Abstract
The reaction of 4,5-dichlor-l-(2-carboxyethyl)-pyridazone-(6) with mercaptans was studied by kinetic measurements and by isolation of the reaction products: it is an SN2-reaction with RSo as the nucleophilic agent. The ratio of the rate of reaction with the SH-group of cysteine and the rate of reaction with amino or imidazole groups is about 50 times greater for the above compound than for iodoacetamide and iodoacetate.