Mixtures of ring-opened and other products of reactions of acetic or benzoic acids, or ethanol, or phenol with styrene oxide under various conditions can be qualitatively and quantitatively analyzed without isolation of the components by the use of n.m.r. This method, in the case of the ester products, avoids confusing the initial ring-opening result with the results observed after subsequent acyl migrations which readily occur in this type of system.