EM and the synthesis of ring compounds

A major reason for these disadvantages is that polymerisation can, and 

Because yields of ring products depend on competition between cyclisation and polymerisation, the relevant quantity is the cyclisation constant C (Section 2). However, since cyclisation constants are generally unknown, arguments will be mainly based on the more readily available EM-values. The possible difference in magnitude between the two quantities is relatively unimportant for the purposes of the present discussion. 

The simplest way to carry out a cyclisation reaction is one where the bifunctional reactant M is charged over a relatively short time into the reaction medium, where proper reaction conditions are set. Here short time means that the reaction proceeds to a negligible extent during the addition time. In the absence of competing reactions other than polymerisation, the outcome of a batchwise cyclisation experiment is almost entirely determined by the ratio between [M]o and C, as shown by the plots reported in Fig. 1. 

The difficulties encountered in the synthesis of ring systems with low EM s are partly overcome by the well-known Ziegler high dilution technique (Ziegler et al., 1933). Here the bifunctional reactant M is introduced very slowly into the reaction medium in order to prevent it accumulating. Since 

The rate of feed Vf (in mol 1 s ) of the reactant into the reaction medium is now the critical parameter to adjust for a favourable outcome of a cyclisation experiment. A kinetic treatment of the open system under influxion incurs the same difficulties already discussed for the closed system in Section 

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