[(1R,3S)-2,2-Dichloro-3-(hydroxymethyl)cyclopropyl]methanol

The title compound, C5H8Cl2O2, represents a meso isomer crystallizing in a chiral space group with two molecules per asymmetric unit. The molecules form helical associates with a pitch of 6.31 Å along the a axis via O—H⋯O hydrogen bonds. The overall three-dimesional supramolecular architecture is stabilized by C—Cl⋯O halogen bonding, with a Cl⋯O separation of 3.139 (3) Å and a C—Cl⋯O angle of 162.5 (2)°.

The title compound, C 5 H 8 Cl 2 O 2 , represents a meso isomer crystallizing in a chiral space group with two molecules per asymmetric unit. The molecules form helical associates with a pitch of 6.31 Å along the a axis via O-HÁ Á ÁO hydrogen bonds. The overall three-dimesional supramolecular architecture is stabilized by C-ClÁ Á ÁO halogen bonding, with a ClÁ Á ÁO separation of 3.139 (3) Å and a C-ClÁ Á ÁO angle of 162.5 (2) .   Although the title compound is a meso-isomer, it crystallizes in a chiral supramolecular architecture. Abe et al. (2012) suggested that the presence of two hydroxy groups, which form intramolecular hydrogen bonds, can result in formation of one-handed helical structures in polymers, even in an absence of chiral moieties.

Related literature
The title compound, (I), crystallizes with two molecules in the asymmetric unit, as shown in Fig. 1. Although the title compound is expected to be achiral in solution due to presence of the internal plane of symmetry, in the solid state both of the molecules are found to lack a plane of symmetry. In addition, both of said molecules were found to be not superimposable with each other, resulting in a chiral, orthorhombic P2(1)2(1)2(1) space group. The structure also has a long range chiral order, helical hydrogen bonded O-H···O chains with a pitch of 6.311 Å, running along the a axis (Fig.   2). These chains are further reinforced by C1B-Cl1B···O1A halogen bonding interactions with interaction parameters of 3.139 (3) Å and 162.5 (2)° resulting in the three-dimensional supramolecular structure, as shown in Fig. 3.
The lack of plane of symmetry in each molecule in the asymmetric unit is mainly caused by the differences in the spatial arrangements of the oxygen atoms within each molecule. This is thought to be caused by the presence of high concentration of strongly associating groups, two hydroxy groups and two Cl atoms, in the relatively small title compound.

Experimental
The title compound was prepared according to literature procedure, Kailani et al. (2012), which was a modification of reported procedure, Pustovit et al. (1994), in order to improve the yield.

Refinement
The structure represents a merohedral twin with 8.2% contribution of the opposite chirality. All carbon-attached hydrogen atoms were placed in the calculated positions using riding model with U eq . of 1.2 times that of the riding atom. Oxygenattached hydrogen atoms were located from Fourier map difference, and then refined isotropically without restraints.  Two independent molecules in asymmetric unit with numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
Left-handed hydrogen-bonded helix (oxygens are in red and hydrogens -in blue), running along a-axis with supporting halogen bonding interactions, shown as black dotted lines.  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.