N.M.R. Experiments on Ketals III. P.M.R. Spectrum and conformations of the glycolketal of 1,2‐propanediol with acetone and acetaldehyde

Abstract

Abstract The P.M.R. spectra of 2,2,4‐trimethyl‐1,3‐dioxolane and both cis and trans 2,4‐dimethyl‐1,3‐dioxolane are qualitatively analysed. The magnetic anisotropy of a methylgroup causes an upfield shift of the cis‐γ protons of about 0,15 ppm, and an analogous shift of 0,05 ppm for the cis‐γ methyl resonance. This can be used for structure elucidation. In the acetonide and the cis ‐compound (III) long range coupling between H A and 4‐CH 3 (see II and III) is observed, while in the trans compound (II) it is not.