Manufacturing of .alpha.,.beta.-unsaturated aldehydes and ketones

A process for the preparation of an .alpha.,.beta.-unsaturated aldehyde or ketone of the formula I

• O.dbd.C(R.sup.1)--CR.sup.2 .dbd.CR.sup.3 R.sup.4 I,
• in which the substituents R.sup.1, R.sup.2, R.sup.3, and R.sup.4 independently denote hydrogen, alkyl, substituted alkyl, aryl, or substituted aryl, by acid hydrolysis of the corresponding cyclic .alpha.,.beta.-unsaturated acetal or ketal of the formula II ##STR10## in which Z stands for an unsubstituted or substituted carbon chain having 2 to 3 carbon atoms, wherein the substituted alkyl, substituted aryl, or substituted carbon chain may be interrupted by heteroatoms, such as nitrogen, oxygen, and sulfur, or substituted with radicals, such as halogen, nitro, sulfonyl, arylsulfonyl, carboxyl, cycloalkyl, or cycloalkenyl, wherein the hydrolysis is carried out in the presence of a saturated aldehyde, wherein the saturated aldehyde is used in an amount of 1 to 3 molar equivalents, based on the amount of cyclic .alpha.,.beta.-unsaturated acetal or ketal of the formula II used, and wherein the hydrolysis is carried out at a temperature from 0.degree. to 150.degree. C.