Dissociative mechanism competition ratios

A concerted insertion mechanism with highly ordered transition state, close to three-centered, was corroborated by examination of the kinetic isotope effect, which was measured by competitive GeC insertion reactions into the C—Cl bonds of labeled 14CCl4 and 12CC14. The value obtained, ku/k 2 = 1.01 0.01, is very close to that calculated from the stretching frequencies and the ratio of the masses and moments of inertia of the isotopic molecules for a synchronous reaction (0.993) and differs significantly from the calculated value for a dissociative mechanism (0.900)52. 

We have briefly looked at the electronic effects on this mechanism by the competition experiment of two primary alcohols (2-phenethyl ethanol and benzyl alcohol). The information we obtained only explained the importance of the nucleophilicity of the alcohol. In order to determine the electronic effects on the dissociating alcohol, an experiment could be performed that treats the silyl ether of a primary alcohol with a second primary alcohol, both alcohols having different electronic environments (Scheme 40). The ratio of exchange product (B) to expected product (A) would be an indication of the effect of the electronic environment on the dissociating alcohol in intermediate IV of Figure 11. 

The base catalyzed solvolysis and substitution reactions of cobalt(III) complexes has provided some of the most fertile ground for the study of dissociatively activated processes and the attempts to distinguish between and D mechanisms in terms of the lifetime of the intermediate species. The dissociative intimate mechanism has been demonstrated by a variety of trapping, competition and stereochemical studies, The base catalyzed substitutions of [Co(NH3)5X]"+, in which addition of small amounts of OH in the presence of excess leads to a mixture of [Co(NH3)5Y] and [Co(NH3)50H], are all consistent with a dissociatively activated process in which there is competition between Y and H2O for the place vacated by At the first approximation, the ratio... 

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