How do protons catalyze this reaction? The overall process requires the pulling apart of a C-O bond in ethyl acetate, and an O-H bond in water, and a rejoining of the pieces in a different way.

In pure water, we might imagine the reaction to occur via an intermediate activated complex like that at the center in the diagram above. This activated complex, or transition state, would be a very unstable entity, and the reaction would have a high energy of activation, E_a. Chemical reaction by this mechanism would be extremely slow.

The actual proton-catalyzed reaction, as it has been pieced together by chemists after many years of study, is outlined on page 40. Any C-O bond is polarized to some extent, because the oxygen atom is more electronegative than the carbon atom and draws electrons from the double bond to itself. (This slight polarization of charge is represented by delta symbols, d⁺ and d^-, in contrast to + and -, which represent full electron charges.)