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Pure Appl. Chem., 2005, Vol. 77, No. 11, pp. 1823-1833

Is the single transition-state model appropriate for the fundamental reactions of organic chemistry?

Vernon D. Parker

Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300, USA

In recent years, we have reported that a number of organic reactions generally believed to follow simple second-order kinetics actually follow a more complex mechanism. This mechanism, the reversible consecutive second-order mechanism, involves the reversible formation of a kinetically significant reactant complex intermediate followed by irreversible product formation. The mechanism is illustrated for the general reaction between reactant and excess reagent under pseudo-first-order conditions in eq. i where kf' is the pseudo-first-order rate constant equal to kf[Excess Reagent].
Reactant + Excess reagent = Reactant complex = Products (i)
The mechanisms are determined for the various systems, and the kinetics of the complex mechanisms are resolved by our "non-steady-state kinetic data analysis". The basis for the non-steady-state kinetic method will be presented along with examples. The problems encountered in attempting to identify intermediates formed in low concentration will be discussed.