Proton-acceptor and proton-donor properties of phenol and its substitutes

The donor-acceptor ability of phenols (phenol, 4-chlorphenol, 4-methylphenol, 4-bromphenol, hydroquinone, 4-methyl, and 2-aminophenol) and their complexes with water are investigated by the quantum-chemical method. Incorporation of NH₂ and CH₃ substitutes in the phenol molecule leads to the intensification of the electron density transfer on the carbon atoms of the aromatic ring. The formation of the planar complex increases, and the formation of the nonplanar complex, on the contrary, decreases the proton-acceptor ability of phenols in the ground state. The formation of the nonplanar complex leads to an increase in the proton-donor properties of phenols under excitation. The incorporation of the chlorine atom into the para-position results in the dependence of the donor-acceptor properties of the molecule on the excitation energy. The incorporation of OH-and CH₃-groups in para-position does not influence the proton-donor properties of the isolated phenol molecule. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 28–33, December, 2005.