6533b82cfe1ef96bd128eacf
RESEARCH PRODUCT
Substituent effects on the mechanism changeover in a multipathway reaction: A model for the behavior of biological systems?
Giovanni PetrilloSusanna GuernelliDomenico SpinelliVincenzo FrennaFrancesca D'annaGabriella MacalusoEgon Rizzatosubject
substituents effectbase-catalysiProtonStereochemistryChemistryOrganic ChemistrySubstituentChangeoverSettore CHIM/06 - Chimica OrganicaCatalysisSolventTurn (biochemistry)chemistry.chemical_compoundComputational chemistryMechanism (philosophy)Reactivity (chemistry)mononuclear rearrangementdescription
By studying the rearrangement in dioxane/water of a series of (Z)-arylhydrazones of 5-amino-3- benzoyl-1,2,4-oxadiazole (1a-k) into the relevant (2-aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas (2a-k) in a wide range of pS + (an operational scale of proton concentration in the mixed solvent used; dioxane/water, 1:1, v:v), the occurrence of three different reaction pathways (specific-acid- catalyzed, uncatalyzed, and general-base-catalyzed) for the relevant SNi process has been recently enlightened. The significantly different substituent effects on the three pathways cause some crossovers in the log kA,R versus pS + plots. Both the pS + value at which the crossover occurs and the width of the uncatalyzed pathway appear in turn substituent-dependent. Thus, thanks to the wide and complete range of substituents examined, the data obtained have been treated by using free-energy relationships. Interestingly enough, these results also furnish valuable information concerning the effects of "small" variations in chemical structures able to produce "large" reactivity variations in some way recalling what can occur in biological systems.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2009-01-01 |