6,10,16,19-Tetraoxatrispiro[4.2.2.4.2.2]nonadecane

The asymmetric unit of the title compound, C15H24O4, contains one half-molecule; a twofold rotation axis passes through the central C atom. The non-planar six- and five-membered rings adopt chair and envelope conformations, respectively. In the crystal structure, intermolecular C—H⋯O hydrogen bonds link the molecules.

The asymmetric unit of the title compound, C 15 H 24 O 4 , contains one half-molecule; a twofold rotation axis passes through the central C atom. The non-planar six-and fivemembered rings adopt chair and envelope conformations, respectively. In the crystal structure, intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules.

Structure Reports Online
The asymmetric unit of the title compound, (I), contains one-half molecule ( Fig. 1), in which the bond lengths are within normal ranges (Allen et al., 1987).
In the crystal structure, intermolecular C-H···O hydrogen bonds (Table 1) link the molecules, in which they may be effective in the stabilization of the structure.

Experimental
The title compound was prepared from a mixture of 2,2-bis-(hydroxymethyl) propane-1,3-diol (0.68 g, 5 mmol), cyclopentanone (10 mmol), freshly activated catalyst TiO2/SO4(2-)(0.6 g, 0.32 mmol) and cyclohexane (80 ml), heated with stirring at refluxing temperature for 2 h, using a Dean-Stark apparatus in a nitrogen atmosphere (Sun et al., 2001). The progress of the reaction was monitored by thin-layer chromatography. After cooling to room temperature, the catalyst was filtered off, the crude product was isolated by distillation and the solid was recrystallized from ethanol. Crystals of (I) were obtained by dissolving the title compound (1.0 g) in toluene (15 ml) and evaporating the solvent slowly at room temperature for about 7 d.

Refinement
H atoms were positioned geometrically, with C-H = 0.97 Å for methylene H, and constrained to ride on their parent atoms, with U iso (H) = 1.2U eq (C).  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.