2,3-Dichloro-3’,4’-dihydroxybiphenyl

Abstract

2,3-Dichloro-3',4'-dihydroxybiphenyl, C₁₂H₈Cl₂O₂, is a putative dihydroxylated metabolite of 2,3-dichlorobiphenyl (PCB 5). The title structure displays intramolecular O—H···O hydrogen bonding, and the π-π stacking distance between inversion related chlorinated benzene rings of the title compound is 3.371 (3) Å. The dihedral angle between two benzene rings is 59.39 (8)°.

Structure description

Polychlorinated biphenyls (PCBs) are a class of environmental pollutants banned under the Stockholm Convention on Persistent Organic Pollutants (Stockholm Convention, 2008). Exposure to PCBs is associated with a range of adverse health effects, for example cancer and adverse neurotoxic outcomes (ATSDR 2000, IARC 2017). Cytochrome P450 enzymes oxidize PCB congeners in two steps to dihydroxylated metabolites (Lu et al. 2013, McLean et al. 1996). PCB metabolites with ortho or para substituted hydroxyl groups can be further oxidized to reactive and highly toxic PCB quinones (Dhakal et al. 2018, Grimm et al. 2015). Only a few solid-state structures of dihydroxylated PCBs have been reported to date (Lehmler et al. 2001 a, McKinney & Singh 1988). 2,3-Dichloro-3',4'-dihydroxybiphenyl is a putative metabolite of PCB 5, a minor constituent of technical PCB mixtures, such as Aroclor 1221 (Frame, 1997). The present study reports the solid-state structure of this dihydroxylated PCB metabolite, thus adding to the number of available crystal structures of this important class of PCB metabolites.

2,3-Dichloro-3',4'-dihydroxybiphenyl crystallizes in the monoclinic P2₁/n space group. The dihedral angle between the least-squares planes of the two benzene rings, an important determinant of the three-dimensional structure of PCB derivatives, is 59.39 (8)°. Similarly, the solid-state dihedral angle of other mono ortho-chlorine substituted PCB derivatives ranges from 47.34 (5)° to 59.92 (9)° (Boyarskiy et al. 2010, Kania-Korwel et al. 2004, Lehmler et al. 2001 b, Li et al. 2010, Luthe et al. 2007, van der Sluis et al. 1990, Sutherland & Ali-Adib, 1987, Vyas et al. 2006). In the crystal, the title compound displays intra and intermolecular O—H…O hydrogen bonds involving both of the two hydroxy groups. The intramolecular bond distance for O1—H1…O2 is 2.763 (2) Å, while that for O2—H2…O1 is 2.677 (2) Å, Table 2. The π-π stacking distance between inversion related C1—C6 rings of the title compound is 3.371 (3) Å.

Table 2.

Hydrogen-bond geometry (Å, °) for (I)

D—H…A	D—H	H…A	D…A	D—H…A
01—H1O…O2i	0.79	1.98	2.763 (2)	168
02—H2O…O1	0.79	2.24	2.677 (2)	116

Symmetry code: (i) x–1/2, −y+1/2, z+1/2.

Synthesis and crystallization

The title compound was synthesized via Suzuki cross-coupling reaction of 4-bromo-1,2-dimethoxybenzene with 2,3-dichlorophenylboronic acid in the presence of Pd(PPh₃)₄, and 2M aqueous solution of Na₂CO₃ followed by demethylation with BBr₃ (Bauer et al. 1995, Lehmler & Robertson 2001). Crystals suitable for crystal structure analysis were obtained by recrystallization of the title compound from diethyl ether : hexanes (approximately 1:3, v/v) as described (Bauer et al. 1995, Lehmler & Robertson 2001).

Figure 1.

View of the title compound showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2.

A packing plot viewed approximately along the c-axis. Hydrogen bonds are drawn as solid dashed lines, and the π-π interactions are depicted as dashed open lines between the centroids of stacked rings.

Scheme 1.

Table 1.

Experimental details

Crystal data
Chemical formula	C12H8Cl2O2
Mr	255.08
Crystal system, space group	Monoclinic, P21/n
Temperature (K)	90
a, b, c (Å)	6.8542 (4), 19.9526 (11), 7.6704 (4)
β(°)	95.762 (3)
V (Å3)	1043.7 (1)
Z	4
Radiation type	Mo Kα
μ (mm−1)	0.60
Crystal size (mm)	0.25 × 0.15 × 0.10
Data collection
Diffractometer	Nonius KappaCCD diffractometer
Absorption correction	Multi-scan SCALEPACK (Otwinowski & Minor, 2006)
Tmin, Tmax	0.865, 0.942
No. of measured, independent and observed [I > 2σ(I)] reflections	6305, 1834, 1333
Rint	0.078
(sin θ/λ)max (Å−1)	0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S	0.046, 0.074, 1.05
No. of reflections	1834
No. of parameters	149
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)	0.37, −0.35

Computer programs: COLLECT (Nonius, 1998), SCALEPACK (Otwinowski & Minor, 2006), DENZO-SMN (Otwinowski & Minor, 2006), SHELXS (Sheldrick, 2008), SHELXL-2018/1 (Sheldrick, 2015), XP in SHELXTL (Sheldrick, 2008), SHELX (Sheldrick, 2008) and CIFFIX (Parkin, 2013).