Methyl 4′,5-dichloro-2-hydroxy-4,6-dimethylbiphenyl-3-carboxylate

In the title compound, C16H14Cl2O3, the dihedral angle between the mean planes of the two benzene rings is 55.30 (5)°. The methyl ester group lies within the ring plane due to an intramolecular O—H⋯O hydrogen bond [maximum deviation from the C8O2 mean plane is 0.0383 (13) Å]. In the crystal, molecules are held together by rather weak C—H⋯O hydrogen bonds.


Related literature
In the title compound ( Fig. 1), the dihedral angle between the mean planes of the two benzene rings is 55.30 (5)°. The methyl ester group lies within the ring plane due to an intramolecular O-H···O hydrogen bond; the maximum deviation of any atom from the mean-plane of atoms C1-C8/O1/O2 is 0.0383 (13) Å for C2. In the crystal, molecules are held together by rather weak intermolecular C-H···O hydrogen bonds along the a-axis ( Fig. 2 & Table 1).
Crystallization from a saturated dichloromethane/methanol (9:1) solution at ambient temperature gave colourless crystals suitable for X-ray crystallographic studies.

Refinement
An absolute structure was determined by using 1569 Friedel pairs. The H atom bonded to O1 was located from a difference Fourier map and refined freely. Other H atoms were positioned geometrically and refined using a riding model, with C-H = 0.98 (methyl) or 0.95 Å (aryl) with U iso (H) = 1.5 times U eq (C) (methyl H) or 1.2 times U eq (C) (aryl H); torsion angles of all methyl groups were allowed to refine.  The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are presented as small spheres of arbitrary radius.

Figure 2
A view of the intermolecular (C--H···O) and intramolecular (O-H···O and C-H···Cl) hydrogen bonds (dotted lines) in the crystal structure of the title compound. H atoms non-participating in hydrogen-bonding were omitted for clarity.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq