New Publication: Determination of pKa values of fluorocompounds in water using 19F NMR

Our group is well-known for pKa measurements in different solvents. So far, mostly UV-Vis spectrophotometric method has been used. Recently Elisabeth Parman (on the photo) from our group has been developing a method for measuring pKa values of fluorocompounds, using 19F NMR. NMR measurements to determine pKa values have several advantages compared to UV-Vis spectrophotometry. For example, accurate concentrations are not needed, the method is much more tolerant to impurities and several compounds can be measured simultaneously. The newly developed method has now been published in the Journal of Physical Organic Chemistry: Determination of pKa values of fluorocompounds in water using 19F NMR by E. Parman, L. Toom, S. Selberg and I. Leito.
In this work, the developed method was applied to 19 fluorocompounds – fluorinated phenols, carboxylic acids and sulfonamides, hexafluoroisopropanol (HFIP), perfluoropinacol, etc – with the aim of determining their pKa values in water, in the range from about 3.5 to 10. Several advantages of the 19F NMR method were demonstrated in pKa measurement. In particular, using multiple relative measurements against several reference compounds with known acidities it is possible to obtain highly reliable pKa values. Elisabeth convincingly demonstrated that the literature pKa values of two of the investigated compounds were inaccurate and provided more reliable values for them.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.