Journal of Chemical Thermodynamics, Vol.54, 346-351, 2012
Thermochemical and structural properties of DMAN-"proton sponges"
We report a study on the energetics and structural properties of naphthalene-based proton sponges and their corresponding protonated cations. In particular, we have determined the experimental standard enthalpies of formation in the gas phase at T = 298.15 K, Delta fH(m)(o) m (g), for the neutral and protonated DMAN [1,8-bis (dimethylamino)-naphthalene], (221.0 +/- 7.3) and (729.0 +/- 11.1) kJ.mol(-1), respectively. A reliable experimental estimation of enthalpy associated with "strain'' effect and hydrogen bond intramolecular (included within "enhanced basicity'', EB) contributions to the basicity of DMAN, were deduced from isodesmic reactions, -(29.1 +/- 4.6) and (87.1 +/- 11.9) kJ.mol(-1), respectively. The gas-phase basicities (GB) of naphthalene-based proton sponges are compared with the corresponding aqueous basicities (pKa), covering a range of 149 kJ.mol(-1) in GB and 11.5 in pKa. Density functional calculations at the M05-2X/6-311++G(d,p) level of theory were used to check the consistency of the experimental results and also to estimate the unavailable GB values of the considered species. (C) 2012 Elsevier Ltd. All rights reserved.