Currently, a wide variety of organic chemistry textbooks list the pKa of water as around 15.7, while many general chemistry textbooks list it as 14.0. The goal of this experiment is to quantify the relative acidity of several weak organic acids, while demonstrating the correct pKa value of water is 14.0. This clarification is important as reporting two pKa’s of water is confusing to students and is also thermodynamically indefensible. Using a previously published NMR method, the pKa’s of several alcohols were measured and compared to that of water. Aqueous solutions of alcohols containing high concentrations of hydroxide were monitored using proton-decoupled 13C NMR. Observed shifts in peak position with hydroxide concentration were used to construct titration curves and measure pKa of the alcohols. In addition to determination of relative acidities, unexpected splitting in the carbon spectra at very high pH is also investigated.

Quantitative measurement of the relative acidities of alcohols in water

2019 Spring National Meeting

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