Syntheses of Many-Membered Rings. Computer Simulated Kinetics of Irreversible Cyclization of Bifunctional Chains under Ziegler High Dilution Conditions

The reaction of a bifunctional reactant A--B under Ziegler high-dilution (influxion)conditions to give families of oligomeric macrocycles has been simulated by numerical integration of the proper system of differential rate equations. This was set up considering all the possible processes of concurrent cyclisation and polymerisation up to a polymerisation degree of 12. In order to obtain meaningful data for the yields of the cyclooligomers, realistic sets of effective molarities (EM) have been considered. The results show how the yields of the various cyclooligomers vary as a function of the monomer feed rate, and provide useful guidelines to achieve maximum selectivity in the synthesis of a given ring. Merits and limitations of more simplified kinetic schemes dealing with the monomeric ring only are outlined by the present calculations. A comparison with the batch-wise procedure shows that the two techniques give somewhat analogous results in terms of yields and selectivities. The criteria of choice between the two procedures, which are established on the basis of practical convenience, are indicated.