会合吸収帯の分光化学的研究 (第2報)

ピリジン-N-オキシド及びキノリン-N-オキシドの紫外部吸収に対する溶媒効果及び水素結合能について

抄録

1) Hydrogen bond energy of systems of pyridine 1-oxide (I) and quinoline 1-oxide (II), added with phenol (III) and methanol (IV) as the proton donor, was examined by the measurement of ultraviolet absorption. Such energy was 6 kcal./mole in the system (II)-(III), and 5 kcal./mole in (I)-(IV) and (II)-(IV) systems. The decrease of entropy, Δ, S, in these cases was -9 E. U. in (II)-(III) system, -13 in (I)-(IV) system, and -14 E. U. in (II)-(IV) system. The energy of hydrogen bonding was considered from the electrostatic and charge transfer forces.
2) In the above cases, absorption in the ultraviolet region shows a marked blue shift according to the formation of a hydrogen bonding. This fact has repeatedly been pointed out by the writer and it is assumed that the stabilization of the polar structure in the ground state in accordance with hydrogen bonding with the solvent is making the chief contribution. It is difficult to assume that the dielectric constant of the solvent acts primarily in such an effect. Some considerations were also made on this point.