The data in Table show that the added Lewis acid has a substantial effect on the acidity of the Brønsted acids. FeCl3 provides more stabilization to chloride ion than to trifluoroacetate (ΔΔG° = -6.7 kcal•mol -1 ) and more stabilization than FeBr3 provides to bromide ion (ΔΔG° = -2.8 kcal•mol -1 ). In addition, the biggest increase is achieved for the HF/BF3 These results suggest a synergistic effect between the conjugate base and Lewis acid may be a significant factor for determining We next used eq. 6 to gain a better sense for the acidity of the HA/L pairs relative to HCl/FeCl3 to assess their overall reactivity: