Design, Synthesis and Study of Catalysts for Organophosphate Ester Hydrolysis.
Annual rept. 15 Mar 84-14 Mar 85,
ALBERTA UNIV EDMONTON DEPT OF CHEMISTRY
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The hydrolyses of tris-p-nitrophenylphosphate 5, tris-2-pyridylphosphate 6 and ethyl-p-nitrophenylphosphonate 7 catalyzed by two tris-imidazol-yl-phosphine cobalt 2 complexes Co23 and Co24 were studied as a function of pH. In the hydrolyses of both 6 and 7, Co23 which contains no hydroxyethyl pendant appears to act as its anionic form, generated by ionization of a Co2- bound water having a pka approx. 8 at 37 C in 80 ethanol-water. On the other hand, which possesses a hydroxyethyl pendant catalyzes the hydrolyses of 6 and 7 with an activity that increases linearly with pH up to at least pH 8.3. Above this pH, precipitation of Co2 OH- x becomes a problem. In the latter case, the active form of Co24 has a pKa in excess of 8.3 that apparently obtains from ionization of the Co2-associated hydroxyethyl group. Evidence is presented that Co24 functions as a general base catalyst in the hydrolysis of 6. Keywords Alkaline phosphatase, Models, Catalysis, Organophosphate ester, Hydrolysis, Metal ion.
- Organic Chemistry