  Solvation effect might have a tremendous influence on chemical reactions.
However, precise quantum chemistry calculations are most often done either in
vacuum neglecting the role of the solvent or using continuum solvent model
ignoring its molecular nature. We propose a new method coupling a quantum
description of the solute using electronic density functional theory with a
classical grand-canonical treatment of the solvent using molecular density
functional theory. Unlike previous work, both densities are minimized self
consistently, accounting for mutual polarization of the molecular solvent and
the solute. The electrostatic interaction is accounted using the full electron
density of the solute rather than fitted point charges. The introduced
methodology represents a good compromise between the two main strategies to
tackle solvation effect in quantum calculation. It is computationally more
effective than a direct quantum-mechanics/molecular mechanics coupling,
requiring the exploration of many solvent configurations. Compared to continuum
methods it retains the full molecular-level description of the solvent. We
validate this new framework onto two usual benchmark systems: a water solvated
in water and the symmetrical nucleophilic substitution between chloromethane
and chloride in water. The prediction for the free energy profiles are not yet
fully quantitative compared to experimental data but the most important
features are qualitatively recovered. The method provides a detailed molecular
picture of the evolution of the solvent structure along the reaction pathway.
