Constant flow rate experiment, concerns

Rooney has recently revived work on this monomer in an investigation of its polymerisation by trityl hexafluoroantimonate - He used a spectroscopic stop-flow apparatus to follow initiation and an adiabatic calorimeter to measure rates of polymerisation. Propagation was shown to compete effectively with initiation to the point that some initiator was often present at the end of the polymerisations. These observations cast some doubts on the assumption made in the paper by the Liverpool school discussed above. A kinetic analysis of the initiation reaction showed it to be bimolecular, with a rate constant of about 130 sec at 20°C. The determination of the propagation rate constant was less strai tforward despite the fact that further monomer-addition experiments seemed to rule out any appreciable termination. The kp values fluctuated considerably as the initial catalyst concentration was varied, a fact which induced Rooney to propose that the empirical constant was a composite function of kp and kp. Experiments with a common-anion salt supported this proposal and their kinetic treatment led to the individual values of kp = 6 x 10 sec and kp = 5 x 10 sec. It is difficult to assess the reliability of these values in view of the following statement by the author the reaction at a 5 x 10 M concentration of initiator, thought to proceed exclusively through paired ions. .. . This statement is certainly incorrect as far as the initiator is concerned for which the proportion of ion pairs for a concentration 5 x 10 M at 20°C is only about 20% in methylene chloride However, the experiments... 

A surprising amount of insight concerning nuclear spin relaxation can be obtained simply by treating the various available spin states as analogous to chemical states linked by kinetics. Although the spin transition probabilities such as W+ remain to be determined either by experiment or by quantum mechanical theory, as do kinetic rate constants, nevertheless the flow of spins obeys essentially the same kinetic laws as does any other equilibrating system. 

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