3′,4′-Dichlorobiphenyl-4-yl 2,2,2-trichloroethyl sulfate

The four independent molecules in the asymmetric unit of the title compound, C14H9Cl5O4S, are related by pseudo-inversion centres. The molecules have Caromatic—O bond lengths ranging from 1.426 (10) to 1.449 (9) Å and biphenyl-4-yl sulfate ester bond lengths ranging from 1.563 (6) to 1.586 (6) Å, which is comparable to structurally related sulfuric acid diesters. The dihedral angles between the benzene rings range from 22.5 (4) to 29.1 (4)° and are significantly smaller than the calculated dihedral angle of 41.2°.

The four independent molecules in the asymmetric unit of the title compound, C 14 H 9 Cl 5 O 4 S, are related by pseudo-inversion centres. The molecules have C aromatic -O bond lengths ranging from 1.426 (10) to 1.449 (9) Å and biphenyl-4-yl sulfate ester bond lengths ranging from 1.563 (6) to 1.586 (6) Å , which is comparable to structurally related sulfuric acid diesters. The dihedral angles between the benzene rings range from 22.5 (4) to 29.1 (4) and are significantly smaller than the calculated dihedral angle of 41.2 .

Related literature
For the structures of similar sulfuric acid biphenyl-4-yl ester 2,2,2-trichloro-ethyl esters, see: Li et al. (2008Li et al. ( , 2010a. For a review of the structures of sulfuric acid aryl mono esters, see: Brandao et al. (2005). For further discussion of dihedral angles in chlorinated biphenyl derivatives, see: Lehmler et al. can be further metabolized to PCB glucuronides (Tampal et al., 2002) or sulfates (Liu et al., 2006;Liu et al., 2009;Sacco & James, 2005). The chemical structure and toxicity of these glucuronide and sulfate metabolites are only poorly investigated, in part because authentic standards are not readily available or because of their limited chemical stability. Here we report the crystal structure of a 2,2,2-trichloroethyl-protected sulfate of 3',4'-dichloro-biphenyl-4-ol, an intermediate of the synthesis of the corresponding sulfate monoester.

Molecules with the
The corresponding solid state dihedral angles of other sulfate diesters without ortho chlorine substituents range from 4.9 to 41.8° (Li et al., 2010a;Li et al., 2008). Typically, the dihedral angles of such sulfate diester derivatives are smaller than the calculated dihedral angle of 41.2° (calculated using semi-empirical SCF-MO calculations with an Austin Model 1 (AM1) Hamiltonian as implemented by the Spartan 02 package [Carpenter et al., 1980]). These deviations from the calculated dihedral angles are likely due to crystal packing effects, which allow the sulfate diester molecule to adopt an energetically supplementary materials sup-2 unfavorable dihedral angle to maximize intermolecular interactions in the crystal. Overall, the differences between solid state and calculated dihedral angles indicate that the biphenyl moiety of biphenyl-4-yl sulfate ester has considerable conformational freedom in interacting with cellular target molecules.

Refinement
H atoms were found in difference Fourier maps and subsequently placed in idealized positions with constrained C-H distances of 0.99 Å (CH 2 ), and 0.95 Å (C Ar H) with U iso (H) values set to 1.2U eq of the attached atom.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2σ(F 2 ) is used only for calculating Rfactors(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.
There is a pseudo inversion at (0.75070 0.50000 0.62576), but it does seem as if the space group really is P2 1 . This came as a great surprise because there seems to be no obvious reason why this structure would be non-centrosymmetric. All indications are that the crystals themselves are non even inversion twins because the Flack (and Hooft 'y') parameters are both zero within a couple of SUs.
Although these SUs are a bit larger than the recommendation suggested by Flack. Further tests with various procedures in PLATON (including ADDSYM) suggest "No Obvious Spacegroup Change Needed/Suggested", but the checkCIF implementation of ADDSYM does suggest "ADDSYM Detects Additional (Pseudo) Symm. Elem··· m", but on inspection the structure does not seem to have any kind of mirror plane. Further, the checkCIF implementation of ADDSYM/MISSYM suggests "Potential lattice centering or halving", but again, on inspection of the model and the diffraction data this does not appear to be the case.