Influence of solvents on the properties of chemical compounds

Theoretical description of solvent effects. V. The medium influence on the lactim‐lactam tautomerism of hydroxyazines

“…The terms E,,, and EvdW of the corresponding tautomers were calculated by means of formerly reviewed models using the macroscopic surface tension for E,,, and classical potential functions for Evdw [43], respectively. In order to estimate the electrostatic contribution to the solvation energy we have used two principally different models both in a classical (A) and in a quantum chemical (B) version.…”

“…rAB represents the distance between the atoms A and B and rAAr is a n empirical parameter, which has a value of 0.8 A for all atoms. The cavity radius R necessary for the reaction field calculations and the estimation of the cavity energy follows from simple geometricd considerations of the solute molecule [43].…”

Theoretical conformational analysis considering solvent effects

“…Based on a continuum model calculation, a qualitative explanation for the destabilization of the perpendicular conformation relative to the planar form was given considering the distinctly different values of the dipole moments in both arrangements [7]. For this system, it can be expected that specific solute-solvent interactions may be of decisive importance for the solvation process.…”

“…The comparison between a value of 18.2 kcal/mol [12] obtained by means of exact calculations on the basis of the general valence-bond concept and the value of 2 1.3 kcal/mol experimentally determined in water [ 131 indicates the strong influence of the solvent. Based on a continuum model calculation, a qualitative explanation for the destabilization of the perpendicular conformation relative to the planar form was given considering the distinctly different values of the dipole moments in both arrangements [7]. For this system, it can be expected that specific solute-solvent interactions may be of decisive importance for the solvation process.…”

“…For such cases, the situation in solution can often satisfactorily be described based on the classical continuum model considering above all the electrostatic energy and the van der Waals interaction energy between the solute and the solvent continuum and the cavitation energy. Therefore, we have used for this case a continuum model version described in former papers [7,22,23]. There are some indications that the coenzyme is placed in a strongly apolar region of the enzyme [ 171.…”