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

Parker, Vernon D.

doi:10.1351/pac200577111823

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

http://dx.doi.org/10.1351/pac200577111823

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

Abstract:

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 k_f' is the pseudo-first-order rate constant equal to k_f[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.