H (kcal/mol) B = KOtBu NaOEt NaOPh 18.8 19.3 20.2 decreasing basicity, decreasing [BH]/[B-], less exothermic, later, higher-energy TS. H (kcal/mol) X = OBz OAc Cl 20.6 19.8 19.3 increasing leavinggroup quality, more exothermic, earlier, lower-energy TS. Can model reaction coordinate as inverse parabolic potential well. What happens when we make X a better leaving group? Model by tilting entire plot forward. What happens when we make X a better leaving group?