Autoxidation of thiols with cobalt(II) phthalocyaninetetrasulfonate, attached to poly(vinylamine). 1. pH and viscometric effects

The oxidation of 2-mercaptoethanol with molecular oxygen in water with cobalt(II)phthalocyanine-tetra-sodium sulfonate attached to poly(vinylamine) has been investigated. Specially attention was paid to the effect of pH and chain dimensions on polymer activity. The polymer catalyst possesses a large conformational freedom at neutral pH, but at higher pH a shrinkage of the polymer coil occurs and diffusion limitations cannot be excluded. The catalyst shows an enzyme-like behaviour in the autoxidation of thiol. Overall activation energies appear to decrease with increasing pH. At pH = 7.4, Ea = 61 KJ mole–1; at pH = 9.5, Ea = 3 KJ mole–1. Electrostatic effects are of major importance in the chemical reactivity since they affect the local thiol-anion concentration in the close vicinity of the polymer attached oxidation sites