cis-Cycloheptane-1,2-diol

The title compound, C7H14O2, is a vicinal diol derived from cycloheptane with cis-orientated hydroxy groups. The molecules shows no non-crystallographic symmetry. The O—C—C—O torsion angles of both molecules present in the asymmetric unit [−66.4 (2) and −66.9 (2)°] are similar to those in trans-configured cyclohexane derivatives (including pyranoses) as well as rac-trans-cycloheptane-1,2-diol, but smaller than those in trans-configured cyclopentane derivatives (including furanoses). In the crystal structure, O—H⋯O hydrogen bonds furnish the formation of sheets parallel to [110].

The title compound, C 7 H 14 O 2 , is a vicinal diol derived from cycloheptane with cis-orientated hydroxy groups. The molecules shows no non-crystallographic symmetry. The O-C-C-O torsion angles of both molecules present in the asymmetric unit [À66.4 (2) and À66.9 (2) ] are similar to those in trans-configured cyclohexane derivatives (including pyranoses) as well as rac-trans-cycloheptane-1,2-diol, but smaller than those in trans-configured cyclopentane derivatives (including furanoses). In the crystal structure, O-HÁ Á ÁO hydrogen bonds furnish the formation of sheets parallel to [110].

Comment
During our investigation of the chelation abilities of selected cis-and trans-configured cyclic vicinal diols and the influence of bonding to various metals, semi-metals and non-metals on the geometry of the chelating molecule, the structure of ciscycloheptane-1,2-diol was determined.
Both molecules present in the asymmetric unit adopt chair-like conformations (Fig. 1). The O-C-C-O torsion angle is found at 60° and 66°, respectively. Both molecules possess (RS/SR)-configuration.
A disorder of a methylene group in one of the molecules was accounted for by a split model. The major position dominates by a 4:1 ratio.
In the crystal structure, hydrogen bonds furnish the formation of sheets parallel to [1 1 0]. The hydrophobic cycloheptane moieties form the surfaces of these sheets. The description of the hydrogen bonding pattern can be done in two ways: first, it can be seen as a combination of annealated ten-and eighteen-membered rings with diverging directions of rotation.
As an alternative, the pattern may be seen as a set of two cooperative, antidromic chains (Fig. 2). In terms of graph-set analysis (Etter et al., 1990;Bernstein et al., 1995), the descriptor on the unitary level is DDR 2 2 (10)R 2 2 (10). While the eighteen-membered rings appear on the ternary level of graph-set analysis with a R 6 6 (18) descriptor, the cooperative chains appear on the quarternary level with a C 4 4 (8) descriptor.

Experimental
The title compound was prepared by standard procedures upon neutral aqueous dihydroxylation of cycloheptene with potassium permanganate (Becker et al., 2001). Crystals suitable for X-ray diffraction were directly obtained from the solidified reaction product.

Refinement
All carbon bonded H-atoms were placed in calculated positions (C-H 1.00 Å for methine groups, C-H 0.99 Å for methylene groups) and were included in the refinement in the riding model approximation, with U(H) set to 1.2U eq (C) for both groups. Hydroxyl H atoms were allowed to rotate with a fixed angle around the C-O bond to best fit the experimental electron density (HFIX 147 in the SHELX program suite (Sheldrick, 2008)). For the refinement their U(H) was set to 1.5U eq (O).
supplementary materials sup-2 Figures Fig. 1. The two molecules comprising the asymmetric unit of (I), with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level) for non-H atoms. Only the major component of the split C atom (C 16) is shown for clarity. For clarity, the carbocyclic moieties were not depicted and the labelling of atoms was replaced by the following colour code: blue arrows indicate hydrogen bonds between the first molecule of the asymmetric unit and its symmetry-generated equivalents, green arrows between the second molecule and its equivalents. Yellow arrows denote hydrogen bonds between the two molecules.