What is the difference between "reaction pathway" and "reaction mechanism"?
Are these expressions synonyms?
Some textbooks authors use both without making clear to the learner if they are synonyms or not.
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3 Answers
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Usually with the reaction mechanism the sequence of events (electron transfers) is indicated, while the term reaction pathway usually refers to the reaction coordinate diagram associated with the reaction, i.e. the change in energy with an extra notion on the transition states.
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3$\begingroup$ Just to expound, a reaction pathway deals with the potential energy landscape for a given reaction mechanism. $\endgroup$ Commented Jan 5, 2015 at 20:34
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As far as my knowledge is concerned when we talk about Reaction Mechanism then we mean the Steps through which the reactants are passed and reach to the Product. Say for example the making of water from Hydrogen and Oxygen which involves 40 steps and at the end we get what we know H2 +1/2 O2 giving H2O Another example can be the chlorination of Methane to form CCl4. While in Reaction pathway we talk about the inside of the reactions involved like talking about electrons movement .
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No, Khair Muhammabd. Go through the reaction mechanism. Actually, the reaction mechanism is about sequence and detailed understanding of elementary reactions(that are here called elementary steps in the term of Composite Reaction) for conversion of reactants to the desired products. It is accompanied with the formation of Reaction Intermediate at each elementary step(except last one). Where the overall reaction can be obtained by adding all elementary reactions together. So as the overall rate of reaction can be obtained by adding the rates of all elementary steps. But what happens, every composite reaction has one elementary step (Mostly 1st step) that is carried out very fast as compared to other steps. Say, T1=1sec for 1st step. and T2=0.0000000001 sec reaction. So the total time of the composite reaction will almost be equal to first step (T(total)=T1) while T2 is neglected. Basically the first step is called Rate dertermining step(RDS). So overall reaction rate will be taken equal to the rate of RDS. R(r*n)=R(RDS). While I know nothing about Reaction Pathways, still going through it.