Department of Chemistry, Punjabi University, Patiala-147 002 On the basis of the directions of the shifts in the ir frequencies of \(v\)asym OCO and \(v\)sym OCO from those for ionic carboxylate, the various modes .or carboxylate building -unidentate, chelating bidentate (unsymmetricaI and symmetrical) and bridgadg bidentate (unsymmetrical and symmetrical)-are distinguished. This criterion is superior to the previously better-known ir spectral. criterion because or Its uniform applicability and its capability or making even finer distinctions between symmetrical and unsymmetrical types within the chelating and bridging bidentate modes. This finding as based on the analysis or ir spectral data or a very large number or acetato- and trifluoroacetato compounds with known crystal structures.