Continuous process for producing pseudoionones and ionones

Abstract

The invention relates to a continuous process for producing pseudoionones of general formulas (I) and (I') as well as isomers thereof, whereby: Rrepresents CHor (a); Rand Rrepresent hydrogen, CHor CH, and; Rand Rrepresent hydrogen or CH. These pseudoionones are produced by reacting an aldehyde of formula (II) with an excess of a ketone of general formula (III), whereby R, Rand Rhave the aforementioned meanings, in the presence of water and alkali hydroxide at an increased temperature and in a homogeneous solution. The inventive process is characterized in that: a) the intermixing of the homogeneous solution consisting of aldehyde, ketone and aqueous alkali lye occurs at a temperature ranging from 10 to 120° C.; b) the undissolved water and alkali hydroxide contained in the reaction mixture are subsequently separated out; c) while avoiding back mixing, the homogeneous reaction mixture is then guided through a reactor, which permits a residence time ranging from 2 to 300 minutes, at a temperature that is 10 to 120° C. higher than the boiling point of the lowest-boiling component and under a vapor pressure p ranging from 10to 10Pa; d) the reaction mixture is cooled by expansion; e) ketone is removed from the reaction mixture using vapor flowing in the opposite direction and; f) the raw product is dried and rid from excessive aldehyde and secondary components via a rectification column