N-(4-Bromo­phen­yl)pyrazine-2-carbox­amide

The mol­ecule of the title compound, C₁₁H₈BrN₃O, is close to planar (r.m.s. deviation of all 16 non-H atoms = 0.103 Å), a conformation stabilized by an intra­molecular N—H...N hydrogen bond, which generates an S(5) ring. In the crystal structure, supra­molecular chains mediated by C—H...O contacts (along a) are linked into a double layer via N...Br halogen bonds [3.207 (5) Å] and C—Br...π inter­actions [Br...ring centroid(pyrazine) = 3.446 (3) Å]. The layers stack along the b axis via weak π–π inter­actions [ring centroid(pyrazine)...ring centroid(benzene) distance = 3.803 (4) Å].

Key indicators

• Single-crystal X-ray study
• T = 120 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.054
• wR factor = 0.163
• Data-to-parameter ratio = 14.3

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT341_ALERT_3_C Low Bond Precision on  C-C Bonds (x 1000) Ang ..          9
PLAT431_ALERT_2_C Short Inter HL..A Contact  Br1    ..  N2      ..       3.21 Ang.
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600          4
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600          9

Alert level G
PLAT860_ALERT_3_G Note: Number of Least-Squares Restraints .......          1

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   4 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

Pyrazinamide has well known anti-mycobacterial activity and is the one of the most important drugs used in tuberculosis treatment (Chaisson et al., 2002; Gordin et al., 2000; de Souza, 2006). In continuation of our studies on pyrazinamide derivatives (Wardell et al., 2008; Baddeley et al., 2009; Howie et al., 2010a,b,c,d), we report the structure of N-(4-bromophenyl)pyrazine-2-carboxamide, the title compound, (I).

The molecular structure of (I), Fig. 1, is essentially planar with the dihedral angle formed between the pyrazine and benzene rings being 10.2 (3)°; the r.m.s. deviation of all 16 non-H atoms = 0.103 Å (Spek, 2009). The observed conformation is stabilized by an intramolecular N—H···N hydrogen bond, Table 1.

An analysis of the crystal packing reveals C—H···O, N···Br, Br···π, and π–π interactions. The C—H···O contacts lead to the formation of a supramolecular chain with a flat topology along the a axis. These are sustained in the crystal packing by N···Br halogen bonding [N2···Br1 = 3.207 (5) Å for i: 1 + x, y, 1 + z] (Metrangolo et al., 2008; Pennington et al., 2008), as well as Br···π contacts [C5—Br1···Cg(N2,N3,C8–C11)ⁱⁱ = 3.446 (3) Å, angle at Br1 = 94.59 (18)° for ii: 1 - x, 1 - y, -z]. The resulting double layers stack along the b axis, Fig. 3, with the closest interactions between them being of the form π–π [ring centroid(N2,N3,C8–C11)···ring centroid(C2–C7)ⁱⁱⁱ = 3.803 (4) Å, angle of inclination = 10.2 (3)° for iii: 1 - x, -y, -z].

Related literature

For the antimycobacterial activity of pyrazinamide, see: Chaisson et al. (2002); Gordin et al. (2000); de Souza (2006). For structural studies of pyrazinamide derivatives; see: Baddeley et al. (2009); Howie et al. (2010a,b,c,d). For the synthesis, see: Wardell et al. (2008); Vontor et al. (1989). For background to halogen bonding, see: Metrangolo et al. (2008); Pennington et al. (2008). For graph-set nomenclature of hydrogen bonds, see: Bernstein et al. (1995). For details of software used to analyse the shape of the molecule, see: Spek (2009). [Please confirm added references]

S2. Experimental

N-(4-Bromophenyl)pyrazine-2-carboxamide was prepared following the general procedure for N-arylpyrazine-2-carboxamides (Wardell et al., 2008). Yield: 48%; m.p. 473 K, lit. value 471–474 K (Vontor et al., 1989). The colourless plate of (I) used for the structure determination was grown from the slow evaporation of its ethanol solution.

S3. Refinement

The C-bound H atoms were geometrically placed (C—H = 0.95 Å) and refined as riding with U_iso(H) = 1.2U_eq(C). The N-bound H atom was located from a difference map and refined with the distance restraint N—H = 0.88 (1) Å, and with U_iso(H) = 1.2U_eq(N).

Computing details

Data collection: COLLECT (Nonius, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT (Nonius, 1998); data reduction: DENZO (Otwinowski & Minor, 1997) and COLLECT (Nonius, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

	Fig. 1. The molecular structure of (I) showing displacement ellipsoids at the 50% probability level.
	Fig. 2. Supramolecular chain in (I) aligned along the a axis. The C—H···O contacts are as orange dashed lines.
	Fig. 3. A view in projection down the a axis of the crystal packing in (I) highlighting the stacking of double layers. The C—H···O, N···Br, and Br···π contacts are shown as orange, blue, and purple dashed lines, respectively.

N-(4-Bromophenyl)pyrazine-2-carboxamide

Crystal data

C11H8BrN3O	Z = 2
Mr = 278.11	F(000) = 276
Triclinic, P1	Dx = 1.802 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 5.8396 (4) Å	Cell parameters from 22175 reflections
b = 7.3317 (7) Å	θ = 2.9–27.5°
c = 13.3362 (12) Å	µ = 3.99 mm^−1
α = 101.670 (4)°	T = 120 K
β = 96.728 (5)°	Plate, colourless
γ = 110.524 (5)°	0.18 × 0.10 × 0.02 mm
V = 512.55 (8) Å^3

Data collection

Enraf–Nonius KappaCCD diffractometer	2110 independent reflections
Radiation source: Enraf–Nonius FR591 rotating anode	1792 reflections with I > 2σ(I)
10 cm confocal mirrors monochromator	Rint = 0.078
Detector resolution: 9.091 pixels mm^-1	θmax = 26.5°, θmin = 3.1°
φ and ω scans	h = −7→7
Absorption correction: multi-scan (SADABS; Sheldrick, 2007)	k = −9→9
Tmin = 0.764, Tmax = 1.000	l = −16→16
8923 measured reflections

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)] = 0.054	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.163	H atoms treated by a mixture of independent and constrained refinement
S = 1.18	w = 1/[σ^2(Fo^2) + (0.1P)^2] where P = (Fo^2 + 2Fc^2)/3
2110 reflections	(Δ/σ)max = 0.001
148 parameters	Δρmax = 0.55 e Å^−3
1 restraint	Δρmin = −0.52 e Å^−3

Special details

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
Br1	0.20472 (10)	0.24870 (9)	−0.39064 (4)	0.0227 (2)
O1	0.8942 (7)	0.2880 (7)	0.0884 (3)	0.0259 (10)
N1	0.4828 (9)	0.2414 (8)	0.0622 (4)	0.0204 (10)
H1N	0.366 (9)	0.234 (10)	0.099 (5)	0.024*
N2	0.9106 (9)	0.2715 (8)	0.3965 (4)	0.0223 (11)
N3	0.4723 (9)	0.2202 (8)	0.2621 (4)	0.0212 (11)
C1	0.6982 (10)	0.2603 (8)	0.1192 (4)	0.0193 (12)
C2	0.4304 (10)	0.2444 (8)	−0.0435 (4)	0.0170 (11)
C3	0.1796 (10)	0.1859 (9)	−0.0902 (5)	0.0211 (12)
H3	0.0531	0.1461	−0.0512	0.025*
C4	0.1156 (10)	0.1861 (9)	−0.1937 (5)	0.0215 (12)
H4	−0.0549	0.1452	−0.2257	0.026*
C5	0.2979 (11)	0.2453 (8)	−0.2498 (5)	0.0192 (12)
C6	0.5492 (11)	0.3087 (9)	−0.2035 (5)	0.0210 (12)
H6	0.6745	0.3519	−0.2427	0.025*
C7	0.6156 (11)	0.3088 (9)	−0.1011 (5)	0.0205 (12)
H7	0.7868	0.3525	−0.0694	0.025*
C8	0.6915 (11)	0.2522 (9)	0.2304 (4)	0.0203 (12)
C9	0.9064 (11)	0.2777 (9)	0.2980 (5)	0.0198 (12)
H9	1.0565	0.3004	0.2724	0.024*
C10	0.6933 (11)	0.2377 (10)	0.4279 (5)	0.0229 (13)
H10	0.6870	0.2303	0.4979	0.028*
C11	0.4790 (11)	0.2134 (10)	0.3620 (5)	0.0243 (13)
H11	0.3300	0.1909	0.3883	0.029*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0268 (4)	0.0286 (4)	0.0140 (3)	0.0123 (3)	0.0025 (2)	0.0066 (2)
O1	0.021 (2)	0.040 (3)	0.019 (2)	0.0123 (19)	0.0067 (17)	0.010 (2)
N1	0.018 (2)	0.031 (3)	0.013 (2)	0.011 (2)	0.0028 (18)	0.005 (2)
N2	0.022 (2)	0.030 (3)	0.020 (3)	0.013 (2)	0.003 (2)	0.012 (2)
N3	0.018 (2)	0.024 (3)	0.017 (3)	0.005 (2)	0.0011 (19)	0.004 (2)
C1	0.020 (3)	0.015 (3)	0.019 (3)	0.005 (2)	0.003 (2)	0.002 (2)
C2	0.025 (3)	0.017 (3)	0.008 (3)	0.006 (2)	0.003 (2)	0.005 (2)
C3	0.016 (3)	0.026 (3)	0.020 (3)	0.008 (2)	0.005 (2)	0.004 (2)
C4	0.019 (3)	0.027 (3)	0.019 (3)	0.011 (2)	0.002 (2)	0.004 (2)
C5	0.026 (3)	0.016 (3)	0.018 (3)	0.011 (2)	0.005 (2)	0.007 (2)
C6	0.023 (3)	0.026 (3)	0.017 (3)	0.011 (2)	0.009 (2)	0.008 (2)
C7	0.018 (3)	0.023 (3)	0.021 (3)	0.007 (2)	0.000 (2)	0.010 (2)
C8	0.026 (3)	0.022 (3)	0.015 (3)	0.011 (2)	0.004 (2)	0.004 (2)
C9	0.022 (3)	0.020 (3)	0.019 (3)	0.010 (2)	0.007 (2)	0.004 (2)
C10	0.029 (3)	0.034 (3)	0.013 (3)	0.014 (3)	0.012 (2)	0.013 (2)
C11	0.024 (3)	0.033 (3)	0.021 (3)	0.012 (3)	0.014 (3)	0.012 (3)

Geometric parameters (Å, º)

Br1—C5	1.901 (6)	C3—H3	0.9500
O1—C1	1.226 (6)	C4—C5	1.369 (8)
N1—C1	1.337 (7)	C4—H4	0.9500
N1—C2	1.413 (7)	C5—C6	1.394 (8)
N1—H1N	0.88 (6)	C6—C7	1.375 (8)
N2—C9	1.321 (8)	C6—H6	0.9500
N2—C10	1.339 (8)	C7—H7	0.9500
N3—C11	1.340 (8)	C8—C9	1.387 (8)
N3—C8	1.352 (8)	C9—H9	0.9500
C1—C8	1.501 (8)	C10—C11	1.376 (8)
C2—C3	1.398 (8)	C10—H10	0.9500
C2—C7	1.402 (8)	C11—H11	0.9500
C3—C4	1.387 (8)
C1—N1—C2	128.5 (5)	C6—C5—Br1	120.2 (4)
C1—N1—H1N	113 (5)	C7—C6—C5	120.0 (5)
C2—N1—H1N	119 (5)	C7—C6—H6	120.0
C9—N2—C10	116.0 (5)	C5—C6—H6	120.0
C11—N3—C8	115.2 (5)	C6—C7—C2	120.0 (5)
O1—C1—N1	125.4 (6)	C6—C7—H7	120.0
O1—C1—C8	119.5 (5)	C2—C7—H7	120.0
N1—C1—C8	115.1 (5)	N3—C8—C9	121.6 (5)
C3—C2—C7	119.4 (5)	N3—C8—C1	118.2 (5)
C3—C2—N1	117.1 (5)	C9—C8—C1	120.2 (5)
C7—C2—N1	123.5 (5)	N2—C9—C8	122.6 (5)
C4—C3—C2	120.0 (5)	N2—C9—H9	118.7
C4—C3—H3	120.0	C8—C9—H9	118.7
C2—C3—H3	120.0	N2—C10—C11	122.1 (5)
C5—C4—C3	120.1 (5)	N2—C10—H10	119.0
C5—C4—H4	120.0	C11—C10—H10	119.0
C3—C4—H4	120.0	N3—C11—C10	122.6 (5)
C4—C5—C6	120.6 (6)	N3—C11—H11	118.7
C4—C5—Br1	119.1 (4)	C10—C11—H11	118.7
C2—N1—C1—O1	1.4 (10)	N1—C2—C7—C6	−179.5 (6)
C2—N1—C1—C8	179.5 (5)	C11—N3—C8—C9	−0.6 (8)
C1—N1—C2—C3	169.0 (5)	C11—N3—C8—C1	179.6 (5)
C1—N1—C2—C7	−13.3 (9)	O1—C1—C8—N3	−179.6 (5)
C7—C2—C3—C4	2.0 (9)	N1—C1—C8—N3	2.2 (8)
N1—C2—C3—C4	179.8 (5)	O1—C1—C8—C9	0.6 (8)
C2—C3—C4—C5	−0.6 (9)	N1—C1—C8—C9	−177.6 (5)
C3—C4—C5—C6	−1.0 (9)	C10—N2—C9—C8	0.4 (9)
C3—C4—C5—Br1	−178.8 (4)	N3—C8—C9—N2	0.3 (9)
C4—C5—C6—C7	1.2 (9)	C1—C8—C9—N2	−179.9 (5)
Br1—C5—C6—C7	179.0 (4)	C9—N2—C10—C11	−0.8 (9)
C5—C6—C7—C2	0.2 (9)	C8—N3—C11—C10	0.2 (9)
C3—C2—C7—C6	−1.8 (9)	N2—C10—C11—N3	0.5 (10)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···N3	0.88 (6)	2.22 (6)	2.708 (7)	115 (5)
C3—H3···O1^i	0.95	2.39	3.177 (8)	140

Symmetry code: (i) x−1, y, z.