(E)-3-(4-Bromo-5-methyl­thio­phen-2-yl)acrylo­nitrile

In the title structure, C₈H₆BrNS, the molecules are planar with the exception of the methyl H atoms. In the crystal, molecules are linked by intermolecular C-H...N interactions to form ribbons parallel to the b axis. Groups of ribbons are arranged in a herringbone pattern to form a layered structure parallel to the ab plane.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.008 Å
• R factor = 0.048
• wR factor = 0.120
• Data-to-parameter ratio = 18.7

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT341_ALERT_3_C Low Bond Precision on  C-C Bonds ...............     0.0083 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          7

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF          ? Do !
PLAT371_ALERT_2_G Long   C(sp2)-C(sp1) Bond  C1     -   C2     ...       1.43 Ang.

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   3 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   2 ALERT level G = General information/check it is not something unexpected

   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
   3 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

During the research focused on new synthetic routes towards novel substituted thiophene derivatives, we have synthesized the title compound (I), which was isolated in high yield. Thiophene derivatives are interesting compounds (Zhao et al., 2009). They can be used in a wide range of applications such as enzyme inhibitors (Perner et al., 2003), photochromic materials (Kose, 2004; Pu et al., 2010), bioprobes (Chandra et al., 2006) and dyes (Dinçalp et al., 2011).

In the structure, the molecules of (E)-3-(4-bromo-5-methylthiophen-2-yl)-acrylonitrile (I) are planar, except for H atoms of the methyl group (Fig. 1). The molecules are linked by C—H···N interactions (Table 1) to form corrugated ribbons. The ribbons run parallel to the b axis and, within a ribbon, the orientation of consecutive molecules alternates to the left and right (Fig. 2). Groups of ribbons are arranged in a herringbone pattern to form a layered structure with layers parallel to the ab plane (Fig. 3).

Related literature

For related structures and their applications, see: Perner et al. (2003); Kose (2004); Chandra et al. (2006); Zhao et al. (2009); Pu et al. (2010); Dinçalp et al. (2011).

S2. Experimental

Synthesis of E-3-(4-bromo-5-methylthiophen-2-yl)acrylonitrile (I)

Diethyl (cyanomethyl)phosphonate (0.94 g, 5.3 mmol) was added to sodium hydride (6.25 mmol) suspended in dry THF (50 ml) under inert atmosphere. The mixture was stirred for 1 h, 3-bromo-2-methylthiophene-5-carboxaldehyde (1.00 g, 4.90 mmol) was added and stirring was continued overnight. Saturated aqueous ammonium chloride solution (25 ml) was added and the mixture was extracted with diethyl ether (4 × 50 ml). The organic phase was washed with saturated aqueous sodium hydrogen carbonate solution (50 ml) and brine (25 ml) and dried over anhydrous magnesium sulfate. The solvent was removed under reduced pressure and the crude product was separated by column chromatography (silica gel, Et₂O:hexane in 1:1 by volume) to give a mixture of E- and Z-isomers of 3-(4-bromo-5-methylthiophen-2-yl)acrylonitrile in 4:1 ratio. m.p. 80–81°C. ¹H NMR (400 MHz, CDCl₃, δ, p.p.m.): 7.23 (d, J = 16.3 Hz, 0.8H), 7.20 (d, J = 11.7 Hz, 0.2H), 6.98 (s, 1H), 5.46 (d, J = 16.3 Hz, 0.8H), 5.15 (d, J = 11.7 Hz, 0.2H), 2.37 (s, 0.6H), 2.35 (s, 2.4H). ¹³C NMR (100 MHz, CDCl₃, δ, p.p.m.): 141.6 (d), 140.0 (d), 138.9 (s), 135.2 (s), 134.8 (d), 133.5 (d), 117.8 (s), 110.9 (s), 94.5 (d), 91.2 (d), 15.4 (q). EI–MS (m/z, %): 229 ([M ⁸¹Br]⁺, 80), 227 ([M ⁷⁹Br]⁺, 78), 148 (100), 121 (10). HRMS (EI): Calculated for C₈H₆BrNS [M ⁷⁹Br]⁺ 226.9404; found: 226.9402. FT–IR (ν_max, cm^-1): 2211. Recrystallization from diethyl ether gave colorless crystals of the E-isomer (I).

S3. Refinement

H atoms were positioned geometrically and refined using a riding model. For sp² H atoms, U_iso(H) is constrained to 1.2 times the U_eq for the atoms they are bonded to and the C—H distance is 0.93 Å. For the methyl group, U_iso(H) is 1.5 times the U_eq for C atom they are bonded to and the C—H distance is 0.96 Å, with free rotation about the C—C bond.

Computing details

Data collection: COLLECT (Nonius, 2000); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997); data reduction: 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: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: WinGX (Farrugia, 2012) and CHEMDRAW Ultra (Cambridge Soft, 2001).

Figures

	Fig. 1. A molecule of I showing atom labels and 50% probability displacement ellipsoids for non-H atoms.
	Fig. 2. A segment of the crystal structure showing C—H···N interactions as dashed lines.
	Fig. 3. A segment of the crystal structure of I showing the herringbone arrangement to form layers of ribbons.

(E)-3-(4-Bromo-5-methylthiophen-2-yl)acrylonitrile

Crystal data

C8H6BrNS	F(000) = 448
Mr = 228.11	Dx = 1.752 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 1769 reflections
a = 6.1347 (5) Å	θ = 3.0–28.4°
b = 7.1124 (3) Å	µ = 4.92 mm^−1
c = 19.8245 (13) Å	T = 150 K
V = 864.99 (10) Å^3	Plate, yellow
Z = 4	0.40 × 0.30 × 0.10 mm

Data collection

Nonius KappaCCD diffractometer	1910 independent reflections
Radiation source: fine-focus sealed tube	1769 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.060
CCD scans	θmax = 27.4°, θmin = 3.0°
Absorption correction: empirical (using intensity measurements) (DENZO/SCALEPACK; Otwinowski & Minor, 1997)	h = −4→7
Tmin = 0.243, Tmax = 0.639	k = −9→7
3294 measured reflections	l = −25→20

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.048	w = 1/[σ^2(Fo^2) + (0.0412P)^2 + 2.3854P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.120	(Δ/σ)max < 0.001
S = 1.05	Δρmax = 0.74 e Å^−3
1910 reflections	Δρmin = −1.12 e Å^−3
102 parameters	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.030 (3)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack (1983), 699 Friedel pairs
Secondary atom site location: difference Fourier map	Absolute structure parameter: 0.03 (2)

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	−0.4336 (10)	−0.1420 (8)	0.7590 (3)	0.0265 (11)
C2	−0.2429 (10)	−0.1841 (9)	0.7200 (3)	0.0264 (12)
H2	−0.1959	−0.3079	0.7159	0.032*
C3	−0.1322 (9)	−0.0462 (8)	0.6895 (3)	0.0258 (12)
H3	−0.1824	0.0764	0.6946	0.031*
C4	0.0617 (10)	−0.0763 (7)	0.6489 (3)	0.0235 (11)
C5	0.1860 (10)	0.0569 (8)	0.6186 (3)	0.0222 (11)
H5	0.1553	0.1849	0.6203	0.027*
C6	0.3668 (10)	−0.0199 (8)	0.5843 (3)	0.0241 (12)
C7	0.3838 (8)	−0.2120 (7)	0.5887 (2)	0.0191 (11)
C8	0.5528 (11)	−0.3400 (7)	0.5583 (3)	0.0264 (12)
H8A	0.5059	−0.3791	0.5142	0.040*
H8B	0.5713	−0.4485	0.5865	0.040*
H8C	0.6888	−0.2741	0.5546	0.040*
N1	−0.5883 (9)	−0.1203 (8)	0.7912 (3)	0.0331 (11)
S1	0.1701 (3)	−0.2987 (2)	0.63524 (7)	0.0246 (3)
Br1	0.57000 (10)	0.12692 (8)	0.53635 (3)	0.0319 (2)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.022 (3)	0.028 (3)	0.030 (3)	−0.001 (3)	0.000 (2)	0.000 (2)
C2	0.024 (3)	0.027 (3)	0.029 (3)	0.003 (2)	0.001 (2)	−0.005 (2)
C3	0.023 (3)	0.025 (3)	0.029 (3)	0.006 (2)	−0.002 (2)	−0.003 (2)
C4	0.016 (2)	0.025 (3)	0.030 (3)	0.003 (2)	−0.002 (2)	−0.001 (2)
C5	0.023 (3)	0.018 (2)	0.026 (3)	0.004 (2)	−0.006 (2)	−0.006 (2)
C6	0.025 (3)	0.024 (3)	0.023 (3)	−0.001 (2)	−0.001 (2)	−0.004 (2)
C7	0.021 (3)	0.019 (2)	0.017 (2)	0.002 (2)	−0.0057 (19)	0.0017 (19)
C8	0.032 (3)	0.019 (3)	0.028 (3)	0.002 (2)	0.002 (2)	0.003 (2)
N1	0.031 (3)	0.031 (2)	0.038 (3)	−0.008 (3)	0.002 (2)	−0.004 (2)
S1	0.0240 (7)	0.0207 (6)	0.0291 (7)	0.0007 (6)	0.0021 (6)	−0.0004 (5)
Br1	0.0332 (3)	0.0259 (3)	0.0368 (3)	−0.0021 (3)	0.0065 (3)	0.0040 (2)

Geometric parameters (Å, º)

C1—N1	1.154 (8)	C5—H5	0.9300
C1—C2	1.434 (8)	C6—C7	1.373 (7)
C2—C3	1.338 (8)	C6—Br1	1.884 (6)
C2—H2	0.9300	C7—C8	1.506 (8)
C3—C4	1.452 (8)	C7—S1	1.717 (5)
C3—H3	0.9300	C8—H8A	0.9600
C4—C5	1.356 (8)	C8—H8B	0.9600
C4—S1	1.737 (5)	C8—H8C	0.9600
C5—C6	1.412 (8)
N1—C1—C2	175.6 (7)	C7—C6—C5	114.5 (5)
C3—C2—C1	120.3 (5)	C7—C6—Br1	122.3 (4)
C3—C2—H2	119.8	C5—C6—Br1	123.3 (4)
C1—C2—H2	119.8	C6—C7—C8	128.9 (5)
C2—C3—C4	123.9 (5)	C6—C7—S1	109.5 (4)
C2—C3—H3	118.0	C8—C7—S1	121.6 (4)
C4—C3—H3	118.0	C7—C8—H8A	109.5
C5—C4—C3	127.1 (5)	C7—C8—H8B	109.5
C5—C4—S1	110.6 (4)	H8A—C8—H8B	109.5
C3—C4—S1	122.3 (4)	C7—C8—H8C	109.5
C4—C5—C6	112.6 (5)	H8A—C8—H8C	109.5
C4—C5—H5	123.7	H8B—C8—H8C	109.5
C6—C5—H5	123.7	C7—S1—C4	92.8 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H3···N1^i	0.93	2.59	3.501 (8)	166

Symmetry code: (i) −x−1, y+1/2, −z+3/2.