CHEMICAL STRUCTURE AND ADSORPTION OF ORGANIC MOLECULES AT THE POLARIZED MERCURY–ELECTROLYTE INTERFACE

Abstract

Previous studies on electrochemical adsorption at mercury of a series of heterocyclic and aromatic nitrogen bases and their respective conjugate ions by electrocapillary measurements are extended to simple saturated heterocyclic compounds containing oxygen and to aliphatic alcohols with different degrees of unsaturation. Adsorption isotherms for various electrode potentials are derived, and standard electrochemical free energies of adsorption are calculated as before, to relate the influence of molecular and electronic structure of the adsorbates on the properties of the electrical double layer. Oxygen as the heteroatom in cyclic compounds and in the hydroxyl group of the alcohols plays a distinct role in the characteristics of metal–adsorbate and adsorbate–solvent interactions through its higher electronegativity as compared with nitrogen. Considerations of the different geometric areas of adsorbed molecules due to isomerism of the saturated heterocyclic compounds, and the varying unsaturation of the alcohols lead to more realistic interpretation of orientation effects, surface coverages, and degrees of adsorbability. Improvement in pressure control in the electrocapillarometer assembly gives better precision in surface tension measurements. Some preliminary results on the adsorption of furfurylamines and related analogues which constitute a newly available class of corrosion inhibitors are briefly discussed.