KINETIC-ANALYSIS OF THE REBEK SELF-REPLICATING SYSTEM - IS THERE A CONTROVERSY

The Rebek self-replication reaction of 1 and 2, catalyzed by complexat ion 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. Re s. 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 o ur experiments with the same systems and comparing the absolute rates of different (model) reactions, we have identified five pathways of th e 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)), t ermolecular (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 fo r 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 pictur e of a ternary complex as the only complex that leads to the rate enha ncement 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 term olecular 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 o f template 3 in the self-replication process.