Bulletin of the Korean Chemical Society

Korean Chemical Society (대한화학회)
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A Kinetic Study of the Fe(Ⅲ)-Catalyzed Aquation of Bis(malonato)Diaquochromate(Ⅲ) Ion

  • Shim, Jeong-Ae (Department of Chemical Education, Pusan National University) ;
  • Moon, Jung-Dae (Department of Chemical Education, Pusan National University) ;
  • Park, Heung-Jae (Department of Chemistry, Pusan National University) ;
  • Choi, Sung-Nak (Department of Chemistry, Pusan National University)
  • Published : 1990.08.20
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Abstract

The bis(malonato)diaquochromate(III) ion, $Cr(C_3H_2O_4)_2^-$ in acidic solution hydrolyzes to give $Cr(C_3H_2O_4)^{+}.$ This reaction is catalyzed by ferric ion and the rate law for this cation catalyzed-aquation in a $HClO_4/NaClO_4$ medium, $I = 1.00 M, is-d[Cr(C_3H_2O_4)_2^-]/dt = ({\kappa}_1[Fe^{3+}] + {\kappa}_2[H^+])[Cr(C_3H_2O_4)_2^-]$ where ${\kappa}_1(25^{\circ}C) = 4.72×10^{-5} M^{-1}sec^{-1} ({\Delta}H^{\neq} = 22.5 Kcal/mol, {\Delta}S^{\neq} = - 2.58 eu) and {\kappa}_2(25^{\circ}C) = 4.75{\times}10^{-5} M^{-1}sec^{-1} ({\Delta}H^{\neq} = 21.2 Kcal/mol, {\Delta}S^{\neq} = - 7.13 eu).$ Rapid preequilibrium association of basic Cr-bound oxygen with $Fe^{3+},$ followed by rate-determining ring opening, is proposed to account for the ${\kappa}_1,$ hydrolysis pathway.

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