Basf Aktiengesellschaft

Thomas M Kahl

Jochem Henkelmann

Leopold Hupfer

Wolfgang Schwarz

Wolfgang Franzischka

Irene Troetsch-Schaller

A process for the preparation of a carboxylic chloride of the general formula I ##STR1## in which R denotes C.sub.1 -C.sub.30 -alkyl, C.sub.2 -C.sub.30 -alkenyl or C.sub.2 -C.sub.30 -alkynyl, from a carboxylic acid of the general formula II ##STR2## in which R has the meanings stated, and phosgene COCl.sub.2 (III), in the presence of a catalyst adduct comprising phosgene and N,N-disubstituted formamide of the general formula IV ##STR3## in which R.sup.1 and R.sup.2 are independently C.sub.1 -C.sub.3 -alkyl or R.sup.1 and R.sup.2 together form a C.sub.4 - or C.sub.5 -alkylene chain which may or may not be interrupted by an oxygen atom or by a nitrogen atom carrying a C.sub.1 -C.sub.3 -alkyl group or CHO, the product being isolated by phase separation, wherein the amount of phosgene added to the formamide (IV) is from 20 to 70% molar, based on the formamide.

Preparation of carboxylic chlorides

To remove phosgene from off-gases, the former is reacted in a washing zone with a liquid which contains or is composed of compounds of the formula ##STR1## where R.sub.1 and R.sub.2 are identical or different and are each aliphatic or cycloaliphatic alkyl of 1 to 8 carbons, or R.sub.1 and R.sub.2 are --(CH.sub.2).sub.n -- where n is 4 or 5, R.sub.3 is hydrogen or aliphatic or cycloaliphatic alkyl of 1 to 6 carbon atoms, or R.sub.1 or R.sub.2 and R.sub.3 are --(CH.sub.2).sub.m -- where m is 3, 4 or 5. The liquid can be regenerated by the addition of water, and the regenerated liquid can be returned to the washing zone.

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Roemerberg, Germany

Thomas M Kahl