**6. Conclusions**

In this chapter some theoretical and experimental reports in order to elucidate solvent effects over nucleophilic aromatic substitution reactions were examined. Solvent effects are introduced over mechanistic behaviors highlighting the HB role mainly in RTILs, a new generation of solvents that can be designed in order to improve the reactivities of the reacting pair and intermediate species through the PES. For instance, (i) solvent polarity could be modulating the reaction pathways differently; (ii) the ability of the solvent to establish HB could drive the reaction mechanism opening the possibility of preferential solvation; (iii) in mixtures of solvents and depending on the constituents of them could be affecting the reaction rate by solvent structural organization, viscosity, and HB interactions; and (iv) in ionic liquids the solvent effect could be attributed to an anion effect being it related to the size and HB abilities of the anions.
