Synthesis, X-Ray Crystallography, Theoretical Investigation and Optical Properties of 2-Chloro-N-(2,4-dinitrophenyl) Acetamide

Article abstract of DOI:10.1007/s10870-020-00875-w

Abstract: 2-Chloro-N-(2,4-dinitrophenyl) acetamide, 1, was synthesized and characterized by ¹H and ¹³C NMR spectroscopy, ESI–MS, X-ray crystallography, and elemental analysis. This compound crystallizes in the monoclinic space group

Full text of DOI:10.1007/s10870-020-00875-w

Journal of Chemical Crystallography
https://doi.org/10.1007/s10870-020-00875-w
ORIGINAL PAPER
Synthesis, X‑Ray Crystallography, Theoretical Investigation and Optical
Properties of 2‑Chloro‑N‑(2,4‑dinitrophenyl) Acetamide
Piangkwan Jansukra1 · Worawat Wattanathana2 · Tanwawan Duangthongyou1 · Suttipong Wannapaiboon3 ·
Apisit Songsasean1 · Songwut Suramitr4,5 · Thawatchai Tuntulani6 · C. Scott Browning7 · Boontana Wannalerse1
Received: 4 July 2020 / Accepted: 11 December 2020
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature 2021
Abstract
2-Chloro-N-(2,4-dinitrophenyl) acetamide, 1, was synthesized and characterized by 1H and 13C NMR spectroscopy, ESI–MS,
X-ray crystallography, and elemental analysis. This compound crystallizes in the monoclinic space group P21/n. The crystal
structure of compound 1 revealed the intramolecular H-bonding with the S(6) motif between H atom of the amide group and
the nitro group at the ortho position. Several intermolecular C–H⋯O interactions hold diferent molecules of the compound
1 together resulting in the crystal packing. Red faint spots observed in the Hirshfeld surface of the compound 1 confrm the
presence of N–H⋯O hydrogen bond as well as C–H⋯O interactions. According to the Hirshfeld surface, C–H⋯Cl interaction
is also found, of which distance is relatively longer than the C–H⋯O distance. Moreover, the analysis of the corresponding
fngerprint plots indicates the signifcant interactions within the crystal namely H⋯O/O⋯H (39.0%), C⋯O/O⋯C (10.6%),
H⋯Cl/Cl⋯H (8.5%), H⋯H (7.3%), and H⋯C/C⋯H (5.9%) contacts. The optical properties of compound 1 in various sol-
vents were investigated using UV–vis spectrophotometry. Compound 1 showed solvatochromic efects upon the varying
polarity of the solvent. Time-dependent DFT calculations (TD-DFT) of compound 1 suggest that the deprotonation process
occurs in polar solvents such as DMF.
4
Department of Chemistry, Faculty of Science, Kasetsart
* Boontana Wannalerse
University, Chatuchak, Bangkok 10900, Thailand
fscibnw@ku.ac.th
5
Center for Advanced Studies in Nanotechnology
1
for Chemical, Food and Agricultural Industries, KU Institute
for Advanced Studies, Kasetsart University, Bangkok 10900,
Thailand
Department of Chemistry and Center of Excellence
for Innovation in Chemistry, Faculty of Science, Kasetsart
University, Chatuchak, Bangkok 10900, Thailand
6
7
2
3
Supramolecular Chemistry Research Unit, Department
of Chemistry, Faculty of Science, Chulalongkorn University,
Bangkok 10330, Thailand
Department of Materials Engineering, Faculty
of Engineering, Kasetsart University, Chatuchak,
Bangkok 10900, Thailand
Davenport Chemical Research Building, Department
of Chemistry, University of Toronto, 80 St. George St.,
Toronto M5S 3H6, Canada
Synchrotron Light Research Institute (Public Organization),
111 University Avenue, Suranaree Sub-district, Muang,
Nakhon Ratchasima 30000, Thailand
Vol.:(0123456789)
1 3

Journal of Chemical Crystallography
Graphic Abstract
Crystal structure of 2-Chloro-N-(2,4-dinitrophenyl) acetamide (1) revealed the intramolecular N–H⋯O hydrogen bonding
with the S(6) motif within the molecule as well as several intermolecular C–H⋯O interactions between molecules. Moreover,
the compound 1 exhibited solvatochromic efects upon the varying polarity of the solvents.
Keywords Crystal structure · 2,4-Dinitroaniline derivative · Hydrogen bonding interactions
of rapid photo-induced proton transfer in dinitroanilines,
that varies in its extent with solvent polarity [8–14]. Many
techniques, for example, IR, 1H-NMR, and UV–vis spec-
troscopies have been used to examine such proton transfer
processes through the study of metastable intermediates
forming during the process. However, it is quite difcult
to investigate these molecules since it is difcult to termi-
nate the reaction process at the formation of metastable
intermediates and separates them for further spectroscopic
characterizations. A TD-DFT calculation is a quick and
facile method that can predict and optimize the energy
level of these compounds [7, 15, 16]. Singh et al. synthe-
sized isomeric hydrazone derivatives containing 2,4-dini-
trophenyl hydrazine group, and studied the various elec-
tronic transition within a molecule in two diferent solvents
(ethanol and dichloromethane) by UV–vis spectroscopy,
DFT and AIM approach. The result indicates that these
derivatives in two diferent solvents displayed the signif-
cant redshift in the spectrum stemming from characteristic
Introduction
Dinitroaniline and its derivatives, which consist of both
electron-donating and electron-withdrawing groups con-
nected by a π-conjugated system, have received a great deal
of attention in the feld of optoelectronic devices. There are
many types of dinitroaniline species having either a linear or
non-linear arrangement of the electron-donating and with-
drawing groups. They are employed to produce aggregated
molecular structures in one (1-D), two (2-D), and three
dimensional (3-D) networks via the intermolecular forces
such as hydrogen bonding, π–π stacking, CH–π interactions,
and van der Waal forces [1–6]. Furthermore, dinitroaniline
derivatives are known as solvatochromic chromophores [7],
possessing the color alteration by means of a variation of
solvent polarities. Dinitroaniline and its derivatives may
undergo several photophysical processes, including elec-
tron transfer (ET), internal charge transfer (ICT), and proton
transfer (PT). The keto-enol isomerization is an example
1 3

Journal of Chemical Crystallography
hydrogen bonding interaction between the derivatives and
solvents. Moreover, their structures were stabilized by both
the hyper-conjugation and the electron delocalization via
the π-conjugated bridge, which consequently lead to the
internal charge transfer (ICT) process [17].
recrystallization in a mixture of dichloromethane/hexane (1:1
v/v). m.p. 116.5 °C. IR (KBr, cm−1): 3328, 1686, 1604, 1511,
1343, 1227, 593 1H NMR (400 MHz, CDCl3): δ 11.77 (s, 1H,
-NH), 9.18 (d, J=6.9 Hz, 1H, -ArH), 9.11 (d, J=8.4 Hz 1H,
-ArH), 8.59 (d, J=7.1 Hz, 1H, -ArH), 4.45 (s, 2H, -CH2). 13
C
This recent work describes the synthesis, charac-
terization, and investigation of the optical properties of
2-chloro-N-(2,4-dinitrophenyl) acetamide (1) in various
solvents using UV–vis spectrophotometry. The crystal struc-
ture of this compound is examined. TD-DFT calculations
are used to support the study of the intramolecular proton
transfer process of this compound in solution.
NMR (100 MHz, CDCl3): 165.7, 142.6, 140.1, 136.4, 128.9,
124.9, 121.3, 43.1 ESI–MS: m/z 260.0 [M+H+] Elemental
Anal: Calcd for C8H6N3O5Cl: C, 37.01; H, 2.33; N, 16.19
Found: C, 37.03; H, 2.28; N, 16.09.
Crystallography
Single crystal data of compound 1 were collected at 276 K
on a Bruker APEXII CCD camera by Ψ and ω scans using
graphite-monochromated radiation (MoKα, λ=0.71073 Å).
Refections of the single crystal were measured in a 2Ɵ
range of 2.0°–25.1°, and 1740 independent refections were
measured for compound 1. The structure solution and refne-
ment were performed using Olex2 software [18]. The struc-
ture was solved by the intrinsic phasing method using the
SHELXT program [19] and was then refned by full-matrix
least-squares using SHELXL package [20]. Non-hydrogen
atoms were isotropically refned at frst and refned aniso-
tropically to obtain their thermal parameters. All hydrogen
atoms of compound 1 apart from H3 were treated anisotropi-
cally while the H atoms were refned by a riding model with
d(C–H)=0.95 Å and Uiso(H)=1.2Ueq(C) for aromatic hydro-
gen atoms, with d(C–H)=0.99 Å and Uiso(H)=1.2Ueq(C)
for –CH2– hydrogen atoms and d(C–H) = 0.98 Å,
Uiso(H)=1.5Ueq(C) for the terminal methyl hydrogen atoms.
located from a diferent Fourier map and refned. The fnal
least-square cycle of refnement gave out R1 =0.0391 and
wR2 = 0.0956. The crystal data and refnement details of
compound 1 are listed in Table 1. Mercury software is used
to acquire molecular graphics for this manuscript [21].
Experimental
General Information
1H-NMR spectrum was collected using a 400 MHz NMR
spectrometer. UV–vis spectra were recorded on a Shimadzu
spectrophotometer. Mass spectroscopy (MS) was carried out
on an Agilent 1100 Series LC/MSD Trap mass spectrometer.
Infrared spectra (4000–400 cm−1) were obtained from a Perkin
Elmer system 2000 Fourier transform infrared spectrometer.
A Buchi melting point B-540 analyzer determined the melting
point of the sample. All solvents and reagents were purchased
from Sigma Aldrich and used without further purifcation.
Synthesis and Characterization
The synthesis route to prepare 2-chloro-N-(2,4-dinitrophe-
nyl)acetamide is summarized in Scheme 1. Firstly, 2,4-dini-
troaniline (2.0 g, 14.48 mmol) and triethylamine (4 mL,
28.96 mmol) in dichloromethane (3 mL) were stirred under N2
for 30 min. Then, solution of 2-chloroacetyl chloride (2.3 mL,
28.96 mmol) in dichloromethane (3 mL) was added drop-
wise to the mixture. The reaction mixture was continuously
stirred for 24 h. The reaction mixture was poured into water
and extracted with dichloromethane (3 times). The organic
layer was dried with anhydrous Na2SO4. 2-Chloro-N-(2,4-
dinitrophenyl)acetamide, 1, was purifed by column chroma-
tography using dichloromethane as an eluent to give a yellow
solid (0.56 g, 19.6%). The yellow crystals were obtained by
Computational Details
The optimized structure of compound 1 obtained from
X-ray diffraction data was calculated using the density
functional theory (DFT) level of CAM-B3LYP [22] with
a 6-311G(d,p) basis set using Gaussian 09 program [23]. A
polarizable-continuum model (PCM) [24] was employed for
Scheme 1 The synthesis pathway of 2-chloro- N-(2,4-dinitrophenyl)acetamide, 1
1 3

Journal of Chemical Crystallography
Table 1 Crystallographic data and structure refnement for compound
torsion angles of compound 1 together with the structural
parameters from the other 2-chlorophenylacetamide deriva-
tives reported in the CSD database [27–29]. It was found
that the signifcant bond lengths and bond angles regard-
ing the nitro and 2-chloroacetamide groups in all the com-
pounds are quite similar, but the torsion angles are diferent,
depending on the substituent groups. Within the molecule
of compound 1, one of the oxygen atoms in the nitro group
at the ortho position with respect to the amide group (O4)
is twisted to locate near the H2 atom leading to the forma-
tion of an intramolecular hydrogen bond with S(6) motif
from an O4–N2–C3–C4–N3–H3 synthon. The H atom (H3)
regarding the S(6) graph set, which was refned freely, was
found to locate at distances of 0.88 (3) Å and 2.10 (3) Å
from N3 atom and O4 atom, respectively. The amide func-
tional group adopts a trans conformation with the four atoms
nearly coplanar, as shown by the O5–C7–N3–H3 torsion
angle of 172 (2)°. From the literature survey of the related
crystal structure, a number of 2-chloro-N-phenylacetamide
derivatives can form a hydrogen bonding chain with the
C(4) graph set via a secondary amide group (–NHC(=O)–)
[28–34]. However, in our work, the compound 1 cannot cre-
ate the C(4) intermolecular hydrogen-bonding chains to sta-
bilize the crystal packing as the amide H is already used to
form the intramolecular H-bond with an adjacent nitro sub-
stituent. Instead, several intermolecular C–H⋯O interactions
with the H-acceptor distances < 2.6 Å are major contributors
in crystal packing. Figure 1b illustrates two C–H⋯O inter-
actions, C2–H2⋯O2, and C5–H5⋯O5, constructed from
two inversion-related molecules of the compound 1. The
C2–H2⋯O2 and C5–H5⋯O5 interactions establish R2(8)-
1
CCDC number
Empirical formula
Formula weight
1419554
C8H6N3O5Cl
259.61
Temperature/K
Crystal system
Space group
296.15
Monoclinic
P21/n
a/Å
b/Å
c/Å
α/°
13.486 (2)
4.6294 (7)
16.081 (3)
90
β/°
γ/°
92.245 (9)
90
1003.2 (3)
4
1.719
0.397
Volume/Å3
Z
ρcalcg/cm3
μ/mm−1
F(000)
528.0
Crystal size/mm3
Radiation
0.48×0.08×0.05
MoKα (λ=0.71073)
6.046–50.12
2Θ range for data collection/°
Index ranges
− 13≤h≤16, − 5≤k≤5,
− 19≤l≤17
Refections collected
5142
Independent refections
Data/restraints/parameters
Goodness-of-ft on F2
Final R indexes [I≥2σ (I)]
1740 [Rint =0.0243, Rsigma =0.0300]
1740/0/158
1.049
R1 =0.0391, wR2 =0.0956
and-R2(10)-like motifs. For the molecules related by m2irror
the investigation of solute–solvent interactions in dimeth-
ylformamide (DMF). All tautomers were fully optimized
in solution. Frequency calculations were performed on the
optimized structures to confrm that these structures corre-
spond to energy minima. To simulate the absorption spectra,
the vertical excitation energies were calculated at the opti-
mized tautomers obtained with a restricted planar structure
for the ground state using the time-dependent DFT (TD-
DFT) method [25, 26] with the CAM-B3LYP/6-311G(d,p)
basis set.
2
planes, the C–H⋯O interaction (C8–H8B⋯O) can also be
found. The C8–H8B⋯O linkage joins the molecules of the
compound 1, giving rise to the infnite C(4)-like molecu-
lar chain. The full geometric parameters of the H-bond and
C–H⋯O interactions are tabulated in Table 4.
The intermolecular interactions in the crystal of the com-
pound 1 were investigated by performing a Hirshfeld sur-
face (HS) analysis [35, 36] using Crystal Explorer 17.5 [37].
The HS is plotted over the dnorm range − 0.2293 to 0.9126
a.u. (Fig. 2). Red faint spots confrm the presence of both
the hydrogen bonding and C–H⋯O interactions mentioned
earlier. Moreover, there are some more spots locate on H6
and Cl1 atoms. It might be due to the interactions with the
H-acceptor distances more than 2.6 Å, such as C6–H6⋯Cl1
interaction. The study on the full two-dimensional fnger-
print plot regarding the HS surface allows us to get a piece
of insight information about the contribution of each contact
to the crystal packing. The fngerprint plot can be delineated
into the individual fngerprint plots for individual interac-
tions [38]. Herein, the signifcant contacts within the crystal
of the compound 1 are H⋯O/O⋯H (39.0%), C⋯O/O⋯C
Results and Discussion
Crystal Structure and Hirshfeld Surface Analysis
The ORTEP plot showing the molecular structure of
compound 1 is displayed in Fig. 1a. Inspection of torsion
angles of the peripheral groups attached to the benzene
ring (Table 2) shows that neither two nitro groups nor the
amide group is oriented coplanar with the benzene ring.
Table 3 shows the selected bond lengths, bond angles and
1 3

Journal of Chemical Crystallography
Fig. 1 a The molecular struc-
ture of the compound 1, show-
ing the atom-labelling scheme.
Displacement ellipsoids are
drawn at the 50% probability
level. The non-IUPAC atom
labelling is for the convenience
of discussion. Crystal packing
of the compound 1 showing
C–H⋯O interactions formed
from the molecules related by b
inversion centers and c mirror
planes
1 3

Journal of Chemical Crystallography
pale yellow to yellow with respect to an increase of solvent
polarity, as shown in Fig. 4. The absorption spectra of 1 in
various solvents are shown in Fig. 5. An absorption maximum
is observed at 296–298 nm in solvents of low polarity (296 nm
in CHCl3, 297 nm in CH2Cl2, 298 nm in CH3CN). In addition,
the molar absorptions of compound 1 in diferent solvents can
be calculated and listed in Table 5. As a highlight, the appear-
ance of new absorption band at 425 nm suggests that the sol-
vents of higher polarity induce a greater stabilization of the
excited state than of the ground state, leading to the structural
alteration of compound 1 [39]. This phenomenon is under the
solvatochromism process [40, 41]. Using DMF and DMSO as
solvent [42–46], there are two possible conformations of 1 in
(10.6%), H⋯Cl/Cl⋯H (8.5%), H⋯H (7.3%), and H⋯C/
C⋯H (5.9%) contacts (Fig. 3). The contributions of the other
contacts are Cl⋯Cl (3.5%), O⋯Cl/Cl⋯O (5.3%), N⋯Cl/
Cl⋯N (1.4%), C⋯Cl/Cl⋯C (1.2%), O⋯O (7.5%), N⋯O/
O⋯N (5.0%), H⋯N/N⋯H (1.8%), C⋯N/N⋯C (0.7%), C⋯C
(2.5%).
The Study of the Solvatochromic Efect
on 2‑chloro‑N‑(2,4‑dinitrophenyl)acetamide
2-Chloro-N-(2,4-dinitrophenyl)acetamide, 1, consists of an
amide group and two nitro groups on the aromatic ring. Com-
pound 1 dissolves in several organic solvents (i.e., CH2Cl2,
CHCl3, CH3CN, CH3OH, DMF, and DMSO). Solutions of
1 in diferent solvents showed a color variation ranging from
Table 2 Selected torsion angles
Torsion angle
Angle/°
Table 4 Geometries of hydrogen bonds and C–H⋯O interactions in
the crystal structure of the compound 1
O1–N1–C1–C2
O1–N1–C1–C6
O2–N1–C1–C2
O2–N1–C1–C6
O3–N2–C3–C2
O3–N2–C3–C4
O4–N2–C3–C2
O4–N2–C3–C4
C7–N3–C4–C3
C7–N3–C4–C5
− 151.3 (2)
28.9 (3)
28.3 (3)
− 151.5 (2)
33.3 (3)
− 144.7 (2)
− 146.9 (2)
35.1 (3)
147.5 (2)
− 30.2 (4)
D–H⋯A
d(D–H)/Å d(H–A)/Å d(D–A)/Å D–H–A/°
Hydrogen bond
N3–H3⋯O4
0.88 (3)
2.10 (3)
2.732 (3)
129 (3)
C–H⋯O interactions
C2–H2⋯O2i
C5–H5⋯O5ii
0.93
0.93
2.52
2.56
2.40
3.246 (3)
3.227 (3)
3.291 (3)
135
129
153
C8–H8B⋯O5iii 0.97
Symmetry codes: (i) − x, 1 − y, 1 − z; (ii) 1 − x, 2 − y, 1 − z; (iii) x,
− 1+y, z
Table 3 Comparison of bond
lengths, bond angles and torsion
angles of compound 1 and
other 2-chlorophenylacetamide
derivatives reported in the CSD
database
Crystal data
This work
Ref. [27]
Ref. [27]
Ref. [28]
Ref. [29]
Ref. code
–
CAKVAO
723202
CAKVES
723202
REZPES
613384
WEPKOS
624978
CCDC no.
Bond length (Å)
N2–C3
N2–O3
N2–O4
N3–C4
N3–C7
O5–C7
Cl1–C8
1419554
1.456 (3)
1.225 (3)
1.225 (3)
1.399 (3)
1.367 (3)
1.211 (3)
1.749 (3)
1.4709 (16)
1.2343 (14)
1.2215 (15)
1.4178 (15)
1.3340 (16)
1.2321 (16)
1.7789 (14)
1.4679 (13)
1.2286 (12)
1.2232 (13)
1.4124 (13)
1.3494 (13)
1.2252 (12)
1.7626 (12)
1.452 (6)
1.203 (5)
1.233 (5)
1.392 (5)
1.368 (5)
1.220 (5)
1.775 (4)
1.467 (3)
1.214 (2)
1.229 (2)
1.398 (3)
1.348 (3)
1.207 (3)
1.779 (3)
Bond angle (°)
C7–C8–Cl1
N3–C7–O5
O3–N2–O4
O5–C7–C8
Torsion angle (°)
C4–N3–C7–C8
C4–N3–C7–O5
N3–C7–C8–Cl1
O5–C7–C8–Cl1
111.26 (18)
123.5 (2)
123.7 (2)
123.4 (2)
114.84 (9)
122.96 (11)
122.99 (11)
118.88 (11)
112.24 (8)
123.62 (9)
123.62 (10)
122.84 (10)
115.8 (3)
124.5 (4)
121.5 (5)
117.7 (4)
116.55 (17)
125.6 (2)
121.5 (2)
117.1 (2)
−173.7 (2)
5.0 (4)
−177.57 (18)
3.7 (4)
−178.58 (11)
−0.75 (19)
−11.19 (15)
170.89 (10)
−178.36 (10)
1.04 (17)
−175.82 (8)
4.78 (15)
179.9 (4)
0.4 (7)
10.3 (5)
−177.6 (2)
−1.5 (4)
−15.7 (3)
167.9 (2)
−170.2 (3)
1 3

Journal of Chemical Crystallography
species was found in the solution. Note that, there were no
deprotonated species in the nonpolar solvents.
Computational Study
For a better understanding of the electronic properties of 1
(Fig. 8), the excitation energy, based on the frst and second
singlet–singlet electronic transitions were studied. Quan-
tum calculation was investigated in order to understand the
structural properties of the two forms of the 1. The most
stable structure for the normal form (N) and deprotonated
form (DPT) molecule was investigated (Fig. 8). Both of their
structures are corresponding to diferent orientations with
respect to C–N and N–C distance.
The vertical frst and second excitation energies were
calculated by TD-DFT with PBE0 functional with the
6-311G(d,p) basis set, using PBE0/6-311G(d,p) optimized
geometries at the global minimum of all molecules. The
electronic properties in terms of excitation energy (Eex) and
oscillator strength (f) were then calculated. In Table 6, the
theoretical results are in good agreement with the experi-
mentally measured absorption maxima. The calculated
absorption peaks at 300 nm and 392 nm should be attributed
to the normal form (N) and deprotonated DPT-form, respec-
tively, which are consistent with the experimental absorption
spectra of the two forms, N-form and DPT-form, for 1.
Table 6 shows that the S0 →S1 state of the N-form and
DPT-form mainly corresponds to the orbital transition from
the highest occupied molecular orbital (HOMO) to the low-
est unoccupied molecular orbital (LUMO). Frontier molecu-
lar orbitals (MOs) are widely used to understand the nature
of the excited states. The HOMO and LUMO of the N and
DPT forms are presented in Fig. 9. The HOMO and LUMO
are the π and π* character, respectively. Hence, it is evi-
dent that the S0 →S1 state is ππ* feature. Molecular orbitals
suggested that a ππ* state facilitates the deprotonated form.
Note that, the electron density on the amine group in the
LUMO in comparison to the HOMO is decreased, while the
one on the carbonyl group is increased. The results of elec-
tronic spectra demonstrate that both the N-form and DPT-
form of 1 could occur. The maximum absorption at 392 nm
in DMF and DMSO related to the HOMO→LUMO transi-
tions of the deprotonated form. It was suggested that the
deprotonated form was found in the polar solvent.
Fig. 2 Two views of the three-dimensional Hirshfeld surface of the
compound 1 plotted over dnorm in the range− 0.2293 to 0.9126 a.u
the equilibrium. The former, 1 might bind to DMF and DMSO
using the hydrogen bonding interaction, and the latter, the NH
proton of 1 can be loosened being deprotonated form in this
solvent. The result signifed that a new species of 1 appeared in
the solution, as shown in Scheme 2. This evidence was evalu-
ated by adding hydroxide ions to 1 in DMF solvent and further
investigated by UV–vis and 1H NMR techniques. Upon addi-
tion of 1 equivalent OH− to 1 in the DMF solvent, the signal of
UV-vis spectra at 301 nm assigned to the normal form of 1 was
decreased, while the one at 425 nm was enhanced, as shown
in Fig. 6. Adding 2 equivalents of OH−, the absorption band
at 425 nm was signifcantly observed, while the other bands
were vanished. It was indicated that the deprotonated form
of 1 occurred in the solution exhibiting the UV-vis spectra at
425 nm, as shown in Fig. 6. The similar results are observed in
the case of compound 1 in DMSO solvent. The other solvents
showed only the band at 301 nm of the normal form of 1. For
further confrmation using 1H NMR, the addition of 1–2 equiv.
OH− to 1 in the mixing DMF and DMSO-d6, the NH proton
at 11.77 ppm disappeared via the deprotonation process in
Fig. 7. The ArH- and CH2- protons moved to the upfeld shift
due to an increase of the electron density within the structure
of compound 1. These results indicated that a deprotonated
Conclusion
2-Chloro- N-(2,4-dinitrophenyl)acetamide, 1 was success-
fully synthesized and fully characterized by NMR, MS,
and EA. Although intermolecular hydrogen bonding is not
observed in the crystal structure of 1, the intramolecu-
lar H-bond is formed between the H atom of the amide
1 3

Journal of Chemical Crystallography
Fig. 3 The full two-dimensional fngerprint plots for the title compound, showing a all interactions and those delineated into b H⋯O/O⋯H
(39.0%), c C⋯O/O⋯C (10.6%), d H⋯Cl/Cl⋯H (8.5%), e H⋯H (7.3%), and f H⋯C/C⋯H (5.9%) interactions
1 3

Journal of Chemical Crystallography
Fig. 4 2-Chloro- N-(2,4-dinitro-
phenyl)acetamide 1 (1×10–4 M)
in organic solvents (from left to
right: CH2Cl2, CHCl3, CH3CN,
CH3OH, DMSO and DMF)
Fig. 5 The UV–vis spectra of
2-chloro- N-(2,4-dinitrophenyl)
acetamide 1 (1×10–4 M) in dif-
ferent solvents
Table 5 Absorption maximum (nm) and molar absorptivity of
2-chloro- N-(2,4-dinitrophenyl)acetamide 1 in diferent solvents
group and the nitro group at the ortho position. The crystal
structure of 1 is stabilized by C–H⋯O interactions. Hirsh-
feld surface analysis revealed that the signifcant contacts
within the crystal of compound 1 are H⋯O/O⋯H (38.4%),
C⋯O/O⋯C (10.4%), H⋯Cl/Cl⋯H (8.5%), H⋯H (7.7%),
and H⋯C/C⋯H (6.2%) contacts. The optical properties of
compound 1 in various solvents were investigated using
UV–vis spectrophotometry. Compound 1 showed solva-
tochromic efects upon the variation of solvent polarity.
Solvents
λmax (nm) Dielectric
Molar absorptivity (ε)
constant
[23]
Dichloromethane
Chloroform
Acetonitrile
Methanol
297
296
298
296
10.42
4.81
36.64
32.60
15,174.4
22,731.37
13,14,221
9623.89
Dimethyl forma-
301
38.25
13,175.51
mide
425
–
6018.88
Dimethy sulfoxide
301
425
47.00
–
13,159.23
2617.3
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Journal of Chemical Crystallography
Scheme 2 The normal and
deprotonated forms of 1
Fig. 6 UV spectra of 1
(1×10–4 M) without OH− and
1 with diferent equivalent
OH−(tetrabutyl ammonium
hydroxide was used for OH−)
in DMF
Acknowledgements This research is supported by the Thailand
Research Fund (MRG 5580182), Kasetsart University Research and
Development Institute, and Department of Chemistry, Kasetsart
University, and the Center of Excellent for Innovation in Chemis-
try (PERCH-CIC), Commission on Higher Education, Ministry of
Education.
Time-dependent DFT calculations (TD-DFT) suggest that
the deprotonation process of compound 1 occurs in polar
solvents such as DMF. Based on the DFT calculation, the
deprotonation of 1 are responsible for the enhanced signal
of the UV–vis band at 425 nm and correspondingly the
change in the 1H NMR result.
1 3

Journal of Chemical Crystallography
Fig. 7 1H NMR spectra of 1 (1×10–2 M) without OH− and 1 with diferent equivalent OH−(tetrabutyl ammonium hydroxide was used for OH−)
in DMSO-d6
1 3

Journal of Chemical Crystallography
Fig. 8 Structures of 1 of normal (N) and deprotonate forms (DPT)
Table 6 Comparison of experimental and calculated absorbances;
excitation energy, oscillator strength (f), and major transition con-
tributions of the N and DPT forms at PCM-TD-HSEH1PBE/6-
311G(d,p) level in DMF solvent
States
Excitation energy
Major contribution
eV
nm
f
N form
S0 →S1
S0 →S2
S0 →S3
S0 →S4
DPT form
S0 →S1
S0 →S2
S0 →S3
S0 →S4
3.68
3.95
3.96
4.13
337
314
313
300
0.1223
0.0000
0.0000
0.4334
HOMO→LUMO (94%)
H-3→L+1 (90%)
H-6→LUMO (53%)
HOMO→L+1 (93%)
3.05
3.16
3.37
3.44
406
392
368
361
0.0001
0.1219
0.0001
0.6351
H-1→L+1 (89%)
HOMO→LUMO (49%)
H-1→LUMO (87%)
HOMO→LUMO (50%)
Fig. 9 Frontier molecular
orbitals of normal form (N)
and deprotonate form (DPT)
computed at PCM-TD-
CAMB3LYP/6-311G (d,p) level
1 3

Journal of Chemical Crystallography
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Conflict of interest The authors declare no confict of interest.
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