Abstract: Novel compounds of the formula ##STR1## wherein R.sub.1 is chlorine, bromine or nitro, R.sub.2 is chlorine or bromine, R.sub.3 is hydrogen or fluorine, R.sub.4 is C.sub.1 -C.sub.9 alkyl which is unsubstituted or substituted by halogen or C.sub.1 -C.sub.3 alkoxy, or is C.sub.2 -C.sub.7 alkenyl, C.sub.2 -C.sub.4 alkynyl or C.sub.3 -C.sub.6 cycloalkyl, each of which is unsubstituted or substituted by halogen or aryl, or is phenyl which is unsubstituted or substituted by halogen, nitro or C.sub.1 -C.sub.4 alkyl, or is a 5-membered heterocyclic ring system which contains a hetero-atom, or is X-R.sub.5, wherein X is oxygen or sulfur and R.sub.5 is C.sub.1 -C.sub.6 alkyl or C.sub.3 -C.sub.6 alkenyl, each of which is unsubstituted or substituted by halogen or C.sub.1 -C.sub.3 alkoxy, or is phenyl which is unsubstituted or substituted by halogen, nitro, C.sub.1 -C.sub.3 alkyl or C.sub.1 -C.sub.3 alkoxy, or is benzyl which is unsubstituted or substituted by halogen or nitro.

Abstract: An improved process is disclosed for the preparation of polyalkenyl-substituted succinic anhydride comprising a final thermal treatment after removal of excess maleic anhydride from the reaction mixture, resulting in lowered chlorine content of the desired product.