Solution stability and thermal degradation of some cyclic dithiocarbamates

Abstract

Although cyclic dithiocarbamates (DTC) present better solution and solid state stability when compared to aliphatic analogues, relatively few thermo-analytical and solution stability studies have so far been reported which concern these important substances. In solution, the degradation of dithiocarbamates undergoes via a protonated intermediate and is very fast in acidic media. A spectrophotometric method based on diode array detection has been proposed for a fast and accurate determination of pK a and degradation kinetic constants of these cyclic DTC's and is discussed here. Thermal analytical data were also collected regarding ammonium, sodium, potassium salts as well as for zinc, cadmium, lead, cobalt, nickel, copper, mercury, silver, iron and manganese complexes of pyrrolidinedithiocarbamate (pyr), piperidinedithiocarbamate (pip), morpholinedithiocarbamate (mor) and hexamethyleneiminedithiocarbamate (hex) and are summarized in this article. Differences in the decomposition intermediates permitted to conclude that structural differences make the decomposition to occur by specific pathways, depending on the number and nature of members of the aminic ring.