.of these parameters were all somewhat related to ring-size; the 2JC,H value was most closely related. The sign of 2JC,H was shown to be positive for 2-methy l-l,3-dioxolane and Z-methy l-l,3-dioxane by means of selective population transfer experiments. Comparison of the 13C NMR chemical shifts of the acetal with the parent diol was found to give information about acetal location.