Abstract We have investigated the effects of a thin, structureless dielectric layer between a metal electrode and a surrounding aqueous solution on the electrostatic work terms, the solvent reorganization energy and the rate of simple electrochemical processes. This layer represents the compact double-layer or a region enriched in the organic component in mixed aqueous—organic solvents. Close to the electrode the work terms increase due to less favourable solvation. This effect is, however, only significant for very small ions. The solvent reorganization energy first increases due to resolvation of an infinite manifold of image charges in addition to the real ion. As the ion crosses the boundary to the interlayer, the solvent reorganization energy drops drastically due to the low polarity of this region. As a result, electron transfer from the contact distance of the ion to the metal surface, i.e. inside the interlayer, is always more favourable than electron transfer across the layer.