Figure 2. Correlation between changes in the Gibbs free energy (∆G) for the A- + CO2 reactions in the gas phase and the gas phase basicity (GPB) of the anions. Also indicated is the square of the residuals.
The nature of the atom that interacts with CO2determines the changes in the Gibbs free energies (figure 3). Specifically, the reactions with anions containing nitrogen atoms are found to be more spontaneous than those with analog anions containing oxygen, followed by those containing phosphorous and then sulfur atoms (Figure 3). The anions CH3-, H-, NH2- and OH-, which do not have any special stabilization effect and are small species, are among those leading to the most negative change in the Gibbs free energy.