Reaction Schemes That Are Easily Confused with a Reversible First–Order Reaction

A detailed kinetic analysis of two schemes, one involving coupled consecutive processes and another featuring the simultaneous association reaction and decay of a component, is presented here using Taylor series expansion. It is shown that both of these schemes are easily confused with the reversible second–order reaction in a routine kinetic study. The kinetic traces predicted by both schemes are sufficiently close to pseudo–first–order curves so that it is practically impossible to identify the deviations based on data with the usual experimental errors, which was also demonstrated by fitting simulated theoretical curves to exponential functions. The dependence of the pseudo–first–order rate constants on the concentration of the excess reagent features the same trend as in the case of a reversible reaction: A straight line with an intercept is observed. This analysis emphasizes that the reversible nature of reactions should be demonstrated by direct equilibrium studies when elements of reversibility are implied by kinetic results.