Accessing reaction rate constants in on-column reaction chromatography: an extended unified equation for reaction educts and products with different response factors.

An extension of the unified equation of chromatography to directly access reaction rate constants k(1) of first-order reaction in on-column chromatography is presented. This extended equation reflects different response factors in the detection of the reaction educt and product which arise from structural changes by elimination or addition, e.g., under pseudo-first-order reaction conditions. The reaction rate constants k(1) and Gibbs activation energies DeltaG(double dagger) of first-order reactions taking place in a chromatographic system can be directly calculated from the chromatographic parameters, i.e., retention times of the educt E and product P (t(R)(A) and t(R)(B)), peak widths at half height (w(A) and w(B)), the relative plateau height (h(p)) of the conversion profile, and the individual response factors f(A) and f(B). The evaluation of on-column reaction gas chromatographic experiments is exemplified by the evaluation of elution profiles obtained by ring-closing metathesis reaction of N,N-diallytrifluoroacetamide in presence of Grubbs second-generation catalyst, dissolved in polydimethylsiloxane (GE SE 30).