Basicity of 2-phenyl-5-R-1,3,4-oxadiazoles
We have studied the basicity of 2-phenyl-5-R-1,3,4-oxadiazoles (R = H, Me, CH2Ph, t-Bu, CH2Cl, CCl3, CF3) in aqueous sulfuric acid solutions. These compounds are weak organic bases (pKBH+ is −1.8 to −5.2). The values of pKBH+ determined on the H0 and X acidity function scales agree well with each other. The substituent at the 5 position has a substantial effect on the basicity of the 1,3,4-oxadiazole ring.