Electric field effect was investigated on 1-hydroxyacetone (HA) as a model compound of the acyclic form of saccharide moiety employing infrared electroabsorption spectroscopy. We examined the structural tautomerization of the hydroxyacetyl group of HA in detail by monitoring change in IR absorption intensity of the C=O stretching band in the range of 1650-1850 cm(-1). The observed changes in absorbance were analyzed by considering a change in the equilibrium of HA dimer, HA monomer, endiol, and enol forms, as well as the orientational polarization of each tautomer. Conversion from the HA dimer to the enol was detected.