Basicity of phenyl-substituted 1,3-oxazoles

Phenyl substituents in positions 2, 4, and 5 of the oxazole ring exert diff erent effects on the electronic structure of the heteroring, which are refl ected in the basicity constants of isomeric phenyl-substituted oxazoles and in changes of the spectral patterns on protonation. The calculated (AMI) g as-phase proton affinities and energies of ionization of isomeric methyl-, phenyl-, and methylphenyloxazoles were correlated with the experimental pK( BH+) values. In acid medium specific solvation of phenyloxazoles is possibl e with participation of the heterocyclic fragment.