Is Coupling Reactions, Heck Reaction for example, different from Coupled Reactions like the production of Glucose 6-phosphate in living organism?


A simplistic answer is as follows (though, please do refer to the links given by Greg in a comment to the question):

According to the University of Wisconsin page Coupling Reactions, coupling reactions are

a reactant-favored reaction is linked to a product-favored reaction so that both reactions yield products.

A main point in the related University of Wisconsin website is that if the reaction is reactant-favoured ($\Delta{G} > 0$), then it is not going to happen, so it is coupled with a product-favoured reaction ($\Delta{G} < 0$), leading to coupled reactions are

When chemical reactions are coupled, the free energy released by the exergonic reaction is used to drive the endergonic one toward the formation of products.

where the overall reation is product-favoured.

(The website uses an analogy of a coupled train).

A great explanation is in this YouTube clip from Dr. John Pollard, of the University of Arizona.

  • 1
    $\begingroup$ The two definitions given here do not distinguish "coupling" and "coupled": they are both alternative statements for "coupled reactions". Coupling in chemistry (i.e. in the context of the Heck reactions mentioned in the original question) is the covalent linking of one molecular entity to another. $\endgroup$
    – The Quark
    May 14 at 9:45

To cite the Oxford Dictionary of Biochemistry and Molecular Biology (2006 - 2nd edition) :

"coupled reaction either of two reactions, one endergonic and the other exergonic, that are linked energetically, occur simultaneously, and share a common intermediate, such that the overall free energy change for the two reactions is negative." (the highlight is by me)

"coupling 1 (in chemistry) the covalent linking of one chemical entity to another; see covalent bond."


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