(2-tert-Butyl-5-hydroxymethyl-1,3-dioxan-5-yl)methanol

In the title compound, C10H20O4, the dioxane ring adopts a chair conformation. The tert-butyl group occupies an equatorial position, and is staggered with respect to the O atoms of the dioxane ring. In the crystal, molecules are connected by O—H⋯O hydrogen-bonds into zigzag chains of R 4 4(8) and R 2 2(12) ring motifs that run parallel to the a axis.

In the title compound, C 10 H 20 O 4 , the dioxane ring adopts a chair conformation. The tert-butyl group occupies an equatorial position, and is staggered with respect to the O atoms of the dioxane ring. In the crystal, molecules are connected by O-HÁ Á ÁO hydrogen-bonds into zigzag chains of R 4 4 (8) and R 2 2 (12) ring motifs that run parallel to the a axis.

Comment
The synthesis and conformational studies of several 1,3-dioxanes have been reported in the literature (Vázquez-Hernández et al., 2004;Juaristi et al., 1987Juaristi et al., , 1989Bailey et al., 1978). The preparation and some spectroscopic information for the title compound was reported by Anderson et al. (1967).
In our development work, while searching rigid molecules to incorporate fluorophore groups, we synthesized 5,5-dihydroxymethyl-2-tert-butyl-1,3-dioxane as a reaction intermediate. In the molecule of C 10 H 20 O 4 (Scheme 1, Fig. 1), the tert-butyl group occupies an equatorial position, and is staggered with respect to the O atoms of the dioxane ring. The hydroxyl groups act as both hydrogen bond donor and acceptor to neighboring molecules. The hydrogen-bonds (table 1) form zigzag chains of R 4 4 (8) and R 2 2 (12) ring motifs that run parallel to the a axis ( Fig. 2).

Experimental
The synthesis of the title compound included reagents and solvents of reagent grade, which were used without further purification. In a 25 ml round bottom flask provided with a magnetic stirrer, was placed 1.2 g (8.8 mmol) of pentaerythritol, 5 ml of water, 0.01 ml of HCl as catalyst and 0.46 ml (7.35 mmol) of pivalaldehyde. 3 ml of dimethylformamide was then added to complete dissolution of the solid, and the reaction mixture was stirred for 24 h. The precipitate thus formed was filtered and washed with a solution of NaHCO 3 (10ml, 3 times) and H 2 O (10 ml, 3 times).

Refinement
All H atoms were positioned geometrically and refined using a riding model with C-H = 0.96 Å for -CH 3 , C-H = 0.97 Å for -CH 2 -groups and O-H = 0.82 Å. U iso (H) values were set to 1.2 U eq (CH 2 ) or 1.5 U eq (CH 3 , OH).

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 > σ(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.