Abstract
The autoxidation of various thiols, viz. 2-mercaptoethanol (ME), 3-mercaptopropane-1,2-diol (MP), mercaptoacetic acid (MA) and dodecylmercaptan (DM) with cobalt(II) phthalocyanine-tetra(sodium sulfonate) (CoPc(NaSO 3) 4) as a catalyst in the absence and presence of the basic poly-(vinylamine) has been studied. Differences among the oxidation rates of the various thiols are discussed qualitatively in terms of p K SH, charge, water solubility and size of the substrates. The effect of anionic, nonionic and cationic surfactant on the oxidation rate of these thiols has been investigated. In the absence of polymer the effect of various types of surfactant was small for the hydrophilic ME, MP and MA. However, for DM a micellar catalytic effect of cationic surfactant was observed, whereas anionic surfactant retarded the reaction. When CoPc(NaSO 3) 4 was used in the presence of poly(vinylamine), large differences were observed between the effects of various types of surfactant on the oxidation rate of ME. Nonionic surfactant did not affect the high reaction rate, whereas cationic and anionic surfactants appeared to diminish the rate considerably, even at far below the critical micelle concentration. These effects are discussed in terms of interactions between the polymer catalyst and surfactant. Furthermore, similarities and differences between polymeric catalysis and micellar catalysis in thiol oxidation are shown.
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