Characterization of Substituted 1,3-Dioxolanes and 1,3-Dioxanes by Gas Chromatography–Mass Spectrometry

Until recently, one of the reasons for the unsatisfactory characterization of alicyclic ketals of aliphatic and alkylaromatic ketones was the absence of any mention of the presence of such compounds in natural samples. Another reason is in the low yields of such ketals on the interaction of ketones and diols under the conditions of conventional acid catalysis. To optimize the synthesis of trace amounts of such ketals, we used cobalt(II) bromide and dimethyl glyoxime as catalysts. The simplest chromatographic parameters, including the difference between the retention indices of the products and the starting compounds (difference in retention indices, DRI), are effective for identifying the target ketals in reaction mixtures. Such combined chromatography–mass spectrometric characteristics as homologous increments of retention indices (iRI) are informative not only for the group identification of analytes (assignment to the corresponding homologous series) and the assessment of their molecular weights (at low-intense signals of molecular ions). They are also useful for the determination of the total number of branches of the sp3-carbon skeleton of molecules (N) using the regression of N ≈ aiRI + b.