Tautomerism in 4-chlorophenyl benzoylcarbamodithioate: Experimental and DFT study

Article abstract of DOI:10.1016/j.molstruc.2017.02.057

The title dithiocarbamate compound was synthesized, and characterised by means of spectroscopic and single-crystal X-ray diffraction methods. Density functional theory method with the 6?311++G(d,p) basis set was employed to affirm the spectroscopic and st

Full text of DOI:10.1016/j.molstruc.2017.02.057

Accepted Manuscript
Tautomerism in 4-chlorophenyl benzoylcarbamodithioate: Experimental and DFT
study
Fatma Aydın, N. Burcu Arslan, Namık Özdemir
PII:
S0022-2860(17)30203-X
10.1016/j.molstruc.2017.02.057
MOLSTR 23451
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 1 September 2016
Revised Date: 12 February 2017
Accepted Date: 13 February 2017
Please cite this article as: F. Aydın, N.B. Arslan, N. Özdemir, Tautomerism in 4-chlorophenyl
benzoylcarbamodithioate: Experimental and DFT study, Journal of Molecular Structure (2017), doi:
10.1016/j.molstruc.2017.02.057.
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Tautomerism in 4-chlorophenyl benzoylcarbamodithioate:
Experimental and DFT study
Fatma Aydına, N. Burcu Arslanb,*, Namık Özdemirc
aDepartment of Chemistry, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University,
17100 Çanakkale, Turkey
bDepartment of Computer Education and Instructional Technology, Faculty of Education,
Giresun University, 28200 Giresun, Turkey
cDepartment of Mathematics and Science Education, Faculty of Education,
Ondokuz Mayıs University, 55139 Samsun, Turkey
* Tel.: +90 454 3101200; Fax: +90 454 3101287, e-mail: burcu.arslan@giresun.edu.tr
Abstract
The title dithiocarbamate compound was synthesised, and characterised by means of spectroscopic
and single-crystal X-ray diffraction methods. Density functional theory method with the
6−311++G(d,p) basis set was employed to affirm the spectroscopic and structural properties and
also to study the tautomerism in the compound. The obtained theoretical parameters clearly support
the experimental findings. Among the six structural forms of the title compound, the syn-keto-
amine-thione is found to be the most stable one, and the stability sequence is as the followings: syn-
keto-amine-thione > anti-enol-imine-thione > anti-keto-amine-thione > anti-keto-imine-thiol > syn-
keto-imine-thiol > syn-enol-imine-thione. The energy difference between the anti and syn forms
changes from ca. 8 to 59 kJ mol−1 with or without barriers. The energetic and thermodynamic
findings of the syn-keto-amine-thione ⇄ syn-keto-imine-thiol reaction display that the single proton
exchange is unfavoured in both directions. Although the reverse barrier energy of the anti-enol-
imine-thione ⇄ anti-keto-imine-thiol tautomeric transformation is found to be small, neither the
forward nor the reverse reaction appears to happen from the thermodynamic point of view.
Keywords: crystal structure; spectroscopy; density functional theory; rotamerism; tautomerism

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1. Introduction
Tautomerism is the ability of certain organic molecules to exist in isomeric structures, which
are related by the movement of an atom, usually a hydrogen atom, with simultaneous rearrangement
of a double bond [1]. It is known as keto/enole [2], nitroso/oxime [3] thioketo/thioenol [4],
azo/hydrazone [5], thioamide/iminothiol [6,7] etc. One of the most commonly encountered
examples is keto-enol tautomerism resulting from the migration of a hydrogen atom from carbon to
oxygen [O=C-CH3 ⇄ HO-C=CH2].
In biology, tautomers of some molecules play very important role in hydrogen bonding
interactions and stabilize the structure of molecules [8]. Mutations in DNA are thought to arise from
tautomeric alterations and unusual base pairing [9]. Considering the importance of tautomerism in
the pharmaceutical industry, identification of the correct tautomer is recognized as one of the
important tasks in pharmacophore-based virtual screening and drug discovery programs [10].
Therefore, tautomeric structure stability of the synthesized molecule may determine their activity
[11]. Organic dithiocarbamates are organosulfur compounds and they can also consist of the
tautomeric structure. At the same time, they can act as ligands for transition metals because of these
properties [12].
On the other hand, organic dithiocarbamates are valuable synthetic intermediates, which are
ubiquitously found in a variety of biologically active compounds [13,14], whereas they are used as
accelerators in vulcanisation, as high-pressure lubricants [15] and as fungicides and pesticides [16].
In this work, 4-chlorophenyl benzoylcarbamodithioate was synthesized and characterised
with elemental analysis and spectroscopic techniques such as IR and NMR, and single-crystal X-ray
crystallography. We focus our attention on the tautomerism in the compound and report the results
from both theoretical and experimental points of view. The effect of solvents with different polarity
on the tautomerism was examined by applying the integral equation formalism polarizable
continuum model (IEF-PCM). Chloroform, methanol and water were chosen as solvent.
2. Materials and methods
2.1. General remarks
Reagents such as potassium thiocyanate, benzoyl chloride, 4-chlorothiophenol and solvents
from Sigma-Aldrich were used without purification. The melting point was measured on an Electro
Thermal IA 9100 apparatus using a capillary tube and is uncorrected. Reactions were monitored by
thin-layer chromatography (TLC) on silica-gel 60 F254 plates (Merck) and an UV lamp. The IR
spectrum of the title compound was recorded in the range 4000-650 cm−1 with a Perkin Elmer

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1
Spectrum 100 FT-IR spectrometer using KBr pellets. The H NMR and 13C NMR spectra were
recorded on a Bruker AVANCE DPX NMR spectrometer operating at 400 and 101.6 MHz,
respectively, using TMS as an internal standard and DMSO-d6 as solvent.
2.2. Synthesis
The mixture of benzoyl chloride (1) (2.32 ml, 20 mmol) in 20 mL acetone with the
equimolar amount of potassium thiocyanate (1.94 g, 20 mmol) in 20 mL acetone was refluxed with
stirring for 1 h to obtain white colour benzoyl isothiocyanate and then cooled to room temperature.
A solution of the appropriate of 4-chlorothiophenol (2) (2.89 g, 20 mmol) in 20mL acetone was
added dropwise to the benzoyl isothiocyanate within 15 min and was stirred for ca. 3 h at room
temperature (Scheme 1). The progress of reaction was controlled by TLC. As the reaction was
completed, yellow solution was filtered and organic solvent was concentrated with a rotary
evaporator under reduced pressure. After then, raw product was chromatographed over silica gel
using ethyl acetate-hexane (4:1) as the eluent to separate the product. After evaporation the solvent,
the fairly pure, brilliant yellow product (4-chlorophenyl benzoylcarbamodithioate, (3)) was
crystallized out, mp. 109-110 °C, yield 90%, anal. calc. for C14H10ClNO2S2 : C, 54.63; H, 3.27; Cl,
11.52; N, 4.55; S, 20.83 Found: C, 53.97; H, 3.19; Cl, 11.66; N, 4.49; S, 20.64 [17].
<Scheme 1>
2.3. X-ray crystallography
Intensity data of the compound were collected on a STOE diffractometer with an IPDS II
image plate detector. The diffraction measurements were performed at room temperature (296 K)
using graphite monochromated Mo Kα radiation (λ=0.71073 Å) by applying the ω-scan method.
Data collection and cell refinement were carried out using X-AREA [18] while data reduction was
applied using X-RED32 [18]. The structure was solved by direct methods using SHELXS-2013 [19]
and refined with full-matrix least-squares calculations on F2 using SHELXL-2016 [20]
implemented in WinGX [21] program suit. All H atoms bonded to C atoms were positioned
geometrically and refined as a riding model with C─H = 0.93 Å and Uiso(H) = 1.2Ueq(C), while the
H atom bonded to the N atom was located in a difference Fourier map and refined isotropically
[N─H = 0.818(18) Å]. Details of the data collection conditions and the parameters of refinement
process are given in Table 1. The general-purpose crystallographic tool PLATON [22] was used for
the structure analysis and presentation of the results. The molecular graphics were generated using
ORTEP-3 [21].

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<Table 1>
2.4. Computational procedure
The stationary structures were optimized using the three-parameter hybrid density functional
(B3LYP) [23, 24] and 6−311++G(d,p) [25, 26] basis set. The vibrational frequencies were obtained
at the same level to characterize the local minimum and the transition state (TS). The stable
structures exhibited all positive frequencies, whereas the TSs possessed one imaginary frequency.
The recommended scale factor of 0.9679 [27] has been applied to correct the theoretical harmonic
1
vibrational frequencies. The H and 13C NMR chemical shifts were calculated within the gauge-
independent atomic orbital (GIAO) approach [28, 29] at the same level, in which solvent effects
were included by means of the IEF-PCM method [30]. All the calculations in the current paper were
performed via the GaussView molecular visualisation program [31] and Gaussian 03W package
[32].
3. Results and discussion
3.1. Experimental and theoretical structures
The structure of the compound was established by X-ray diffraction, which crystallizes in
the monoclinic space group C2/c with Z = 8, and is depicted in Figure 1(a).
<Figure 1>
The structure contains three essentially planar fragments; a chlorobenzene ring (Cl1/C1-C6),
a N-carbonylcarbamodithioate group (S1/C7/S2/N1/C8/O1) and a benzene ring (C9-C14). The
central N-carbonylcarbamodithioate moiety makes dihedral angles of 56.17(6) and 13.76(8)° with
the chlorobenzene and benzene rings, respectively, while the chlorobenzene and benzene rings are
inclined to one another at 44.78(9)°. The bond lengths of the carbonyl and thiocarbonyl groups have
usual double-bond character with distances of 1.210(2) and 1.649(17) Å, respectively. The C─N
bonds [1.379(2) and 1.383(2) Å] are intermediate between 1.48 Å for a normal C─N single bond
and 1.25 Å for a normal C═N double bond [33]. These results agree with expected delocalisation in
this part of the molecule, and indicate that the compound has a keto-amine-thione form. All other
bond lengths and angles present no unusual features.

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The molecular structure does not include any intramolecular hydrogen bonds, and there are
no important interactions in the crystal structure of the compound, other than van der Waals
contacts.
<Table 2>
The corresponding DFT structure is shown in Figure 1(b), while the experimental and
computed structural parameters are tabulated in Table 2. As can be seen in the table, the biggest
deviation of the bond lengths is 0.19 Å at N1─H1 and the biggest deviation of the bond angles is
2.92° at N1─C8─C9. Theoretically, the N-carbonylcarbamodithioate moiety makes dihedral angles
of 89.37 and 24.82° with the chlorobenzene and benzene rings, respectively, while the
chlorobenzene and benzene rings are tilted at an angle of 65.53°.
When the experimental and computed structures are fitted by PLATON as shown in Figure
1(c), the obtained root mean square (RMS) bond fit and angle fit values of 0.019 Å and 1.493°
emphasize the close relationship between them. As a result, the theoretical structure sufficiently
resembles to the experimental one, and the level of theory can be applied to obtain the other
properties.
3.2. Spectroscopic characterisation
The FT-IR spectrum of the compound is shown in Fig. 2 while the observed and calculated
frequencies with their proposed assignments are given in Table 3.
<Figure 2>
<Table 3>
A series of absorptions appearing in the high-energy region (3500-2500 cm−1) of the infrared
spectrum are associated with the N─H and C─H stretching modes [34]. The experimental band at
3286 cm−1 corresponds to the stretching vibration of the N─H group, which has been calculated at
3472 cm−1. The C─H aromatic stretching modes were observed at 3078 and 3060 cm−1
experimentally and were calculated at 3091 and 3082 cm−1. We assigned the absorption band at
1689 cm−1 due to the C═O stretching vibrations [35], which is in coincidence with its theoretical
value of 1693 cm−1. The thiocarbonyl C═S stretching mode recorded at 1078 cm−1 [36] is in good
agreement with theoretical result of 1056 cm−1. The bands at 1598 and 1573 cm−1 in the FT-IR

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spectrum of the compound, which can be attributed to the ring C═C stretching vibrations, were
calculated at 1588 and 1561 cm−1. The infrared spectrum shows a very strong absorption at 1459
cm−1, which is tentatively assigned to the rocking deformation mode on the N─H group and has
been calculated at 1449 cm−1. The C─N and C─S stretching modes recorded at 1196 and 679 cm−1
is in good agreement with theoretical results of 1188 and 669 cm−1, respectively. The stretching of
the C─Cl bond was confirmed at 744 cm−1 [37] while this band appeared at 730 cm−1 in the
theoretical spectrum.
As a result, the IR spectrum of the compound do not exhibit the S─H and O─H vibration
modes indicating that in the solid state this compound exists in the keto-amine-thione form.
The NMR spectra of the compound is given in Fig. S1 in the supplementary material while the
experimental and calculated chemical shifts are tabulated in Table 4. The proposed structure of the
1
13
compound was confirmed by use of H and C NMR spectroscopy. The N─H proton is an amid
proton rather than imide due to the resonance with the carbonyl (C═O) and thiocarbonyl (C═S)
groups. The compound shows a peak at 10.17 ppm corresponding to the proton of the N─H group,
which has been calculated at 10.29 ppm. The aromatic protons were observed at 7.96-7.28 ppm that
13
have been appeared at 8.59-7.70 ppm in the theoretical spectrum. In the C NMR spectrum, the
signals of the characteristic thiocarbonyl and carbonyl carbons were monitored at 204.55 and
166.53 ppm, while these peaks were calculated at 224.67 and 170.78 ppm, respectively.
<Table 4>
3.3. Molecular conformation and tautomerism
The three tautomeric forms can be expected for the compound; namely keto-amine-thione
(I), keto-imine-thiol (II) and enol-imine-thione (III) (Scheme 2). Besides, the conformational
flexibility over the central C7─N1 bond permits the structure to possess various rotameric forms.
So, possible rotamers of the three tautomers were searched at the same level by changing the
φ(S1─C7─N1─C8) torsion angle from −180° to 180° in steps of 5°. The potential energy curves are
shown in Fig. 3. The results show that the molecule may be found in six structural forms, namely
syn-keto-amine-thione, anti-keto-amine-thione, syn-keto-imine-thiol, anti-keto-imine-thiol, syn-
enol-imine-thione and anti-enol-imine-thione (Scheme 2).
<Scheme 2>
The energy trend of the six conformers was obtained as syn-keto-amine-thione < anti-enol-
imine-thione < anti-keto-amine-thione < anti-keto-imine-thiol < syn-keto-imine-thiol < syn-enol-
imine-thione. Especially, the syn-keto-amine-thione conformer was demonstrated as the most stable

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one. The relative energy of the anti and syn conformers was determined as ca. 21 kJ mol−1 for the
keto-amine-thione tautomer and ca. 8 kJ mol−1 for the keto-imine-thiol tautomer. The energy
barriers for syn → anti isomerisation were calculated as ca. 42 and 37 kJ mol−1 for the keto-amine-
thione and keto-imine-thiol tautomers, while these barriers were found to be 20 and 45 kJ mol−1 for
anti → syn isomerisation, respectively. The anti form of the enol-imine-thione tautomer is more
stable than its syn form by ca. 59 kJ mol−1 without barrier (Table 5).
<Figure 3>
<(Table 5).>
As shown in Scheme 2, two possible tautomeric transformations can occur. The structural
parameters belonging to these two transformations are also listed in Table 2, while their energetic
and thermodynamic parameters are given in Table 6. During the discussion of these reactions, the
forward direction is chosen as the proton transfer from the more stable tautomer to the less stable
one, and the reverse is the opposite one.
<Table 6>
In the syn-keto-amine-thione ⇄ syn-keto-imine-thiol tautomerisation, the imaginary
wavenumber at the TS is calculated at 1641i, 1666i, 1678i and 1679i cm−1 for the gas phase,
chloroform, methanol and water, respectively. During the syn-keto-amine-thione → TS → syn-keto-
imine-thiol single proton transfer reaction, the N1─H1 (1.011 Å) bond breaks and the S2─H1 bond
(1.349 Å) forms simultaneously. The N1···H1 and S2···H1 distances in the TS structure are found
as 1.402 and 1.633 Å, respectively. When going from the syn-keto-amine-thione to syn-keto-imine-
thiol form, the N1─C7 bond length is reduced from 1.387 to 1.285 Å, which shows corresponding
N─C single bond is transformed into N=C double bond after the hydrogen transfer. In adition, the
S2─C7 distance increases from 1.655 to 1.780 Å indicating that the π bond in this S═C bond is
broken down and the S═C double bond is transformed into an S─C single bond. The other bond
distances remain almost unchanged. In the bond angles, the C7─N1─C8 and S2─C7─S1 angles
decrease while the N1─C7─S1 angle increases.
< Figure 4>

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Fig. 4 displays the relative energy curve for the syn-keto-amine-thione ⇄ syn-keto-imine-
thiol isomerisation. The energy difference between them is obtained as −45.24, −49.55, −51.28 and
−51.49 kJ mol−1 in going from the gas phase to water, respectively. The reaction barrier is high and
in the range 143.50-151.46 kJ mol−1 for the forward reaction and in the range 98.26-99.97 kJ mol−1
for the reverse reaction. Consequently, it is obvious that the proton transfer for both directions
requires very high energy to happen. This fact is also verified by the standard enthalpy and free
energy changes since these are obtained as large positive values implying its endothermicity
In the anti-enol-imine-thione ⇄ anti-keto-imine-thiol tautomerisation, the imaginary
wavenumber at the TS is calculated at 736i, 791i, 810i and 812i cm−1 for the gas phase, chloroform,
methanol and water, respectively. The anti-enol-imine-thione → TS → anti-keto-imine-thiol
transition happens in a concerted way with the breaking of the O1─H1 (1.008 Å) bond and the
formation of the S2─H1 bond (1.374 Å). The O1···H1 and S2···H1 distances in the TS structure are
found as 1.379 and 1.490 Å, respectively. On going from the anti-enol-imine-thione to anti-keto-
imine-thiol form, the O1─C8 bond length is reduced from 1.318 to 1.234 Å, while the S2─C7
distance increases from 1.682 to 1.767 Å. This corresponds to the breaking of the S═C double bond
and the formation of a O═C double bond. A shortening in the N1─C7 bond and a lengthening in the
N1─C8 and C8─C9 bonds are also noteworthy. In the bond angles, the S2─C7─S1 and
N1─C8─C9 angles decrease as the N1─C7─S1 and O1─C8─C9 angles increase.
< Figure 5>
Fig. 5 exhibits the relative energy curve for the anti-enol-imine-thione ⇄ anti-keto-imine-
thiol isomerisation. The energy difference between them is computed as −21.44, −20.32, −20.10
and −20.09 kJ mol−1, while the energy of the TS is higher than the anti-enol-imine-thione tautomer
by 25.23, 25.17, 25.33 and 25.37 kJ mol−1 in going from the gas phase to water, respectively. These
energies together with the positive standard enthalpy and free energy changes make the forward
reaction a disfavoured process. In the case of the reverse reaction, very low energy barriers are
found as 3.79, 4.85, 5.23 and 5.27 kJ mol−1 in going from the gas phase to water, respectively. The
values of the standard enthalpies for the reverse reaction show that all the proton transfers are
enthalpically favoured (exothermic). However, the proton transfer reaction needs larger entropy
change rather than energy change to occur (|T∆S298|>| ∆H298|). Therefore, the reverse reaction is
thermodynamically disfavoured for all phases (∆G298 > 0) [38].

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4. Conclusions
In this study, the title dithiocarbamate molecule was obtained and characterised by IR and NMR
spectroscopies. The structure of the molecule was confirmed by single-crystal X-ray diffraction
technique. To support spectroscopic and structural characterisation and also to investigate the
tautomerisation of the compound, theoretical computations have been fulfilled by DFT/B3LYP
method with the 6−311++G(d,p) basis set, in which the IEF-PCM method is further used to expose
the solvent effects on the tautomerisation. Experimental and quantum chemical calculations show
that the keto-amine-thione form is the predominant one among the three possible tautomers.
According to the predicted relative energies of the six conformers of the title compound, syn-keto-
amine-thione conformer is again obtained to be the most stable one. The barrier energy for anti ↔
syn conformational interconversion for the keto-amine-thione and keto-imine-thiol tautomers is
very high and above ca. 42 kJ mol−1, while the two conformations are separated from each other by
59 kJ mol−1 without barrier for the enol-imine-thione tautomer. When the two possible tautomeric
transitions within the six conformers are considered, the corresponding energy barriers for the syn-
keto-amine-thione ⇄ syn-keto-imine-thiol tautomerisation are bigger than ca. 98 kJ mol−1 in both
directions. In the case of the anti-enol-imine-thione ⇄ anti-keto-imine-thiol tautomerisation, it
seems impossible to happen thermodynamically for both directions even if the reverse reaction
barrier energy is small.
Acknowledgments
We gratefully acknowledge the financial support of this work by the Giresun University
Scientific Research Foundation (FEN-BAP-A-200515-57).
Appendix A. Supplementary data
Crystallographic data for the structure reported in this paper have been deposited at the
Cambridge Crystallographic Data Centre (CCDC) with quotation number CCDC 1041602 and can
be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
[Fax:
+44
1223
336
033,
e-mail:
deposit@ccdc.cam.ac.uk,
http://www.ccdc.cam.ac.uk/getstructures].

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References
[1] M.B. Smith and J. March, Advanced Organic Chemistry (John Wiley & Sons, New York,
(2001).
[2] T.A. Gadosy and R.A. McClelland, J. Mol. Struct. Theochem 369 (1996) 1-8.
[3] V. Enchev, G. Ivanova, A. Ugrinov, G.D. Neykov, S. Minchev and N. Stoyanov, J. Mol.
Struct. 440 (1998) 227-235.
[4] F. Aydın, H. Ünver, D. Aykaç and N.O. İskeleli, J. Chem. Crystallogr. 40 (2010) 1082-1086.
[5] A.S. Shawali, M.A. Abdallah, M.A. Mosselhi and Y.F. Mohamed, Z. Naturforsch. B 57
(2002) 552-556.
[6] M.J. Cook, A.R. Katritzky, P. Linda and R.D. Tack, J. Chem. Soc. Perkin Trans. 2 (10)
(1972) 1295-1301.
[7] N.T. Kochev, V.H. Paskaleva and N. Jeliazkova, Mol. Inf. 32 (2013) 481-504.
[8] V.L. Golo and Y.S. Volkov, Int. J. Mod. Phys. 14 (2003) 133-156.
[9] M. Orozco, B. Hernández and F.J. Luque, J. Phys. Chem. B. 102 (1998) 5228-5233.
[10] D. Venkateswarlu and J. Leszczynski, J. Comput. Aid. Mol. Des. 12 (1998) 373-382.
[11] A.R. Katritzky and A.J. Waring, J. Chem. Soc. (1962) 1540-1544.
[12] M.A. Malik, T. Saeed and P. O’Brien, Polyhedron 12 (1993) 1533-1538.
[13] P. Francis, M. Markman, T. Hakes, B. Reichman, S. Rubin, W. Jones, J.L. Lewis Jr., J.
Curtin, R. Barakat, M. Phillips and W. Hoskins, J. Cancer Res. Clin. Oncol. 119 (1993) 360-
362.
[14] H. Nabipour, S. Ghammamy, S. Ashuri and Z.S. Aghbolagh, Org. Chem. J. 2 (2010) 75-80.
[15] L. Monser and N. Adhoum, Sep. Purif. Technol. 26 (2002) 137-146.
[16] M.A. Hussein, A.-N. El-Shorbagi, A.-R. Khallil, Arch. Pharm. 334 (2001) 305-308.
[17] F. Aydın, D. Aykac, E. Dagcı, Asian J. Chem. 22 (2010) 3881-3884.
[18] Stoe & Cie, X-AREA (Version 1.18) and X-RED32 (Version 1.04) Stoe & Cie, Darmstadt,
Germany 2002.
[19] G.M. Sheldrick, Acta Crystallogr. A64 (2008) 112-122.
[20] G.M. Sheldrick, Acta Crystallogr. C71 (2015) 3-8.
[21] L.J. Farrugia, J. Appl. Crystallogr. 45 (2012) 849-854.
[22] A.L. Spek, Acta Crystallogr. D65 (2009) 148-155.
[23] A.D. Becke, J. Chem. Phys. 98 (1993) 5648-5652.
[24] C. Lee, W. Yang and R.G. Parr, Phys. Rev. B 37 (1988) 785-789.
[25] R. Krishnan, J.S. Binkley, R. Seeger and J.A. Pople, J. Chem. Phys. 72 (1980) 650-654.
[26] M.J. Frisch, J.A. Pople and J.S. Binkley, J. Chem. Phys. 80 (1984) 3265-3269.

11
ACCEPTED MANUSCRIPT
[27] M.P. Andersson and P. Uvdal, J. Phys. Chem. A 109 (2005) 2937-2941.
[28] R. Ditchfield, J. Chem. Phys. 56 (1972) 5688-5691.
[29] K. Wolinski, J.F. Hinton and P. Pulay, J. Am. Chem. Soc. 112 (1990) 8251-8260.
[30] J. Tomasi, B. Mennucci and R. Cammi, Chem. Rev. 105 (2005) 2999-3094.
[31] R. Dennington II, T. Keith and J. Millam, GaussView, Version 4.1.2 Semichem, Inc.,
Shawnee Mission, KS, 2007.
[32] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, J.A.
Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J. Tomasi,
V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.
Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, V. Bakken, C.
Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg,
V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D.
Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J.
Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J.
Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill,
B. Johnson, W. Chen, M.W. Wong, C. Gonzalez and J.A. Pople, Gaussian 03W, Revision
E.01,Gaussian, Inc., Wallingford, CT, 2004.
[33] G. Binzet, U. Flörke, N. Külcü and H. Arslan, Z. Kristallogr. NCS 219 (2004) 395-397.
[34] R.M. Silverstein, F.X. Webster and D.J. Kiemle, Spectrometric Identification of Organic
Compounds, John Wiley and Sons, New York, 2005.
[35] A. Saeed, A. Khurshid, M. Bolte, A.C. Fantoni and M.F. Erben, Spectrochim. Acta A 143
(2015) 59-66.
[36] H. Arslan, U. Flörke, N. Külcü and G. Binzet, Spectrochim. Acta A 68 (2007) 1347-1355.
[37] A. Saeed, M.F. Erben and U. Flörke, J. Mol. Struct. 982 (2010) 91-99.
[38] V.B. Delchev, I.G. Shterev, H. Mikosch and N.T. Kochev, J. Mol. Model. 13 (2007) 1001-
1008.

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Table 1. Crystal data and structure refinement parameters for 4-chlorophenyl
benzoylcarbamodithioate.
CCDC deposition no.
Colour/shape
1041602
Yellow/prism
C14H10ClNOS2
307.80
Chemical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
296
0.71073 Mo Kα
Monoclinic
C2/c (No. 15)
Space group
Unit cell parameters
a, b, c (Å)
28.9120(12), 4.1382(2), 24.0699(11)
α, β, γ (°)
90, 107.043(3), 90
2753.3(2)
8
Volume (Å3)
Z
Dcalc (g/cm3)
µ (mm−1)
1.485
0.570
Absorption correction
Tmin, Tmax
Integration
0.7039, 0.8930
1264
F000
Crystal size (mm3)
Diffractometer/measurement method
Index ranges
0.76 × 0.43 × 0.19
STOE IPDS II/ω scan
−36 ≤ h ≤ 36, −5 ≤ k ≤ 5, −30 ≤ l ≤ 30
1.473 ≤ θ ≤ 27.155
17554
θ range for data collection (°)
Reflections collected
Independent/observed reflections
Rint
3052/2141
0.1294
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
∆ρmax, ∆ρmin (e/Å3)
Full-matrix least-squares on F2
3052/0/176
1.008
R1 = 0.0339, wR2 = 0.0775
R1 = 0.0584, wR2 = 0.0833
0.25, −0.12

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13
Table 2. Experimental and optimized structural parameters in the gas phase for the tautomeric transformation of 4-chlorophenyl
benzoylcarbamodithioate.
Parameters
X-ray
B3LYP/6−311++G(d,p)
syn-keto-amine-thione TS
syn-keto-imine-thiol
anti-enol-imine-thione
TS
anti-keto-imine-thiol
Bond lengths (Å)
Cl1─C4
1.757
1.796
1.787
1.655
-
1.755
1.755
1.805
1.789
1.780
1.349
1.223
-
1.756
1.790
1.787
1.682
-
1.755
1.794
1.780
1.737
-
1.754
1.795
1.785
1.767
1.374
1.234
-
1.743(2)
1.770(2)
1.741(2)
1.649(2)
-
1.805
1.743
1.726
-
S1─C1
S1─C7
S2─C7
S2─H1
1.215
-
1.223
-
1.318
1.008
1.355
1.312
-
1.259
-
O1─C8
1.210(2)
-
O1─H1
1.387
1.396
1.011
1.498
1.339
1.395
-
1.285
1.403
-
1.310
1.365
-
1.289
1.391
-
N1─C7
1.379(2)
1.383(2)
0.818(18)
1.485(2)
N1─C8
N1─H1
1.492
1.492
1.475
1.483
1.490
C8─C9
Bond angles (°)
C1─S1─C7
C7─N1─C8
C7─N1─H1
C8─N1─H1
C8─O1─H1
N1─C7─S2
N1─C7─S1
S1─C7─S2
C7─S2─H1
O1─C8─N1
101.29
130.11
112.10
117.71
-
101.14 102.10
124.36 121.04
104.50
124.38
-
104.31 104.70
122.66 125.07
104.12(8)
127.72(17)
112.7(12)
119.6(12)
-
-
-
-
-
-
-
-
-
-
-
-
-
-
108.47
129.63
106.96
123.41
-
118.73
115.34
125.93
-
106.54 118.14
125.10 125.38
128.36 116.48
127.68 129.68
111.52 112.49
120.81 117.83
118.82(13)
115.79(13)
125.38(10)
-
-
92.62
-
90.04
122.17
121.70 123.46
125.91
124.98 125.28
120.36(17)

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14
122.70
115.12
122.63 121.94
115.67 114.60
114.90
119.19
118.95 120.44
116.07 114.28
O1─C8─C9
121.59(16)
118.04(16)
N1─C8─C9
Dihedral angles (°)
C8─N1─C7─S2
C8─N1─C7─S1
C1─S1─C7─N1
C1─S1─C7─S2
C7─N1─C8─O1
C7─N1─C8─C9
178.54(14) 178.55
−2.5(2) −1.62
−176.32(12) −178.08
−180.00 180.00
−0.01
180.00
−180.00
0.01
0.00
0.00
0.00
0.00
−180.00 180.00
180.00 −180.00
180.00 −179.99
2.55(13)
−5.6(3)
1.74
0.00
0.00
0.02
0.00
0.00
0.00
−3.73
−0.01
−0.00
180.00
−0.00
173.94(15) 177.08
−180.00 180.00
−180.00 −180.00

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15
Table 3. Experimental and calculated vibrational frequencies (cm−1) for 4-chlorophenyl benzoylcarbamodithioate.
Assignments
Experimental
Calculated
ν N—H
ν C—H
3286
3078
3060
1689
1598
1573
1459
1196
1078
744
3472
3091
3082
1693
1588
1561
1449
1188
1056
730
ν C—H
ν C=O
ν C=C
ν C=C
γ N—H
ν C—N
ν C=S
ν C—Cl
ν C—S
679
669
ν, stretching; γ, rocking.

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16
Table 4. Experimental and theoretical 1H and 13C NMR chemical shifts from TMS for 4-chlorophenyl benzoylcarbamodithioate.
Atom
Experimental
Calculated
Atom
Experimental
Calculated
H1
H2
10.17
7.28
10.29
7.75
7.72
7.84
7.70
8.01
7.83
7.99
7.95
8.59
C3
C4
129.52
132.07
129.52
131.26
204.55
166.53
138.22
129.08
130.11
133.90
130.11
129.08
137.15
153.56
137.38
144.41
224.67
170.78
139.89
133.35
136.10
142.07
136.84
137.93
H3
7.48
C5
H5
7.48
C6
H6
7.28
C7
H10
H11
H12
H13
H14
C1
7.96
C8
7.57
C9
7.67
C10
C11
C12
C13
C14
7.57
7.96
135.86
131.26
143.08
145.06
C2
Notes: The atom numbering according to Fig. 1(a) used in the assignment of chemical shifts.

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17
Table 5. Energies of the tautomers in hartree, and the relative energy between the anti and syn conformers of the tautomers in kJ mol−1.
tautomers
E
∆E
syn-keto-amine-thione
anti-keto-amine-thione
syn-keto-imine-thiol
anti-keto-imine-thiol
syn-enol-imine-thione
anti-enol-imine-thione
−1926.33199085
−1926.32363827
−1926.31476043
−1926.31794323
−1926.30360050
−1926.32610911
21.93
8.36
59.10

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18
Table 6. Energies of the tautomers in Hartree, and energy differences, activation energies and thermodynamic parameters in kJ mol−1.
E1
E2
∆E
Ea(f)
Ea(r) ∆H298(f) ∆G298(f) T∆S298(f) ∆H298(r) ∆G298(r) T∆S298(r)
syn-keto-amine-thione syn-keto-imine-thiol
gas phase
chloroform −1926.34071439
−45.24 143.50 98.26 126.00 126.99 −0.99
−49.55 148.97 99.42 131.30 131.17 0.14
−51.28 151.19 99.91 133.51 133.93 −0.41
−51.49 151.46 99.97 133.78 134.33 −0.55
90.00
91.22
91.72
91.77
90.79
93.13
93.54
93.60
−0.78
−1.92
−1.82
−1.82
−1926.33199085
−1926.31476043
−1926.32184233
−1926.32475166
−1926.32508936
methanol
water
−1926.34428320
−1926.34470047
anti-enol-imine-thione anti-keto-imine-thiol
gas phase
−21.44 25.23 3.79 11.10
−20.32 25.17 4.85 10.92
−20.10 25.33 5.23 11.06
−20.09 25.37 5.27 11.09
13.94
14.71
14.33
14.19
−2.85
−3.78
−3.27
−3.10
−3.37
−2.59
−2.28
−2.24
1.38
2.40
3.29
3.41
−4.75
−5.00
−5.57
−5.65
−1926.32610911
−1926.31794323
−1926.32347318
−1926.32567508
−1926.32592782
chloroform −1926.33121266
methanol
water
−1926.33333080
−1926.33358081
∆E = E1 – E2, Ea(f) = forward activation energy, Ea(r) = reverse activation energy.

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Figure Captions
Scheme 1. Synthesis pathway of 4-chlorophenyl benzoylcarbamodithioate.
Scheme 2. Tautomerism in 4-chlorophenyl benzoylcarbamodithioate.
Figure 1. (a) The molecular structure of 4-chlorophenyl benzoylcarbamodithioate showing the
atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H
atoms are shown as small spheres of arbitrary radii. (b) The theoretical geometric structure of 4-
chlorophenyl benzoylcarbamodithioate. (c) A molecular fit of the experimental and calculated
structures shown in red and black, respectively.
Figure 2. (a) FT-IR spectrum of 4-chlorophenyl benzoylcarbamodithioate.
(b) Simulated IR spectrum of 4-chlorophenyl benzoylcarbamodithioate.
Figure 3. The potential energy profiles for interconversion between two low energy forms of the
keto-amine-thione (a), keto-imine-thiol (b) and enol-imine-thione (c) tautomers of 4-chlorophenyl
benzoylcarbamodithioate.
Figure 4. Relative energy profile of the syn-keto-amine-thione ⇄ syn-keto-imine-thiol tautomerism
in the gas phase and various solvents.
Figure 5. Relative energy profile of the anti-enol-imine-thione ⇄ anti-keto-imine-thiol tautomerism
in the gas phase and various solvents.

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Cl
SH
O
O
O
(2)
acetone
Cl
S
S
+
KSCN
acetone, reflux
3 h
reflux
1 h
Cl
NH
N=C=S
(1)
(3)
Scheme 1

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Scheme 2

22
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Figure 1

23
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Figure 2

24
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Figure 3

25
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Figure 4

26
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Figure 5

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Research Highlights
•
In this work, 4-chlorophenyl benzoylcarbamodithioate was synthesized and characterised with
elemental analysis and spectroscopic techniques such as IR and NMR, and single-crystal X-ray
crystallography.
•
We focus our attention on the tautomerism in the compound and report the results from both
theoretical and experimental points of view.
•
The effect of solvents with different polarity on the tautomerism was examined by applying the
integral equation formalism polarizable continuum model (IEF-PCM). Chloroform, methanol
and water were chosen as solvent.