Bis(dicyclohexylaminium) 2-carboxymethyl-2-hydroxysuccinate ethanol monosolvate

In the title compound, 2C12H24N+·C6H6O7 2−·C2H6O, the cyclohexane rings of the cations adopt chair conformations. In the anion, intramolecular O—H⋯O hydrogen bonds occur. In the crystal, the cations link with the anions via N—H⋯O hydrogen bonds. Weak C—H⋯O hydrogen bonds are also observed. The hydroxy group of the ethanol solvent molecule is disordered over two sets of sites with an occupancy ratio of 0.766 (5):0.234 (5).

In the title compound, 2C 12 H 24 N + ÁC 6 H 6 O 7 2À ÁC 2 H 6 O, the cyclohexane rings of the cations adopt chair conformations. In the anion, intramolecular O-HÁ Á ÁO hydrogen bonds occur. In the crystal, the cations link with the anions via N-HÁ Á ÁO hydrogen bonds. Weak C-HÁ Á ÁO hydrogen bonds are also observed. The hydroxy group of the ethanol solvent molecule is disordered over two sets of sites with an occupancy ratio of 0.766 (5):0.234 (5).
The asymmetric unit of the title compound consist of two protonated cyclohexylamine as cation, one deprotonated citrate as anion, and one ethanol molecule. The asymmetric unit of the title compound is shown in Fig.1

Experimental
The solution of citric acid monohydrate (0.334 g, 1 mmol) in 5 ml ethanol was added to solution of dicyclohexylamine (0.6 ml, 3 mmol) in 10 ml ethanol in 1:3 molar ratios. The reaction mixture was stirred for 3 h at 298 K. The colorless crystals of the title compound appeared after slow evaporation of solvent at room temperature in darkness.

Refinement
The hydrogen atoms bonded to O and N atoms were found in difference Fourier map and refined isotropically. Hydroxyl group of ethanol solvent molecule was disordered over two sites with relative occupancies of 0.766 (5) and 0.234 (5).  The molecular structure of the title compound. Displacement ellipsoids are drawn at 30% probability level.

Figure 2
The packing diagram of the title compound showing intermolecular hydrogen bonding as blue dash lines.  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.