This LO was created to introduce Drago’s ECW model, which is an important contribution to the discussion of Lewis acid-base interactions. Unlike the qualitative Pearson’s HSAB model (Hard Soft Acid-Base model,) the quantitative ECW model can be used to correlate and predict the enthalpies of adduct formation and to obtain enthalpy changes for displacement or exchange reactions involving many Lewis acids and bases.  Unlike all other acid-base models, graphical displays of the ECW model clearly show that there is no one order of acid or base strengths, and illustrate that two parameters are needed for each acid and base to provide an order of acid or base strength.  The ECW model can also provide a measure of steric strain energy or pi bonding stabilization energy accompanying adduct formation, which is not possible with any other acid-base model. 

This set of slides is intended to provide a basic introduction to the model and several examples of predicting energy changes using the model. It also illustrates how to construct and interpret a graphical display of the model.

 It should be noted that this LO is not in the PowerPoint format, but instead is a more extensive set of notes for instructors who are not familiar with the ECW model. It could be condensed and rewritten in the more standard PowerPoint format.

There is also an ECW problem set LO that can used to supplement this LO.