Crystal structures of 4-chlorophenyl N-(3,5-dinitrophenyl)carbamate and phenyl N-(3,5-dinitrophenyl)carbamate

In the title compounds, the planes of the two aromatic rings are inclined to one another by 7.60 (8) and76.19 (8)°. In the crystals of both compounds, molecules are linked via N—H⋯O hydrogen bonds, forming chains along [010].


Structural commentary
The molecular structures of the title compounds, (I) and (II), are shown in Figs. 1 and 2, respectively. The molecules have different conformations. In compound (I), the benzene rings (C1-C6 and C8-C13) are almost coplanar, making a dihedral angle of 7.60 (8) . The mean plane of the carbamate group (N3/C7/O5/O6) is twisted out of the planes of the rings by 14.00 (9) and 20.96 (9) , respectively. In compound (II), the benzene and phenyl rings (C1-C6 and C8-C13, respectively) are roughly normal to one another, making a dihedral angle of 76.19 (8) . Here, the mean plane of the carbamate group (N3/ C7/O5/O6) is twisted out of the planes of the rings by 37.51 (8) and 80.90 (9) , respectively.

Figure 2
The molecular structure of compound (II), showing the atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Database survey
A search of the Cambridge Structural Database (Version 5.36, February 2015; Groom & Allen, 2014) for phenyl N-phenylcarbamate gave 16 hits for similar compounds, including two orthorhombic poylmorphs of phenyl N-phenylcarbamate itself (YEHPOQ: Lehr et al., 2001;YEHPOQ01;Shahwar et al., 2009). In the first polymorph (YEHPOQ), the phenyl rings are inclined to one another by 25.76 , while in the latter (YEHPOQ01) the equivalent dihedral angle is 42.50 . These values are quite different to those observed for compounds (I) and (II); cf. 7.60 (8) in (I), and 76.19 (8) in (II).

Synthesis and crystallization
The title compounds were prepared in a similar manner using a stirred solution of of 3,5 dinitroaniline (1.0 g, 5.45 mmol) dissolved in 100 ml of dry THF, and to it was added the calculated amount (with 5% excess) of 4-chlorophenylchloroformate for compound (I), or phenylchloroformate for compound (II), dissolved in 50 ml of dry THF. The addition rate was such that it took 90 min for complete transfer of 4chlorophenylchloroformate for compound (I), and phenylchloroformate for compound (II). After the addition was over, stirring was continued overnight. Excess THF was removed under vacuum at room temperature. The crude product was 746 Raja et al. A view along the a axis of the crystal packing of compound (II). The hydrogen bonds are shown as dashed lines (see Table 2 for details). extracted with ethyl acetate (3 Â 100 ml). The organic layer was dried over anhydrous sodium sulfate. Removal of solvent under vacuum at room temperature yielded a light-yellow product. It was dried under vacuum to constant weight. It was dissolved in ethyl acetate and just warmed-up using a water bath, and then kept at room temperature. The solvent was slowly evaporated and light-yellow crystals of each of the title compounds were obtained (yields 99%).

Refinement details
Crystal data, data collection and structure refinement details are summarized in Table 3. The N-and C-bound H atoms were positioned geometrically (N-H = 0.86 Å , C-H = 0.93 Å ) and allowed to ride on their parent atoms, with U iso (H) = 1.2U eq (N,C). For both compounds, data collection: APEX2 (Bruker, 2008); cell refinement: SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015) and PLATON (Spek, 2009).  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.