Electronegative elements electrophilic attack

Proton transfers between electronegative elements, and especially between oxygen and nitrogen acids and bases, are extremely fast and diffusion controlled (18). In fact, acids with completely diffusion-controlled proton transfer reactions are defined as normal acids. In this case, the proton transfer occurs before the rate-determining step of the reaction. In contrast, when carbon atoms are the basic centers, proton transfers usually take place in a slow, rate-determining step. In such reactions, protonation is considered as the electrophilic attack of the... 

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