Many organic chemists believe that the pKa of water is 15.7 and that the pKa of H3O+ is -1.74. Both of the values are incorrect, and neither one is supported by even a single example of experimental evidence. Yet the values persist because of the accepted wisdom that methanol is a stronger acid than water in dilute aqueous solutions. This presentation will describe the history behind the appearance of the erroneous values, present the thermodynamically-correct derivation of the pKa of water, and show that calculation errors, misinterpretations, and poor referencing have led to the propagation of the incorrect value of 15.7 as the pKa of water, and to the erroneous belief that methanol is a stronger acid than water in aqueous solution.

Propagation of an error: Water's pKa is not 15.7

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.