Comparison of Various Quantum Chemistry Methods for the Computation of Equilibrium Constants

Abstract

Ab initio as well as density functional computations have been carried out to test their ability to reproduce experimental equilibrium constants. Three kinds of equilibriums in the gaseous phase have been studied: equilibriums involving nitrogenized compounds or methanol or chlorinated compounds. The basis set effect is also examined. In this work, we show that hybrid HF-DFT and G2 methods seem to be the best adapted to compute this thermodynamic parameter.

Theoretical study of the reaction OH + acetone: a possible kinetic effect of the presence of water?

“…These are in acceptable agreement with the experimental results, 27 in particular in view of the fact that the equilibrium constants depend critically on the computed reaction enthalpies, and (to a lesser extent) reaction entropies. 50,51 Comparison of our theoretical DH1 298 and DS1 298 data, obtained for the equilibrium HO 2 þ H 2 O $ HO 2 Á Á ÁH 2 O, shows a fair agreement with the literature values. 27,52,53 (Table 3).…”

Theoretical Study of the Proton Transfer of Uracil and (Water)n (n = 0−4): Water Stabilization and Mutagenicity for Uracil

“…b Δ(Δ G ) = Δ G (U - n W1 - m W2 → U* - n W1 - m W2) − Δ G (U → U*) , ( n = 0−3, m = 0−3). c Equilibrium constants were calculated (ref ) using free-energy changes with BSSE correction at 298.15 K.…”

Mutagenic Mechanism of the A-T to G-C Transition Induced by 5-Bromouracil: An ab Initio Study

“…The NBO second-order perturbation stabilization energy ∆E 2 is calculated as where F ˆis the Fock operator and i and j correspond to the energy eigenvalues of the donor molecular orbital Φ i and the acceptor molecular orbital Φ j , respectively (25). The equilibrium constant K eq is provided by a statistical thermodynamic treatment (27) with All calculations have been performed with the Gaussian 98 suite of packages (28).…”