Abstract
Infrared spectra of 1, 3-cyclohexanedione derivatives in dioxane solution were measured. It was found that the enol compounds of these derivatives underwent intermolecular hydrogen bonding with dioxane, by which dimerization was inhibited. The infrared spectra on did not show the coupling vibrations (ν3, near 1610cm-1 and ν4, near 1560cm-1) present in the solid and two sharp absorption bands were observed for νC=O at 1640-1656cm-1 and for νC=C at 1609-1612cm-1. The position of νC=O indicated linear relationship with Hammet's constant σ but there was no marked difference in intensity ratio between that and νC=C.
Similar examinations were made on 3-anilino-2-cyclohexenone derivatives and the infrared spectra showed the absence of characteristic bands of the solid at 1610 and 1575cm-1, and two sharp absorption bands of νC=O at 1628-1638cm-1 and νC=O at 1590cm-1 were observed.
