Among the conformers of the title compounds, all stable structures found reveal hydrogen bonding to an sp(2) oxygen atom in five- or six-membered rings and usually cooperative effects. Nonlocal density functional calculations using different functionals prove the applicability of DFT to study geometries of systems containing intramolecular hydrogen bonds. The hydrogen bond parameters obtained applying the B3LYP approximation exhibit perfect agreement with those calculated at the MP2 level. The local gradient correction does not provide encouraging results.