Biphenyl-4-yl 2,2,2-trichloroethyl sulfate

The molecular structure of the title compound, C14H11Cl3O4S, displays a biphenyl dihedral angle of 4.9 (2)° between the benzene rings, which is significantly smaller than the calculated dihedral angle of 41.2° of biphenyl derivatives without ortho substituents. The CAr—O bond length of 1.432 (4) Å is comparable with other sulfuric acid biphenyl-4-yl ester 2,2,2-trichloroether ester derivatives without electronegative substituents in the sulfated phenyl ring.

The molecular structure of the title compound, C 14 H 11 Cl 3 O 4 S, displays a biphenyl dihedral angle of 4.9 (2) between the benzene rings, which is significantly smaller than the calculated dihedral angle of 41.2 of biphenyl derivatives without ortho substituents. The C Ar -O bond length of 1.432 (4) Å is comparable with other sulfuric acid biphenyl-4-yl ester 2,2,2-trichloroether ester derivatives without electronegative substituents in the sulfated phenyl ring.

Comment
Exposure to biphenyl and structurally related chlorinated biphenyls has been associated with a range of adverse human health effects, including cancer and arteriosclerosis (Robertson & Hansen, 2001;Umeda et al., 2005Umeda et al., , 2002Letcher et al., 2000).
Biphenyl and many lower chlorinated biphenyls are metabolized via hydroxylated biphenyl metabolites to sulfuric acid esters (Liu et al., 2006(Liu et al., , 2009Ohnishi et al., 2000Ohnishi et al., , 2001Sacco & James, 2005) and glucuronide conjugates (Cravedi et al., 1999;Tampal et al., 2002). While currently little is known about the toxicity of sulfate conjugates of chlorinated biphenyls, it is well established that sulfuric acid biphenyl-4-yl ester is involved in the formation of urinary calculi and, thus, plays a role in the induction of urinary bladder cancer (Ohnishi et al., 2000(Ohnishi et al., , 2001. Unfortunately, crystal structures of (chlorinated) sulfuric acid biphenyl-4-yl esters have not been reported, partly because of their chemical instability (Li et al., 2010). Here we report the crystal structure of a structurally related sulfuric acid biphenyl-4-yl ester 2,2,2-trichloro-ether ester.
In particular the C Ar -O bond length of sulfuric acid mono-and diesters may be predictive of the stability of the corresponding sulfuric acid conjugates (Brandao et al., 2005;Li et al., 2010). The C Ar -O (i.e. C4-O1) bond length of the title compound is 1.432 (4) Å, which is comparable to other, chlorinated sulfuric acid biphenyl-4-yl ester 2,2,2-trichloro-ether esters with no chlorine substituents in the sulfated benzene moiety (1.426 to 1.435 Å) (Li et al., 2010(Li et al., , 2008. In contrast, the C Ar -O bond of sulfuric acid 2',3,5,5'-tetrachloro-biphenyl-4-yl ester 2,2,2-trichloro-ethyl ester, an analogous sulfuric acid diester with two chlorine substituents in the sulfated benzene moiety, is slightly shorter (1.405 (4) Å) due to the presence of the electronegative chlorine substituents (Li et al., 2010). Therefore, the sulfuric acid biphenyl-4-yl ester corresponding to the title compound is expected to be relatively stable under physiological conditions, especially compared to aromatic sulfuric acid esters with electronegative substituents in the sulfated benzene ring.
The dihedral angle of biphenyl derivatives is associated with their affinity for cellular target molecules and, therefore, can correlate with their toxicity. The title compound adopts an almost planar conformation, with a solid state dihedral angle of the biphenyl moiety of 4.9 (2)°. Similarly, the parent compound, biphenyl, adopts a planar confirmation in the solid state with a dihedral angle of 0° (Trotter, 1961). These solid state dihedral angles are significantly smaller compared to the calculated dihedral angle of 41.2° of biphenyl derivatives without ortho substituents (Shaikh et al., 2008). These deviations from the energetically most favorable conformation are most likely due to crystal packing effects, which allow the title compound to adopt an energetically less favorable conformation in the solid state by maximizing the lattice energy.

Experimental
The title compound was synthesized from biphenyl-4-ol and 2,2,2-trichloroethyl sulfonyl chloride using 4-dimethylaminopyridine as catalyst (Li et al., 2008). Crystals of the title compound suitable for crystal structure analysis were obtained by slow evaporation of a solution of the title compound in methanol.
supplementary materials sup-2 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 C atom. Fig. 1

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.57446 (