(2E)-1-(2-Bromo­phen­yl)-3-(4-meth­oxy­phen­yl)prop-2-en-1-one

In the title compound, C₁₆H₁₃BrO₂, two benzene rings form a dihedral angle of 44.3 (9)°. In the crystal, weak inter­molecular C—H...O hydrogen bonds link the mol­ecules into chains propagating in [010]. The crystal packing also exhibits short Br...Br contacts of 3.4787 (8) Å. A comparison of the DFT-optimized gas-phase mol­ecular geometry with that in the crystal structure revealed only small differences.

Key indicators

• Single-crystal X-ray study
• T = 110 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.034
• wR factor = 0.091
• Data-to-parameter ratio = 9.5

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT915_ALERT_3_B Low Friedel Pair Coverage ......................      16.86 Perc.

Alert level C
PLAT230_ALERT_2_C Hirshfeld Test Diff for    Br     --  C2      ..       6.11 su
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          2
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600          9
PLAT913_ALERT_3_C Missing # of Very Strong Reflections in FCF ....          5
PLAT912_ALERT_4_C Missing # of FCF Reflections Above STh/L=  0.600         42

Alert level G
REFLT03_ALERT_4_G  WARNING: Large fraction of Friedel related reflns may
                     be needed to determine absolute structure
           From the CIF: _diffrn_reflns_theta_max           74.12
           From the CIF: _reflns_number_total               1641
           Count of symmetry unique reflns         1506
           Completeness (_total/calc)            108.96%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured       135
           Fraction of Friedel pairs measured     0.090
           Are heavy atom types Z>Si present        yes
PLAT431_ALERT_2_G Short Inter HL..A Contact  Br     ..  Br      ..       3.48 Ang.
PLAT431_ALERT_2_G Short Inter HL..A Contact  Br     ..  Br      ..       3.48 Ang.
PLAT850_ALERT_4_G Check Flack Parameter Exact Value 0.00 and su ..       0.03

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

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   3 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
   3 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Chalcones, or 1,3-diaryl-2-propen-1-ones, belong to the flavonoid family. Chemically they consist of open-chain flavonoids in which the two aromatic rings are joined by a three-carbon α,β-unsaturated carbonyl system. A vast number of naturally occurring chalcones are polyhydroxylated in the aryl rings. The radical quenching properties of the phenolic groups present in many chalcones have raised interest in using the compounds or chalcone rich plant extracts as drugs or food preservatives (Dhar, 1981). The crystal structures of some closely related chalcones, viz., 1-(4-bromophenyl)-3-(3-methoxy-phenyl)prop-2-en-1-one (Patil et al., 2007); 4-bromo-4'-methoxy-chalcone (Li et al., 1992), 4-bromo-4'-methoxychalcone (Arai et al., 1994) and 1-(4-bromophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one (Shettigar et al., 2006) have been reported. Hence in continuation with the synthesis and crystal structure determination and also owing to the importance of these flavonoid analogs, this new bromo chalcone, (I), C₁₆H₁₃BrO₂, is synthesized and its crystal structure is reported.

The title compound, (I), C₁₆H₁₃BrO₂, is a chalcone with 4-methoxyphenyl and 2-bromophenyl rings bonded at opposite rings of a propene group (Fig. 1). The dihedral angle between mean planes of the para-methoxy and ortho-bromo substituted benzene rings is 44.3 (9)°. The angles between the mean plane of the prop-2-ene-1-one group and the mean planes of the 4-meyhoxyphenyl and 2-bromophenyl rings are 6.3 (1)° and 44.6(36°, respectively. Bond distances and angles are in normal ranges (Allen et al., 1987). While no classical hydrogen bonds are present, a weak intermolecular C12—H12A···O1 interaction (Table 1) is observed which contributes to the stability of crystal packing.

A density functional theory (DFT) geometry optimization molecular orbital calculation (Schmidt & Polik, 2007) was performed on (I) with the B3LYP 6–31-G(d) basis set (Hehre et al., 1986). The dihedral angle between mean planes of the para-methoxy and ortho-bromo substituted benzene rings becomes 45.98°, an increase of 1.59°. The angles between the mean plane of the prop-2-ene-1-one group and the mean planes of the 4-meyhoxyphenyl and 2-bromophenyl rings become 3.65° and 42.40°, changes of -2.65° and +0.74°, respectively. These observations suggest that the weak intermolecular C12—H12A···O1 interaction produces a small effect on crystal stability.

Related literature

For the radical quenching properties of included phenol groups, see: Dhar (1981). For related structures, see: Arai et al. (1994); Li et al. (1992); Patil et al. (2007); Shettigar et al. (2006). For standard bond lengths, see Allen et al. (1987). For density functional theory, see: Schmidt & Polik (2007); Hehre et al. (1986).

S2. Experimental

A 50% KOH solution was added to a mixture of 2-bromo acetophenone (0.01 mol, 1.99 g) and 4-methoxy benzaldehyde (0.01 mol, 1.36 g) in 25 ml of ethanol (Fig. 2). The mixture was stirred for an hour at room temperature and the precipitate was collected by filtration and purified by recrystallization from ethanol. The single-crystal was grown from ethyl acetate by slow evaporation method and yield of the compound was 50% (m.p.336–338 K). Analytical data, composition (%): found (calculated): C: 60.52 (60.59%); H: 4.10 (4.13%).

S3. Refinement

The H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C–H distances = 0.95–0.98Å and with U_iso(H) = 1.17–1.47 U_eq(C).

Computing details

Data collection: CrysAlis PRO (Oxford Diffraction, 2007); cell refinement: CrysAlis PRO (Oxford Diffraction, 2007); data reduction: CrysAlis PRO (Oxford Diffraction, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. Molecular structure of (I) showing the atom labeling scheme and 50% probability displacement ellipsoids.
	Fig. 2. Scheme for the synthesis of (I).

(2E)-1-(2-Bromophenyl)-3-(4-methoxyphenyl)prop-2-en-1-one

Crystal data

C16H13BrO2	F(000) = 320
Mr = 317.17	Dx = 1.616 Mg m^−3
Monoclinic, P21	Cu Kα radiation, λ = 1.54184 Å
Hall symbol: P 2yb	Cell parameters from 1981 reflections
a = 12.7300 (8) Å	θ = 4.5–74.1°
b = 4.0061 (3) Å	µ = 4.25 mm^−1
c = 13.0035 (6) Å	T = 110 K
β = 100.671 (5)°	Chunk, colourless
V = 651.68 (7) Å^3	0.48 × 0.41 × 0.28 mm
Z = 2

Data collection

Oxford Diffraction Xcalibur diffractometer with Ruby (Gemini Cu) detector	1641 independent reflections
Radiation source: Enhance (Cu) X-ray Source	1621 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.018
Detector resolution: 10.5081 pixels mm^-1	θmax = 74.1°, θmin = 4.5°
ω scans	h = −9→15
Absorption correction: multi-scan (CrysAlis RED; Oxford Diffraction, 2007)	k = −2→4
Tmin = 0.423, Tmax = 1.000	l = −15→16
2117 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.034	H-atom parameters constrained
wR(F^2) = 0.091	w = 1/[σ^2(Fo^2) + (0.0718P)^2 + 0.5775P] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max = 0.001
1641 reflections	Δρmax = 0.71 e Å^−3
173 parameters	Δρmin = −0.65 e Å^−3
1 restraint	Absolute structure: Flack (1983), 133 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.00 (3)

Special details

Experimental. IR data (KBr) ν cm^-1: 2998 cm^-1, 2937 cm^-1, 2839 cm^-1 (C—H al.str), 3058 cm^-1 (C—H ar. str) 1646 cm^-1 (C=O), 1580 cm^-1 (C=C); 1245 cm^-1 (C—O—C).

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
Br	0.38764 (3)	0.18817 (18)	0.46303 (2)	0.01538 (15)
O1	0.2178 (2)	0.2427 (10)	0.1406 (2)	0.0211 (8)
O2	0.8860 (2)	0.2977 (9)	0.1659 (2)	0.0209 (7)
C1	0.2190 (3)	0.4727 (13)	0.3077 (3)	0.0149 (9)
C2	0.2577 (3)	0.4233 (12)	0.4142 (3)	0.0119 (8)
C3	0.2022 (3)	0.5312 (12)	0.4896 (3)	0.0166 (9)
H3A	0.2299	0.4917	0.5616	0.020*
C4	0.1060 (3)	0.6971 (19)	0.4599 (3)	0.0223 (8)
H4A	0.0679	0.7740	0.5116	0.027*
C5	0.0651 (3)	0.7513 (12)	0.3545 (3)	0.0211 (11)
H5A	−0.0008	0.8660	0.3342	0.025*
C6	0.1203 (3)	0.6385 (14)	0.2797 (3)	0.0187 (10)
H6A	0.0913	0.6732	0.2078	0.022*
C7	0.2730 (3)	0.3590 (12)	0.2195 (3)	0.0173 (9)
C8	0.3891 (3)	0.4058 (13)	0.2303 (3)	0.0160 (9)
H8A	0.4255	0.5526	0.2824	0.019*
C9	0.4441 (3)	0.2431 (12)	0.1673 (3)	0.0161 (10)
H9A	0.4037	0.1037	0.1154	0.019*
C10	0.5595 (3)	0.2564 (10)	0.1697 (3)	0.0145 (11)
C11	0.5999 (3)	0.1064 (11)	0.0878 (3)	0.0164 (10)
H11A	0.5519	−0.0064	0.0344	0.020*
C12	0.7083 (3)	0.1171 (11)	0.0822 (3)	0.0155 (10)
H12A	0.7334	0.0191	0.0248	0.019*
C13	0.7787 (3)	0.2733 (11)	0.1619 (3)	0.0156 (10)
C14	0.7411 (4)	0.4183 (13)	0.2470 (3)	0.0186 (9)
H14A	0.7897	0.5209	0.3022	0.022*
C15	0.6327 (3)	0.4102 (13)	0.2495 (3)	0.0175 (9)
H15A	0.6075	0.5107	0.3065	0.021*
C16	0.9272 (3)	0.1512 (18)	0.0810 (3)	0.0223 (11)
H16A	0.9121	−0.0888	0.0783	0.033*
H16B	1.0046	0.1870	0.0916	0.033*
H16C	0.8930	0.2553	0.0151	0.033*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br	0.0159 (2)	0.0153 (2)	0.0148 (2)	−0.0005 (2)	0.00224 (13)	0.00195 (19)
O1	0.0204 (13)	0.028 (2)	0.0151 (11)	−0.0044 (15)	0.0031 (10)	−0.0034 (14)
O2	0.0169 (14)	0.027 (2)	0.0207 (14)	−0.0012 (13)	0.0070 (12)	−0.0027 (13)
C1	0.0154 (18)	0.016 (2)	0.0154 (17)	−0.0033 (18)	0.0081 (15)	−0.0001 (17)
C2	0.0083 (16)	0.008 (2)	0.0179 (17)	0.0027 (16)	−0.0026 (13)	0.0032 (17)
C3	0.021 (2)	0.014 (2)	0.0160 (18)	−0.0060 (18)	0.0067 (15)	−0.0023 (16)
C4	0.0242 (18)	0.018 (2)	0.0292 (19)	−0.004 (3)	0.0173 (15)	−0.006 (3)
C5	0.0136 (17)	0.016 (3)	0.034 (2)	0.0014 (18)	0.0047 (16)	0.0002 (19)
C6	0.0165 (17)	0.016 (3)	0.0228 (17)	−0.003 (2)	0.0023 (14)	0.0024 (19)
C7	0.023 (2)	0.015 (2)	0.0152 (18)	−0.0028 (19)	0.0061 (16)	0.0040 (17)
C8	0.0176 (19)	0.015 (3)	0.0155 (17)	−0.0006 (18)	0.0036 (14)	0.0011 (17)
C9	0.0189 (17)	0.016 (3)	0.0131 (15)	−0.0011 (18)	0.0025 (13)	0.0027 (18)
C10	0.0197 (18)	0.014 (3)	0.0113 (15)	0.0016 (17)	0.0058 (14)	0.0018 (15)
C11	0.0208 (19)	0.015 (3)	0.0135 (16)	0.0001 (17)	0.0037 (14)	0.0000 (15)
C12	0.0200 (18)	0.015 (3)	0.0124 (15)	0.0016 (17)	0.0062 (14)	−0.0020 (15)
C13	0.0179 (18)	0.014 (3)	0.0159 (17)	0.0019 (16)	0.0068 (14)	0.0034 (16)
C14	0.024 (2)	0.019 (2)	0.0122 (16)	−0.001 (2)	0.0024 (15)	−0.0014 (18)
C15	0.022 (2)	0.020 (3)	0.0116 (16)	0.002 (2)	0.0071 (15)	0.0001 (18)
C16	0.0181 (17)	0.025 (3)	0.0261 (18)	0.000 (2)	0.0101 (14)	−0.004 (2)

Geometric parameters (Å, º)

Br—C2	1.907 (4)	C8—H8A	0.9500
O1—C7	1.224 (5)	C9—C10	1.464 (5)
O2—C13	1.361 (5)	C9—H9A	0.9500
O2—C16	1.433 (5)	C10—C11	1.401 (6)
C1—C2	1.396 (5)	C10—C15	1.403 (6)
C1—C6	1.408 (6)	C11—C12	1.396 (6)
C1—C7	1.512 (5)	C11—H11A	0.9500
C2—C3	1.380 (6)	C12—C13	1.387 (6)
C3—C4	1.384 (7)	C12—H12A	0.9500
C3—H3A	0.9500	C13—C14	1.410 (6)
C4—C5	1.390 (6)	C14—C15	1.387 (6)
C4—H4A	0.9500	C14—H14A	0.9500
C5—C6	1.379 (6)	C15—H15A	0.9500
C5—H5A	0.9500	C16—H16A	0.9800
C6—H6A	0.9500	C16—H16B	0.9800
C7—C8	1.471 (6)	C16—H16C	0.9800
C8—C9	1.341 (6)
C13—O2—C16	116.7 (3)	C8—C9—H9A	116.4
C2—C1—C6	117.3 (4)	C10—C9—H9A	116.4
C2—C1—C7	125.7 (4)	C11—C10—C15	117.6 (4)
C6—C1—C7	117.1 (4)	C11—C10—C9	118.5 (4)
C3—C2—C1	121.9 (4)	C15—C10—C9	123.9 (4)
C3—C2—Br	116.4 (3)	C12—C11—C10	122.2 (4)
C1—C2—Br	121.7 (3)	C12—C11—H11A	118.9
C2—C3—C4	119.7 (4)	C10—C11—H11A	118.9
C2—C3—H3A	120.2	C13—C12—C11	118.9 (4)
C4—C3—H3A	120.2	C13—C12—H12A	120.6
C3—C4—C5	120.1 (4)	C11—C12—H12A	120.6
C3—C4—H4A	120.0	O2—C13—C12	124.5 (4)
C5—C4—H4A	120.0	O2—C13—C14	115.1 (4)
C6—C5—C4	119.9 (4)	C12—C13—C14	120.4 (4)
C6—C5—H5A	120.1	C15—C14—C13	119.5 (4)
C4—C5—H5A	120.1	C15—C14—H14A	120.2
C5—C6—C1	121.3 (4)	C13—C14—H14A	120.2
C5—C6—H6A	119.4	C14—C15—C10	121.3 (4)
C1—C6—H6A	119.4	C14—C15—H15A	119.3
O1—C7—C8	122.6 (4)	C10—C15—H15A	119.3
O1—C7—C1	118.7 (4)	O2—C16—H16A	109.5
C8—C7—C1	118.6 (4)	O2—C16—H16B	109.5
C9—C8—C7	120.5 (4)	H16A—C16—H16B	109.5
C9—C8—H8A	119.7	O2—C16—H16C	109.5
C7—C8—H8A	119.7	H16A—C16—H16C	109.5
C8—C9—C10	127.2 (4)	H16B—C16—H16C	109.5
C6—C1—C2—C3	0.1 (7)	C1—C7—C8—C9	164.4 (4)
C7—C1—C2—C3	−179.0 (4)	C7—C8—C9—C10	−178.4 (4)
C6—C1—C2—Br	177.7 (4)	C8—C9—C10—C11	−170.9 (4)
C7—C1—C2—Br	−1.3 (7)	C8—C9—C10—C15	9.4 (7)
C1—C2—C3—C4	−0.8 (7)	C15—C10—C11—C12	−2.4 (6)
Br—C2—C3—C4	−178.6 (4)	C9—C10—C11—C12	177.9 (4)
C2—C3—C4—C5	0.7 (8)	C10—C11—C12—C13	1.9 (6)
C3—C4—C5—C6	0.2 (9)	C16—O2—C13—C12	0.2 (7)
C4—C5—C6—C1	−1.1 (8)	C16—O2—C13—C14	179.6 (5)
C2—C1—C6—C5	0.9 (7)	C11—C12—C13—O2	179.4 (4)
C7—C1—C6—C5	180.0 (4)	C11—C12—C13—C14	0.0 (6)
C2—C1—C7—O1	139.4 (5)	O2—C13—C14—C15	179.2 (4)
C6—C1—C7—O1	−39.6 (7)	C12—C13—C14—C15	−1.4 (7)
C2—C1—C7—C8	−43.2 (7)	C13—C14—C15—C10	0.8 (7)
C6—C1—C7—C8	137.8 (5)	C11—C10—C15—C14	1.0 (7)
O1—C7—C8—C9	−18.2 (7)	C9—C10—C15—C14	−179.3 (4)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12A···O1^i	0.95	2.59	3.541 (5)	174

Symmetry code: (i) −x+1, y−1/2, −z.