N-(2-Bromo­phen­yl)acetamide

The title compound, C₈H₈BrNO, posseses normal geometrical parameters. The crystal packing is influenced by an inter­molecular N—H⋯O hydrogen bond.

Comment

The title compound, C₈H₈BrNO, (I), (Fig. 1) was prepared as an inter­mediate in a natural product synthesis.

The dihedral angle between the mean planes of the benzene ring (atoms C1–C6) and the N1/O1/C7/C8 side-chain grouping in (I) is 42.75 (14)°. This is inter­mediate between the situation in acetanilide [i.e. (I) without the Br atom], C₈H₉NO (Brown, 1966; Wasserman et al., 1985), where the aromatic ring and side chain are twisted by 17.6°, and N-methyl­acetanilide, C₉H₁₁NO (Pederson, 1967), where the two corresponding groups of atoms are constrained by symmetry to be perpendicular. The C_ar—N (ar = aromatic) bond distances are almost identical in (I) and acetanilide (Brown, 1966), being 1.418 (4) and 1.417 (2) Å respectively, as are the C_c—N (c = carbonyl) distances, at 1.358 (4) and 1.355 (2) Å, respectively. The equivalent distances in N-methyl­acetanilide (Pederson, 1967), where any electronic conjugation between the benzene ring and amide group is presumably impossible because of their perpendicular orientation, are distinctly different, with C_ar—N much longer at 1.474 Å and C_c—N significantly shorter at 1.325 Å.

The bond angle sum about N1 in (I) is 360.0°, suggesting that this atom is essentially sp²-hybridized. All the other geometrical parameters for (I) lie within their expected ranges (Allen et al., 1995).

The crystal packing in (I) is influenced by an N—H⋯O hydrogen bond (Table 1 and Fig. 2) that links the mol­ecules into chains propagating along [100]. There are no π–π stacking inter­actions in (I). The packing is shown in Fig. 3.

Figure 1 View of (I) (50% probability displacement ellipsoids; H atoms are drawn as small spheres of arbitrary radii).

Figure 2 Detail of (I) showing how the N—H⋯O hydrogen bond (dashed lines) links mol­ecules into a chain. The view direction is perpendicular to the mean plane of the benzene ring of the central mol­ecule, showing that no π–π stacking occurs. All H atoms except atom H1 and its symmetry equivalents have been omitted for clarity. [Symmetry codes: (i) x − 1, y, z; (ii) x + 1, y, z.]

Figure 3 The packing in (I), viewed down [100], with all H atoms except H1 omitted for clarity.

Experimental

2-Bromo­aniline (3.44 g, 20.0 mmol) was added to a solution of acetyl chloride (1.88 g, 24.0 mmol) and DIPEA (N,N-diisopropyl­ethyl­amine) (3.12 g, 24.0 mmol) in dry tetra­hydro­furan (20 ml) at 273 K. On completion (as monitored by thin-layer chromatography), the reaction mixture was diluted with water (20 ml) and the product was extracted with EtOAc (3 × 20 ml). The organic phase was then washed with water (2 × 20 ml) and brine (20 ml), then dried (MgSO₄) and evaporated under reduced pressure to yield the crude product, which was recrystallized from CH₂Cl₂ to give (I) (yield 97%, 4.13 g) as clear needles; one of these was cut to a block for data collection; m.p. 363–364 K; R_F = 0.12 [hexane/EtOAc (5:1)]. IR (KBr disc, cm⁻¹): ν_max 3272 (NH), 3159 (Ar—H), 1647 (C=O), 1518 (Ar C=C); ¹H NMR (250 MHz; CDCl₃): δ_H 2.21 (3H, s, CH₃), 6.97 (1H, t, J = 7.5 Hz, Ar—H), 7.29 (1H, t, J = 7.5 Hz, Ar—H), 7.51 (1H, d, J = 8.0 Hz, Ar—H), 7.61 (1H, bs, NH), 8.31 (1H, d, J = 7.5 Hz, Ar—H); ¹³C NMR (CDCl₃): δ_C 24.9 (–COCH₃), 113.2 (Ar C—Br), 122.0, 125.2, 128.4, 132.2 (4 × Ar C), 135.7 (–CO—NH—C–), 168.3 (–C=O). Mass spectrum: [M+H]⁺ 212.979, C₈H₈BrNO requires 212.979.

Crystal data

• C₈H₈BrNO

• M_r = 214.06

• Monoclinic, P 2₁ /n

• a = 4.7790 (1) Å

• b = 11.9257 (4) Å

• c = 14.6703 (3) Å

• β = 96.8173 (16)°

• V = 830.19 (4) ų

• Z = 4

• D_x = 1.713 Mg m⁻³

• Mo Kα radiation

• Cell parameters from 1977 reflections

• θ = 2.9–27.5°

• μ = 4.89 mm⁻¹

• T = 120 (2) K

• Block, colourless

• 0.24 × 0.10 × 0.07 mm

Data collection

• Nonius KappaCCD diffractometer

• ω and φ scans

• Absorption correction: multi-scan(SADABS; Bruker, 2003)T_min = 0.387, T_max = 0.726

• 9212 measured reflections

• 1905 independent reflections

• 1750 reflections with I > 2σ(I)

• R_int = 0.037

• θ_max = 27.5°

• h = −6 → 5

• k = −15 → 15

• l = −18 → 19

Refinement

• Refinement on F²

• R[F² > 2σ(F²)] = 0.032

• wR(F²) = 0.074

• S = 1.26

• 1905 reflections

• 106 parameters

• H atoms treated by a mixture of independent and constrained refinement

• w = 1/[σ²(F_o²) + 1.9011P] where P = (F_o² + 2F_c²)/3

• (Δ/σ)_max = 0.001

• Δρ_max = 0.76 e Å⁻³

• Δρ_min = −0.38 e Å⁻³

• Extinction correction: SHELXL97

• Extinction coefficient: 0.0163 (11)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯O1^i	0.83 (4)	2.10 (4)	2.896 (3)	161 (3)
Symmetry code: (i) x-1, y, z.

All the C-bound H atoms were placed in idealized positions (C—H = 0.95–0.98 Å) and refined as riding on their carriers with the constraint U_iso(H) = 1.2U_eq(carrier) or U_iso(H) = 1.5U_eq(methyl carrier) applied. The methyl group was allowed to rotate about the C7—C8 bond as a rigid group. The N-bound H atom was located in a difference map and its position was freely refined with the constraint U_iso(H) = 1.2U_eq(N).

Data collection: COLLECT (Nonius, 1998); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK, DENZO (Otwinowski & Minor, 1997) and SORTAV (Blessing, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Supporting information

S1. Comment

The title compound, C₈H₈BrNO, (I), (Fig. 1) was prepared as an intermediate in a natural product synthesis.

The dihedral angle between the mean planes of the benzene ring (atoms C1–C6) and the N1/O1/C7/C8 side-chain grouping in (I) is 42.75 (14)°. This is intermediate between the situation in acetanilide [i.e. (I) without the Br atom], C₈H₉NO (Brown, 1966; Wasserman et al., 1985), where the aromatic ring and side chain are twisted by 17.6°, and N-methylacetanilide, C₉H₁₁NO (Pederson, 1967), where the two equivalent groups of atoms are constrained by symmetry to be perpendicular. The C_ar—N (ar = aromatic) bond distances are almost identical in (I) and acetanilide (Brown, 1966), being 1.418 (4) and 1.417 (2) Å respectively, as are the C_c—N (c = carbonyl) distances, at 1.358 (4) and 1.355 (2) Å, respectively. The equivalent distances in N-methylacetanilide (Pederson, 1967), where any electronic conjugation between the benzene ring and amine group is presumably impossible because of their perpendicular orientation, are distinctly different, with C_ar—N much longer at 1.474 Å and C_c—N significantly shorter at 1.325 Å.

The bond angle sum about N1 in (I) is 360.0°, suggesting that this atom is more or less sp²-hybridized. All the other geometrical parameters for (I) lie within their expected ranges (Allen et al., 1995).

The crystal packing in (I) is influenced by an N—H···O hydrogen bond (Table 1 and Fig. 2) that links the molecules into chains propagating in [100]. There are no π–π stacking interactions in (I). The unit-cell packing is shown in Fig. 3.

S2. Experimental

2-Bromoaniline (3.44 g, 20.0 mmol) was added to a solution of acetyl chloride (1.88 g, 24.0 mmol) and DIPEA (N,N-diisopropylethylamine) (3.12 g, 24.0 mmol) in dry tetrahydrofuran (20 ml) at 273 K. On completion (as monitored by thin-layer chromatography), the reaction mixture was diluted with water (20 ml) and the product was extracted with EtOAc (3 × 20 ml). The organic phase was then washed with water (2 × 20 ml) and brine (20 ml), then dried (MgSO₄) and evaporated under reduced pressure to yield the crude product, which was recrystallized from CH₂Cl₂ to give (I) (yield 97%, 4.13 g) as clear needles; one of these was cut to a block for data collection; m.p. 363–364 K; R_F = 0.12 [hexane/EtOAc (5:1)]. IR (KBr disc, cm⁻¹): ν_max 3272 (NH), 3159 (Ar—H), 1647 (C═O), 1518 (Ar C═C); ¹H NMR (250 MHz; CDCl₃): δ_H 2.21 (3H, s, CH₃), 6.97 (1H, t, J = 7.5 Hz, Ar—H), 7.29 (1H, t, J = 7.5 Hz, Ar—H), 7.51 (1H, d, J = 8.0 Hz, Ar—H), 7.61 (1H, bs, NH), 8.31 (1H, d, J = 7.5 Hz, Ar—H); ¹³C NMR (CDCl₃): δ_C 24.9 (–COCH₃), 113.2 (Ar C—Br), 122.0, 125.2, 128.4, 132.2 (4 × Ar C), 135.7 (–CO—NH—C–), 168.3 (–C═O). Mass spectrum: [M+H]⁺ 212.979, C₈H₈BrNO requires 212.979.

S3. Refinement

All the C-bound hydrogen atoms were placed in idealized positions (C—H = 0.95–0.98 Å) and refined as riding on their carriers with the constraint U_iso(H) = 1.2U_eq(carrier) or U_iso(H) = 1.5U_eq(methyl carrier) applied. The methyl moiety was allowed to rotate about the C7—C8 bond as a rigid group. The N-bound H atom was located in a difference map and its position was freely refned with the constraint U_iso(H) = 1.2U_eq(N).

Computing details

Data collection: COLLECT (Nonius, 1998); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK, DENZO (Otwinowski & Minor, 1997) and SORTAV (Blessing, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. View of (I) (50% probability displacement ellipsoids; H atoms are drawn as small spheres of arbitrary radii).
	Fig. 2. Detail of (I) showing how the N—H···O hydrogen bond (dashed lines) links molecules into a chain. The view direction is perpendicular to the mean plane of the benzene ring of the central molecule, showing that no π–π stacking occurs. All H atoms except atom H1 have been omitted for clarity. [Symmetry codes: (i) x − 1, y, z; (ii) x + 1, y, z.]
	Fig. 3. Unit cell packing in (I), viewed down [010], with all H atoms except H1 omitted for clarity.

N-(2-Bromophenyl)acetamide

Crystal data

C8H8BrNO	F(000) = 424
Mr = 214.06	Dx = 1.713 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 1977 reflections
a = 4.7790 (1) Å	θ = 2.9–27.5°
b = 11.9257 (4) Å	µ = 4.89 mm^−1
c = 14.6703 (3) Å	T = 120 K
β = 96.8173 (16)°	Block, colourless
V = 830.19 (4) Å^3	0.24 × 0.10 × 0.07 mm
Z = 4

Data collection

Nonius KappaCCD diffractometer	1905 independent reflections
Radiation source: fine-focus sealed tube	1750 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.037
ω and ϕ scans	θmax = 27.5°, θmin = 3.3°
Absorption correction: multi-scan (SADABS; Bruker, 2003)	h = −6→5
Tmin = 0.387, Tmax = 0.726	k = −15→15
9212 measured reflections	l = −18→19

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difmap (N-H) and geom (others)
R[F^2 > 2σ(F^2)] = 0.032	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.074	w = 1/[σ^2(Fo^2) + 1.9011P] where P = (Fo^2 + 2Fc^2)/3
S = 1.26	(Δ/σ)max = 0.001
1905 reflections	Δρmax = 0.76 e Å^−3
106 parameters	Δρmin = −0.38 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0163 (11)

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 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
C1	0.4653 (6)	0.4807 (2)	0.7214 (2)	0.0159 (6)
C2	0.5507 (7)	0.5852 (3)	0.7562 (2)	0.0203 (6)
H2	0.4860	0.6123	0.8109	0.024*
C3	0.7304 (7)	0.6492 (3)	0.7106 (2)	0.0219 (7)
H3	0.7915	0.7203	0.7343	0.026*
C4	0.8223 (7)	0.6099 (3)	0.6300 (2)	0.0205 (6)
H4	0.9479	0.6538	0.5992	0.025*
C5	0.7307 (6)	0.5067 (3)	0.5946 (2)	0.0167 (6)
H5	0.7918	0.4807	0.5390	0.020*
C6	0.5493 (6)	0.4406 (2)	0.63992 (19)	0.0140 (6)
C7	0.6102 (6)	0.2594 (2)	0.56501 (19)	0.0153 (6)
C8	0.4592 (7)	0.1544 (3)	0.5295 (2)	0.0209 (7)
H8A	0.2575	0.1702	0.5151	0.031*
H8B	0.4863	0.0957	0.5765	0.031*
H8C	0.5355	0.1291	0.4739	0.031*
N1	0.4490 (5)	0.3362 (2)	0.60299 (16)	0.0135 (5)
H1	0.280 (8)	0.322 (3)	0.604 (2)	0.017 (9)*
O1	0.8634 (4)	0.27188 (19)	0.56131 (16)	0.0229 (5)
Br1	0.23224 (6)	0.39129 (3)	0.78845 (2)	0.02046 (13)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0132 (13)	0.0170 (14)	0.0177 (14)	0.0019 (11)	0.0025 (11)	0.0014 (11)
C2	0.0200 (15)	0.0194 (15)	0.0214 (15)	0.0018 (12)	0.0023 (12)	−0.0045 (12)
C3	0.0218 (16)	0.0149 (15)	0.0281 (17)	−0.0019 (12)	−0.0007 (13)	−0.0035 (13)
C4	0.0187 (15)	0.0175 (14)	0.0249 (16)	−0.0034 (12)	0.0012 (12)	0.0037 (13)
C5	0.0158 (14)	0.0193 (15)	0.0154 (14)	−0.0002 (11)	0.0029 (11)	0.0023 (12)
C6	0.0122 (13)	0.0136 (13)	0.0159 (13)	0.0021 (11)	0.0006 (10)	0.0013 (11)
C7	0.0157 (14)	0.0161 (14)	0.0143 (13)	0.0000 (11)	0.0029 (11)	0.0017 (11)
C8	0.0191 (15)	0.0181 (15)	0.0264 (16)	−0.0023 (12)	0.0059 (12)	−0.0065 (13)
N1	0.0107 (12)	0.0141 (12)	0.0164 (12)	−0.0016 (9)	0.0048 (9)	−0.0018 (10)
O1	0.0129 (10)	0.0239 (12)	0.0330 (13)	−0.0014 (9)	0.0069 (9)	−0.0054 (10)
Br1	0.02191 (19)	0.02130 (19)	0.01987 (19)	−0.00046 (12)	0.00956 (12)	0.00033 (12)

Geometric parameters (Å, º)

C1—C2	1.390 (4)	C5—H5	0.9500
C1—C6	1.390 (4)	C6—N1	1.418 (4)
C1—Br1	1.899 (3)	C7—O1	1.227 (4)
C2—C3	1.380 (5)	C7—N1	1.358 (4)
C2—H2	0.9500	C7—C8	1.507 (4)
C3—C4	1.390 (4)	C8—H8A	0.9800
C3—H3	0.9500	C8—H8B	0.9800
C4—C5	1.387 (4)	C8—H8C	0.9800
C4—H4	0.9500	N1—H1	0.83 (4)
C5—C6	1.397 (4)
C2—C1—C6	121.6 (3)	C1—C6—C5	118.3 (3)
C2—C1—Br1	118.5 (2)	C1—C6—N1	120.8 (3)
C6—C1—Br1	119.9 (2)	C5—C6—N1	121.0 (3)
C3—C2—C1	119.3 (3)	O1—C7—N1	123.2 (3)
C3—C2—H2	120.3	O1—C7—C8	121.3 (3)
C1—C2—H2	120.3	N1—C7—C8	115.5 (3)
C2—C3—C4	120.3 (3)	C7—C8—H8A	109.5
C2—C3—H3	119.9	C7—C8—H8B	109.5
C4—C3—H3	119.9	H8A—C8—H8B	109.5
C5—C4—C3	120.0 (3)	C7—C8—H8C	109.5
C5—C4—H4	120.0	H8A—C8—H8C	109.5
C3—C4—H4	120.0	H8B—C8—H8C	109.5
C4—C5—C6	120.6 (3)	C7—N1—C6	124.5 (2)
C4—C5—H5	119.7	C7—N1—H1	118 (2)
C6—C5—H5	119.7	C6—N1—H1	118 (2)
C6—C1—C2—C3	−2.1 (5)	Br1—C1—C6—N1	3.9 (4)
Br1—C1—C2—C3	177.1 (2)	C4—C5—C6—C1	−0.4 (4)
C1—C2—C3—C4	0.7 (5)	C4—C5—C6—N1	178.4 (3)
C2—C3—C4—C5	0.8 (5)	O1—C7—N1—C6	2.2 (5)
C3—C4—C5—C6	−0.9 (5)	C8—C7—N1—C6	−179.6 (3)
C2—C1—C6—C5	2.0 (4)	C1—C6—N1—C7	−138.6 (3)
Br1—C1—C6—C5	−177.3 (2)	C5—C6—N1—C7	42.6 (4)
C2—C1—C6—N1	−176.9 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^i	0.83 (4)	2.10 (4)	2.896 (3)	161 (3)

Symmetry code: (i) x−1, y, z.