The nature of cation-pi binding: interactions between tetramethylammonium ion and benzene in aqueous solution.
A combined quantum mechanical and molecular mechanical Monte Carlo simulation method was used to determine the free energy of binding between tetramethylammonium ion (TMA+) and benzene in water. The computed free energy as a function of distance (the potential of mean force) has two minima that represent contact and solvent-separated complexes. These species are separated by a broad barrier of about 3 kJ/mol. The results are in good accord with experimental data and suggest that TMA+ binds to benzene more favorably than to chloride ion, with an association constant of about 0.8 M-1.
Gao
J
J
Department of Chemistry, State University of New York, Buffalo 14214.
Chou
L W
LW
Auerbach
A
A
D001554:Benzene / Q000737:chemistry*; D055592:Biophysical Phenomena; D001703:Biophysics; D002412:Cations / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009010:Monte Carlo Method; D011789:Quantum Theory; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012996:Solutions; D013816:Thermodynamics; D014867:Water
D002412:Cations; D000644:Quaternary Ammonium Compounds; D012996:Solutions; D014867:Water; C027917:tetramethylammonium; D001554:Benzene