Complete resolution of the ionization equilibria of 5-deoxypyridoxal in water-dioxane mixtures

被引:9
作者
Llor, J [1 ]
Ros, MP [1 ]
Asensio, SB [1 ]
机构
[1] Univ Granada, Fac Ciencias, Dept Quim Fis, Granada 18003, Spain
关键词
5-deoxypyridoxal; thermodynamic ionization equilibrium constants; water-dioxane mixtures;
D O I
10.1007/BF02768827
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We have used a potentiometric method to determine the thermodynamic equilibrium constants for the macroscopic ionization processes of 5-deoxypyridoxal (DPL) in water-dioxane mixtures (0-70% weight fraction in dioxane) at temperatures ranging from 10 degrees C to 50 degrees C. These data, together with previously published equilibrium constants for the tautomerism and hydration processes, have allowed us to resolve the complete microconstant system. We have also calculated the microscopic ionization equilibrium constants under all the experimental conditions. The changes of standard thermodynamic function for the macroscopic and microscopic ionization processes were obtained in various water-dioxane mixtures at 25 degrees C. The values of a given microscopic pK with different solvents and temperatures fit very well to an equation which relates this magnitude with the thermodynamic parameters, the solvation of the components of the reaction, and a solvent parameter. We have obtained an interesting linear correlation between the thermodynamic parameters corresponding to all the microscopic ionizations of DPL and the net change of the solvation during the process: enthalpies correlate linearly for all the microscopic ionizations, while entropies do so for the phenols and pyridinium ions separately.
引用
收藏
页码:1021 / 1036
页数:16
相关论文
共 27 条
[1]   THE THERMODYNAMICS OF THE IONIZATION OF 3-HYDROXYPYRIDINE AND PYRIDOXINE IN WATER DIOXANE MIXTURES [J].
ASENSIO, SB ;
LOPEZCANTARERO, E ;
LLOR, J .
CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 1992, 70 (06) :1635-1689
[2]  
Christen P., 1985, TRANSAMINASES
[3]   EVALUATION OF THERMODYNAMIC FUNCTIONS FROM EQUILIBRIUM CONSTANTS [J].
CLARKE, ECW ;
GLEW, DN .
TRANSACTIONS OF THE FARADAY SOCIETY, 1966, 62 (519P) :539-&
[4]  
CORTIJO M, 1988, J BIOL CHEM, V263, P17960
[5]   FREE-ENERGIES AND ENTROPIES OF TRANSFER OF HYDROGEN HALIDES FROM WATER TO AQUEOUS-SOLUTIONS OF TETRAHYDROFURAN, DIOXANE, AND 1,2-DIMETHOXYETHANE AND THE STRUCTUREDNESS OF THE SOLVENTS [J].
DATTA, J ;
KUNDU, KK .
CANADIAN JOURNAL OF CHEMISTRY-REVUE CANADIENNE DE CHIMIE, 1981, 59 (22) :3149-3156
[6]   BAND-SHAPE ANALYSIS AND RESOLUTION OF ELECTRONIC-SPECTRA OF PYRIDOXAL-PHOSPHATE AND OTHER 3-HYDROXYPYRIDINE-4-ALDEHYDES [J].
HARRIS, CM ;
JOHNSON, RJ ;
METZLER, DE .
BIOCHIMICA ET BIOPHYSICA ACTA, 1976, 421 (02) :181-194
[7]  
ISAACS NS, 1992, PHYSICAL ORGANIC CHE
[8]  
IWATA C, 1968, BIOCHEM PREP, V12, P117
[9]  
LLOR J, 1987, AN QUIM A-FIS TEC, V83, P317
[10]   Thermodynamics of the tautomeric, hydration and hemiacetalization of 5-deoxypyridoxal and pyridoxal in water-dioxane mixtures [J].
Llor, J ;
Asensio, SB .
JOURNAL OF SOLUTION CHEMISTRY, 1996, 25 (07) :667-679