キノン系分子化合物とその赤外部吸収スペクトル (第1報)

p-ベンゾキノンの分子化合物と複合物の形成について

抄録

Infrared absorption spectra were measured of a mixture of p-benzoquinone containing phenol or hydroquinone in various ratios. An equal mixture of these two components in nonpolar solvent was found to form a molecular compound of 1 mole each of these two components from the shift of infrared absorption band. In this case, ν_C=O and δ_C-H bands of p-benzoquinone shift to a lower wave number and the absorptions were in approximately the same position in the case of either phenol or hydroquinone. It follows, therefore, that p-benzoquinone in these mixtures takes the same electronic state. On the other hand, infrared absorption spectra of a mixture of p-benzoquinone and phenol or hydroquinone in various ratios, taken in Nujol, showed a shift of both ν_C=O and δ_C-H in p-benzoquinone due to electron charge. The shift of δ_C-H absorption is completed in a mixture at a certain ratio so that further increase in the amount of phenol or hydroquinone does not cause any change in the position of δ_C-H absorption band while that of ν_C=O alone undergoes shift. This was considered to be due to the receipt of proton from phenol or hydroquinone by p-benzoquinone after completion of electron charge. From such a fact, it was assumed that the so-called quinhydrone-type double compound is formed by acceptance of an electron on the one hand and proton on the other by deviation of electron charge due to quinonoid resonance in the quinone.