Crystal Structure of 2,5‐Dimethyl‐2,5‐hexanediol Tetrahydrate: A Water‐Hydrocarbon Layer Structure

The crystal structure of 2,5‐dimethyl‐2,5‐hexanediol tetrahydrate, $C8H18O2 · 4H2O,$ has been determined at room temperature from diffractometer data with MoKα radiation. The structure is monoclinic, P2₁/c with two formula units in a cell of dimensions a=6.158(2), b=6.169(2), c=17.854(5) Å, β=101.8(2)°. The parameters were refined anisotropically by least squares to R=0.057 for 1015 reflections. The structure consists of layers of hydrogen bonded hydroxyl and water molecules alternating with layers of hydrocarbon chains. The water hydroxyl layers consist of puckered sheets of edge‐sharing pentagons analogous to the water structure found in the pinacol and piperazine hexahydrates. The hydrocarbon chains of the glycol molecules are aligned parallel, analogous to the long‐chain hydrocarbons and fatty acids, but spaced further apart. There are no hydrogen bonds between the puckered sheets of pentagons, and therefore the three‐dimensional hydrogen bond framework which characterizes the hexahydrates as ``semiclathrates'' does not occur in this tetrahydrate.