ANALYSIS OF SEQUENTIAL REACTIONS

The determination of reaction mechanisms through kinetic analysis is generally a difficult and tedious problem. Ordinarily a mechanism is postulated, analyzed, and tested against the experimental data. If the data do not fit the mechanism, it is modified and the procedure repeated. The test of the mechanism selected usually involves the evaluation of rate constants or composite constants; however, it is the “constancy” of these constants and not their specific values that verifies the satisfactory character of the mechanism. The labor required for success in this indirect approach is strongly dependent on a judicious choice for the post.ulated mechanism. An attempt has been made to develop a method that can relate the kinetic properties directly to the reaction mechanism. In principle the method involves the study of general types of mechanisms to determine the qualitative and quantitative kinetic properties which can be used as distinguishing features. Particular emphasis is placed on properties sensitive to the stoichiometry without regard to the specific values of the rate constants. Such properties have been established for a large class of sequential reactions by a technique combining computer study with mathematical analysis.’ As the use of the computer has been discussed elsewhere,* results primarily due to its application will only be summarized. However, one particular mathematical technique, baaed on the concept of a “stoichiometric reflection coefficient,” will be discussed in greater detail. This technique provides not only a mathematical approach to the analysis of complex mechanisms, but also an experimental method for the partial determination of the mechanism from studies of the stationary or steadystate characteristics.