The method of preparing 4,4-dimethyldioxane-1,3 consists in the interaction of isobutylene and formaldehyde in an aqueous medium at from 90.degree. to 115.degree. C in the presence of a catalyst, the capacity of which such inorganic salts of mineral acids may be used with the pH value of the aqueous solutions whereof being within 2.2 to 4.5, resulting in the formation of an organic and an aqueous phase containing the end product, followed by the separation of said phases, washing the organic phase with water, and isolation of the end product. When a catalyst of such salts is used, the acidity of the aqueous solutions of which is either invariable or decreases with an increase in the salt concentration, it is expedient that the aqueous phase and the wash water be evaporated to a level of from 85 to 90 percent to form a fraction containing the unreacted formaldehyde, and a distillation residue which is in fact an oil bed and a salt bed with the latter, after having been separated, being returned to the stage of interaction of the starting reagents.
In an improved catalytic process for preparing trialkylsilyl ethers from trialkylsilyl compounds and carbonyl group-containing compounds, the improvement consisting of using an organic or inorganic bifluoride (HF.sub.2.sup..crclbar.) as the catalyst.
