Automated pH and Temperature Control

This case study describes avoiding impurity formation with automated pH and temperature control while dosing reagents in a chemical reaction.  Tight control of crucial process parameters, including temperature, pH, dosing rates, and mixing in a chemical synthesis process can minimize side products caused by temperature and/or pH variations.  Reaction temperature and pH can have direct impact on reaction rate, type, and concentration of the by-products and decomposition.  Variations in temperatures and pH often lead to more by-products and decomposition of unstable intermediates.  Because of the importance of automated pH control, the number of publications focused on pH-dependent processes have increased in recent years, especially for enantio- chemo, and regioselective reactions.

This case study investigates the importance of these parameters for automating a temperature and pH-sensitive two-phase reaction:  the synthesis of triethyl-2,2, -dichlorophosphonoacetate.  Phosphonoacetate derivatives are of interest for various reasons, including their connection with antiviral activity and powerful insecticides and/or herbicides.

This case study describes automated gravimetric dosing and control of third party syringe pumps, measurement, and control of pH.  The performance of gravimetric dosing and automated pH control in this study is reproducibly achieved in this pH-sensitive two-phase reaction. In order to achieve good yield and selectivity and to avoid by-product formation, temperature and pH control must be constant during the entire reaction.