I am studying a proton transfer reaction from benzoic acid to two different molecules. One molecule has two oxygen (O1, O2) atoms to abstract the proton while the other molecule has one oxygen (O3). The reaction barrier (Free energy of activation) is calculated to be higher (by 8 kcal/mol) for the former molecule than the latter. How do I compare the reaction paths? It is obvious the reaction will be faster for the latter molecule (low barrier) however, does two reaction sites in the first molecule affect the overall rate of reaction and make it comparable to the proton transfer rate to 2nd molecule?
If we consider all the proton transfers are equally probable and the reactions follow a parallel mechanism then the yield of proton transfer product is the ratio of the individual rate constants. Presence of another proton transfer channel does not affect other rate constants, it affects the yield of the particular channel. For example, if the rate constant (energy barrier) of two channels are same you will get two product with the same yield. Rate is entire about the energy barrier since the first molecule has higher energy of activation this path will not be favoured in the reaction. Having another Oxygen will not change the scenario (unless it helps decreasing the energy barrier).
Tuhin Khan Thank you for the detailed answer. Yes, that makes sense. However, I am considering the overall rate of deprotonation of benzoic acid. Though, the molecule with two possible sites for reaction have higher reaction barrier, however, if we consider that both the sites are taking part in the deprotonation and add up the two rates by two sites, that might come up with a higher overall rate than the molecule with lower barrier. What do you say?
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