Croatica Chemica Acta, Vol. 89 No. 3, 2016.
Izvorni znanstveni članak
https://doi.org/10.5562/cca3040
Nucleofugality of Pentafluorophenolate in Various Solvents: Solvolytic Behavior of Phenolates
Mirela Matić
; University of Zagreb, Faculty of Pharmacy and Biochemistry, Ante Kovačića 1, HR-10000 Zagreb, Croatia
Nives Bebek
; University of Zagreb, Faculty of Pharmacy and Biochemistry, Ante Kovačića 1, HR-10000 Zagreb, Croatia
Bernard Denegri
orcid.org/0000-0001-6335-6723
; University of Zagreb, Faculty of Pharmacy and Biochemistry, Ante Kovačića 1, HR-10000 Zagreb, Croatia
Olga Kronja
; University of Zagreb, Faculty of Pharmacy and Biochemistry, Ante Kovačića 1, HR-10000 Zagreb, Croatia
Sažetak
The leaving group ability (nucleofugality) of the pentafluorophenolate anion has been determined from first order solvolytic rate constants (k) of X,Y-substituted benzhydryl pentafluorophenolates measured in a series of solvents, by using the three parameter LFER equation: log k = sf (Ef + Nf). Comparison with other leaving groups reveals that pentafluorophenolate is a moderate leaving group, whose nucleofugality (Nf value) is between the nucleofugalities of phenyl carbonate and 3,5-dinitrobenzoate leaving groups. However, due to its high reaction constant (sf = 1.29 in 80 % aq. ethanol), relative reactivities of benzhydryl pentafluorophenolates and corresponding benzhydryl carboxylates vary with the electrofugality of a carbocation formed in the heterolytic step, i.e., inversion of the reactivity of benzhydryl series with different leaving groups occurs. The plots of Δ‡G° vs. ΔrG° for solvolysis of benzhydryl phenolates and carboxylates reveal that phenolates solvolyze over the lower Marcus intrinsic barrier than corresponding carboxylates.
This work is licensed under a Creative Commons Attribution 4.0 International License.
Ključne riječi
nucleofugality; leaving group; LFER; phenolate; intrinsic barrier; solvolysis
Hrčak ID:
172243
URI
Datum izdavanja:
28.9.2016.
Posjeta: 2.259 *