TITLE

Acid—base characterization of 5-hydroxypyrazine-2-carboxylic acid and the role of ionic equilibria in the optimization of some process conditions for its biocatalytic production

AUTHOR(S)
Sak-Bosnar, M.; Kovar, K.
PUB. DATE
October 2005
SOURCE
Analytical & Bioanalytical Chemistry;Oct2005, Vol. 383 Issue 3, p539
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
This paper describes the use of potentiometric titration to determine the relevant acid–base properties of 5-hydroxypyrazine-2-carboxylic acid (5OH-PYCA), an important intermediate in the production of tuberculostatics. The data obtained were used for calculation of the dissociation constants of 5OH-PYCA. It was found that 5OH-PYCA dissociates in two steps, with the corresponding dissociation constants p K a1=3.42 and p K a2=7.96, designating 5OH-PYCA as a medium weak acid (1st step). The distribution diagram of dissociated species and the buffer-strength diagram of 5OH-PYCA provide useful information about its behaviour at different pH. The ionic equilibria data obtained can be used for selection of the optimum pH for biotransformation of pyrazine-2-carboxylic acid (PYCA) and for prediction of pH changes during the biotransformation. These data can also be used for selection of the optimum pH for precipitating 5OH-PYCA in downstream processing. All computations have been optimized by mathematical modelling using Solver.
ACCESSION #
18591374

 

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