Principle of imperfect synchronization

In connection with factors 2 and 3, it has been proposed that any factor that stabilizes the product (e.g., by resonance or solvation) lowers the rate constant if it develops late on the reaction coordinate, but increases the rate constant if it develops early. This is called the principle of imperfect synchronization. 

This year marks the 25th anniversary of the principle of nonperfect synchronization (PNS) it was introduced in 19851 as the principle of imperfect synchronization (PIS) but in later papers and reviews2 4 the name was changed due to the awkwardness of the acronym PIS. The foundations of the PNS rest mainly on a marriage between two fundamental concepts of physical organic chemistry, i.e., the concept of intrinsic barriers and that of transition state imbalances. 

One of the key goals of physical organic chemistry is to understand variation in reaction barriers resulting from reactant and solvent variation. In Chapter 8, Bernasconi uses his intriguing principle of imperfect synchronization to explain trends in intrinsic barriers resulting from substituent... 

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