section_path: Rationalizing the strength of Lewis acid–base interactions/ECW model
section_name: ECW model
paragraph_text: ECW model
  
  The ECW model created by Russell S. Drago is a quantitative model that describes and predicts the strength of Lewis acid base interactions, −Δ H. The model assigned E and C parameters to many Lewis acids and bases. Each acid is characterized by an E and a C. Each base is likewise characterized by its own E and C. The E and C parameters refer, respectively, to the electrostatic and covalent contributions to the strength of the bonds that the acid and base will form. The equation is − Δ H = E A E B + C A C B + W {\displaystyle -\Delta H=E_{\rm {A}}E_{\rm {B}}+C_{\rm {A}}C_{\rm {B}}+W}
  
  The W term represents a constant energy contribution for acid–base reaction such as the cleavage of a dimeric acid or base. The equation predicts reversal of acids and base strengths. The graphical presentations of the equation show that there is no single order of Lewis base strengths or Lewis acid strengths.