Orientational disorder in 4-chloro­nitro­benzene

The crystal structure of 4-chloro­nitro­benzene, C₆H₄ClNO₂, a material that exhibits disorder in the solid state, is re-examined using multiple-temperature single-crystal X-ray diffraction. Our results show a marked improvement on previous crystal structure determinations and our comprehensive multiple temperature measurements help to rationalize the structural anomalies. 4-Chloro­nitro­benzene exhibits twofold orientational disorder of the NO₂/Cl substituents, with the mol­ecule lying across an inversion centre. There is also evidence of large thermal motion, which exists at all temperatures and reflects the presence of significant disorder in this material. The nitro group shows possible libration, with one O atom exhibiting larger thermal motion than the other across the whole temperature range. This is explained by a difference in hydrogen-bonding environment.

S1. Comment

4-Chloronitrobenzene (p-ClNB) is one in a series of chloronitrobenzene derivatives that have a disordered structure in their crystalline state. Phase transitions are commonly associated with this disorder in these materials. Furthermore, there appears to be a correlation between this molecular disorder and the unusual dielectric behaviour that this series of materials tend to exhibit (Hall & Horsfall, 1973; Tanaka et al., 1974; Khotsyanova et al., 1969; Sakurai, 1962). Hitherto, three attempts to determine the crystal structure of p-ClNB have been made.

An initial indication of the nature of the crystal structure of p-ClNB was given by Toussaint (1952) who postulated that the space group could be P2₁/c with Z = 2 and a disordered crystal structure, or Pc with an ordered structure. It was concluded that Pc was more likely than P2₁/c.

A subsequent study on p-ClNB at room temperature (Mak & Trotter, 1962) revealed that the crystal structure was disordered over two possible orientations. The resulting disordered model, once refined, yielded R = 0.23 in the [100] projection and R = 0.26 in the [010] projection. An accurate determination of the bond geometry was not possible because of the disorder. However, basic analysis of intermolecular separations was able to show that all such separations corresponded to expected sums of relevant van der Waals radii. This implied that the two disordered orientations existed in the crystal structure without any steric or electronic hindrance. The fact that no diffuse scattering was observed in the measurements also led to the conclusion that the two possible disordered orientations were randomly positioned throughout the crystal structure.

More recently, a third attempt was made to reveal the nature of disorder in p-ClNB (Meriles et al., 2000). This study employed powder X-ray diffraction at a range of temperatures. Meriles et al. determined that a first-order phase-transition exists in p-ClNB at 282 K. Above this temperature, the crystal structure was found to be disordered as determined by Mak & Trotter (1962). For T < 282 K, the powder study indicated an ordered structure in space group P2₁, Z = 2. It is worthy of note that the crystal structure of the ordered phase was derived from a sample that had been stored cryogenically at T = 250 K for three months prior to the experiment. Such storage conditions were deemed necessary in order to ensure complete transformation to the ordered phase. Furthermore, a much higher level of background, present with a marked modulated profile, was noted in the diffraction pattern of this disordered phase compared with the low background associated with data from the ordered structure. This was attributed to diffuse scattering caused by molecular disorder.

Previously, nuclear quadrupolar resonance (NQR) has also been used to investigate this disorder on a local scale, with somewhat contradictory results (Meriles et al., 1996, 1997; González & Pusiol, 1996). In light of the limitations of the powder diffraction study, and the uncertainties observed in the various NQR spectroscopy studies, the molecular disorder in p-ClNB has been reinvestigated using multi-temperature single-crystal X-ray diffraction.

We were interested in exploring changes in the structure as a function of temperature. Data were therefore collected at 260, 250, 240, 230, 200, 150 and 100 K, and then again at 260 K to check for any hysteresis effects. The crystal was also observed to show a significant degree of sublimation at 270 K, making it difficult to collect data at this temperature. Subsequent thermogravimetric analysis (TGA) indicated that a sample the size of that used would diminish to around 10% of its initial volume in 50 min when held at 310 K, confirming its propensity to sublimation. The crystal structure solves to a twofold orientationally disordered model with the molecule lying across an inversion centre, as shown in Fig. 1. As the most accurate available determination, the 100 K structure is discussed further.

Owing to the molecular disorder, the Cl and N atomic fractions on each benzene-substituted site lie very close to one another in the model, resulting in a severe overlap of electron density contributions to scattering on each site. This, combined with the fact that Cl possesses a much higher electron density, makes it difficult to determine accurately the position of the N atom (and hence to draw any conclusions on its thermal motion, see above). Fourier maps calculated in the region of the NO₂/Cl groups, however, clearly confirm the presence of both groups on this site (Fig. 2).

The difficulty in assigning the electron density associated with the N and Cl atoms due to the presence of the disorder results in the apparent C—Cl distance from the refinement being longer than expected [1.903 (3) Å at100 K], whilst the apparent C—N distance is shorter than expected [1.330 (6) Å at 100 K]. The mean C—Cl distance in the Cambridge Structural Database (CSD; Allen, 2002; Bruno et al., 2002) for a Cl atom bonded to a benzene ring is 1.734 Å, the total range of values present being between 1.592 and 1.789 Å. The value found here is outside that range. The mean N—C bond length for an N atom within a nitro group bonded to a benzene ring is 1.467 Å, and the range found in the CSD is 1.396–1.544 Å. Again, the observed value for the unconstrained refinement here lies outside of this range. These bond lengths could be explained by consideration of the displacement ellipsoids of the C atoms in the benzene ring, as they are all elongated in the direction of the Cl atom/nitro group (Fig. 1). This could be interpreted in terms of the presence of two positions on each lattice point shifted relative to one another depending on the orientation of the molecule. The N atom is also located slightly off-centre, and thus one N—O bond length is considerably shorter than the other, with asymmetric O—N—C bond angles. The electron density associated with the O atoms is well defined and isolated from any other atoms, as shown in the difference Fourier maps (Fig. 2), and thus their positions could be considered to be more certain than the position of the N atom, whose electron density is located close to that of the Cl atom.

In the light of these abnormal bond lengths, a series of restraints and constraints were applied to the refinement to augment the initial unconstrained refinement and the visual information from the Fourier difference maps. Initially, the O—N bond lengths were restrained to take the same value – this geometry would be expected in a disorder-free symmetric nitro group (Fig. 3a). This restraint resulted in an increase in the R factor at 100 K from 0.0456 to 0.0464. The effect of applying this restraint is to equalize the N—O bond distances somewhat, but at the expense of shortening the N—C bond length further (Table 8). A stronger constraint could be applied, but this resulted in a further rise in the R factor and a further shortening of the N—C bond length, although it does force the O—N bond lengths to be equivalent and the O—N—C angles to be more similar (Fig. 3b). Application of the equivalent similarity restraints for the O—N—C angles resulted in similar effects. A refinement was also attempted to force the C—Cl and C—N bond lengths to take more conventional values (1.74 and 1.47 Å, respectively). This has the effect of shortening the N—O bond lengths to values shorter than those reported in the CSD (Bruno et al., 2002), but the values of the N—O distances and O—N—C angles are more symmetric. However, there is a significant rise in the R factor, and the Fourier difference map arising from the model clearly shows excess electron density around both the Cl and the N atoms, and some areas where too much electron density has been allocated (Fig. 3c). The anisotropic atomic displacement parameters also become extremely elongated, suggesting that this is not a good model. Fixing the N—O bond lengths to a more conventional value of 1.221 Å caused the R factor to rise to 0.0480 (Fig. 3d). However, the N—O bond lengths become relatively similar, as do the O—N—C bond angles. The N—C bond length is shorter than that found in the freely refined case, and the C—Cl bond length is slightly longer. This perhaps provides the best model for the molecule, as the nitro group is forced to adopt a more regular geometry. The model is still limited in the sense that it fails to deal adequately with the abnormal N—C and Cl—C bond lengths. This may suggest that the disorder is not simply a case of the molecule being flipped about a central point; rather, there is some translational component in the superposition of the two molecular orientations. Attempts were made to refine the structure in P2₁, but these gave a poorer agreement while not affecting the refined occupancies; P2₁/c appears to be the most appropriate space group for this refinement.

The average structure reveals two contacts that are shorter than the sum of the van der Waals radii (VDW). The first creates a dimer unit with a close O···H distance of 2.47 (2) Å at 100 K (VDW = 2.72 Å), and the second, a close O···Cl contact of 3.112 (4) Å (VDW = 3.27 Å). The dimers are not quite coplanar (Fig. 4). The O···Cl contact lies approximately along the line of the C—Cl bond (Fig. 5).

In general, the thermal motion of p-ClNB (Fig. 1) appears to be large at all temperatures (e.g. Table 9). It is possible that there is complex static disorder present, where two possible orientations that do not entirely overlap are are translationally displaced from one another. It is not possible to reach any firm conclusions regarding the potential disorder using standard Bragg scattering techniques – instead, modelling of diffuse scattering can yield information on this (e.g. Thomas et al., 2007). The most significant thermal motion of the NO₂ group is observed in U₃₃. The electron density spatial overlap problems corresponding to the N and Cl atoms may place some limitations on the accuracy of the atomic positions for these atoms (Fig. 2). However, atom O1 is found to be librating more than atom O2. This may be explained by considering the number of close intermolecular contacts in the packing of the molecules. Atom O2 [O1 according to Table 7; please check other references to O1 and O2 in this paragraph] is involved in a weak hydrogen bond (Desiraju & Steiner, 2001), where the interatomic distance [2.47 (2) Å] is less than the sum of the van der Waals radii of the twSD = Cambridge structural database.o atoms (2.72 Å) (Fig. 4). Atom O1 [O2?] has a close interatomic contact between the O and H atoms that is on the limit of the sum of the van der Waals radii [2.68 (2) Å]. There is also a close Cl···O intermolecular contact [3.112 (4) Å] involving O2 (Fig. 5). These interactions may place restrictions on the freedom of atom O2 to librate relative to that of O1, which may lead to the enhanced motion of one relative to the other.

Whilst no crystallographic phase transition was found in the temperature range 100–260 K, the possible drop in the cell parameter b (and possibly in c) at temperatures higher than 250 K (Fig. 6) hints at an incipient phase transition in this temperature region. This observation could relate to the phase transition revealed by Meriles et al. (2000), though there is a temperature mismatch. Analysis of U_ii as a function of temperature also show nitrogen to behave slightly anomalously upon cooling, in the temperature region 230–250 K, though this effect can be complicated in this case as a result of the disorder present. We could not collect a corresponding single-crystal data set for this material at temperatures above 282 K, however, since we observed that the sample sublimed before a full data set could be collected.

In conclusion, the crystal structure of p-ClNB has been studied at multiple temperatures to investigate the possibility of a phase transition at low temperature. The structure was found to be the same at all the temperatures studied, with the orientational disorder persisting at least down to 100 K; the refined disordered structure is of far higher quality than that obtained previously. The freely refined structure finds the O—N bond lengths to be asymmetric, and the N—C and Cl—C distances to be shorter and longer, respectively, than would be expected. The application of a series of restraints and constraints addressed the asymmetry of the N—O bond lengths but at the expense of perturbing the Cl—C and N—C bond lengths. This result potentially highlights a translational component to the disorder. The material shows significant thermal motion, but hydrogen bonding places restrictions upon the movement of one O atom relative to the other, resulting in an asymmetric libration of the nitro group. It is noted that the displacment ellipsoid model does not provide a comprehensive description of the possible libration of the NO₂ group of this compound. This fact suggests that a different modelling technique may be needed to understand better the thermal motion and possible libration observed. In this regard, total scattering studies of this material are in progress, since an analysis of both diffuse and Bragg scattering should also allow us to understand more fully the nature of the disorder – in particular, if there is a latent dynamic component of the disorder or a static translational shift in the positions of the two orientations. Indeed, structured diffuse scattering has already been observed in the diffraction pattern of p-ClNB (Thomas, 2007). These more sophisticated disorder models will be constructed using techniques similar to those in a study of the related compound pentachloronitrobenzene (Thomas et al., 2007).

Related literature

For related literature, see: Bruno et al. (2002); Khotsyanova et al. (1969); Meriles et al. (1996); Meriles et al. (1997); Meriles et al. (2000); Thomas et al. (2007); Allen (2002); Desiraju & Steiner (2001); Hall & Horsfall (1973); Mak & Trotter (1962); Sakurai (1962); Sheldrick (1997); Thomas (2007); Toussaint (1952).

S2. Experimental

A single crystal of p-ClNB was grown from diethyl ether by slow evaporation at room temperature. Data were collected at 100, 150, 200, 230, 240, 250 and 260 K to check for any signs of a phase transition. Attempts were also made to collect data at room temperature but the crystal sublimed before a full data set could be collected. An open-flow nitrogen Oxford Cryosystems cryostream was used for the multiple-temperature measurements.

S3. Refinement

The molecule exhibits twofold disorder (50:50 Cl:N occupancy). This disorder persists to low temperature, at least to 100 K. H atoms were located from Fourier difference maps and their fractional coordinates and isotropic displacement parameters were refined.

Computing details

For all compounds, data collection: COLLECT (Nonius, 1998); cell refinement: HKL SCALEPACK (Otwinowski & Minor, 1997); data reduction: HKL DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL-Plus (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. The disorder in 4-chloronitrobenzene at (a) 100 K, (b) 200 K and (c) 260 K. Displacement ellipsoids are plotted at the 50% probability level.
	Fig. 2. (a) A difference Fourier image showing the NO2 group calculated using a model with NO2 removed and (b) an Fobs image of the Cl atom in the structure of p-ClNB at 100 K. (Areas of high electron density are coloured red in the online version of the journal and areas of low electron density are blue.)
	Fig. 3. Fourier difference maps for the restrained and constrained models, with all atoms defined in the structure. (a) The restrained N—O bond lengths with 0.02 Å standard deviation; (b) the restrained N—O bond lengths with 0.002 Å standard deviation; (c) the case where the Cl—C and N—C bond lengths are forced to be close to their standard values; and (d) the case where the N—O bond lengths are restrained to be close to their standard values. The Fourier difference maps for (a), (b) and (d) are similar. The Fourier difference map for (c) clearly shows the unaccounted and over-accounted for electron density. (Areas of high electron density are coloured red in the online version of the journal and areas of low electron density are blue.)
	Fig. 4. The shortest hydrogen bonds in p-ClNB. (a) The chains of molecules connected by hydrogen bonds. Hydrogen bonding is shown with dashed lines. (b) The molecules are close to coplanar.
	Fig. 5. (a) The Cl—O close contacts between molecules in p-ClNB. (b) The nonplanar nature of the related molecules. Cl—O intermolecular interactions are represented by dashed lines. Adjacent molecules are related by the symmetry operation (-x, y + 1/2, -z + 1/2).
	Fig. 6. Unit-cell lengths of p-ClNB, normalized as length/(length at 100 K), as a function of temperature.

(I_260) 4-chloronitrobenzene

Crystal data

C6H4ClNO2	F(000) = 160
Mr = 157.55	Dx = 1.534 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.8011 (8) Å	Cell parameters from 1163 reflections
b = 6.7639 (14) Å	θ = 1.0–27.5°
c = 13.364 (3) Å	µ = 0.49 mm^−1
β = 96.82 (3)°	T = 260 K
V = 341.17 (12) Å^3	Needle, white
Z = 2	0.4 × 0.16 × 0.1 mm

Data collection

Nonius KappaCCD diffractometer	730 independent reflections
Radiation source: fine-focus sealed tube	365 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
CCD scans	θmax = 27.2°, θmin = 3.4°
Absorption correction: multi-scan multi-scan from symmetry-related measurements (SORTAV; Blessing, 1995)	h = −4→4
Tmin = 0.842, Tmax = 0.952	k = −8→8
2014 measured reflections	l = −16→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.046	Hydrogen site location: difference Fourier map
wR(F^2) = 0.134	All H-atom parameters refined
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0562P)^2 + 0.0122P] where P = (Fo^2 + 2Fc^2)/3
730 reflections	(Δ/σ)max < 0.001
72 parameters	Δρmax = 0.17 e Å^−3
0 restraints	Δρmin = −0.20 e Å^−3

Special details

Experimental. disordered material, sample sublimes at room temperature

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. The disordered model where the asymmetric unit is half a molecule has a 50% occupancy of chlorine:nitro group as the one non-hydrogen substituent.

Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cl1	0.1529 (11)	0.3364 (8)	0.3476 (4)	0.1081 (16)	0.50
C1	0.3526 (6)	0.1339 (5)	0.4342 (2)	0.0752 (8)
C3	0.3945 (6)	0.1828 (5)	0.5336 (2)	0.0808 (8)
C2	0.4554 (6)	−0.0456 (5)	0.3993 (2)	0.0848 (8)
O2	0.1509 (13)	0.2141 (8)	0.2787 (4)	0.1142 (17)	0.50
O1	0.1142 (19)	0.4178 (10)	0.4009 (8)	0.149 (3)	0.50
N1	0.196 (3)	0.2529 (16)	0.3630 (12)	0.105 (4)	0.50
H1	0.418 (6)	−0.064 (4)	0.335 (2)	0.093 (8)*
H2	0.321 (7)	0.311 (4)	0.5560 (19)	0.110 (9)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0848 (13)	0.132 (5)	0.1042 (19)	−0.008 (2)	−0.0009 (11)	0.040 (3)
C1	0.0548 (13)	0.094 (2)	0.0775 (17)	−0.0127 (12)	0.0123 (11)	−0.0012 (17)
C3	0.0710 (14)	0.091 (2)	0.0811 (19)	−0.0116 (13)	0.0132 (11)	−0.0176 (17)
C2	0.0771 (14)	0.115 (2)	0.0632 (17)	−0.0191 (14)	0.0125 (11)	−0.0222 (17)
O2	0.134 (4)	0.118 (4)	0.087 (3)	0.010 (3)	−0.002 (3)	0.021 (3)
O1	0.151 (5)	0.087 (4)	0.208 (7)	0.028 (3)	0.016 (5)	0.015 (5)
N1	0.075 (5)	0.069 (6)	0.177 (13)	−0.005 (4)	0.039 (7)	0.012 (6)

Geometric parameters (Å, º)

Cl1—C1	1.892 (4)	C3—H2	0.97 (3)
C1—N1	1.332 (11)	C2—C3^i	1.367 (4)
C1—C3	1.360 (3)	C2—H1	0.87 (3)
C1—C2	1.374 (4)	O2—N1	1.149 (17)
C3—C2^i	1.367 (4)	O1—N1	1.279 (17)
N1—C1—C3	122.8 (7)	C2^i—C3—H2	121.2 (15)
N1—C1—C2	114.4 (7)	C3^i—C2—C1	119.4 (3)
C3—C1—C2	122.8 (3)	C3^i—C2—H1	124.2 (16)
C3—C1—Cl1	114.4 (3)	C1—C2—H1	116.4 (16)
C2—C1—Cl1	122.8 (3)	O2—N1—O1	125.0 (11)
C1—C3—C2^i	117.8 (3)	O2—N1—C1	124.3 (10)
C1—C3—H2	120.9 (15)	O1—N1—C1	110.6 (12)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H2···O1^ii	0.97 (3)	2.58 (3)	3.493 (8)	157 (2)
C2—H1···O2^iii	0.87 (3)	2.80 (2)	3.374 (6)	125.3 (19)

Symmetry codes: (ii) −x, −y+1, −z+1; (iii) −x+1, y−1/2, −z+1/2.

(I_250) 4-chloronitrobenzene

Crystal data

C6H4ClNO2	F(000) = 160
Mr = 157.55	Dx = 1.534 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.7938 (3) Å	Cell parameters from 1300 reflections
b = 6.7564 (6) Å	θ = 1.0–27.5°
c = 13.3672 (15) Å	µ = 0.49 mm^−1
β = 96.639 (3)°	T = 250 K
V = 340.34 (6) Å^3	Needle, white
Z = 2	0.4 × 0.16 × 0.1 mm

Data collection

Nonius KappaCCD diffractometer	748 independent reflections
Radiation source: fine-focus sealed tube	385 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.037
CCD scans	θmax = 27.6°, θmin = 3.4°
Absorption correction: multi-scan multi-scan from symmetry-related measurements (SORTAV; Blessing, 1995)	h = −4→4
Tmin = 0.844, Tmax = 0.944	k = −8→8
2071 measured reflections	l = −17→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.052	Hydrogen site location: difference Fourier map
wR(F^2) = 0.139	All H-atom parameters refined
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0603P)^2 + 0.002P] where P = (Fo^2 + 2Fc^2)/3
748 reflections	(Δ/σ)max = 0.001
72 parameters	Δρmax = 0.13 e Å^−3
0 restraints	Δρmin = −0.15 e Å^−3

Special details

Experimental. disordered material, sample sublimes at room temperature

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. The disordered model where the asymmetric unit is half a molecule has a 50% occupancy of chlorine:nitro group as the one non-hydrogen substituent.

Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cl1	0.1499 (9)	0.3349 (7)	0.3480 (3)	0.0999 (14)	0.50
C1	0.3532 (6)	0.1341 (5)	0.43434 (19)	0.0707 (7)
C3	0.3950 (6)	0.1824 (5)	0.5338 (2)	0.0772 (8)
C2	0.4547 (6)	−0.0464 (5)	0.3997 (2)	0.0800 (8)
O2	0.1481 (13)	0.2122 (8)	0.2788 (4)	0.1092 (17)	0.50
O1	0.1115 (18)	0.4201 (9)	0.3984 (7)	0.134 (3)	0.50
N1	0.207 (3)	0.2521 (15)	0.3610 (11)	0.106 (5)	0.50
H1	0.418 (6)	−0.063 (4)	0.336 (2)	0.092 (8)*
H2	0.319 (6)	0.311 (4)	0.5554 (17)	0.095 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0761 (15)	0.123 (4)	0.0984 (19)	0.000 (2)	0.0017 (11)	0.033 (3)
C1	0.0473 (12)	0.0897 (19)	0.0759 (16)	−0.0104 (12)	0.0110 (10)	0.0021 (16)
C3	0.0673 (14)	0.093 (2)	0.0725 (18)	−0.0092 (13)	0.0133 (11)	−0.0188 (15)
C2	0.0686 (14)	0.113 (2)	0.0592 (16)	−0.0162 (14)	0.0115 (11)	−0.0173 (17)
O2	0.128 (4)	0.113 (4)	0.083 (3)	0.010 (3)	−0.006 (2)	0.024 (3)
O1	0.134 (5)	0.077 (4)	0.190 (7)	0.027 (3)	0.018 (4)	0.014 (4)
N1	0.059 (5)	0.066 (6)	0.196 (14)	0.003 (4)	0.029 (6)	0.005 (7)

Geometric parameters (Å, º)

Cl1—C1	1.887 (4)	C3—H2	0.97 (3)
C1—N1	1.334 (11)	C2—C3^i	1.358 (4)
C1—C3	1.360 (3)	C2—H1	0.86 (3)
C1—C2	1.375 (4)	O2—N1	1.128 (16)
C3—C2^i	1.358 (4)	O1—N1	1.308 (14)
N1—C1—C3	124.5 (7)	C1—C3—H2	120.0 (14)
N1—C1—C2	113.0 (6)	C3^i—C2—C1	119.5 (3)
C3—C1—C2	122.5 (3)	C3^i—C2—H1	125.0 (17)
C3—C1—Cl1	114.8 (3)	C1—C2—H1	115.5 (17)
C2—C1—Cl1	122.8 (3)	O2—N1—O1	123.2 (11)
C2^i—C3—C1	118.1 (3)	O2—N1—C1	126.3 (10)
C2^i—C3—H2	122.0 (14)	O1—N1—C1	110.3 (11)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H2···O1^ii	0.97 (3)	2.56 (3)	3.482 (7)	158 (2)
C2—H1···O2^iii	0.86 (3)	2.82 (3)	3.384 (6)	124.9 (19)

Symmetry codes: (ii) −x, −y+1, −z+1; (iii) −x+1, y−1/2, −z+1/2.

(I_240) 4-chloronitrobenzene

Crystal data

C6H4ClNO2	F(000) = 160
Mr = 157.55	Dx = 1.540 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.7880 (3) Å	Cell parameters from 1282 reflections
b = 6.7482 (6) Å	θ = 1.0–27.5°
c = 13.3755 (14) Å	µ = 0.49 mm^−1
β = 96.47 (3)°	T = 240 K
V = 339.73 (5) Å^3	Needle, white
Z = 2	0.4 × 0.16 × 0.1 mm

Data collection

Nonius KappaCCD diffractometer	747 independent reflections
Radiation source: fine-focus sealed tube	390 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.047
CCD scans	θmax = 27.4°, θmin = 3.4°
Absorption correction: multi-scan multi-scan from symmetry-related measurements (SORTAV; Blessing, 1995)	h = −4→4
Tmin = 0.850, Tmax = 0.945	k = −8→8
2069 measured reflections	l = −17→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.045	Hydrogen site location: difference Fourier map
wR(F^2) = 0.122	All H-atom parameters refined
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0499P)^2 + 0.0142P] where P = (Fo^2 + 2Fc^2)/3
747 reflections	(Δ/σ)max = 0.002
72 parameters	Δρmax = 0.16 e Å^−3
0 restraints	Δρmin = −0.20 e Å^−3

Special details

Experimental. disordered material, sample sublimes at room temperature

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. The disordered model where the asymmetric unit is half a molecule has a 50% occupancy of chlorine:nitro group as the one non-hydrogen substituent.

Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cl1	0.1503 (8)	0.3347 (6)	0.3477 (2)	0.0926 (11)	0.50
C1	0.3528 (5)	0.1331 (4)	0.43350 (16)	0.0668 (6)
C3	0.3944 (5)	0.1831 (4)	0.53347 (18)	0.0739 (7)
C2	0.4538 (5)	−0.0470 (4)	0.3993 (2)	0.0752 (7)
O2	0.1471 (12)	0.2114 (7)	0.2783 (4)	0.1030 (15)	0.50
O1	0.1135 (16)	0.4206 (8)	0.3982 (6)	0.127 (2)	0.50
N1	0.201 (3)	0.2496 (13)	0.3606 (10)	0.100 (4)	0.50
H1	0.414 (5)	−0.075 (3)	0.3311 (18)	0.081 (6)*
H2	0.314 (6)	0.311 (4)	0.5574 (16)	0.094 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0736 (12)	0.111 (3)	0.0912 (15)	−0.0028 (19)	0.0002 (9)	0.031 (2)
C1	0.0458 (11)	0.0858 (18)	0.0694 (15)	−0.0117 (11)	0.0088 (9)	−0.0006 (14)
C3	0.0612 (12)	0.0872 (19)	0.0747 (17)	−0.0097 (12)	0.0128 (10)	−0.0180 (14)
C2	0.0645 (12)	0.105 (2)	0.0569 (14)	−0.0142 (12)	0.0107 (10)	−0.0238 (15)
O2	0.116 (3)	0.108 (3)	0.082 (3)	0.004 (2)	−0.004 (2)	0.021 (3)
O1	0.128 (4)	0.073 (3)	0.178 (6)	0.022 (2)	0.010 (4)	0.004 (4)
N1	0.062 (4)	0.050 (5)	0.193 (12)	0.001 (3)	0.034 (6)	0.006 (6)

Geometric parameters (Å, º)

Cl1—C1	1.886 (3)	C3—H2	0.98 (2)
C1—N1	1.331 (9)	C2—C3^i	1.366 (3)
C1—C2	1.368 (3)	C2—H1	0.93 (2)
C1—C3	1.371 (3)	O2—N1	1.127 (14)
C3—C2^i	1.366 (3)	O1—N1	1.316 (11)
N1—C1—C2	113.2 (5)	C1—C3—H2	122.0 (13)
N1—C1—C3	124.1 (6)	C3^i—C2—C1	119.3 (2)
C2—C1—C3	122.6 (3)	C3^i—C2—H1	121.6 (13)
C2—C1—Cl1	123.2 (2)	C1—C2—H1	119.1 (13)
C3—C1—Cl1	114.2 (3)	O2—N1—O1	123.2 (9)
C2^i—C3—C1	118.0 (3)	O2—N1—C1	126.6 (8)
C2^i—C3—H2	119.9 (13)	O1—N1—C1	110.2 (10)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H2···O1^ii	0.98 (2)	2.54 (3)	3.476 (6)	158.6 (19)
C2—H1···O2^iii	0.93 (2)	2.75 (2)	3.376 (5)	126.0 (15)

Symmetry codes: (ii) −x, −y+1, −z+1; (iii) −x+1, y−1/2, −z+1/2.

(I_230) 4-chloronitrobenzene

Crystal data

C6H4ClNO2	F(000) = 160
Mr = 157.55	Dx = 1.546 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.7801 (3) Å	Cell parameters from 1212 reflections
b = 6.7338 (6) Å	θ = 1.0–27.5°
c = 13.3758 (15) Å	µ = 0.49 mm^−1
β = 96.34 (3)°	T = 230 K
V = 338.39 (6) Å^3	Needle, white
Z = 2	0.4 × 0.16 × 0.1 mm

Data collection

Nonius KappaCCD diffractometer	719 independent reflections
Radiation source: fine-focus sealed tube	396 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.049
CCD scans	θmax = 27.3°, θmin = 3.4°
Absorption correction: multi-scan multi-scan from symmetry-related measurements (SORTAV; Blessing, 1995)	h = −4→4
Tmin = 0.857, Tmax = 0.943	k = −8→8
1934 measured reflections	l = −17→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.049	Hydrogen site location: difference Fourier map
wR(F^2) = 0.126	All H-atom parameters refined
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0475P)^2 + 0.0323P] where P = (Fo^2 + 2Fc^2)/3
719 reflections	(Δ/σ)max = 0.003
72 parameters	Δρmax = 0.21 e Å^−3
0 restraints	Δρmin = −0.25 e Å^−3

Special details

Experimental. disordered material, sample sublimes at room temperature

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. The disordered model where the asymmetric unit is half a molecule has a 50% occupancy of chlorine:nitro group as the one non-hydrogen substituent.

Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cl1	0.1500 (8)	0.3347 (6)	0.3472 (3)	0.0886 (11)	0.50
C1	0.3513 (5)	0.1336 (4)	0.43346 (17)	0.0635 (7)
C3	0.3942 (6)	0.1839 (5)	0.5331 (2)	0.0707 (7)
C2	0.4544 (6)	−0.0479 (5)	0.3997 (2)	0.0735 (8)
O2	0.1468 (12)	0.2115 (7)	0.2784 (4)	0.0964 (15)	0.50
O1	0.1123 (16)	0.4216 (8)	0.3987 (6)	0.120 (2)	0.50
N1	0.198 (3)	0.2499 (13)	0.3612 (10)	0.089 (3)	0.50
H1	0.420 (6)	−0.072 (3)	0.3351 (19)	0.079 (7)*
H2	0.314 (7)	0.314 (4)	0.5534 (18)	0.094 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0711 (12)	0.107 (3)	0.0858 (16)	−0.0033 (19)	0.0012 (9)	0.031 (2)
C1	0.0442 (12)	0.0849 (18)	0.0622 (15)	−0.0119 (11)	0.0091 (9)	0.0000 (14)
C3	0.0590 (13)	0.0835 (19)	0.0704 (17)	−0.0108 (12)	0.0109 (11)	−0.0148 (14)
C2	0.0609 (14)	0.105 (2)	0.0554 (16)	−0.0157 (13)	0.0113 (11)	−0.0222 (16)
O2	0.113 (3)	0.099 (3)	0.074 (3)	0.007 (2)	−0.007 (2)	0.021 (3)
O1	0.119 (4)	0.069 (3)	0.169 (6)	0.018 (2)	0.013 (4)	0.002 (4)
N1	0.059 (4)	0.051 (5)	0.159 (10)	−0.001 (3)	0.023 (5)	0.010 (5)

Geometric parameters (Å, º)

Cl1—C1	1.884 (4)	C3—H2	0.98 (3)
C1—N1	1.326 (9)	C2—C3^i	1.364 (4)
C1—C3	1.368 (3)	C2—H1	0.87 (2)
C1—C2	1.374 (4)	O2—N1	1.133 (13)
C3—C2^i	1.364 (4)	O1—N1	1.315 (12)
N1—C1—C3	124.0 (6)	C1—C3—H2	119.0 (15)
N1—C1—C2	113.7 (6)	C3^i—C2—C1	119.6 (2)
C3—C1—C2	122.2 (3)	C3^i—C2—H1	122.1 (15)
C3—C1—Cl1	114.6 (3)	C1—C2—H1	118.2 (15)
C2—C1—Cl1	123.2 (2)	O2—N1—O1	123.4 (9)
C2^i—C3—C1	118.2 (3)	O2—N1—C1	126.2 (8)
C2^i—C3—H2	122.8 (15)	O1—N1—C1	110.4 (9)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H2···O1^ii	0.98 (3)	2.53 (3)	3.455 (7)	158 (2)
C2—H1···O2^iii	0.87 (2)	2.77 (2)	3.372 (5)	127.4 (18)

Symmetry codes: (ii) −x, −y+1, −z+1; (iii) −x+1, y−1/2, −z+1/2.

(I_200) 4-chloronitrobenzene

Crystal data

C6H4ClNO2	F(000) = 160
Mr = 157.55	Dx = 1.556 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.7635 (3) Å	Cell parameters from 1399 reflections
b = 6.7201 (6) Å	θ = 1.0–27.5°
c = 13.3762 (14) Å	µ = 0.50 mm^−1
β = 96.13 (3)°	T = 200 K
V = 336.37 (5) Å^3	Needle, white
Z = 2	0.4 × 0.16 × 0.1 mm

Data collection

Nonius KappaCCD diffractometer	736 independent reflections
Radiation source: fine-focus sealed tube	448 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.046
CCD scans	θmax = 27.4°, θmin = 3.1°
Absorption correction: multi-scan multi-scan from symmetry-related measurements (SORTAV; Blessing, 1995)	h = −4→4
Tmin = 0.838, Tmax = 0.946	k = −8→8
2051 measured reflections	l = −17→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.047	Hydrogen site location: difference Fourier map
wR(F^2) = 0.119	All H-atom parameters refined
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0446P)^2 + 0.0385P] where P = (Fo^2 + 2Fc^2)/3
736 reflections	(Δ/σ)max = 0.004
72 parameters	Δρmax = 0.15 e Å^−3
0 restraints	Δρmin = −0.26 e Å^−3

Special details

Experimental. disordered material, sample sublimes at room temperature

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. The disordered model where the asymmetric unit is half a molecule has a 50% occupancy of chlorine:nitro group as the one non-hydrogen substituent.

Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cl1	0.1506 (8)	0.3339 (5)	0.3462 (2)	0.0800 (9)	0.50
C1	0.3508 (5)	0.1338 (4)	0.43350 (15)	0.0586 (6)
C3	0.3939 (5)	0.1847 (4)	0.53332 (17)	0.0639 (7)
C2	0.4536 (5)	−0.0484 (4)	0.39946 (19)	0.0657 (7)
O2	0.1452 (10)	0.2104 (6)	0.2780 (3)	0.0837 (11)	0.50
O1	0.1124 (13)	0.4226 (7)	0.3973 (5)	0.1081 (19)	0.50
N1	0.196 (2)	0.2515 (12)	0.3625 (8)	0.080 (3)	0.50
H1	0.420 (6)	−0.076 (3)	0.3337 (18)	0.073 (7)*
H2	0.323 (6)	0.312 (4)	0.5546 (15)	0.074 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0625 (10)	0.099 (3)	0.0771 (12)	−0.0048 (17)	0.0003 (7)	0.0296 (17)
C1	0.0396 (11)	0.0776 (16)	0.0593 (13)	−0.0102 (10)	0.0089 (9)	−0.0004 (13)
C3	0.0519 (12)	0.0769 (17)	0.0642 (15)	−0.0093 (11)	0.0118 (10)	−0.0189 (13)
C2	0.0543 (12)	0.0953 (19)	0.0482 (13)	−0.0141 (11)	0.0093 (9)	−0.0194 (13)
O2	0.098 (3)	0.085 (3)	0.065 (2)	0.0046 (19)	−0.0047 (19)	0.019 (2)
O1	0.102 (3)	0.063 (3)	0.159 (5)	0.020 (2)	0.013 (3)	0.002 (3)
N1	0.052 (4)	0.052 (5)	0.140 (9)	−0.007 (3)	0.024 (5)	0.011 (4)

Geometric parameters (Å, º)

Cl1—C1	1.885 (3)	C3—H2	0.95 (2)
C1—N1	1.323 (8)	C2—C3^i	1.366 (3)
C1—C3	1.371 (3)	C2—H1	0.89 (2)
C1—C2	1.376 (3)	O2—N1	1.159 (11)
C3—C2^i	1.366 (3)	O1—N1	1.291 (10)
N1—C1—C3	123.2 (5)	C1—C3—H2	120.6 (13)
N1—C1—C2	114.4 (5)	C3^i—C2—C1	119.5 (2)
C3—C1—C2	122.4 (2)	C3^i—C2—H1	120.8 (14)
C3—C1—Cl1	115.1 (2)	C1—C2—H1	119.7 (14)
C2—C1—Cl1	122.5 (2)	O2—N1—O1	122.8 (8)
C2^i—C3—C1	118.1 (2)	O2—N1—C1	124.8 (8)
C2^i—C3—H2	121.3 (13)	O1—N1—C1	112.3 (9)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H2···O1^ii	0.95 (2)	2.55 (2)	3.440 (6)	156.0 (18)
C2—H1···O2^iii	0.89 (2)	2.74 (2)	3.363 (5)	128.1 (16)

Symmetry codes: (ii) −x, −y+1, −z+1; (iii) −x+1, y−1/2, −z+1/2.

(I_150) 4-chloronitrobenzene

Crystal data

C6H4ClNO2	F(000) = 160
Mr = 157.55	Dx = 1.574 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.7372 (2) Å	Cell parameters from 1413 reflections
b = 6.6991 (5) Å	θ = 1.0–27.5°
c = 13.3748 (13) Å	µ = 0.50 mm^−1
β = 96.84 (3)°	T = 150 K
V = 332.47 (4) Å^3	Needle, white
Z = 2	0.4 × 0.16 × 0.1 mm

Data collection

Nonius KappaCCD diffractometer	734 independent reflections
Radiation source: fine-focus sealed tube	490 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.042
CCD scans	θmax = 27.6°, θmin = 3.4°
Absorption correction: multi-scan multi-scan from symmetry-related measurements (SORTAV; Blessing, 1995)	h = −4→4
Tmin = 0.864, Tmax = 0.946	k = −8→8
2046 measured reflections	l = −17→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.046	Hydrogen site location: difference Fourier map
wR(F^2) = 0.113	All H-atom parameters refined
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0403P)^2 + 0.0675P] where P = (Fo^2 + 2Fc^2)/3
734 reflections	(Δ/σ)max = 0.017
72 parameters	Δρmax = 0.17 e Å^−3
0 restraints	Δρmin = −0.22 e Å^−3

Special details

Experimental. disordered material, sample sublimes at room temperature

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. The disordered model where the asymmetric unit is half a molecule has a 50% occupancy of chlorine:nitro group as the one non-hydrogen substituent.

Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cl1	0.1481 (6)	0.3346 (5)	0.3449 (2)	0.0664 (8)	0.50
C1	0.3501 (5)	0.1339 (3)	0.43288 (14)	0.0493 (6)
C3	0.3945 (5)	0.1869 (4)	0.53304 (15)	0.0532 (6)
C2	0.4532 (5)	−0.0503 (4)	0.39927 (17)	0.0556 (6)
O2	0.1452 (9)	0.2088 (5)	0.2771 (3)	0.0663 (9)	0.50
O1	0.1101 (11)	0.4229 (6)	0.3972 (5)	0.0866 (14)	0.50
N1	0.1947 (19)	0.2540 (10)	0.3626 (7)	0.060 (2)	0.50
H1	0.420 (6)	−0.078 (3)	0.3323 (17)	0.063 (6)*
H2	0.316 (6)	0.318 (3)	0.5549 (16)	0.066 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0488 (9)	0.087 (2)	0.0616 (9)	−0.0051 (12)	0.0002 (6)	0.0262 (14)
C1	0.0284 (9)	0.0709 (15)	0.0489 (11)	−0.0116 (9)	0.0055 (8)	−0.0030 (11)
C3	0.0403 (10)	0.0674 (15)	0.0529 (13)	−0.0091 (10)	0.0087 (9)	−0.0155 (11)
C2	0.0432 (11)	0.0834 (17)	0.0414 (12)	−0.0145 (10)	0.0097 (8)	−0.0199 (12)
O2	0.075 (2)	0.071 (2)	0.0507 (18)	0.0037 (16)	−0.0023 (15)	0.0140 (17)
O1	0.085 (3)	0.055 (3)	0.120 (4)	0.0197 (19)	0.010 (3)	0.002 (3)
N1	0.038 (3)	0.041 (4)	0.106 (7)	−0.003 (2)	0.019 (3)	0.005 (3)

Geometric parameters (Å, º)

Cl1—C1	1.884 (3)	C3—H2	0.98 (2)
C1—N1	1.319 (7)	C2—C3^i	1.363 (3)
C1—C3	1.377 (3)	C2—H1	0.91 (2)
C1—C2	1.384 (3)	O2—N1	1.176 (9)
C3—C2^i	1.363 (3)	O1—N1	1.277 (9)
N1—C1—C3	121.9 (4)	C1—C3—H2	120.9 (12)
N1—C1—C2	115.4 (4)	C3^i—C2—C1	119.6 (2)
C3—C1—C2	122.7 (2)	C3^i—C2—H1	120.8 (13)
C3—C1—Cl1	114.6 (2)	C1—C2—H1	119.6 (13)
C2—C1—Cl1	122.67 (19)	O2—N1—O1	124.3 (7)
C2^i—C3—C1	117.8 (2)	O2—N1—C1	122.8 (6)
C2^i—C3—H2	121.3 (12)	O1—N1—C1	112.9 (7)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H2···O1^ii	0.98 (2)	2.49 (2)	3.417 (5)	157.5 (17)
C2—H1···O2^iii	0.91 (2)	2.72 (2)	3.356 (4)	128.3 (16)

Symmetry codes: (ii) −x, −y+1, −z+1; (iii) −x+1, y−1/2, −z+1/2.

(I_100) 4-chloronitrobenzene

Crystal data

C6H4ClNO2	F(000) = 160
Mr = 157.55	Dx = 1.586 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.7139 (2) Å	Cell parameters from 1816 reflections
b = 6.6746 (5) Å	θ = 1.0–27.5°
c = 13.3712 (13) Å	µ = 0.51 mm^−1
β = 95.49 (3)°	T = 100 K
V = 329.93 (4) Å^3	Needle, white
Z = 2	0.4 × 0.16 × 0.1 mm

Data collection

Nonius KappaCCD diffractometer	745 independent reflections
Radiation source: fine-focus sealed tube	534 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.042
CCD scans	θmax = 27.4°, θmin = 3.1°
Absorption correction: multi-scan multi-scan from symmetry-related measurements (SORTAV; Blessing, 1995)	h = −4→4
Tmin = 0.860, Tmax = 0.942	k = −8→8
2151 measured reflections	l = −15→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.046	Hydrogen site location: difference Fourier map
wR(F^2) = 0.106	All H-atom parameters refined
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0283P)^2 + 0.1307P] where P = (Fo^2 + 2Fc^2)/3
745 reflections	(Δ/σ)max < 0.001
72 parameters	Δρmax = 0.19 e Å^−3
0 restraints	Δρmin = −0.30 e Å^−3

Special details

Experimental. disordered material, sample sublimes at room temperature

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. The disordered model where the asymmetric unit is half a molecule has a 50% occupancy of chlorine:nitro group as the one non-hydrogen substituent.

Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Cl1	0.1467 (5)	0.3349 (4)	0.34411 (15)	0.0500 (5)	0.50
C1	0.3492 (5)	0.1342 (3)	0.43270 (14)	0.0410 (5)
C3	0.3948 (5)	0.1885 (4)	0.53263 (15)	0.0440 (6)
C2	0.4517 (5)	−0.0517 (4)	0.39913 (16)	0.0454 (6)
O2	0.1429 (8)	0.2064 (5)	0.2761 (2)	0.0516 (8)	0.50
O1	0.1096 (10)	0.4249 (6)	0.3957 (4)	0.0653 (11)	0.50
N1	0.1931 (15)	0.2529 (8)	0.3617 (5)	0.0454 (17)	0.50
H1	0.418 (6)	−0.082 (3)	0.3314 (18)	0.055 (6)*
H2	0.317 (6)	0.317 (4)	0.5551 (16)	0.052 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0362 (7)	0.0663 (16)	0.0467 (8)	−0.0048 (9)	0.0002 (5)	0.0199 (10)
C1	0.0215 (9)	0.0630 (15)	0.0389 (11)	−0.0116 (9)	0.0053 (7)	−0.0065 (10)
C3	0.0291 (10)	0.0617 (15)	0.0424 (12)	−0.0094 (10)	0.0093 (8)	−0.0156 (10)
C2	0.0317 (10)	0.0734 (17)	0.0320 (11)	−0.0147 (10)	0.0083 (8)	−0.0190 (11)
O2	0.0561 (19)	0.054 (2)	0.0435 (18)	0.0021 (15)	−0.0020 (13)	0.0135 (15)
O1	0.063 (2)	0.040 (2)	0.094 (3)	0.0125 (16)	0.010 (2)	−0.002 (2)
N1	0.026 (2)	0.023 (3)	0.088 (5)	−0.003 (2)	0.012 (3)	0.005 (3)

Geometric parameters (Å, º)

Cl1—C1	1.895 (3)	C3—H2	0.96 (2)
C1—N1	1.326 (6)	C2—C3^i	1.375 (3)
C1—C3	1.379 (3)	C2—H1	0.92 (2)
C1—C2	1.386 (3)	O2—N1	1.183 (7)
C3—C2^i	1.375 (3)	O1—N1	1.284 (7)
N1—C1—C3	122.8 (4)	C1—C3—H2	121.6 (13)
N1—C1—C2	114.7 (3)	C3^i—C2—C1	119.3 (2)
C3—C1—C2	122.5 (2)	C3^i—C2—H1	120.9 (14)
C3—C1—Cl1	115.1 (2)	C1—C2—H1	119.8 (14)
C2—C1—Cl1	122.38 (17)	O2—N1—O1	123.8 (6)
C2^i—C3—C1	118.2 (2)	O2—N1—C1	123.6 (5)
C2^i—C3—H2	120.1 (13)	O1—N1—C1	112.6 (6)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H2···O1^ii	0.96 (2)	2.47 (2)	3.381 (5)	157.4 (18)
C2—H1···O2^iii	0.92 (2)	2.68 (2)	3.323 (4)	127.6 (17)

Symmetry codes: (ii) −x, −y+1, −z+1; (iii) −x+1, y−1/2, −z+1/2.