4-Nitrophenyl N-phenylcarbamate

The title compound, C13H10N2O4, was synthesized as an intermediate for the preparation of ureas. The two aromatic rings are twisted about the central carbamate group with a C—C—N—C torsion angle of 139.6 (2)° and a C—C—O—C torsion angle of 95.9 (2)°. The molecules are linked into one-dimensional chains by N—H⋯O hydrogen bonds along the b axis. Weak interactions between O atoms of the nitro groups (O⋯O = 3.012 Å) connect two adjacent chains.

The title compound, C 13 H 10 N 2 O 4 , was synthesized as an intermediate for the preparation of ureas. The two aromatic rings are twisted about the central carbamate group with a C-C-N-C torsion angle of 139.6 (2) and a C-C-O-C torsion angle of 95.9 (2) . The molecules are linked into onedimensional chains by N-HÁ Á ÁO hydrogen bonds along the b axis. Weak interactions between O atoms of the nitro groups (OÁ Á ÁO = 3.012 Å ) connect two adjacent chains.
FQ and Y-HX thank Dr Sihui Long for helpful discussions during the preparation of this paper.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FL2180).

Comment
The title compound (I), along with other 4-nitrophenyl carbamates, are important intermediates for the synthesis of ureas (Olma, et al. 2006;Izdebski & Pawlak, 1989). Although it has been used in organic sythesis for a long time, the crystal structure, as far as we know, is reported here for the first time.
The compound, two aromatic rings connected by a carbamate group, is not planar as would be expected. This is evidenced by the dihedral angles between the nitrophenyl ring and the carbamate, C13-C8-O2-C7=95.9 (2)°, and the benzyl ring and the carbamate, C2-C1-N1-C7=139.6 (2)°. Bond lengths and angles for (I) are within normal ranges (Allen et al., 1987). The molecules form one-dimensional chains formed through N-H···O hydrogen bonds along the b axis (Table 1).

In addition, intermolecular O···O interactions exists between nitro groups in neighboring chains (Fig. 2).
Experimental Aniline (1.0 g, 10.7 mmol) was added dropwise to a round-bottom flask containing 4-nitrophenyl chloroformate (2.2 g, 10.9 mmol) and pyridine (0.9 ml, 11.1 mmol) in 20 ml me thylene chloride cooled with ice water. After the solutuion was warmed to ambient temperature, the mixture was refluxed overnight with stirring. The solution was then washed with 1 N NaHCO 3 , water and brine, and then dried with anhydrous Na 2 SO 4 . After removal of the solvent, the product was recovered as a yellow solid (2.5 g, 90%) (Tye, et al. 2002). Colorless crystals of (I) were obtained by recrystallization from ethyl acetate.

Refinement
H atoms were found in difference Fourier maps and subsequently placed in idealized positions with constrained C-H distances of 0.95 Å (C Ar H), and 0.88 Å (NH 1 ). U iso (H) values were set to 1.2U eq for all H atoms. In the absence of significant anomalous scattering effects, Friedel pairs were merged prior to refinement. Fig. 1. The molecular structure of (I), with displacement ellipsoids drawn at the 50% probability level (arbitrary spheres for the H atoms).

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 > 2sigma(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.