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Determination of pKa at the air/water interface by second harmonic generation

✍ Scribed by Xiaolin Zhao; Suchitra Subrahmanyan; Kenneth B. Eisenthal

Publisher: Elsevier Science
Year: 1990
Tongue: English
Weight: 457 KB
Volume: 171
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(90)85263-c

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✦ Synopsis

We have used second harmonic generation to directly observe chemical changes in a lipid monolayer. We observed that pK, of phexadecyl aniline at the air/water interface is 3.6& 0.2 versus 5.3 fO.l in the bulk. This fiftyfold increase in acidity is due to the higher free energy of a charged species at the air/water interface, which favors a shift in the equilibrium towards the neutral form.

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