An explicit set of general methods for the experimental determination of the rates k1 and k2 of consecutive pseudo-first-order reactions is described and discussed. These rely on the direct simultaneous analytical quantitation of the starting material, intermediate, and product of the reaction, and thus differ from present techniques based on measurement of coreactant consumption or coproduct appearance. The quantity kenv = k1k2/(k1 + k2) is shown to define a good “envelope” approximation to product formation according to the simple law 100% [1 − exp(−kenvt)]. The theory of envelopes is useful for comparing overall rates of reactions with widely differing values of κ = k2/k1. The kinetic pattern of thiolysis of dithiasuccinoyl amino acids to carbamoyl disulfide intermediates to product free amino acids is analyzed and shown to agree quantitatively with theory.
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Supported by U. S. Public Health Service Research Fellowship 5 F 32 AM 05806-02. I thank Professor Bruce Merrifield for his encouragement and support. and Dr. Jeff Geronimo for going over mathematics of this paper.
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