I have been using bromoacetaldehyde diethyl acetal recently and noticed something interesting about the 1H NMR. The methylene protons of the ethyl acetal are magnetically non equivalent. You see two quartets integrating for two protons with different shifts.
You can see this in the spectra here.
I have found a short description, however it is a little unclear:
Diethyl acetals such as (1 6) and triglycerides such as triacetin (1 7) have a molecular symmetry plane and consequently are optically inactive. However, this plane does not bisect the connecting line of the geminal protons, which are magnetically non equivalent. This is manifested by the relative complexity of the AA'BB'X type proton spectrum of the glyceryl moiety of triacetin (Figure). Similar magnetic non-equivalence can be induced across an ester bond; e.g., the two methyl groups of the isopropyl ester (18) area non-equivalent.
I don't really understand as there is no restriction of rotation. And does this mean that this would disappear using high temperature NMR?