FOURIER-TRANSFORM INFRARED SPECTROMETRIC STUDY OF TAUTOMERIC (ENOL-KETO) AND DIMERIC EQUILIBRIA IN 2-HYDROXYPYRIDINES AND 1,3-CYCLOHEXANEDIONES IN CHCL3 AND OR CCL4 SOLUTIONS/

The concentration dependence of FTIR and UV spectra of 2-hydroxypyridi ne (HP) and 6-chloro-2-hydroxypyridine was measured in CHCl3 and CCl4 in order to elucidate their tautomeric (enol-keto) equilibrium and to determine the association constants. The time dependence of FTIR spect ra of 1,3-cyclohexanedione and 2-methyl-1,3-cyclohexanedione (MCHD) wa s also measured in CHCl3 solution. The (enol-keto) interconversion in MCHD took about a day, indicating that the monomolecular process is ve ry slow. The crystal structure of the 1:1 complex of HP and lauric aci d was determined by X-ray analysis. In this complex, HP occurs in dime ric keto-form similar to thar formed in solution, although HP in solid state exists in the polymeric keto-form.