(E)-2-(Cyclohexylmethylene)succinic acid

The title compound, C11H16O4, crystallizes with three molecules in the asymmetric unit. The cyclohexane ring adopts a chair conformation. Intermolecular O—H⋯O hydrogen bonds are observed and these help to establish the crystal packing.


Related literature
1 h, and then a solution of cyclohexanecarbaldehyde (2.24 g, 0.02 mol) in anhydrous toluene (20 ml) was added dropwise.
The mixture was stirred at room temperature for 3 h and water (30 ml) was added. The water phase was washed with ethyl acetatethree times and then sodium hydroxide (3 g, 0.075 mol) was added. The mixture was refluxed for 4 and then acidified with hydrochloric acid to PH 2 and extracted with ethyl acetate. The organic layer was dried with anhydrous Mg 2 SO 4 , and then concentrated in vacuo. The title compound (3.65 g) was obtained in powder form in a yield of 86.1%. Crystals of (I) were obtained by slow evaporation of a solution of ethanol (m.p. 477-478 K).

Refinement
All H atoms were positioned geometrically (C-H=0.95-0.99 Å), and refined as riding with U iso (H)=1.2U eq (carrier) or 1.5 eq (methyl groups). Fig. 1. A view of the molecular of (I). Displacement ellopsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.

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 > 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.