Hammett acidity function
To quantify the acidity of superacids led Louis P. Hammett and Alden J. Deyrup 1932, the so-called Hammett function a, since the pH scale by Sørensen suitable only for dilute solutions and the Autoprotolysekonstante is limited to water.
The degree of protonation of a weak organic base in the super acid medium is regarded as a measure of the strength of a super acid.
From the law of mass action for equilibrium we can derive:
with the activity
If one assumes that is the same for different bases in a certain solution, then, if one has determined experimentally, the acid strength can be determined. The experimental determination of can be carried out spectrophotometrically , conductometrically , electrochemically , kinetically , by IR spectroscopy or by NMR spectroscopy .
By Ronald J. Gillespie applies to super acids : .
Depending on the composition, values from −15.1 (HSO 3 F, aHF (a stands for anhydrous = anhydrous)) to −27 (HSO 3 F + SbF 5 ( magic acid ) in a ratio of 1: 9) are possible.
See also
Individual evidence
- ↑ LP Hammett, AJ Deyrup, J. Am. Chem. Soc. 1932 , 54 , 2721. doi: 10.1021 / ja01346a015 .
- ↑ a b G. A. Olah, GKS Prakash, J. Sommer, Superacids , John Wiley & Sons, New York, 1985 .
- ↑ M. Kilpatrick, FE Luborsky, J. Am. Chem. Soc. 1954 , 76 , 5865. doi: 10.1021 / ja01651a098 .
- ↑ M. Couzi, J.-C. Cornut, PV Huong, J. Chem. Phys. 1972 , 56 , 426. doi: 10.1063 / 1.1676884 .
- ^ LP Hammett, Chem. Rev. 1935 , 16 , 67. doi: 10.1021 / cr60053a006 .
- ↑ Gillespie, RJ, Peel TE, Robinson EA, J. Am. Chem. Soc. 1971 , 93 , 5083. doi: 10.1021 / ja00749a021 .
- ^ C. Janiak, TM Klapötke , H.-J. Meyer, E. Riedel, Modern Inorganic Chemistry , 2nd edition, de Gruyter, Berlin, 2004 .