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Effects of metal ions on the hydrolysis of p-nitrophenyl caproate by modified poly(ethylenimine)s

✍ Scribed by Toru Takagishi; Irving M. Klotz

Publisher
Wiley (John Wiley & Sons)
Year
1979
Tongue
English
Weight
471 KB
Volume
18
Category
Article
ISSN
0006-3525

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✦ Synopsis

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 CH~3~COO^−^ or Cl^−^ as counterions than in the presence of ClO~4~^−^. 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.

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