Application of LFER to the N(1)-H Acidities of Five-Membered Nitrogen Heterocyclic Ring Systems: A Review on Graduate Chemical Education Exercise

An attempt is made for the first time in our laboratory to apply the Hammett and Taft equations to the five-membered heterocyclic ring systems pyrroles, pyrazoles, imidazole, and triazoles. It is shown that the pKa values of N(1)-H acidities of 3-X-pyrroles, 3-Xpyrazole, 4-X-pyrazole, 4-X-imidazole, 3-X-1,2,4-triazole and 4-X-1,2,3-triazole correlated well with Hammett σ values.