ON THE NATURE OF THE NONANOIC ACID MONOLAYER ADSORBED AT THE HG AQUEOUS SOLUTION INTERFACE - INFLUENCE OF CONFORMATIONAL FREEDOM IN BULK AQUEOUS-SOLUTION/

The adsorption of the nonanoic acid at the electrified Hg/aqueous solu tion interface is studied by means of capacity and surface tension mea surements. Comparison of the experimental Gamma(max) value with the ca lculated more favoured solvated conformation suggests that the acid is adsorbed in a partially coiled conformation. The adsorption free ener gy here determined, together with previously reported values found in the literature concerning other saturated acids and alcohols, is compa red with reactivity and calculated molecular descriptors. The collecte d evidence suggests that the hydrophobic nature of the acid is respons ible for the adsorption, while the electric field/molecule interaction , occurring at the electrified interface, governs the desorption. Last ly, some experimental (capacitive transients, effect of the temperatur e on the tensammetric curves) and theoretical findings are discussed w hich indicate that the adsorbed acid monolayer should be regarded as a usual, in the field of adsorption at electrodes, disordered network. Thus excluding the occurrence of a two-dimensional phase transition in volving the formation of a 2D solid-like film.