Acta Phys. -Chim. Sin. ›› 1988, Vol. 4 ›› Issue (05): 549-553.doi: 10.3866/PKU.WHXB19880522

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Yu Dingqiong*; Xu Zhigu   

  1. Department of Chemistry; Xiamen University
  • Received:1987-03-16 Revised:1987-10-19 Published:1988-10-15
  • Contact: Yu Dingqiong

Abstract: The isomerization products of fac- and mer-[Co(β-ala)_3] in neutral and acidic media were separated with Na~+-type SP-Sephaex C-25 column and determined by spectrophotometry. At high temperatures(>90 ℃)the fac-isomer readily isomerizes to mer-[Co(β-ala)_3] and simultaneously hydrolyzes to yield a brown slurry in neutral solution.However, in acidic solution hydrolysis does not occur, the products are mer-isomer and a small amount of red complex cation, which is strongly adsorbed at the top of SP-Scphadex column and would probably be the fac-[Co(β-ala)_2[Co(β-alaH)(H_2O]~+.
At 90 ℃ the mer-[Co(β-ala)_3]is hydrolyzed rapidly to yield a brown precipitate in neutral solution and isomerizes in small amount to fac-isomer. In acidic solution the mer-isomer isomerizes slightly to fac-isomer, and at the top of SP-Sephadex column, a violet complex cation which would probably be mer-[Co(β-ala)_2(β-alaH)(H_2O]~+ is abserved.
The kinetic parameters of isomerization of fac-[Co(β-ala)_3] in neutral, basic and acidic solutions have been determined with spectrophotometric method at 534 nm. The resufts obtained indicate that reaction rates v with respect to fac-[Co(β-ala)_3] in neutral, basic and acidic media are all in first order, and under constant initial concentration of fac-[Co(β-ala)_3] the reaction rates v with respect zation of fac-[Co(β-ala)_3] in neutral, [OH~-]=4.04×10~(-4) molL~(-1), [HCl]=1.56×10~(-2) molL~(-1) and [HClO_4]=1.56×10~(-2) molL~(-1) media at 90 ℃ are 0.0195, 57.3, 3.43 and 0.978 min~(-1) while the activation energies are 194.2, 103.1, 134.1 and 113.8 kJ.mol~(-1) respectively.