Crystal Structure Theory and Applications, 2012, 1, 46-51 Published Online December 2012 (
Crystal and Molecular Structure, and Spectral
Characteristics of Sodium
Olga Kovalchukova1, Nguyen Dinh Do1, Adam Stash2, Vitaly Bel’sky2, Paul Strashnov1,
Andrew Alafinov3, Oleg Volyansky3, Svetlana Strashnova 1, Konstantin Kobrakov3
1Department of General Chemistry, Peoples’ Friendship University of Russia, Moscow, Russia
2Karpov Institute of Physical Chemistry, Moscow, Russia
3Department of Organic Chemistry and Chemistry of Dyes, Moscow State Textile University, Moscow, Russia
Received September 26, 2012; revised November 1, 2012; accepted November 12, 2012
Sodium 3,5-bis(hydroxyimino)-1-methyl-2,4,6-trioxocyclohexanide C7H5N2NaO5 (I) has been isolated as the only
product of the reaction of nitrosation of methylphloroglucinol. The structure of the titled compound has been deter-
mined from single crystal X-ray diffraction data. The hydrated C7H5N2NaO5·2.5H2O crystallizes in the monoclinic
space group C2/c, with a(Å) 16.408(3); b(Å) 12.446(3); c(Å) 13.716(3);
(˚) 126.34(3). The planar organic anion exists
in a triketo-dihydroxyimino form with the C–O and C–N distances from 1.220(2) to 1.271(2) Å and from 1.292(2) to
1.293 Å respectively. In the IR spectrum of I, the sharp absorption band occurred at 1681 cm1 due to C=O stretching
indicating the strong H-interactions. The correlations of theoretical (DFT-B3LYP/aug-cc-pVDZ) and experimental
UV-vis absorption spectra in neutral and alkaline ethanolic solutions showed the existence of hydroxyimino-nitroso
tautomerism while ionization of I.
Keywords: Sodium 3,5-Bis(Hydroxyimino)-1-Methyl-2,4,6-Trioxocyclohexanide; Crystal Structure; IR Spectra;
Electronic Absorption Spectra; Quantum Chemical Modeling
1. Introduction
2,4,6-Trihydroxytoluene (methylphloroglucinol, MPG)
possesses strong and attractive synthetic potential be-
cause of its specific structure. However, till recent years
when the economically efficient method of synthesis of
MPG on base of 2,4,6-trinitrotoluene [1,2] was devel-
oped, it practically has not been realized.
The reactions of electrophilic substitution of H-atoms
in the benzene ring of methylphloroglucinol have been
poorly studied till now. Except one paper concerning its
bromination [3], a series of ancient publications on MPG
acylation by HCN and nitriles [4-8], or ethanoil chloride
[6] and anhydride [8] are known. And there is the only
one example of MPG alkylation by formaldehyde in
presence of sulfuric acid [9].
In frames of systematic investigations, some reactions
of MPG electrophylic substitution (bromination, sul-
fation, Hoesch reaction, azo-coupling) were recently re-
ported [10-13]. As it was shown, in all cases except azo-
coupling irrespectively of variations of reaction conditions
mixtures of mono- and bis-substituted products were form-
ed. In case of the reaction of MPG azo-coupling, non-
standard conditions were found which allowed selective
synthesis of mono- and bis azo-compounds based on
In the present paper, we report the crystal structure,
tautomerism, and some spectral characteristics of the pro-
duct of the reaction of MPG nitrosation.
2. Experimental
2.1. Synthesis of the Title Compound
The title compound was prepared by the reaction of
methylphloroglucinol (MPG) with sodium nitrite. 5 g of
MPG (0.0357 mole) were dissolved in 50 ml of water at
0˚C. The solution containing 6.41 g of NaNO2 (0.09
mole) in 25 ml of water was added with an intensive stir-
ring. The solution was stored under 0˚C for 40 min, and
then 0.7 ml of H2SO4 in 28 ml of water were added drop
opyright © 2012 SciRes. CSTA
wise. After 30 min the formed precipitate was filtered off
and dried over P2O5. The product was finally purified by
re-crystallization. Yield 82% M.p. 208˚C (with decom-
position). The authenticity of the compound has been
established by microanalyses, UV and IR spectra, and
single crystal X-ray diffraction analysis.
2.2. Materials and Physical Measurements
The melting point was determined on an Electrothermal
Model 9200 apparatus and is uncorrected. The IR absor-
ption spectrum was obtained in the region of 400 - 4000
cm–1 with a resolution of 4 cm–1 as KBr pellet using a Va-
rian Excalibur HE 3100 IR spectrometer. Microanalysis
was performed with a Carlo Erba Elemental Analyzer,
model 1108. UV-vis spectrum was recorded in the range
of 200 nm to 800 nm using a Varian Cary 50 Scan spec-
trophotometer. Calculations of ionization constants were
performed according to the procedure described in [14].
2.3. The X-Ray Crystallography
For the crystal structure determination, the single-crystal
of the compound I was used for data collection on an
Enraf-Nonius CAD-4 diffractometer. The β-filtered Mo
Kα radiation (λ = 0.71073 Å) and an ω-2θ scan were used
fordata collection. The lattice parameters were determined
using reflections in the range 22 < 2θ < 26˚. The structure
was solved with direct methods using SHELXS-93 [15].
The refinement of the structure was performed by the
full-matrix least square method on F2 for all the data
with anisotropic thermal parameters for non-hydrogen
atoms. CCDC reference number 865,395. The supplemen-
tary crystallographic data can be obtained free of charge
from the Cambridge Crystallographic Data Centre via Molecular struc-
ture of the compound showing the atomic numbering
scheme is shown in Figure 1. The crystallography details
for the structures determination of the compound were
presented in Table 1. Selected bond distances and bond
angles are listed in Table 2.
2.4. Quantum-Chemical Modeling
The geometry optimization of isomers was performed by
means of DFT-B3LYP/aug-cc-pVDZ approach. Elec-
tronic absorption spectra were predicted using TDDFT
approach at the same theory level as geometry optimiza-
tion. In TDDFT calculations, the bulk solvent effects
were taken into account by means of polarizable contin-
uum model (PCM). All calculations have been executed
using the “SKIF-Chebyshev” supercomputer of the Mos-
cow State University with FireFly package available free
Figure 1. Molecular structure of I (O7-H7 represents 0.5
Table 1. Crystallographic data and structure refinement
Empirical formula C7H10N2NaO7.5
Formula weight 265.16 g/mol
Crystal color Dark red
Temperature 293(2) K
Wavelength 0.71073 Å
Crystal system Monoclinic
Space group C2/c
Unit cell dimensions a = 16.408(3) Å, b = 12.446(3) Å, c =
13.716(3) Å, β = 126.34(3)˚
Volume 2256.1(8) Å3
Z, calculated density 8, 1.561 Mg·m–3
Absorption coefficient 0.172 mm–1
F(000) 1096
Crystal size 0.50 × 0.30 × 0.20 mm
Theta range for data collection2.25 to 25.47 deg.
Limiting indices –19 h 15, 0 k 14, –16 l 15
Reflections collected/unique2191/2100 [R(int) = 0.0147]
Completeness to theta = 25.47100%
Refinement method Full-matrix least-squares on F2
Data/restraints/parameters 2100/0/200
Goodness-of-fit on F2 1.056
Final R indices [I > 2 sigma (I)]R1 = 0.0280, wR2 = 0.0868
R indices (all data) R1 = 0.1160, wR2 = 0.1005
Largest diff. peak and hole 0.281 e·Å–3 and –0.294 e·Å–3
Copyright © 2012 SciRes. CSTA
Table 2. Selected bond lengths (Å) and angle s (˚).
O(1)-C(1) 1.220(2) C(2)-N(1)-O(4) 117.52(14)
O(2)-C(3) 1.271(2) C(6)-N(2)-O(5) 118.20(15)
O(3)-C(5) 1.265(2) O(1)-C(1)-C(6) 122.54(15)
O(4)-N(1) 1.3583(19) O(1)-C(1)-C(2) 121.51(15)
O(5)-N(2) 1.348(2) C(6)-C(1)-C(2) 115.95(13)
N(1)-C(2) 1.293(2) N(1)-C(2)-C(3) 125.73(15)
N(2)-C(6) 1.292(2) N(1)-C(2)-C(1) 113.70(14)
C(1)-C(6) 1.471(2) C(3)-C(2)-C(1) 120.43(14)
C(1)-C(2) 1.483(2) O(2)-C(3)-C(4) 123.67(15)
C(2)-C(3) 1.481(2) O(2)-C(3)-C(2) 115.34(15)
C(3)-C(4) 1.395(3) C(4)-C(3)-C(2) 120.98(15)
C(4)-C(5) 1.398(3) C(3)-C(4)-C(5) 120.86(15)
C(4)-C(7) 1.503(2) C(3)-C(4)-C(7) 119.62(18)
C(5)-C(6) 1.482(2) C(5)-C(4)-C(7) 119.52(18)
O(3)-C(5)-C(4) 123.19(16)
O(3)-C(5)-C(6) 115.84(16)
C(4)-C(5)-C(6) 120.97(15)
N(2)-C(6)-C(1) 113.49(14)
N(2)-C(6)-C(5) 125.84(15)
C(1)-C(6)-C(5) 120.62(15)
3. Results and Discussion
Dark-red plates of single crystals of the only product of
MPG nitrosation were obtained by re-crystallization from
ethanolic aqueous solution, and the crystal structure was
determined by X-ray diffraction studies. The title com-
pound crystallizes in a hydrated form of a sodium salt
(C7H5N2NaO5·2.5H2O) in the monoclinic space group
C2/c with Z = 1.
As it is evident (Figure 1, Table 2), the isolated prod-
uct of transformation of MPG exists in the anionic form
of a triketo-dihydroxyimino tautomer. The negative
charge of the anion is neutralized by Na+ cations. The
C–O distances in the planar organic anion (1.220(2);
1.271(2) and 1.265(2) Å for C1–O1, C3–O2 and C5–O3
respectively) as well as N1–C2 (1.293(2) Å) and N2–C6
(1.292(2) Å) are close to the corresponding double bonds.
The C–C bonds of the ring are not equivalent: C1–C6,
C1–C2, C2–C3, and C5–C6 bond lengths (1.471(2) -
1.483(2) Å) indicate a small degree of conjunction as
well as C3–C4 (1.395(3) Å) and C4–C5 (1.398(3) Å)
bonds are much shorter. Similar types of structures of
polyketo-compounds of carbocyclic and heterocyclic
series were reviewed in [16].
H4 and H5 atoms are located at O4 and O5 atoms of
two hydroxyimino-groups of the anion and involved in
the intramolecular H-bonds with the neighboring car-
bonyl O-atoms (Table 3).
The organic anion chelates the Na+ cations by the
oxygen atoms of С=О groups and N-atoms of neighbor-
ing oxime fragments (r O
1Na 25,647(15) Å; r N
26,625(16) Å). The О(1), N(2) atoms as well as the
O-atoms of both oxime groups are also involved in coor-
dination with the Na+ cations of the neighboring mole-
cules. The coordination sphere of Na+ also includes two
water molecules, one of which is bridging. One of H2O
molecules is of the lattice nature. Thus, a 3D lattice is
formed (Figure 2) which is linked by intermolecular
H-bonds involving coordinated and lattice water mole-
cules (Table 3).
The organic anion chelates the Na+ cations by the
oxygen atoms of С=О groups and N-atoms of neighbor-
ing oxime fragments (r O
1Na 25,647(15) Å; r N
26,625(16) Å). The О(1), N(2) atoms as well as the
O-atoms of both oxime groups are also involved in coor-
dination with the Na+ cations of the neighboring mole-
cules. The coordination sphere of Na+ also includes two
water molecules, one of which is bridging. One of H2O
molecules is of the lattice nature. Thus, a 3D lattice is
formed (Figure 2) which is linked by intermolecular
H-bonds involving coordinated and lattice water mole-
cules (Table 3).
Table 3. Hydrogen bonds in I (Å and deg. ).
D-H...A d(D-H)d(H...A) d(D...A)<(DHA)
O(4)-H(4)...O (2)#1 1.06(3)1.46(3) 2.442(2)151(3)
O(5)-H(5)...O (3)#1 0.81(3)1.69(3) 2.470(2)161(3)
O(7)-H(7)...O (8)#1 0.83(3)1.98(3) 2.797(2)165(3)
O(6)-H(61).. .O(2)#40.76(3)2.03(3) 2.748(2)158(3)
O(6)-H(62).. .O(8)#50.88(5)1.86(5) 2.732(2)169(4)
O(8)-H(81).. .O(3)#60.77(4)2.01(4) 2.763(2)170(3)
O(8)-H(82).. .O(6)#10.82(4)2.01(4) 2.737(2)147(4)
Symmetry transformations used to generate equivalent atoms: #1 x, y, z #2
–x + 1, –y + 1, –z #3 – x + 1,y, –z + 1/2 #4 x, –y + 1, z – 1/2 #5 –x + 1/2, –y + 1/2,
–z #6 x, y – 1, z.
Figure 2. Fragment of the crystal structure of I.
Copyright © 2012 SciRes. CSTA
Elemental analyses of the compound I for carbon, hy-
drogen, and nitrogen are in good agreement with theo-
retical values. The theoretical and observed element per-
centages respectively are: %C: 32.07 and 31.71, %H:
3.65 and 3.80, %N: 10.24 and 10.56.
The IR spectrum of the title compound shows sharp
characteristic absorption bands at 1681/1645 cm–1 due to
C=O stretching mode of the keto-groups which are in-
volved into strong H-interactions. The wide absorption
band in the interval 3550 - 3300 cm–1 with two maxima
at 3460 and 3380 cm–1 are
(CO) vibrations of OH groups
of NOH fragments and water molecules [17]. The sharp
skeleton bands observed at 1580 (w), 1520 (s) and 1510
(m) cm–1 characterize the C…C and C…N vibrations.
The electronic absorption spectrum of I (Figure 3) is
characterized by two absorption bands at 273.42 nm
(logε 4.03) and 380.55 nm (logε 3.83). The addition of
HCl till pH 1 does not provoke any changes in the spec-
trum. This may indicate the stability of anionic form of
the organic species in I. In alkaline solutions, the absorp-
tion bands collapse, and an intensive absorbance at
329.08 nm (logε 4.25) appears.
In order to explain the changes in the UV-Vis spectra
recorded at different pH values, quantum chemical calcu-
lations of electronic absorption spectra of ethanolic solu-
tions of the most stable neutral dihydroxyimino- and di-
nitroso-tautomers as well as their anionic forms (Figure 4)
were performed by the TDDFT method.
The calculated UV spectrum of the neutral dixydro-
xyimino-form is characterized by an absorption band at
354.79 nm (f 0.056) and an intensive doublet 280.89 (f
0.383), and 265.62 (f 0.284) nm (Figure 5(a)). In a
dihydroxyimino monoanionic form the bands are
increased in intensity and shifted to 369.36 (f 0.130)
and271.48 (f 0.513) nm (Figure 5(c)). The shape of the
spectrum and relative intensities of the absorption bands
are in a good accordance of the experimental spectrum of
I in neutral solutions.
Figure 3. Experimental electronic absorption spectra of
ethanol solutions of I in the pH range between 6.0 (cur ve 1)
and 11.0 (curve 19).
(a) (b)
(c) (d) (e)
Figure 4. Optimized geometries of the neutral dihydro-
xyimino (a), dinitrozo (b) tautomers of I and its mono- (c),
di- (d) and trianionic (e) forms.
220 260 300 340 380 Wavelength (nm)
220 260 300 340 380 Wavelength (nm)
Figure 5. Calculated UV-Vis spectra of the dihydroxyimino
tautomer of I in a neutral (a) and monoanionic (c ) for ms.
The calculated spectrum of the neutral dinitrozo-
tautomer of I can be characterized by a strong absorption
due to imposing of two transitions at 296.76 (f 0.220) and
288.38 (f 0.522) nm (Figure 6(b)). In the spectrum of the
trianionic form only one strong absorbance occurs at
297.21 nm (f 0.518) (Figure 6(e)). The calculated
spectrum of the dianionic form is much more compli-
cated and consists of transitions at 376.31 (f 0.043),
310.74 (f 0.285), 303.23 (f 0.138), 277.32 (f 0.153), and
266.73 (f 0.032) nm (Figure 7). The imposing of these
transitions should lead to the appearance of a wide
absorption band or a set of absorption bands. This fact
Copyright © 2012 SciRes. CSTA
220 260 300 340 380
Wavelength (nm)
220 260 300 340 380 Wavelength (nm)
Figure 6. Calculated UV-Visctra of the dinitrozo n speeutral
tautomer of I (b) and its trianionic (e) form.
220 260 300 340 380 Wavelength (nm)
Figure 7. Calculated UV-Vis spectrum of the dianion form
ontradicts with the shape of the experimental spectrum
the dihydroxy-
the results of the spectrophotometric titra-
4. Conclusion
novel compound is obtained by the
5. Acknowledgements
nancial support
[1] W. S. Atkins a of Polynitrodiazo-
of I.
of I in alkaline solutions where a sharp intensive ab-
sorption occurs at 329.08 nm (logε 4.25).
Thus, it is possible to conclude that
ino-isomer is more preferable in the crystalline form
and neutral solutions. The process of ionization is ac-
companied by its tautomeric transformation into the dini-
Basing on
n of I, the ionization constant of the oxime groups was
calculated to be pK 7.55 ± 0.42. The calculated value
correlates with the corresponding literature data for other
cyclic oximes [18].
Consequently, the
reaction of nitrosation of methylphloroglucinol. Accord-
ing to the single crystal X-ray diffraction data, it exists in
the anionic form as sodium 3,5-bis(hydroxyl-imino)-1-
methyl-2,4,6-trioxocyclohexanide. In the alkaline solu-
tions, the further dissociation takes place which is ac-
companied by the transformation of the organic anion
into the dinitrozo-tautomer.
The research has been executed under fi
of the Russian Foundation for Basic Researches (project
10-03-00003- а).
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