The Electronic Spectra of Nitrile N-Oxides and the Solvent Effect on Them

Abstract

Abstract The electronic spectra of several substituted benzonitrile N-oxides and 9-anthronitrile N-oxide were recorded in various solvents and compared with those of the corresponding nitriles. The following results were thus obtained. (1) Substituted benzonitrile N-oxides showed a characteristic strong π–π* band at wavelengths much longer than those of the 1La band of the corresponding nitriles. (2) The π–π* band showed a blue shift with an increase in the polarity of the solvents. Quantitative analyses of the solvent effect led to the result of the decreasing dipole moment at π–π* state. (3) The hydrogen-bonding ability of the nitrile N-oxides was found to be weak from experiments on three-component systems and from analyses of the above solvent effect. (4) The electronic structures of the nitrile N-oxides were discussed on the basis of the above-mentioned findings and the measurements of the infrared spectra. It was suggested that the interaction of oxygen 2pπ electrons with the rest of the π electron system should be taken into consideration.