The crystal structure of 2,7-dimethyl-2,7-octanediol tetrahydrate

The crystal structure of 2,7-dimethyl-2,7-octanediol tetrahydrate, HO(CHa)2C(CH2)4C(CH3)2OH.4H20 , is monoclinic P2t/n with a = 6.126 (5), b = 6.128 (5), c = 21.12 (1) A, ~ = 91.66 (6) °, Z = 2. It is a waterlayer structure, related to that of 2,5-dimethyl-2,5-hexanediol tetrahydrate [Jeffrey & Shen, J. Chem. Phys. (1972), 57, 56-61]. The hydroxyl and water O atoms form the vertices of a hydrogen-bonded layer of facesharing pentagons. The O.. . O distances in these layers are between 2.774 and 2.831 A. The two symmetryindependent pentagons of hydrogen-bonded O atoms are non-planar, with envelope and twist conformations. The layers are separated by the hydrocarbon chains in parallel alignment. There is approximate twofold disorder in the orientation of the octanediol molecules between the layers.