| 摘要 |
PROBLEM TO BE SOLVED: To overcome disadvantages of the prior art and to provide a process for preparing an unsaturated acetal which is easy to regulate and can be operated in a stable manner. SOLUTION: This continuous process for preparing the unsaturated acetal of formula I (wherein, R1 to R7 are each independently hydrogen or a straight- chain or a branched, optionally substituted 1-6C alkyl group; R8 is hydrogen or a saturated or a mono- or a polyunsaturated straight-chain or branched, optionally substituted 1-12C alkyl group or a 3- to a 12-membered saturated or a mono- or a polyunsaturated carbocyclic ring) by reacting 1 mol of an aldehyde of formula II (wherein, R1 to R3 are as defined in the following formula I) with at least 1 mol of an alcohol of formula III (wherein, R5 to R8 are as defined by the following formula I) in the presence of a catalytic amount of an acid while removing water formed during the reaction, which comprises only partially reacting the reactants in a reactional column, concentrating the resultant acetal in at least two successive evaporation stages and returning the recovered reactants to the reactional column.
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