Process for the preparing .alpha.-chloroacrylic acid chlorides

A process for preparing .alpha.-chloroacrylic acid chloride by dehydrochlorinating .alpha.,.beta.-dichloropropionic acid chloride at a temperature of from 60.degree. to 120.degree. C and a pressure of below 200 mm of Hg in the presence of a tertiary phosphine of the formula ##STR9## a quaternary phosphonium salt of the formula ##STR10## a tertiary phosphine oxide, sulfide or imine of the formula ##STR11## or a tertiary phosphine halide of the formula ##STR12## wherein R.sub.1, R.sub.2 and R.sub.3 each is alkyl of from 1 to 20 carbon atoms;

• cycloalkyl of from 4 to 8 carbon atoms;
• phenyl;
• phenalkyl of from 7 to 20 carbon atoms;
• said alkyl, cycloalkyl, phenyl or phenalkyl which is substituted;
• ##STR13## R' and R" each being alkyl of from 1 to 20 carbon atoms, phenyl, phenalkyl of from 7 to 20 carbon atoms, or said alkyl, phenyl or phenalkyl which is substituted;
• wherein R.sub.4 is hydrogen;
• alkyl of from 1 to 20 carbon atoms;
• cycloalkyl of from 4 to 8 carbon atoms;
• phenyl;
• phenalkyl of from 7 to 20 carbon atoms;
• or said alkyl, cycloalkyl, phenyl or phenalkyl which is substituted;
• wherein Y is a radical of an organic or inorganic acid;
• wherein Z is oxygen, sulfur, or NR.sub.5, R.sub.5 being alkyl of from 1 to 20 carbon atoms, cycloalkyl of from 4 to 8 carbon atoms, phenyl, phenalkyl of from 7 to 20 carbon atoms, or said alkyl, cycloalkyl, phenyl or phenalkyl which is substituted;
• wherein Hal is halogen;
• and wherein any two of R.sub.1, R.sub.2, R.sub.3, R.sub.4, and R.sub.5 may together form an aliphatic chain or said chain interrupted by nitrogen, oxygen or sulfur.