Conformational preferences of 2-isopropylaminoethanol in aqueous solution using the CPCM continuum solvation model

All possible conformers of 2-Isopropylaminoethanol (2-IPAE) have been optimized in aqueous solution at the DFT level of theory [B3LYP/6-311++G(d,p)] using the conductor-like polarizable continuum model (CPCM). The Gibbs energies of solvation of all conformers, as well as their components, have been computed and discussed. The differences of ΔGsolv between conformers are essentially determined by the electrostatic component. The conformers exhibiting an O-H···N intramolecular H-bond predominate in the gas phase equilibrium, but in aqueous solution their contribution is greatly reduced. On the contrary, conformers with a trans orientation around the OCCN dihedral and those with a gauche OCCN but without intramolecular H-bond increase significantly their population in solution. The effect of the OH group orientation on solvation has been deeply investigated by means of scans of the Gibbs energy of solvation around the HOCC dihedral for different backbone structures. Local solvation around the polar groups has also been investigated by calculating and comparing the interaction energies of the NH and OH groups with one water molecule. The optimized monohydrates, as well as the BSSE corrected interaction energies, were obtained at the B3LYP/6-311++G(d,p) level of theory.