Effect of the competition between the self aggrgation and hydrocarbon-perfluorocarbon interaction on the reactivity of p-nitrophenyl perfluorooctanoate

MARIANA ADELA FERNÁNDEZ; RITA HOYOS DE ROSSI

Roma, Italia

Simposio; 10th European Symposium on Organic Reactivity; 2005

ESOR Conferences

Fluorinated surfactants are more hydrophobic than their hydrogenated counterparts. This difference is manifested in a number of properties that are relevant to applications, e.g. lower critical micelar concentration, cmc, and greather surface activity. We have demonstrated that N-(4-nitrophenyl) perfluorononanamide forms aggregates at concentrations as low as 2x10-6 M. The addition of perfluorononanoic acid or sodium dodecyl sulfate leads to the breakdown of this aggregates at a rate slow enough to be monitored with a conventional UV-vis spectrophotometer.1 Similar results were reported for other cationic and non ionic surfactants.2 We now report the effect of several cationic, anionic and non-ionic surfactants on the hydrolysis reaction of p-nitrophenyl perfluorooctanoate. This compound is aggregated at 8x10-6 M concentration in water and its reactivity is several order of magnitude smaller than expected for a perfluoralkyl ester. The effect of the surfactants on the kinetic of the reactions is strongly dependent on the head group of the surfactant and this is in term attributed to the interaction with the polar transition state of the hydrolysis reaction. With anionic surfactants, perfluorooctanoate and dodecyl sulfate, the observed effect on the rate of hydrolysis seems to be mainly dependent on the interactions of the substrate with the alkyl chain of the surfactants. On the other hand the effect of cationic surfactants is more strongly dependent on the counterion than on the hydrocarbon chain length. All the surfactants breakdown the substrate aggregates and in some cases the rate of hydrolysis and deaggregation are of similar order of magnitude. References (1) Granados, A. M.; Fidelio, G.D.; de Rossi R. H. Langmuir 1997,13, 4079. (2) Fernandez, M. A.; Granados, A. M.; El Seoud, O.A. ; de Rossi R. H. Langmuir 2002, 18, 8786