Kinetic analysis of the Rebek self-replicating system: Is there a controversy?

The Rebek self-replication reaction of 1 and 2, catalyzed by complexation of both reactants to the resulting product 3 (Tijivikua, T.; et al. J. Am. Chem. Soc. 1990, 112, 1249-1250. Nowick, J. S.; et al. J. Am. chem. Soc. 1991, 113, 8831-8839. Wintner, E. A.; et al. Acc. Chem. Res. 1994, 27, 198-203. Conn, M. M.; et al. J. Am. Chem. Soc. 1994, 116, 8823-8824), and related work of Menger et al. (Menger, F. M.; et al. J. Am. Chem. Soc. 1994, 116, 3613-3614, Menger, F. M.; et al. J. Org. Chem. 1995, 60, 2870-2878) have been reinvestigated. On the basis of our experiments with the same systems and comparing the absolute rates of different (model) reactions, we have identified five pathways of the reaction between 1 and 2 in the presence of template 3: background (k(1) = 0.035 M(-1) min(-1)), preassociative (k(2) = 0.0044 min(-1)), termolecular (k(3) = 0.030 min(-1)), and two bimolecular (k(4) = 0.130 M(-1) min(-1), k(5) = 0.020 M(-1) min(-1)). A general kinetic model for self-replicating reactions has been used to analyze the Rebek-Menger controversy. We conclude that self-replication as defined by Rebek et al. operates in this system; other pathways obscure the simple picture of a ternary complex as the only complex that leads to the rate enhancement and one of those (bimolecular) pathways is proposed by Menger et al. Our results show that when 1 and 2 are complexed to 3 in a termolecular complex, the rate of reaction between 1 and 2 is 6.8 times (k(3)/k(2)) faster than when 3 is formed from the bimolecular complex of 1 and 2, and this rate enhancement factor represents the efficiency of template 3 in the self-replication process.