Effects of metal ions on the hydrolysis of p‐nitrophenyl caproate by modified poly(ethylenimine)s
- 1 October 1979
- journal article
- research article
- Published by Wiley in Biopolymers
- Vol. 18 (10) , 2497-2505
- https://doi.org/10.1002/bip.1979.360181009
Abstract
Hydrolysis of nitrophenyl caproate by modified poly(ethylenimine)s containing imidazole moieties is markedly enhanced in the presence of divalent metal ions. The order of effectiveness is Cu(II) > Co(II) > Zn(II) > Ni(II) > Mn(II), with Cu increasing the rate about 20‐fold. The acceleration by the metal ion is much greater in the presence of CH3COO− or Cl− as counterions than in the presence of ClO4−. Turnover experiments, in which moles of substrate cleaved were in substantial excess of moles of metal present, established the catalytic nature of the effects of the metals. The extent of binding of Cu(II) by the polymers was measured. Maximum accentuation in rate of hydrolysis of nitrophenyl ester was observed for the imidazole‐containing polymer when the ratio of imidazole:Cu(II) was 2.75. Some possible mechanisms for the rate enhancement by metal ions are described.Keywords
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