Correlation of the Electronic Absorption Spectra of para-Disubstituted Benzene Series with Some Physical Constants

Abstract

The ultraviolet absorption spectra of para-disubstituted benzene series with two substituent groups of opposite electrical property are measured in n-heptane, ethanol and water. The transition energies of three bands, namely shifted one of 200 mμ band (A_1g→B_1U transition), intramolecular chargetransfer band and 250 mμ band (A_1g→B_2U transition) are discussed with respect to substituent constants and molecular dipole moment. The results are as follows : (1) The chargetransfer band is more sensitive than other band to the character of substituent groups, polarity of solvent and molecular dipole moment. (2) The sum of para-substituent constants, |σ_p1|+|σ_p2| and molecular dipole moment correlate well with the absorption maxima of this series.