Electronic States of Acetic Acid in a Binary Mixture of Acetic Acid and 1-Methylimidazole Depend on the Environment

The unique characteristics of an acetic acid/1-methylimidazole (1-MI) mixture, showing higher electrical conductivity than either neat acetic acid or neat 1-MI, yet consisting of electrically neutral molecules, are reported. We have applied soft X-ray spectroscopy to reveal the electronic states of acetic acid in the acetic acid/1-MI mixture at various mole fractions of acetic acid (χHOAc). The results show that the amount of acetic acid monomer increases in the region of especially high electrical conductivity and the amount of complex of acetic acid and 1-MI formed by sharing molecular orbitals increases in the low electrical conductivity region. There is a little amount of acetic acid monomer in the low electrical conductivity region because the complex inhibits acetic acid from creating its monomer. These results suggest the possibility that the acetic acid monomer is related to electrical conduction.