Liquid-phase geometry optimization

There are no structural data known for carbonyl bromide fluoride. In particular, the microwave spectrum of COBrF has not been recorded, and no X-ray diffraction or electron diffraction studies have been performed. For this reason, the geometries of the molecule in the gas, liquid or solid phases are unknown, and calculations on COBrF that have required bond length and bond angle data have been performed using the known parameters of "closely related" molecules, or from geometry optimization calculations [2251b,2251c]. 

Oi>timization of bond lengths or bond angles. Complete optimization of geometry. Gas phase. Liquid phase. Solution in 1 1 dimetboxymethane-heptane. 

To verify the mechanism presented, the quantum-chemical calculations of proton affinity, Aa, were carried out for modifiers, since the corresponding experimental data are quite rare. The calculations were performed for isolated molecules, since the properties of species in the interlayer space are probably closer to the gas phase rather than the liquid. The values of Ah were calculated as a difference in the total energy between the initial and protonated forms of the modifier. Energies were calculated using the TZV(2df, 2p) basis and MP2 electron correlation correction. Preliminarily, geometries were fully optimized in the framework of the MP2/6-31G(d, p) calculation. The GAMESS suite of ah initio programs was employed [10]. Comparison between the calculated at 0 K proton affinities for water (7.46 eV) and dioxane (8.50 eV) and the experimental data 7.50 eV and 8.42 eV at 298 K, respectively (see [11]), demonstrates a sufficient accuracy of the calculation. 

In practice we often neglect the distinction between AG and AGg(x), although sometimes it is important to optimize the geometry in solution21 or to at least include the conformational part.14 (If one did try to include the rotational part, one would run into the problem that the 3 gas-phase rotations are converted in liquid solution into low-frequency librations that are strongly coupled to low-energy solvent motions). In the rest of this section... 

---