Effect of micelles on pKa* of acridine: a spectroscopic study

The effect of anionic, nonionic and cationic surfactants on the protonation reaction of acridine in an excited state has been studied. In the case of sodium decyl sulfate and sodium dodecyl sulfate, the observed shift in pK * to a more alkaline region was +0.6 and +0.9 units (from 9.9 to 10.5 and 10.8 respectively), which corresponds to a decrease in the Gibbs free energy by 3.5 and 5.0 kJ mol^–1.