Structures des Phényl‐5 et Éthyl‐5 Diméthyl‐2,2 Dioxanne‐1,3 Dione‐4,6

The crystal and molecular structures of two 5-R derivatives of the 2,2-dimethyl-1,3-dioxane-4,6-dione with R = C6H5 or C2H5 were determined by X-ray diffraction and compared with a previous determination of the 5-thienyl compound. The crystal data are as follow: R = C6H5: 2,2-dimethyl-5-phenyl-1,3-dioxane-4,6-dione; C12H12O4, monoclinic, P21/n, a = 5.255(1), b = 13.786(4), c = 15.484(7) A, β = 94.34(3)°, V = 1118.5(7)a3, Dx = 1.31 g cm−3, Z = 4. R = C2H5: 5-ethyl-2,2-dimethyl-1, 3-dioxane-4,6-dione; C8H12O4, orthorhombic, P212121, a = 5.196(1), b = 10.908(4), c = 15.925(6)A, V = 902.7(5)A3Dx = 1.27 g cm−3, Z = 4. The structures have been solved by direct methods (MULTAN) and refined by least squares. In both compounds, the dioxanedione ring is in a boat conformation and the molecules exhibit non-crystallographic mirror symmetry.