Synthesis of Dichlorobenzamide Derivatives: Crystal Structures of 3,5-Dichloro-N-(2-chlorophenyl)benzamide and 3,5-Dichloro-N-(4-chlorophenyl)benzamide

Article abstract of DOI:10.1007/s10870-020-00822-9

Abstract: Reactions of 3,5-dichlorobenzoyl chloride and arylamine compounds in N,N′-dimethylformamidesolution at 60 °C afforded a series of dichlorobenzamidederivatives 4–14 in good yields. These new compounds and accompanyingintermediates were characterized and confirmed by nuclear magneticresonance and infrared spectroscopy, of which structures of compounds 4and 6 were established by X-ray crystallography. Compound 4 crystallizesin triclinic space group Pī, with a = 5.047 (18), b = 10.28 (4), c = 13.36 (5) ?, α =107.59 (5)°, β = 93.55 (5)°, γ = 98.34 (5)°, and Z = 2. The unit cell of 6 has a monoclinic Pn symmetry with the cell parameters a = 9.581 (3), b = 12.217 (4), c = 11.072 (3) ?, β = 92.584 (4)°, and Z = 4. Graphic Abstract: A series of 3,5-dichlorobenzamide compounds were synthesized from reactions of arylamine compounds with 3,5-dichlorobenzoyl chloride, which was prepared from 3,5-dichlorobenzonitrile.[Figure not available: see fulltext.]

Full text of DOI:10.1007/s10870-020-00822-9

Journal of Chemical Crystallography
https://doi.org/10.1007/s10870-020-00822-9
ORIGINAL PAPER
Synthesis of Dichlorobenzamide Derivatives: Crystal Structures
of 3,5-Dichloro-N-(2-chlorophenyl)benzamide and 3,5-Dichloro-N-(4-
chlorophenyl)benzamide
Jun Zhang1 · Yue Li1 · Bei Wang1 · Ai‑Quan Jia1 · Qian‑Feng Zhang1
Received: 26 August 2019 / Revised: 14 January 2020 / Accepted: 31 January 2020
© Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract
Reactions of 3,5-dichlorobenzoyl chloride and arylamine compounds in N,N′-dimethylformamidesolution at 60 °C aforded
a series of dichlorobenzamidederivatives 4–14 in good yields. These new compounds and accompanyingintermediates were
characterized and confrmed by nuclear magneticresonance and infrared spectroscopy, of which structures of compounds
4and 6 were established by X-ray crystallography. Compound 4 crystallizesin triclinic space group Pī, with a = 5.047 (18),
b = 10.28 (4), c = 13.36 (5) Å, α =107.59 (5)°, β = 93.55 (5)°, γ = 98.34 (5)°, and Z = 2. The unit cell of 6 has a monoclinic
Pn symmetry with the cell parameters a = 9.581 (3), b = 12.217 (4), c = 11.072 (3) Å, β = 92.584 (4)°, and Z = 4.
Graphic Abstract
A series of 3,5-dichlorobenzamide compounds were synthesized from reactions of arylamine compounds with 3,5-dichlo-
robenzoyl chloride, which was prepared from 3,5-dichlorobenzonitrile.
Keyword Dichlorobenzamide derivatives · Dichlorobenzoyl chloride · Arylamines · X-ray structure
Introduction
isothiazole-5-carboxylic acid derivatives were treated with
thionyl chloride to give carboxylic chloride, which reacted
with a series of arylamines to aford isothiazole carboxam-
ides [5]. Chlorobenzene derivatives have a lot of applica-
tion ranges of physical, chemical, and biological properties.
Some analogous derivatives showed their biological activity,
such as antitumoral and anticonvulsive activities [6].
As well known, benzene nucleus is of a special structure,
especially its acyl chloride compounds have various appli-
cations [1–4]. For example, 3,5-dichlorobenzoyl chloride is
an important substrate in the syntheses of various benza-
mide derivatives. In 1991, Hitoshi Shimotori reported that
On the other hand, arylamines are versatile organic
chemical materials, whose derivatives exhibit wide appli-
cations in the fields of medicines, industry and biol-
ogy [7]. However, only two structural derivatives, such
as 2,6-dichloro-N- (4-chlorophenyl)benzamide [8] and
* Qian-Feng Zhang
ahutchang@yahoo.com
1
Institute of Molecular Engineering and Applied Chemistry,
Anhui University of Technology, Ma’anshan 243002, Anhui,
People’s Republic of China
Vol.:(0123456789)
1 3

Journal of Chemical Crystallography
N-(2,4-dichlorophenyl)-2-nitrobenzamide [9], have been
confrmed by single-crystal X-ray crystallography, show-
ing relatively stable N‒H⋯O hydrogen bonds. Based on
these results, we are interested in reacting arylamines and
3,5-dichlorobenzoyl chloride to characterize a series of new
dichlorobenzamide derivatives by way of spectroscopical
methods and single crystal X-ray difraction.
mixture was cooled to room temperature and concentrated
under reduced pressure to obtain 3,5-dichlorobenzoyl chlo-
ride (3), which may be used directly in the synthesis of the
following amide derivatives.
General Synthetic Route for Dichlorobenzamide
Derivatives
Under nitrogen atmosphere, to a solution of 3,5-dichlo-
robenzoyl chloride (50 mg, 0.24 mmol) in DMF (5 mL) at
room temperature, the corresponding aryl amine in pyridine
was added. The reaction was heated at 60 °C for 2 h and
monitored by TLC (petroleum ether/ethyl acetate: v/v=4/1).
After the reaction completed, the mixture was cooled to
room temperature. Water (20 mL) was added to the reac-
tion mixture, a large amount of solid precipitated, which
was fltered and washed with water (5 mL×3) to obtain the
crude product. The crude product was purifed by column
chromatography (silica gel, petroleum ether/ethyl acetate
v/v=10/1–2/1) to obtain the corresponding pure products.
Experimental
General Procedure
All solvents were purifed by routine procedures and dis-
tilled under an atmosphere of dry nitrogen before use.
3,5-Dichlorobenzonitrile, 4-chloroaniline, 3-chloroaniline,
2-chloroaniline, 2,6-diisopropylaniline, 4-iodoaniline,
3-iodoaniline, 2-iodoaniline, benzylamine, 4-nitroaniline,
2,6-disopropylaniline and 2,4,6-trimethyl-aniline were pur-
chased from Alfa Aesar Ltd. and used directly without fur-
ther purifcation. The infrared spectra were recorded on a
Digilab FTS-40 spectrophotometer with use of pressed KBr
pellets. 1H NMR spectra were recorded on a Bruker AV 400-
MHz Advance NMR spectrometer. Elemental analysis were
recorded by Perkin Elmer 2400 CHN elementary analyser.
3,5-Dichloro-N-(4-chlorophenyl) benzamide (4)
White powder, yield: 68.5 mg (95%). The calculated of
elemental analysis (%): C 39.93, H 1.66, N 9.32; found of
elemental analysis (%): C 38.90, H 1.76, N 8.99. 1H NMR
(400 MHz, DMSO-d6): δ(ppm) 10.53 (s, 1H, –NH–), 7.97
(d, J=1.9 Hz, 2H, Ph), 7.89–7.84 (m, 1H, Ph), 7.81–7.76
(m, 2H, Ph), 7.43 (d, J=8.8 Hz, 2H, Ph). FT-IR (KBr disc,
cm−1): υas(N–H) 3280, υ(C=O) 1651, δ(N–H) 1563, υ(C–C)
1530 and 1291, β(C–H) 1096, γ(C–H) 745–873.
Synthesis of 3,5‑Dichlorobenzoic Acid (2)
To a solution of sodium hydroxide (2.9 g, 0.073 mol) in 10
mL of deionized water, 3,5-dichlorobenzonitrile (1) (5 g,
0.029 mol) was added slowly. Under stirring, the mixture
was heated and refuxed for 6 h. The reaction was moni-
tored by TLC (methanol/ethyl acetate: v/v=1/4). After the
reaction completed, the mixture was cooled to room tem-
perature and the pH value of the solution was adjusted to
1–3 by hydrogen chloride aqueous (2 mol/L). A white solid
precipitated, which was fltered under reduced pressure,
washed with water, and dried to give a white powder. The
fltrate was extracted with ethyl acetate. The white powder
obtained in two crops was recrystallized from deionized
water to obtain 3,5-dichlorobenzoic acid (2). Yield: 5.1 g
(93%). FT-IR (KBr disc, cm−1): υ(C–H) 3084, υ(O–H) 2663,
υ(C=O) 1706, υ(C–C) 1570 and 1448, β(C–O–H) 1403,
β(C–H) 1289 and 1237, γ(C–H) 769. 1H NMR (400 MHz,
DMSO-d6): δ(ppm) 7.90 (t, J = 2.0 Hz, 1H, Ph), 7.85 (d,
J=2.0 Hz, 2H, Ph).
3,5-Dichloro-N-(3-chlorophenyl) benzamide (5)
White powder, yield: 64.2 mg (89%). The calculated of
elemental analysis (%): C 39.93, H 1.66, N 9.32; found of
elemental analysis (%): C 39.69, H 1.63, N 9.02. 1H NMR
(400 MHz, DMSO-d6): δ(ppm) 10.55 (s, 1H, –NH–), 7.97
(d, J = 1.9 Hz, 2H, Ph), 7.93 (t, J = 1.9 Hz, 1H, Ph), 7.88
(t, J = 1.9 Hz, 1H, Ph), 7.68 (d, J = 7.7 Hz, 1H, Ph), 7.40
(t, J=8.1 Hz, 1H, Ph), 7.21–7.16 (m, 1H, Ph). FT-IR (KBr
disc, cm−1): υ(C–H) 3078, υ(C=O) 1644, δ(N–H) 1589,
υ(C–C) 1566 and 1541, β(C–H) 1310 and 1291, γ(C–H)
676–866.
3,5-Dichloro-N-(2-chlorophenyl) benzamide (6)
Synthesis of 3,5‑Dichlorobenzoyl Chloride (3)
White powder, yield: 63.5 mg (88%). The calculated of
elemental analysis (%): C 39.93, H 1.66, N 9.32; found of
elemental analysis (%): C 38.77, H 1.65, N 9.27. 1H NMR
(400 MHz, DMSO-d6): δ(ppm) 10.36 (s, 1H, –NH–), 7.99
(d, J = 1.9 Hz, 2H Ph), 7.91 (dt, J = 3.8, 2.0 Hz, 1H, Ph),
7.56 (ddd, J=9.7, 7.9, 1.6 Hz, 2H, Ph), 7.40 (td, J=7.7, 1.5
A mixture of 3,5-dichlorobenzoic acid (5.0 g, 26 mmol) and
thionyl chloride (8.2 g, 68 mmol) was heated at refux for
2 hours. The reaction was monitored by TLC (methanol/
ethyl acetate: v/v=1/4). After the reaction completed, the
1 3

Journal of Chemical Crystallography
Hz, 1H, Ph),7.33 (td, J=7.7, 1.7 Hz, 1H, Ph). FT-IR (KBr
disc, cm−1): υas(N–H) 3265, υ(C=O) 1649, δ(N–H) 1587,
υ(C–C) 1557 and 1527, β(C–H) 1307 and 1259, γ(C–H)
664–801.
3,5-Dichloro-N-benzyl benzamide (11)
White powder, yield: 47.7 mg (71%). The calculated of
elemental analysis (%): C 59.98, H 3.93, N 5.00; found of
elemental analysis (%): C 59.88, H 3.73, N 5.12. 1H NMR
(400 MHz, DMSO-d6): δ(ppm) 9.26 (t, J = 5.8 Hz, 1H,
–NH–), 7.91 (d, J = 1.9 Hz, 2H, Ph), 7.82 (t, J = 1.9 Hz,
1H, Ph), 7.35–7.30 (m, 4H, Ph), 7.28–7.22 (m, 1H, Ph),
4.47 (d, J = 5.9 Hz, 2H, –CH2). FT-IR (KBr disc, cm−1):
υas(N–H) 3269, υas(CH2) 3071, υs(CH2) 3065, υ(C–H) 3027,
υ(C=O) 1636, υ(C–C) 1566 and 1549, β(C–H) 1288 and
1233, γ(C–H) 693–866.
3,5-Dichloro-N-(2,6-dimethylphenyl) benzamide (7)
White powder, yield: 52.2 mg (74%). The calculated of
elemental analysis (%): C 61.19, H 4.42, N 4.76; found of
elemental analysis (%): C 61.34, H 4.68, N 4.27. 1H NMR
(400 MHz, DMSO-d6): δ(ppm) 9.99 (s, 1H, –NH–), 8.00
(d, J = 1.9 Hz, 2H, Ph), 7.91 (t, J = 1.9 Hz, 1H, Ph), 7.88
(t, J = 1.9 Hz, 1H, Ph), 7.86 (d, J = 2.0 Hz, 1H, Ph), 2.17
(s, 6H, –CH3). FT-IR (KBr disc, cm−1): υas(N–H) 3427,
υ(CH3) 3074 and 2920, υ(C=O) 1652, υ(C–C) 1572 and
1521, β(C–H) 1307 and 1283, γ(C–H) 649–867.
3,5-Dichloro-N-(4-nitrophenyl)-benzamide (12)
Bright yellow powder, yield: 56.7 mg (76%). The calcu-
lated of elemental analysis (%): C 50.15, H 2.58, N 9.00;
found of elemental analysis (%): C 51.00, H 2.63, N 9.15. 1H
NMR (400 MHz, DMSO-d6): δ(ppm) 10.93 (s, 1H, –NH–),
8.31–8.29 (m, 1H, Ph), 8.28–8.26 (m, 1H, Ph), 8.04 (s, 1H,
Ph), 8.02 (d, J =2.1 Hz, 1H, Ph), 8.00 (d, J=1.9 Hz, 2H,
Ph), 7.91 (dd, J=3.9, 1.9 Hz, 1H, Ph),7.85 (d, J=2.0 Hz,
1H, Ph). FT-IR (KBr disc, cm−1): υas(N–H) 3437, υ(C–H)
3268, υ(C=O) 1634, υ(C–C) 1566 and 1542, υas(NO2) 1506,
υs(NO2) 1384, β(C–H) 1328 and 1295, γ(C–H) 688–858.
3,5-Dichloro-N-(4-iodophenyl) benzamide (8)
White powder, yield: 83.3 mg (89%). The calculated of ele-
mental analysis (%): C 39.77, H 2.04, N 3.57; found of ele-
mental analysis (%): C 38.97, H 2.34, N 3.24. 1H NMR (400
MHz, DMSO-d6): δ(ppm) 10.49 (s, 1H, –NH–), 7.96 (d,
J=1.9 Hz, 2H, Ph), 7.90–7.81 (m, 1H, Ph), 7.81–7.68 (m,
2H, Ph), 7.68–7.52 (m, 2H, Ph). FT-IR (KBr disc, cm−1):
υas(N–H) 3448, υ(C–H) 3080 and 3059, υs(N–H) 2922,
υ(C=O) 1653, υ(C–C) 1585, 1566, 1518 and 1487, υ(C=N)
1390, β(C–H) 1310, 1287 and 1259, γ(C–H) 688–871.
3,5-Dichloro-N-(2,6-diisopropylphenyl) benzamide (13)
Light pink powder, yield: 52.9 mg (63%). The calculated of
elemental analysis (%): C 61.67, H 6.00, N 8.00; found of
elemental analysis (%): C 61.74, H 6.05, N 7.78. 1H NMR
(400 MHz, DMSO-d6): δ(ppm) 10.00 (s, 1H, –NH–), 8.00
(d, J=1.9 Hz, 2H, Ph), 7.94 (s, 1H, Ph), 7.87 (s, 1H, Ph),
3.06–2.98 (m, 2H, –CH–), 1.12 (dd, J=6.8 Hz, 12H, –CH3).
FT-IR (KBr disc, cm−1): υas(N–H) 3437, υ(C–H) 2977,
υ(C=O) 1648, β(C–H) 1126 and 1072, γ(C–H) 603–727.
3,5-Dichloro-N-(3-iodophenyl) benzamide (9)
White powder, yield: 77.2 mg (82%). The calculated of
elemental analysis (%): C 39.77, H 2.04, N 3.57; found of
elemental analysis (%): C 38.09, H 2.44, N 3.56. 1H NMR
(400 MHz, DMSO-d6): δ(ppm) 10.45 (s, 1H, –NH–), 8.20
(s, 1H, Ph), 7.96 (d, J = 1.6 Hz, 2H, Ph), 7.76 (d, J = 7.6
Hz, 1H, Ph), 7.87 (d, J =1.7 Hz, 1H, Ph), 7.48 (d, J=7.8
Hz, 1H, Ph), 7.17 (dd, J=9.8, 6.2 Hz, 1H, Ph). FT-IR (KBr
disc, cm−1): υas(N–H) 3452, υs(N–H) 3267, υ(C=O) 1643,
υ(C–C) 1584, 1565 and 1541, υ(C=N) 1474, β(C–H) 1319,
1262 and 1259, γ(C–H) 678–803.
3,5-Dichloro-N-(2,4,6-trimethylphenyl) benzamide (14)
Beige powder, yield: 57.9 mg (70%). The calculated of
elemental analysis (%): C 55.71, H 4.35, N 4.06; found of
elemental analysis (%): C 54.83, H 4.43, N 4.68. 1H NMR
(400 MHz, DMSO-d6): δ(ppm) 9.90 (s, 1H, : –NH–), 7.99
(d, J=1.9 Hz, 2H, Ph), 7.89–7.85 (m, 1H, Ph), 6.93 (s, 2H,
Ph), 2.25 (s, 3H, –CH3), 2.10 (s, 6H, –CH3). FT-IR (KBr
disc, cm−1): υas(N–H) 3440, υ(C–H) 2977, υ(C–H) 3027,
υ(C=O) 1642, υ(C–C) 1561 and 1520, β(C–H) 1307 and
1300, γ(C–H) 707.
3,5-Dichloro-N-(2-iodophenyl) benzamide (10)
White powder, yield: 73.4 mg, (78%). The calculated of
elemental analysis (%): C 39.77, H 2.04, N 3.57; found of
elemental analysis (%): C 38.77, H 2.74, N 3.39. 1H NMR
(400 MHz, DMSO-d6): δ(ppm) 10.34 (s, 1H, –NH–), 8.00
(d, J=1.8 Hz, 2H, Ph), 7.97–7.89 (m, 2H, Ph), 7.49–7.39
(m, 2H, Ph),7.12–7.06 (m, 1H, Ph). FT-IR (KBr disc, cm−1):
υas(N–H) 3459, υ(C=O) 1636, υ(C=N) 1303, β(C–H) 1126
and 1053, γ(C–H) 612.
X‑ray Crystallography
A summary of crystallographic data and experimental
details for 3,5-dichloro-N-(4-chlorophenyl)benzamide (4)
1 3

Journal of Chemical Crystallography
and 3,5-dichloro-N-(2-chlorophenyl)- benzamide (6) are
summarized in Table 1. Compound 6 crystallizes in the
noncentrosymmetric space group Pn with the Flack param-
eter of 0.5 and has two unique molecules in the asymmet-
ric unit. All the intensity data of the single crystal were
collected on a CCD-Bruker Smart APEX system, using
graphite-monochromated Mo-Kα radiation (λ=0.71073 Å)
at 293(2) K. The collected frames were processed with the
software SAINT [10]. The data was corrected for absorption
using the program SADABS [11]. Structures were solved by
the direct methods and refned by full-matrix least-squares
on F2 using the SHELXTL software package [12, 13]. All
non-hydrogen atoms were refned anisotropically. The posi-
tions of all hydrogen atoms were generated geometrically
(Csp3−H = 0.96 Å), Csp2−H = 0.93 Å, and N−H=0.86 Å),
assigned isotropic thermal parameters, and allowed to ride
on their respective parent carbon or nitrogen atoms before
the fnal cycle of least-squares refnement. Omit commands
are used to delete the most disagreeable refections.
Results and Discussion
As shown in Scheme 1, the key substrate 3,5-dichloroben-
zoic acid (2) was prepared by hydrolysis of 3,5-dichloroben-
zonitrile (1) in sodium hydroxide aqueous solution in a quan-
titative yield. The 1H NMR spectrum of compound 2 showed
the aryl protons as two groups of peaks at around 7.85 and
7.90 ppm, respectively. Treatment of 3,5-dichlorobenzoic
acid with excess thionyl chloride aforded the intermedi-
ate 3,5-dichlorobenzoyl chloride (3), which may directly
reacted with arylamines in DMF at 60 °C to give the target
benzamide derivatives 4–14 in good yields (Scheme 2). In
the 1H NMR spectra of compounds 4–14, the chemical shift
in the range 2.10–4.47 ppm are attributed to the protons of
the alkyl groups, the chemical shift of 7.12–7.99 ppm are
ascribed to the protons on the benzene ring. The character-
istic peaks of –NH– protons were observed as a singlet in the
range of 9.26–13.13 ppm,. In the IR spectra of compounds
414, broad bands at 3265–3452 cm−1 are attributed to the
functional –CO–NH– stretching vibration, while the stretch-
ing vibration peak (amide I band) of C=O are in the range
of 1634–1706 cm−1. The bending vibration of N–H in the
amide group peak (amide II band) is 1563–1589 cm−1 and
is easily covered by the amide I band. The stretching vibra-
tion peak of the benzene ring skeleton is usually bimodal
at 1487–1584 cm−1. The nitro asymmetric group stretch-
ing vibration peak in compound 12 is at 1384 cm−1, the in-
plane bending vibration peak of C‒H on the benzene ring
is 1096–1310 cm−1, and the out-of-plane bending vibration
peak of C‒H on the benzene ring is 649–873 cm−1 [14]. The
characteristic carbonyl groups in compound 4 with 4-chloro-
phenyl moiety and compound 6 with 2-chlorophenyl moiety
are similar to each other (1651 cm‒1 vs. 1649 cm‒1).
Table 1 Crystallographic data and details for compounds 4 and 6
Compound
4
6
Empirical formula
C13H8NOCl3
300.55
Triclinic
Pī
5.047 (18)
10.28 (4)
13.36 (5)
107.59 (5)
93.55 (5)
98.34 (5)
650 (4)
2
C13H8NOCl3
300.55
Monoclinic
Pn
9.581 (3)
12.217 (4)
11.072 (3)
90
92.584 (4)
90
647.35 (3)
4
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V(Å3)
Z
Dcalc (g cm−3
)
1.536
1.542
Temperature (K)
F (000)
296 (2)
304
0.690
296 (2)
608
0.692
µ(Mo-Kα) (mm−1
Total refn
)
3741
3918
Independent refn
Rint
2606
0.0432
163
0.0733, 0.1863
0.1026, 0.2184
0.848
2032.5
0.0259
163
0.0345, 0.0720
0.0450, 0.0786
0.865
Parameters
R1a, wR2b (I>2σ(I))
R1, wR2 (all data)
GoFc
Flack parameter
–
0.5
/
a
ꢀꢀ ꢀ ꢀ ꢀꢀ ꢀ
ꢀ
ꢀ
R1 = Fo − Fc
(
Fo
1
]
ꢀꢀ ꢀ ꢀ ꢀꢀ ꢀ
[
∕
)
2
2
2
bwR2 = w
F
− F
2
2
2
ꢀ
ꢀ ꢀ
ꢀ
ꢀ
w F
ꢀ
ꢀ
Molecular structures of compounds 4 and 6 were further
confrmed by X-ray crystallography, as shown in Figs. 1 and
1
ꢀ
oꢀ ꢀ c ꢀ
oꢀ
[
]
∕
(
) (
)
2
2
cGoF = w Fo − Fc
Nobs − Nparam
ꢀ
ꢀ ꢀ
ꢀ
ꢀ
ꢀ
ꢀ ꢀ
Scheme 1 Synthesis of
O
O
N
3,5-dichlorobenzoyl chloride
Cl
Cl
Cl
NaOH
H2O,reflux
SOCl2
DMF, reflux
Cl
OH
Cl
Cl
Cl
1
2
3
1 3

Journal of Chemical Crystallography
Scheme 2 Synthesis of
3,5-dichlorobenzamide deriva-
tives
O
O
Cl
Cl
R1
Cl
DMF
60oC, 2h
N
H
+
R1NH2
Cl
Cl
CH3
R1=
Cl
Cl
CH3
Cl
4
8
5
6
7
H2
C
I
I
I
9
10
11
CH3
O2N
H3C
CH3
12
13
14
2, respectively. Selected bond lengths and angles are given in
Tables 2 and 3 accordingly, while the hydrogen-bond char-
acteristics and geometric parameters for the two compounds
are listed in Table 4. The C–O bond lengths are 1.225(5) Å
in compound 4, 1.220(3) and 1.230(4) Å in compound 6, an
indication of the carbon-oxygen double-bond character [8].
In compound 4, the N(1)–C(7) and N(1)–C(1) bond lengths
are 1.345(6) and 1.419(6) Å, respectively, while in com-
pound 6, the N–C bond lengths are in the range of 1.343(4)
and 1.430(4) Å, inferring they are partial double bonds. The
dihedral angle between the benzene rings is 79.3(2)° for
compound 4, much larger than those of 11.2(2)° and 12.3(2)°
for compound 6, suggestive of the chloro substituent at dif-
ferent positions having efect on parameters of the dihedral
angles. The C‒N‒C‒C torsion angles are − 169.2(4)° for
compound 4, − 176.0(2)° and − 178.6(2)° for compound 6,
which are compared to those in 2,6-dichloro-N-(4-chloro-
phenyl)benzamide (172.6(3)°) [8] and N-(4-chlorophenyl)-
4-nitrobenzamide (− 179.7(1)°) [15].
(17) Å) [15]. The bond angle of N–H⋯O in molecule 4 is
163.7°, similar to those in compound 6 (163.1° and 165.5°),
and compared to those in compounds N-(4-chlorophenyl)-
4-nitrobenzamide (159°) [15] and 2,6-dichloro-N-(4-
chlorophenyl)-benzamide (176°) [8]. The intermolecular
Cl⋯Cl separations of 3.429 Å in compound 4 and 3.568 Å
in compound 6 are similar to the Cl⋯Cl contact in methyl
N-(4-chlorophenyl)-N’-cyanocarbamimidothioate (3.581
Å) [16]. The intermolecular C−H⋯Cl (C⋯Cl ca. 2.89 Å)
hydrogen bonds in compounds 4 and 6 also contribute to
the stabilization of their crystal structures. Moreover, H-pi
interactions (3.70 Å) of the phenyl groups exist in compound
4. The slightly ofset face-to-face pi stacking interactions
between the two molecules are observed in the compound
6 with a centroid-centroid distance of adjacent phenyl rings
of 3.66 A.
In summary, we have synthesized a series of dichloroben-
zamide derivatives by the reaction of 3,5-dichlorobenzoyl
chloride with arylamines in good yields. Two compounds
were further characterized by X-ray crystallography, display-
ing the solid states being of trans-isomerism characteristic
of the −NH−CO− groups [8, 15]. Diferent dihedral angles
between the benzene rings were observed for compounds 4
(79.3(2)°) and 6 (11.2(2)° and 12.3(2)°), possibly due to the
presence of 4-chloro and 2-chloro substituent on benzene
ring. Short halogen–halogen interactions have been stud-
ied, showing the intermolecular Cl⋯Cl distances being of
Packing views of compounds 4 and 6 are shown in
Figs. 1b and 2b, respectively. Crystal packing in molecules
4 and 6 are governed by the intermolecular N–H⋯O hydro-
gen-bonding interactions (see Table 4). The N⋯O hydro-
gen bonds in compounds 4 (2.908 (10) Å) and 6 (2.940 (3)
and 2.974 (3) Å) agree well to those in related compounds
of 2,6-dichloro-N-(4-chlorophenyl)benzamide (2.828 (4)
Å) [8] and N-(4-chlorophenyl)-4-nitrobenzamide (3.1312
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Journal of Chemical Crystallography
Fig. 1 a Structure of
3,5-dichloro-N-(4-chlorophenyl)
benzamide (4), showing the
atom-labelling scheme of one
molecule in the asymmetric
unit. Displacement ellipsoids
are drawn at 50% probability
level and H atoms are shown
as small spheres of arbitrary
radii. b The crystal structure
of 4, viewed along the c axis.
Dashed lines indicate N–H⋯O,
C–H⋯Cl hydrogen bonds and
Cl···Cl short contacts
3.429 Å in compound 4 and 3.568 Å in compound 6, simi-
lar to the Cl⋯Cl contact in related compound methyl N-(4-
chlorophenyl)-N′-cyanocarbamimidothioate (3.581 Å) [16].
Classical C−H⋯Cl hydrogen bonds in compounds 4 and 6
also contribute to the stabilization of their crystal structures.
Supplementary material
Crystallographic data for 3,5-dichloro-N-(4-chlorophenyl)
benzamide (4) and 3,5-dichloro-N-(2-chlorophenyl)benza-
mide (6) have been deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publication nos.
CCDC 1948596 and 1948597, respectively. Copies of the
data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, UK [fax: (+44)1233-
336-033; e-mail: deposit@ccdc.cam.ac.uk].
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Journal of Chemical Crystallography
Fig. 2 a Structure of3,5-
dichloro-N-(2-chlorophenyl)
benzamide(6), showing the
atom-labelling scheme of
onemolecule in the asymmetric
unit. Displacementellipsoids
are drawn at 50% probability
level and H atoms are shown as
smallspheres of arbitrary radii.
b The crystalstructure of 6,
viewed along the c axis. Dash-
edlines indicate N–H···O,C–
H···Cl hydrogen bonds and
Cl···Cl short contacts
Table 2 Selected bond lengths (Å) and angles (°) for compound 4
Table 3 Selected bond lengths (Å) and angles (°) for compound 6
O(1)–C(7)
N(1)–C(7)
N(1)–C(1)
C(7)–C(8)
C(1)–N(1)–C(7)
O(1)–C(7)–N(1)
1.225 (5)
1.345 (6)
1.419 (6)
1.509 (6)
125.6 (3)
123.7 (4)
Cl(1)–C(4)
Cl(2)–C(10)
Cl(3)–C(12)
1.748 (7)
1.757 (6)
1.731 (6)
O(1)–C(7)
N(1)–C(1)
N(1)–C(7)
C(7)–C(8)
C(1)–N(1)–C(7)
O(1)–C(7)–N(1)
1.230 (4)
1.430 (4)
1.343 (5)
1.499 (5)
123.9 (3)
124.5 (3)
Cl(1)–C(6)
Cl(2)–C(10)
Cl(3)–C(12)
1.733 (4)
1.742 (4)
1.731 (6)
O(1)–C(7)–C(8)
N(1)–C(7)–C(8)
121.3 (3)
115.0 (3)
O(1)–C(7)–C(8)
N(1)–C(7)–C(8)
120.6 (3)
114.9 (3)
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Journal of Chemical Crystallography
Table 4 Hydrogen-bonding
system for compounds 4, 6
Compound
D–H⋯A
d(D–H) (Å)
d(H⋯A) (Å)
d(D⋯A) (Å)
∠(DHA) (deg)
4
6
N(1)–H(1)⋯O(2)i
N(1)–H(1)⋯O(2)ii
N(2)–H(2)⋯O(1)
0.86
0.86
0.86
2.07
2.11
2.13
2.908(10)
2.940(3)
2.974(3)
163.7
163.1
165.5
Symmetry codes: (i) x+1, y, z; (ii) x − 1, y, z
9. Saeed A, Hussain S, Bolte M (2007) Acta Crystallogr
E63:o4843–o4850
Acknowledgements This project was supported by the National Natu-
ral Science Foundation of China (21372007).
10. SMART and SAINT + for Windows NT Version 6.02a; Bruker
analytical X-ray instruments Inc. Madison (1998)
11. Sheldrick GM (1996) SADABS. University of Göttingen,
Göttingen
12. Sheldrick GMSHELXTL (1997) Software reference manual, Ver-
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