App: kpHcalc
Developer: JPG Malthouse
Genres: Education, Productivity

This program calculates the observed rate constant (kobs) for reactions dependent on 1 to 7 protonic states. 

XH6 = XH5 = XH4 = XH3 = XH2 = XH = X

The program calculates and plots the pH curves for the  protonic states XH6, XH5, XH4, XH3, XH2, XH or X as well as the composite curves and experimental data. This allows you to analyze complex pH dependent reactions manually. Graphs and calculated data can be printed or copied and pasted into applications such as Word. The analysis of pH-dependent kinetics in up to four reactive protonic states has been described (Brocklehurst & Brocklehurst 1988, 256, 556-558). Examples of ionization schemes are given in the support site. The program can also be used to analyze pH dependent change in ppm, absorbance etc simply replace k values with the appropriate pH dependent parameter.

Experimental data points can be entered manually. However if data is in an excel file it can be saved as a csv file or tab delimited text file which can be read by the program.

This program can be used to manually analyze pH data which is too complex to analyze using conventional computer fitting programs. The full equations used to calculate all the protonic states are given in "Program information". If you have pH dependent data depending on one or two pKa values you may find the following Mac applications Sigfit, Bellfit and ppmfit useful to fit the experimental data.

Release notes:
The graphics functionality lost when using the Big Sur or higher operating system has been restored.