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Reaction intermediates?

Posted: Sat Mar 09, 2019 8:52 pm
by chloewinnett1L
I know Prof. Lavelle mentioned that intermediates are not products, but what exactly are they? How do we account for them when consolidating the steps of a multistep reaction?

Re: Reaction intermediates?

Posted: Sat Mar 09, 2019 9:39 pm
by Steven Garcia 1H
Intermediates will be the product of one elementary rxn step and the reactant of the following elementary rxn step. For this reason, the intermediate does not appear in the overall chemical equation (we expect it to cancel with itself when adding the elementary rxn steps). However the concentration of an intermediate can show up in the rate law of an individual elementary reaction just like we discussed before with other reactants. However, it will shouldn't appear in the overall rate law!

You can account for an intermediate in the overall rate rxn by setting its net formation to equal zero and then solving for the intermediate in terms other than itself (refer to textbook if this sounds unfamiliar to you). You can then substitute this new term in place of the intermediate in the overall rate law.

Hope this helps!