Acetal prepn. from aldehydes and alcohols - by reaction in a rectification column with distillable acid

摘要

Prepn. of acetals by reaction of aldehydes with alcohols is carried out in the presence of a distillable acid in a reactor comprising a rectification column, the top of which is equipped with a water trap (e.g. a phase separator or reflux separator). The prods. are useful as intermediates for the prodn. of plastics, additives, perfumes and vitamins, 1,1-bis(3-methyl-2-buten-1-yloxy)-3-methyl-2-butene (I) is an intermediate for vitamins A and E. The process gives practically quantitative aldehyde conversions with high selectivity (generally >97%) for the acetal. The use of chemical additives (e.g. dehydrating agents or azeotroping solvents) is avoided. In an example, (I) is prepd. from 3-methyl-2-buten-1-al and 3-methyl-2-buten-1-ol.