Synthesis and crystal structures of (E)-1-Phenyl-3-[(2,4,6-Trimethylphenyl) ]prop-2-En-1-One and (E)-1-Phenyl-3-[(4-Trifluoromethylphenyl)]prop-2-En-1-One

Article abstract of DOI:10.1080/15421406.2013.875740

Two chalcone compounds, namely (E)-1-phenyl-3-[(2,4,6-trimethylphenyl)] prop-2-en- 1-one (1) and (E)-1-phenyl-3-[(4-trifluoromethylphenyl)]prop-2-en-1- one (2), have been synthesized and structurally characterized by elemental analysis, ¹H NMR

Full text of DOI:10.1080/15421406.2013.875740

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Synthesis and Crystal Structures
of (E)-1-Phenyl-3-[(2,4,6-
Trimethylphenyl)]prop-2-En-1-
One and (E)-1-Phenyl-3-[(4-
Trifluoromethylphenyl)]prop-2-En-1-One
a
b
b
b
Yun-Feng Liu , Wen-Jun Liang , Pei-Hua Zhao , Xin-Hang Li , Sheng-
b
b
Nan Liu & Ya-Qing Liu
a
College of Public Health, Shanxi Medical University, Taiyuan, P. R.
China
b
Research Center for Engineering Technology of Polymeric
Composites of Shanxi Province, College of Materials Science and
Engineering, North University of China, Taiyuan, P. R. China
Published online: 27 May 2014.
To cite this article: Yun-Feng Liu, Wen-Jun Liang, Pei-Hua Zhao, Xin-Hang Li, Sheng-Nan Liu & Ya-Qing
Liu (2014) Synthesis and Crystal Structures of (E)-1-Phenyl-3-[(2,4,6-Trimethylphenyl)]prop-2-En-1-
One and (E)-1-Phenyl-3-[(4-Trifluoromethylphenyl)]prop-2-En-1-One, Molecular Crystals and Liquid
Crystals, 593:1, 253-260, DOI: 10.1080/15421406.2013.875740
To link to this article: http://dx.doi.org/10.1080/15421406.2013.875740
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Mol. Cryst. Liq. Cryst., Vol. 593: pp. 253–260, 2014
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2013.875740
Synthesis and Crystal Structures of (E)-1-Phenyl-3-
[
(2,4,6-Trimethylphenyl)]prop-2-En-1-One and
(
E)-1-Phenyl-3-[(4-Trifluoromethylphenyl)]prop-2-
En-1-One
1
2
2,∗
2
YUN-FENG LIU, WEN-JUN LIANG, PEI-HUA ZHAO,
2
2
XIN-HANG LI, SHENG-NAN LIU, AND YA-QING LIU
1
College of Public Health, Shanxi Medical University, Taiyuan, P. R. China
2
Research Center for Engineering Technology of Polymeric Composites of
Shanxi Province, College of Materials Science and Engineering, North
University of China, Taiyuan, P. R. China
Two chalcone compounds, namely (E)-1-phenyl-3-[(2,4,6-trimethylphenyl)]prop-2-en-
1
-one (1) and (E)-1-phenyl-3-[(4-trifluoromethylphenyl)]prop-2-en-1-one (2), have
1
been synthesized and structurally characterized by elemental analysis, H NMR spec-
trum, and single-crystal X-ray diffraction analysis. The chalcone molecules in (1) and (2)
have the common skeleton of 1,3-diaryl-2-propen-1-one and adopt an (E)-configuration
about the C = C double bonds. In addition, X-ray analysis reveals that the π···π stacking
interactions are well observed in the crystal structure of (1) and (2).
Keywords Chalcone; crystal structures; intermolecular interaction; synthesis
Introduction
Chalcones that possess the common skeleton of 1,3-diaryl-2-propen-1-ones have attracted
much attention in recent years due to their extensive use or application in the field of
the synthetical and biological chemistry. On one hand, chalcones and their derivatives
are regarded as the signigficant precursors for the synthesis of different types of hetero-
cyclic compounds such as flavones, which are an important group of bioactive organic
compounds [1, 2]. On the other hand, natural and synthetic chalcones have been re-
ported to show many biological properties including antibacterial [3], antiinflammatory
[4], antifungal [5], antituberculosis [6, 7], and anti-HIV [8], etc. Eespecially, the unique
structures of the chalcone compounds, which contain two aromatic rings separated by
α,β-unsaturated ketone, are resposiber for various activites of these molecules [9]. This
seems very important to better understand the relationship between molecular structure
and biological activity through the study on the synthesis and structures of the chalcone
∗
Address correspondence to Dr. Pei-Hua Zhao, Research Center for Engineering Technology of
Polymeric Composites of Shanxi Province, College of Materials Science and Engineering, North Uni-
gv ec rz sx i 2t y0 1o 2f @C hg imn aa ,i lT. ca oi ym uan 030051, P.R. China. Tel.: +86-351-3559669. E-mail: zph2004@163.com,
253

254
Y.-F. Liu et al.
O
CH3
O
H C
CH3
CF3
3
1
2
Figure 1. The molecular structures of the title compounds (1) and (2).
compounds. In view of the above-mentioned information, we herein report that two chal-
cone compounds, chemically (E)-1-phenyl-3-[(2,4,6-trimethylphenyl)]prop-2-en-1-one (1)
and (E)-1-phenyl-3-[(4-trifluoromethylphenyl)]prop-2-en-1-one (2), have been synthesized
and structurally characterized using the single-crystal X-ray diffraction method as well as
spectroscopic techniques. Their molecular structures are as shown in Fig. 1. In this context,
we now wish to present the detailed crystal structure analyses of the title compounds (1)
and (2) based on X-ray crystallography.
Experimental
Materials and Instruments
All the chemicals were of reagent grade and used without further purification. Melting
points were determined on a YRT-3 apparatus and are uncorrected. Elemental analyses for
1
carbon and hydrogen were performed on a Perkin-Elmer 240C analyzer. H NMR spectra
were obtained on a Bruker Avance 400 MHz spectrometer.
Synthetic Procedures
The synthetic route of the title compounds (1) and (2) is presented in Scheme 1.
Scheme 1. Synthetic route for the title compounds (1) and (2).
Synthesis of (E)-1-phenyl-3-[(2,4,6-trimethylphenyl)]prop-2-en-1-one (1)
In 25 mL round-bottomed flask, the acetophenone (0.60 g, 5.0 mmol) and sodium hydroxide
(
0.30 g, 7.5 mmol) were dissolved in ethanol + water (2 mL + 3 mL), and the mixture was
stirred at room temperature for 5 min followed by addition of 2,4,6-trimethylbenzaldehyde
0.74 g, 5.0 mmol). The reaction mixture was then stirred at room temperature and monitored
(
by TLC until the reaction completed. The solid was filtered, washed with cold water,
recrystallized from ethanol, and dried in vacuo to give a white solid (0.90 g, yield of 72%).
◦
Mp: 101–103 C. Anal. Calcd. (%) for C18H18O: C, 86.36, H, 7.25. Found (%): C, 86.20,

Crystal Structures of Two Chalcone Compounds
255
Table 1. Crystal data and structural refinement details for (1) and (2)
Compounds
(1)
(2)
CCDC number
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
space group
944793
C18H18O
250.32
113 (2)
0.71073
944794
C16H11F3O
276.25
113 (2)
1.54187
Monoclinic
P2(1)/c
Monoclinic
P2(1)
a = 10.882 (8), α = 90
◦
Unit cell dimensions (Å, )
a = 14.7469 (5), α =
90
b = 5.661 (4), β =
b = 14.5697 (4), β =
92.8540 (10)
c = 5.8430 (2), γ = 90
1253.86 (7), 4
1.463
1
06.880 (9)
c = 11.726 (9), γ = 90
691.3 (9), 2
1.203
3
Volume (Å ), Z
Calculated density (g cm )
−3
Absorption coefficient μ
0.073
0.121
−1
(
mm )
F(000)
Crystal size (mm )
268
568
3
0.20 × 0.18 × 0.12
0.20 × 0.18 × 0.08
θ range for data collection
1.81–27.89
1.97–27.93
◦
(
)
Limiting indices
−14< = h< = 13,
−19< = h< = 19,
−14< = k< = 19,
−7< = l< = 7
12984
−
7< = k< = 7,
−
15< = l< = 15
Reflection collected
7270
Independent reflection
Completeness to θmax (%)
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
3199 (Rint = 0.0436)
3005 (Rint = 0.0491)
99.7
99.8
3199/1/175
3005/0/181
0.988
1.117
R1 = 0.0398, wR2 =
R1 = 0.0582, wR2 =
0.0712
0.0730
R indices (all data)
R1 = 0.0615, wR2 =
.0778
0.158 and −0.197
R1 = 0.0542, wR2 =
0.0777
0.221 and −0.267
0
Largest diff.e peak and hole
−
3
(
e A )
1
H, 7.12. H NMR (400 MHz, CDCl3, TMS): 2.31 (s, 3H, CH3), 2.40 (s, 6H, CH3), 6.93
(
s, 2H, PhH), 7.16 (d, J = 16.0 Hz, 1H, = CH), 7.50 (t, J = 8.0 Hz, 2H, PhH), 7.59
(dd, J = 5.2 Hz and 7.8 Hz, 1H, PhH), 7.98 (m, 3H, = CH + PhH) ppm.
Synthesis of (E)-1-phenyl-3-[(4-trifluoromethylphenyl)]prop-2-en-1-one (2)
The procedure was similar to that of 1 except 4-trifluoromethylbenzaldehyde (0.87 g,
5
2
.0 mmol) was used instead of 2,4,6-trimethylbenzaldehyde (0.74 g, 5.0 mmol). Compound
(1.35 g, 98%) was obtained as a slightly-yellow solid. Mp: 130–132 C. Anal. Calcd.
◦

256

Crystal Structures of Two Chalcone Compounds
257
Figure 2. Crystal structure of (1) with 30% probability thermal ellipsoids.
1
(
%) for C16H11F3O: C, 69.56, H, 4.01. Found (%): C, 69.38, H, 4.21. H NMR (400 MHz,
CDCl3, TMS): 7.49 (d, J = 15.6 Hz, 1H, = CH), 7.55 (d, J = 7.6 Hz, 1H, PhH), 7.60
(
(
m, 2H, PhH), 7.68 (d, J = 8.0 Hz, 2H, PhH), 7.75 (d, J = 8.0 Hz, 2H, PhH), 7.82
d, J = 15.6 Hz, 1H, = CH), 8.03 (d, J = 8.4 Hz, 2H, PhH) ppm.
Single-Crystal X-ray Diffraction
Single crystals of the title compounds (1) and (2) suitable for X-ray diffraction analyses
◦
were grown by slow evaporation of the CH2Cl2/hexane solution (v/v = 1:1) at 5 C.
Two single crystals with dimensions of 0.20 mm × 0.18 mm × 0.12 mm for (1) and
0
.16 mm × 0.14 mm × 0.12 mm for (2) were mounted on a Rigaku Saturn CCD area
deterctor. Data were collected at 113 (2) K by using a graphite monochromator with MoKα
radiation (λ = 0.71073 Å) for (1) and (2) in the ω-φ scanning mode. Absorption corrections
were performed by SADABS program [10]. The structures were solved by direct methods
using the SHELXS-97 program [11] and refined by full-matrix least-squares techniques
2
(
SHELXL-97) [12] on F . Hydrogen atoms were located using the geometric method.
Details of crystal data, data collection, and structure refinement for (1) and (2) are listed in
Table 1. Selected bond lengths and angles for (1) and (2) are given in Table 2.
Results and Discussion
Spectral Analyses
1
The as-prepared chalcone compounds were characterized by elemental analysis and H
NMR spectrum. Their structures were unambiguously determined using X-ray diffraction
analysis. The elemental analysis and NMR spectra have been in well agreement with the
formulae proposed by the X-ray crystallography for (1) and (2), respectively.
Crystal Structure Description of the Title Compound (1)
As depicted in Fig. 2, the chalcone molecule in (1) consists of a free phenyl ring and a
2,4,6-trimethylsubstituted phenyl ring linked by a C( O) CH CH unit, in which the
(
E)-configuration of the central propenone is similar to that observed in 1-phenyl-3-(2,4,6-
trimethoxyphenyl)prop-2-en-1-one [13] but different from the (Z)-configuration reported
in 1-phenyl-3-(2,4,6-triphenyphenyl)prop-2-en-1-one [14]. In central propenone system,
the C8 = C9 bond length (1.340 (2) Å) and the C7 = O1 one (1.231 (2) Å) are much
shorter than the C C bond distance (1.3317 (19) Å or 1.322 (3) Å) and the C O one

258
Y.-F. Liu et al.
Figure 3. Crystal packing diagram of (1) along the b-axis.
(1.2244 (17) Å or 1.214 (3) Å) is observed in its analogues [13, 14], respectively. This
suggests that (i) in comparasion with the methoxyl and benzene group, the introduction of
the methyl group into 2,4,6-positions of the phenyl group low the electron density within the
aromatic ring, which is in turn conjugated with the exocyclic propenone moiety [15]; (ii) the
extended π-electron conjugated system ( C( O) CH CH ) is mainly induced by the
2,4,6-trimethylsubstituted phenyl group rather than the free phenyl one [16]. Furthermore,
defined the C1–C6 phenyl ring as plane-I (r.m.s. deviation 0.0076 Å), the C10–C15 phenyl
ring as plane-II (r.m.s. deviation 0.0011 Å), and the central C7–C8 = C9–C10 unit as plane-
III (r.m.s. deviation 0.0040 Å), the dihedral angles between them (namely PLI,II, PLI,III and
◦
◦
◦
PLII,III) are 77.0 , 34.4 , and 45.1 , respectively, indicating that the two phenyl rings are
rotated in opposite directions relative to the central unit of plane-III [17]. The C7–C8 =
◦
C9–C10 torsional angle is 179.2 and the ketone O1 atom deviates from the above-defined
plane-III by 0.3039 Å, showing that the C O bond is not coplanar with the central C7–C8
=
C9–C10 moiety [18].
As shown in Fig. 3, the crystal packing of (1) is stabilized by the C H···O short
contacts involving the H atoms of the methyl group and the O atoms of the ketone group
[19]. For instance, the short nonbonded contact between the O1L atom of the ketone group
and the H atom linked to the methxyl C16A atom, which is 2.453 Å, exits in the adjacent
molecules. Apart from the short intermolecular contacts, there are weak π···π stacking
interactions involving the phenyl rings of two adjacent molecules [15], in which the phenyl
rings are parallel to each other with the centroid-to-centroid separation of 5.661 Å. As
Figure 4. Crystal structure of (2) with 30% probability thermal ellipsoids.

Crystal Structures of Two Chalcone Compounds
259
Figure 5. Crystal packing diagram of (2) along the c-axis.
a result, the two kinds of intermolecular interactions link the molecule into an infinite
three-dimensional network (Fig. 3).
Crystal Structure Description of the Title Compound (2)
As depicted in Fig. 4, the chalcone molecule of (2) has the similar skeleton of two phenyl
rings and one central propenone group as (1), where the (E)-conformation of the exocyclic
olefinic bond agrees quite well with that reported in its analogues such as 1-phenyl-3-(4-
fluorophenyl)prop-2-en-1-one [20], 1-phenyl-3-(4-methoxyphenyl)prop-2-en-1-one [21],
and 1-phenyl-3-(4-pentyloxyphenyl)prop-2-en-1-one [22], etc. In central propenone sys-
tem, the C8 = C9 bond length (1.3249 (16) Å) and the C7 = O1 one (1.2244 (14) Å) are
within the corresponding bond distance (C C for 1.319–1.333 Å and C O for 1.180–1.231
Å) found in its analogues [15 , 16 , 20–22], suggesting that the central π-electron conjugated
system ( C( O) CH CH ) is mainly induced by the mono-substituent in 4-position
of the phenyl ring [16]. Moreover, the dihedral angle between the C10–C15 plane of the
4
-trifluoromethylphenyl group and the C7–C8 = C9–C10 plane of the central propenone
◦
◦
moiety is 14.2 , which is sharply larger than the corresponding angle (45.1 ) in (1). The
dihedral angle made by the C10–C15 plane of the 4-trifluoromethylphenyl ring and the
◦
◦
C1–C6 plane of the free phenyl ring, which is 49.7 , is much greater than that (77.0 ) found
in (1). These observations indicate that the planarity of the entire molecule for (2) is much
better than that of (1), probably because of the steric repulsion of the 2,4,6-trimethylphenyl
substituent in (1) that is a bigger group with respect to the 4-trifluoromethylphenyl group
in (2).
As shown in Fig. 5, the π···π stacking interactions are observed in the crystal packing
of (2), together with normal van der Waals’ contancts. The adjacent molecules are collinear
to each other and arranged in layers via the weak π···π stacking interactions of the parallel
adjacent phenyl rings with the centroid-to-centroid separation of 5.843 Å [15].
Conclusions
In summary, two chalcone compounds [i.e., (E)-1-phenyl-3-[(2,4,6-trimethylphenyl)]prop-
2-en-1-one (1) and (E)-1-phenyl-3-[(4-trifluoromethylphenyl)]prop-2-en-1-one (2)] have

260
Y.-F. Liu et al.
1
been synthesized and structurally characterized elemental analysis and H NMR spec-
troscopy. Particularly, the molecular structures of (1) and (2) were unequivocally deter-
mined by single-crystal X-ray diffraction analysis, where the exocyclic olefinic bond reside
in a (E)-configuration in their solid state. In addition, the weak π···π stacking interactions
are observed in the crystal structures of (1) and (2).
Acknowledgments
This work was financially supported by the National Natural Science Foundation of China
(
(
No. 21301160) and the Natural Science Foundation for Young Scholars of Shanxi Province
No. 2012021007-4).
Supplementary Material
Crystallographic data for the structural analysis have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication number CCDC 944793 and
944794 for the title compounds (1) and (2), respectively. Copies of the data can be obtained
free of charge at http://www.ccdc.cam.ac.uk/conts/retrieving. html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44)
1223-336-033; e-mail: deposit@ccdc.cam.ac.uk.
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