Polyene aldehydes are made by reaction of a carbonyl compound of formula: ##STR1## in which R denotes a hydrocarbon radical and R' denotes hydrogen or alkyl, with a metal derivative of a halogen compound of formula: ##STR2## in which X denotes halogen (preferably bromine), R.sub.3 is alkyl, and either R.sub.1 denotes hydrogen and R.sub.2 denotes an alkoxy radical identical with OR.sub.3 or R.sub.1 and R.sub.2 together form a bond, followed by hydrolysis of the product obtained.
Polyene aldehydes are made by reaction of a carbonyl compound of formula: ##STR1## in which R denotes a hydrocarbon radical and R' denotes hydrogen or alkyl, with a metal derivative of a halogen compound of formula: ##STR2## in which X denotes halogen (preferably bromine), R.sub.3 is alkyl, and either R.sub.1 denotes hydrogen and R.sub.2 denotes an alkoxy radical indentical with OR.sub.3 or R.sub.1 and R.sub.2 together form a bond, followed by hydrolysis of the product obtained.