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Effect of Ester Side Chains and Solvent Polarity on the Electronic Spectra and Coordination Chemistry of Aquacyanocobyrinic Acid Heptamethylester by M.S.A Hamza is a Chemistry article available to read on EtoBox.
What is Effect of Ester Side Chains and Solvent Polarity on the Electronic Spectra and Coordination Chemistry of Aquacyanocobyrinic Acid Heptamethylester about?
Aquacyanocobyrinic acid heptamethyl ester (Aquacyanocobester) has been prepared from vitamin B 12 after converting the seven amide side chains into methyl esters. The solvent dependence of the absorption spectrum of aquacyanocobester has shown that the wavelengths of the c-band varied from 362.5 nm in non-polar solvent (CCl 4 ) through 359.5 nm in a more polar solvent (CH 3 CN) to 353 nm in protic solvents (H 2 O, CH 3 OH). The equilibrium constants u L for the coordination of some selected nitrogen and sulfur containing ligands by aquacyanocobester have been determined spectrophotometrically at 25 C in order to assess the eect of the side chain (COOCH 3 ) on the values of u L . The values of log u L for the coordination of imidazole, 4-aminopyridine, pyridine, 4cyanopyridine, bromoethylamine, N À 3 and SO 2À 3 were 3. 95, 4.3, 2.19, 0.75, 2.25, 2.33 and 4.25, respectively. These values are less than those obtained in the case of aquacyanocobinamide where the side chains are CONH 2 . The LFER (log u L pu a ) has been investigated in water and methanol. The values of a and b of the LFER are 0.49 AE 0X03 and A0.25 AE 0X16 for the coordination of aquacyanocobester by py's in aqueous s
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- Author
- M.S.A Hamza
- Publisher
- Elsevier Science; Elsevier ; Elsevier BV (ISSN 0162-0134)
- Published
- 1998
- Language
- EN
- Field
- Chemistry (Physical Sciences)