A computational study of solvent effects on the conformation of dopamine

Conformation and interactions of dopamine hydrochloride in solution

“…Indeed, the low energy barrier to rotation between the C-C alk1 -C alk2 -N and C Ar -C-C alk1 -C alk2 conformations is noted in numerous theoretical studies. 22,24,25,41 Furthermore, the optimised geometries of selected conformers calculated by DFT often predict non-ideal angles, e.g., transperpendicular has torsion angles of 97. C Ar -C-C alk1 -C alk2 group and the C-C alk1 -C alk2 -N groups, respectively.…”

“…Both Bustard and Egan 21 and Solmajer et al 20 found that at pH 7.4, the gauche:trans conformer ratio was ∼58:42 about the C-C-C-N ϕ 2 torsion angle (selected conformers are depicted in Figure 1). Using theoretical calculations, Urban et al 25 corroborated the importance of solvent effects on the conformer ratio compared to gas phase calculations, while ab-initio density functional theory (DFT) calculations by Alagona and Ghio 23 showed the transperpendicular and gauche-perpendicular conformers to have similar stabilities in aqueous solution. The gauche conformations of the C-C-C-N group enable the NH 3 + group to interact with the π-system of the ring, while the trans conformers of the group are stabilised by the solvent.…”

Quantum-chemical, NMR and X-ray diffraction studies on (±)-1-[3,4-(methylenedioxy)phenyl]-2-methylaminopropane

“…These results are in complete disagreement with the conformer distribution obtained from the experimental data (see Table 1). It may be mentioned that a similar apparent failure of the semiempirical AM1 methodology to account for the relative abundance of the conformers of N-protonated dopamine in polar media has been reported [27].…”

“…Thus, in aqueous solution, protonated MDMA should exist mainly as the ''extended'' conformer A, although the contribution of the ''folded'' form S 1 is by no means negligible, while rotamer S 2 is practically absent, unlike the situation found for the free base in CDCl 3 where these less favored conformers may contribute significantly to the equilibrium mixture. An increased preference for the rotamer with a trans relationship between the benzene ring and the nitrogen atom seems reasonable, considering that in aqueous solution the ammonium function should be strongly hydrated, and that its effective volume should thus be much greater than that of the naked amino group in CDCl 3 [27].…”

Semiempirical calculations of the oxygen equilibrium isotope effect on binding of oxamate to lactate dehydrogenase

“…Several methods of accounting for solvent effects on a semiempirical level have been recently described in the literature (Karelson et al 1989;Truhlar 1991b, 1992;Luzkhov and Warshel 1992) but their accuracy has been primarily tested by evaluating their ability to reproduce free energies of solvation. Only the latest few studies attempted to predict such phenomena as tautomeric or conformational equilibria in solution (Katritzky and Karelson 1991;Urban et al 1992). The applicability of these methods to the vibrational analysis of molecules in solution is still debatable.…”