Jencks libido rule

Jencks libido rule [9, 10] attempts to identify situations in which proton transfer can be expected to be concerted with the making or breaking of covalent bonds "Concerted general acid-base catalysis of complex reactions in aqueous solution can occur only (a) at sites that undergo a large change in pK in the course of the reaction, and (b) when this change in pK converts an unfavorable to a favorable proton transfer with respect to the catalyst i.e., the pK of the catalyst is intermediate between the initial and final pK values of the substrate site. [9]. 

New systems designed to test this conclusion confirm the central importance of the intramolecular hydrogen bond. Note that the proton transfer in mechanism 3.2 follows Jencks libido rule, evolving from strongly unfavorable in the reactant to strongly favorable in the product so the hydrogen bond could be dose to its strongest in the transition state. 

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See also in sourсe #XX -- [ , , ]

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