Tetra-gonal polymorph of 5,5-dichloro-barbituric acid.

The tetra-gonal polymorph of 5,5-dichloro-barbituric acid (m.p. 478 K), C(4)H(2)Cl(2)N(2)O(3), forms an N-H⋯O hydrogen-bonded tape structure along [001]. Two tapes related by a twofold rotation axis are associated via Cl⋯O contacts [3.201 (1) Å], and four such chain pairs are arranged around a fourfold roto-inversion axis. The crystal structures of the monoclinic and ortho-rhom-bic polymorphs have been reported previously [Gelbrich et al. (2011 ▶). CrystEngComm, 13, 5502-5509].

Related literature

The polymorphic nature of 5,5-dichloro­barbituric acid was mentioned in Groth’s compendium on the chemical crystallography of organic compounds, published more than a hundred years ago (Groth, 1910 ▶). For the monoclinic and ortho­rhom­bic polymorphs, see: Gelbrich et al. (2011 ▶). For related structures, see: Gartland & Craven (1971 ▶); Gelbrich et al. (2007 ▶, 2010 ▶, 2010a ▶,b ▶); Nichol & Clegg (2007 ▶); Zencirci et al. (2009 ▶, 2010 ▶); DesMarteau et al. (1994 ▶). For a description of the synthesis, see: Ziegler et al. (1962 ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶); Etter et al. (1990 ▶).

Experimental

Crystal data

C4H2Cl2N2O3

M = 196.98

Tetragonal,

a = 13.8883 (3) Å

c = 6.9126 (2) Å

V = 1333.34 (6) Å3

Z = 8

Mo Kα radiation

μ = 0.92 mm−1

T = 173 K

0.20 × 0.05 × 0.05 mm

Data collection

Oxford Diffraction Xcalibur Ruby Gemini ultra diffractometer

Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2003 ▶) T min = 0.837, T max = 0.955

11025 measured reflections

1310 independent reflections

1242 reflections with I > 2σ(I)

R int = 0.041

Refinement

R[F 2 > 2σ(F 2)] = 0.020

wR(F 2) = 0.050

S = 1.07

1310 reflections

107 parameters

2 restraints

All H-atom parameters refined

Δρmax = 0.20 e Å−3

Δρmin = −0.16 e Å−3

Absolute structure: Flack (1983 ▶), 541 Friedel pairs

Flack parameter: −0.08 (7)

Data collection: CrysAlis PRO (Oxford Diffraction, 2003 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis RED (Oxford Diffraction, 2003 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶) and Mercury (Macrae et al., 2008 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811054626/su2351sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811054626/su2351Isup2.hkl

Supplementary material file. DOI: 10.1107/S1600536811054626/su2351Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

C4H2Cl2N2O3	Dx = 1.963 Mg m−3
Mr = 196.98	Melting point: 478 K
Tetragonal, P421c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P -4 2n	Cell parameters from 5173 reflections
a = 13.8883 (3) Å	θ = 2.9–29.3°
c = 6.9126 (2) Å	µ = 0.92 mm−1
V = 1333.34 (6) Å3	T = 173 K
Z = 8	Needle, colourless
F(000) = 784	0.20 × 0.05 × 0.05 mm

Oxford Diffraction Xcalibur Ruby Gemini ultra diffractometer	1310 independent reflections
Radiation source: Enhance Ultra (Mo) X-ray Source	1242 reflections with I > 2σ(I)
mirror	Rint = 0.041
ω scans	θmax = 26.0°, θmin = 2.9°
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2003)	h = −17→17
Tmin = 0.837, Tmax = 0.955	k = −16→17
11025 measured reflections	l = −7→8

Refinement on F2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	All H-atom parameters refined
R[F2 > 2σ(F2)] = 0.020	w = 1/[σ2(Fo2) + (0.0266P)2 + 0.2183P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.050	(Δ/σ)max < 0.001
S = 1.07	Δρmax = 0.20 e Å−3
1310 reflections	Δρmin = −0.16 e Å−3
107 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
2 restraints	Extinction coefficient: 0.0046 (8)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983), 541 Friedel pairs
Secondary atom site location: difference Fourier map	Flack parameter: −0.08 (7)

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 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.

	x	y	z	Uiso*/Ueq
Cl1	0.40679 (3)	0.41812 (3)	0.32982 (7)	0.01953 (13)
Cl2	0.26242 (3)	0.27671 (3)	0.22840 (7)	0.01938 (13)
O2	0.53042 (10)	0.10721 (9)	−0.1061 (2)	0.0225 (3)
O4	0.37178 (9)	0.39086 (9)	−0.0966 (2)	0.0178 (3)
O6	0.44620 (11)	0.22096 (11)	0.4808 (2)	0.0260 (4)
N1	0.48923 (11)	0.16639 (11)	0.1869 (2)	0.0158 (3)
N3	0.44480 (11)	0.24555 (11)	−0.0993 (2)	0.0127 (3)
C2	0.49068 (12)	0.16895 (13)	−0.0125 (3)	0.0134 (4)
C4	0.40209 (13)	0.32207 (12)	−0.0102 (3)	0.0120 (4)
C5	0.38637 (12)	0.30971 (12)	0.2083 (3)	0.0131 (4)
C6	0.44390 (12)	0.22935 (13)	0.3078 (3)	0.0148 (4)
H1	0.5202 (13)	0.1184 (10)	0.233 (3)	0.018*
H3	0.4508 (14)	0.2465 (15)	−0.2243 (14)	0.018*

	U11	U22	U33	U12	U13	U23
Cl1	0.0247 (2)	0.0140 (2)	0.0199 (2)	0.0036 (2)	−0.0065 (2)	−0.00722 (19)
Cl2	0.0156 (2)	0.0263 (2)	0.0162 (2)	−0.00433 (19)	0.00163 (18)	0.00387 (19)
O2	0.0286 (8)	0.0197 (7)	0.0193 (7)	0.0098 (6)	0.0067 (6)	−0.0037 (6)
O4	0.0212 (7)	0.0149 (7)	0.0172 (7)	0.0031 (5)	0.0002 (6)	0.0056 (6)
O6	0.0414 (9)	0.0266 (8)	0.0100 (7)	0.0112 (7)	−0.0030 (6)	0.0013 (6)
N1	0.0221 (8)	0.0124 (7)	0.0128 (8)	0.0072 (6)	−0.0019 (7)	0.0002 (7)
N3	0.0165 (8)	0.0151 (8)	0.0065 (7)	0.0004 (6)	0.0010 (6)	−0.0011 (7)
C2	0.0122 (9)	0.0134 (9)	0.0148 (10)	−0.0017 (7)	0.0013 (8)	0.0001 (8)
C4	0.0091 (9)	0.0132 (9)	0.0136 (9)	−0.0027 (7)	−0.0006 (8)	−0.0006 (7)
C5	0.0133 (8)	0.0130 (8)	0.0129 (9)	0.0006 (7)	0.0007 (7)	−0.0046 (7)
C6	0.0173 (9)	0.0140 (9)	0.0130 (10)	−0.0002 (7)	−0.0021 (7)	−0.0006 (8)

Cl1—C5	1.7471 (18)	N1—H1	0.856 (9)
Cl2—C5	1.7868 (18)	N3—C4	1.364 (2)
O2—C2	1.208 (2)	N3—C2	1.378 (2)
O4—C4	1.203 (2)	N3—H3	0.868 (9)
O6—C6	1.202 (2)	C4—C5	1.536 (3)
N1—C6	1.363 (2)	C5—C6	1.535 (2)
N1—C2	1.379 (2)
C6—N1—C2	127.07 (17)	N3—C4—C5	114.75 (16)
C6—N1—H1	120.1 (14)	C6—C5—C4	116.60 (15)
C2—N1—H1	112.9 (14)	C6—C5—Cl1	109.07 (12)
C4—N3—C2	127.31 (17)	C4—C5—Cl1	110.70 (13)
C4—N3—H3	118.6 (14)	C6—C5—Cl2	106.27 (12)
C2—N3—H3	113.6 (14)	C4—C5—Cl2	104.00 (12)
O2—C2—N3	121.74 (17)	Cl1—C5—Cl2	109.88 (10)
O2—C2—N1	121.60 (18)	O6—C6—N1	122.37 (18)
N3—C2—N1	116.65 (16)	O6—C6—C5	122.00 (17)
O4—C4—N3	123.15 (18)	N1—C6—C5	115.60 (16)
O4—C4—C5	121.84 (17)

D—H···A	D—H	H···A	D···A	D—H···A
N3—H3···O6i	0.87 (1)	2.07 (1)	2.923 (2)	167.(2)
N1—H1···O2ii	0.86 (1)	2.05 (1)	2.881 (2)	165 (2)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N3—H3⋯O6i	0.87 (1)	2.07 (1)	2.923 (2)	167 (2)
N1—H1⋯O2ii	0.86 (1)	2.05 (1)	2.881 (2)	165 (2)

Symmetry codes: (i) ; (ii) .