Persubstituted p-benzoquinone monoxime alkyl ethers and their molecular structure

Article abstract of DOI:10.1016/j.molstruc.2011.09.053

Theoretical and experimental approaches were applied for the investigation of the reactivity of persubstituted 4-nitrosophenols in the reaction with alkyl iodides, in particular the potassium salt of 2,6-di(alkoxycarbonyl)-3,5- dimethyl-4-nitrosophenol. H

Full text of DOI:10.1016/j.molstruc.2011.09.053

Journal of Molecular Structure 1015 (2012) 173–180
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Persubstituted p-benzoquinone monoxime alkyl ethers and their
molecular structure
D.G. Slaschinin a, Y.A. Alemasov b, D.I. Ilushkin a, W.A. Sokolenko b, M.S. Tovbis a, S.D. Kirik b,c,
⇑
a Siberian State Technological University, Mira Ave., 82, Krasnoyarsk 660049, Russian Federation
b Institute of Chemistry and Chemical Technology, Marx St., 42, Krasnoyarsk 660049, Russian Federation
c Siberian Federal University, Svobodny Ave., 79., Krasnoyarsk 660041, Russian Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
Theoretical and experimental approaches were applied for the investigation of the reactivity of persub-
stituted 4-nitrosophenols in the reaction with alkyl iodides, in particular the potassium salt of 2,6-di(alk-
oxycarbonyl)-3,5-dimethyl-4-nitrosophenol. Hartre–Fock calculations showed that the anion negative
charge was located mostly on the oxygen of hydroxyl group, while estimation of the total energy of
the alkylated products pointed out the benefit of alkylation on the oxygen atom of the nitroso group
yielding p-benzoquinone monoxime alkyl ethers.
Received 19 July 2011
Received in revised form 28 September
2011
Accepted 28 September 2011
Available online 20 October 2011
Methylation and ethylation of persubstituted nitrosophenols were carried out. The products obtained
were investigated using X-ray diffraction, 1H NMR spectroscopy and mass spectrometry. The crystal
structure of the methyl ether of 2,6-di(alkoxycarbonyl)-3,5-dimethyl-1,4-benzoquinone-1-oxime
(C15H19NO6) (I) was determined by the X-ray powder diffraction technique. The unit cell parameters
were: a = 7.3322(6) Å, b = 10.5039(12) Å, c = 21.1520(20) Å, b = 93.742(6)°, V = 1625.58(2) Å3 Z = 4, Sp.Gr.
P21/c. The structure modeling was made in direct space by the Monte-Carlo approach using rigid and soft
restrictions. The structure refinement was completed by the Rietveld method. It was established that the
alkylation occurred on the oxygen atom of the nitroso group. The molecules (I) in the crystal structure
were packed in columns along the axis a with pairwise convergence in a column up to the distance of
3.63 Å due to a 180° turn of every second molecule around the column axis. In the molecular structure
Keywords:
Hexasubstituted nitrosophenols
Alkylation
Nitroso phenols
Alkyl ethers of 1,4-benzoquinone-1-oximes
Polycrystalline X-ray diffraction analysis
Hartree–Fock quantum-chemical
calculations
the methyloxime group was oriented in the benzene plane and had p-conjugation with the ring. The eth-
oxycarbonyl groups were turned nearly perpendicular to the ring. Other compounds obtained had the
structure of the alkyl ethers of 1.4-benzoquinone-1-oxime, which was proved by 1H NMR spectroscopy
and mass-spectrometry.
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
the ethoxycarbonyl groups is not located in the benzene ring
plane but almost perpendicular to it due to the participation of
A number of persubstituted nitrosophenols are known (Fig. 1),
which exist as salts in the monomeric nitroso form. In the free
nitrosophenol form these compounds are dimerized. [1–3]. Their
hydrogenation results in the formation of p-aminophenols [4],
some derivatives of which are applied in chemical and pharmaceu-
tical industry as antiarrhythmic medical agents [5].
both ethoxycarbonyl groups in the potassium coordination. The
nitroso group in the plane of the benzene ring also coordinates
potassium. The peculiarity of the structure is that both atoms
of oxygen and nitrogen (d(KAO) = 2.50 Å and d(KAN) = 2.66 Å)
participate in the potassium coordination sphere. The resulting
orientation can be interpreted as a
p-bond of the nitroso group
Recently, using polycrystalline X-ray diffraction analysis the
crystal structure of the 2,6-diethoxycarbonyl-3,5-dimethyl-4-
nitrosophenolate potassium salt (Fig. 2) belonging to the series
under consideration has been determined [2,3]. In the crystal
structure a potassium cation is located at a significant distance
from the oxygen atom of a phenolate-ion; moreover, one of
to the potassium cation. The nitroso group turns out to be more
active in the coordination of the potassium cation rather than
the phenolate ion, which is likely due to the excessive negative
charge being present in this group. Taking into account the
structure peculiarities of the persubstituted nitroso phenol salts,
it is of interest to determine the reactivity of the considered
groups in reactions with other reagents. In particular, the ques-
tion may be asked to how will the potassium salts of the persub-
stituted nitroso phenols be alkylated by alkyl halides: on the
oxygen atom of the hydroxyl group or on the oxygen atom of
⇑
Corresponding author at: Institute of Chemistry and Chemical Technology,
Marx St., 42, Krasnoyarsk 660049, Russian Federation.
E-mail addresses: Tovbis@bk.ru (M.S. Tovbis), kirik@icct.ru (S.D. Kirik).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.09.053

174
D.G. Slaschinin et al. / Journal of Molecular Structure 1015 (2012) 173–180
The alkylation reactions of usual (non-hexasubstituted) nitros-
OH
ophenols have long been known. Such nitroso phenols almost
entirely exist as tautomeric para-benzoquinones monoximes
(PQMO). When alkylating PQMO silver salt with methyl iodide a
methyl ether of PQMO was obtained, and using ethyl iodide in the
reaction resulted in an ethyl ether of PQMO [6]. The methyl ether
of PQMO was also formed in the alkylation of quinone oxime by
methyl tosylate in methanol in the presence of alkali [7] and using
diazomethane in diethyl ether [8]. In [9] the ethyl ether of the oxime
was obtained in the PQMO alkylation by ethanol in the presence of
p-toluene sulfonic acid, however, here, it was shown that with
methanol acting in the presence of sulfuric acid one obtained
p-nitrosoanisole, i.e. alkylation could proceed on the phenolic
hydroxyl, as well. The reaction of p-nitrosophenol with methanol
occurred on the phenolic hydroxyl [10], forming p-nitrosoanisole.
Thus, both possible courses of the reaction were experimentally
confirmed. Therefore, it is difficult to foresee what the products of
the alkylation of persubstituted para-nitrosophenols will be.
ROOC
H3C
COOR
CH3
NO
I (a-f)
R = Me (a), Et (b), Pr (c), Bu (d), i-Bu (e), i-Am (f)
Fig. 1. Molecular structure of persubstituted nitrosophenols.
the nitroso group? The scheme of possible reaction paths is gi-
ven in Fig. 3.
Fig. 2. Potassium salt of 2,6-ethoxycarbonyl-3,5-dimethyl-4-nitrosophenol structure projection along the a axis. Hydrogen atoms not shown [4].
OR'
OK
ROOC
H3C
COOR
ROOC
H3C
COOR
CH3
a
R'-I
-KI
CH3
NO
O
NO
III (a-l)
II (a-f)
R = Me (a), Et (b), Pr (c), Bu (d), i-Bu (e), i-Am (f)
ROOC
H3C
COOR
b
CH3
N-O-R'
IV (a-l)
a: R=R'=Me; b: R=Me, R'=Et; c: R=Et, R'=Me; d: R=R'=Et; e: R=Pr, R'=Me;
f: R=Pr, R'=Et; g: R=Bu, R'=Me; h: R=Bu, R'=Et; i: R=i-Bu, R'=Me;
j: R=i-Bu, R'=Et; k: R=i-Am, R'=Me; l: R=i-Am, R'=Et.
Fig. 3. The alkylation ways for persubstituted nitrosophenol salts.

D.G. Slaschinin et al. / Journal of Molecular Structure 1015 (2012) 173–180
175
Fig. 4. Experimental (dots), calculated (solid line) and difference X-ray diffraction patterns corresponding to obtained solution for C14H16KNO6. Location of the calculated
reflections positions are indicated by the vertical strips. Giving in the insert is a zoomed high angle area of the X-ray diffraction patterns.
The most probable course of the alkylation reaction has been
determined in the present work using two approaches. Theoretical
quantum-chemical optimization of the nitrosophenolate-anion
structure has been performed and the charge density on the reac-
tion centers estimated. The alkylation of a number of the potas-
sium salts of persubstituted nitrosophenols has experimentally
been made. The structure of the alkylation products has been
established using polycrystalline X-ray diffraction analysis, mass
spectrometry and 1H NMR spectroscopy.
Table 1
Crystallographic parameters of 3,5-di(ethoxycarbonyl)-2,6-dimethyl-1,4-benzoqui-
none-1-oxime methyl ether (I) and details of X-ray structure determination.
Chemical formula
Molecular weight
C15H19NO6
309.31
P21/c
7.3305(3)
Space group
0
a, ÅA
0
10.5034(8)
b, ÅA
0
21.1531(17)
c, ÅA
a
, (°)
90
b, (°)
93.785(5)
90
1625.14(19)
4
1.264
0.827
295
c
, (°)
Vunit cell, Å3
2. Experimental
Z
q
l
cal, g/sm3
, mmꢀ1
2.1. Synthesis
T, K
Diffractometer
X’Pert PRO
CuKa
k1 = 1.54056,
k2 = 1.54439
7.017–89.983
3192
2.1.1. Alkylation of substituted 2,6-di(alkoxy carbonyl)-3,5-dimethyl-
4-nitrosophenols
Radiation
0
k, ÅA
The potassium salt of hexasubstituted para-nitrosophenol
(0,1 g) was suspended in absolute diethyl ether medium (2 ml)
and excess of alkyl iodide was added. The mixture was refluxed
on a water bath for 24 h at atmospheric pressure, with the mix-
ture color changing from green to yellow. The reaction product
was contained in the diethyl ether. The precipitate of potassium
iodide form was filtered, and the filtrate was evaporated. The oily
residue was porphyrized with hexane until solidification, fol-
lowed by recrystallization from the petroleum ether. In all cases
the powder obtained was yellow. The final product was addition-
ally dried in vacuum at room temperature. Some physical–chem-
ical properties and spectral data of the substances obtained are
given below.
Scan range, 2h (°)
Number of points
Number reflections
Number of refinement parameters and
coordinates
Rp, %
Rwp, %
Rexp, %
S = Rwp/Rexp
3369
72
6.86
9.42
7.42
1,27
2.1.3. 3,5-Di(methoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, ethyl ether (IVb)
Yellow crystals, yield 17%, m.p. 86–87 °C. NMR 1H (CDCl3): d
1.43 (t, 3H, NOC2H5), 2.25 (s, 3H, PhCH3), 2.40 (s, 3H, PhCH3),
3.902 (s, 3H, COOCH3), 3.907 (s, 3H, COOCH3), 4.50 (q, 2H,
NOC2H5); mass spectrum M+ 295.
2.1.2. 3,5-Di(methoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, methyl ether (IVa)
Yellow crystals, yield 52%, m.p. 117–118 °C. NMR 1H (CDCl3):
d 2.24 (s, 3H, PhCH3), 2.38 (s, 3H, PhCH3), 3.902 (s, 3H, COOCH3),
3.907 (s, 3H, COOCH3), 4.25 (s, 3H, NOCH3); mass spectrum M+
281.
2.1.4. 3,5-Di(ethoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, methyl ether (IVc)
Yellow crystals, yield 55%, m.p. 115–116 °C. NMR 1H (CDCl3): d
1.371 (t, 3H, COOC2H5), 1.378 (t, 3H, COOC2H5), 2.24 (s, 3H, PhCH3),

176
D.G. Slaschinin et al. / Journal of Molecular Structure 1015 (2012) 173–180
Fig. 5. Molecule 3,5-Di(ethoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-oxime methyl ether (C15H19NO6).
Fig. 6. Location of the molecules of 3,5-di(ethoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-oxime methyl ether within the unit cell.

D.G. Slaschinin et al. / Journal of Molecular Structure 1015 (2012) 173–180
177
Table 2
COOC2H5), 4.378 (q, 2H, COOC2H5), 4.48 (t, 3H, NOC2H5); mass
spectrum M+ 323.
The effective charges of nucleophilic centers.
Anion
Oxygen of hydroxyl group
Oxygen of nitroso group
2.1.6. 3,5-Di(propoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, methyl ether (IVe)
IIa
IIb
IIc
IId
IIe
ꢀ0.545
ꢀ0.539
ꢀ0.539
ꢀ0.523
ꢀ0.536
ꢀ0.373
ꢀ0.374
ꢀ0.376
ꢀ0.389
ꢀ0.372
Yellow crystals, yield 60%, m.p. 55–56 °C. NMR 1H (CDCl3): d
1.01 (t, 6H, 2COOC3H7), 1.75–1.77 (broad m, 4H, 2COOC3H7), 2.24
(s, 3H, PhCH3), 2.38 (s, 3H, PhCH3), 4.24 (s, 3H, NOCH3), 4.28 (t,
4H, 2COOC3H7); mass spectrum M+ 337.
Table 3
2.1.7. 3,5-Di(propoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, ethyl ether (IVf)
Persubstituted para-alkoxynitrosobenzenes and para-benzoquinonemonooximes
alkyl ethers molecules total energy differences.
Yellow crystals, yield 72%, m.p. 92–93 °C. NMR 1H (CDCl3): d
0.99 (t, 6H, 2COOC3H7), 1.43 (t, 3H, NOC2H5), 1.75–1.77 (broad
m, 4H, 2COOC3H7), 2.24 (s, 3H, PhCH3), 2.40 (s, 3H, PhCH3), 4.29
(t, 4H, 2 COOC3H7), 4.49 (q, 2H, NOC2H5); mass spectrum M+ 351.
Molecules
Total energy differences, Hartree (EIII–EIV)
IIIa–IVa
IIIb–IVb
IIIc–IVc
IIId–IVd
IIIe–IVe
IIIf–IVf
0.0135
0.0040
0.0049
0.0062
0.0047
0.0061
0.0010
0.0063
2.1.8. 3,5-Di(butoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, methyl ether (IVg)
Yellow crystals, yield 46%, m.p. 53–55 °C. NMR 1H (CDCl3): d
0.960 (t, 3H, COO-C4H9), 0.964 (t, 3H, COO-C4H9), 1.40–1.44 (m,
4H, 2COOC4H9), 1.65–1.71 (m, 4H, 2COOC4H9), 2.23 (s, 3H, PhCH3),
2.38 (s, 3H, PhCH3), 4.23 (s, 3H, NOCH3), 4.317 (t, 2H, COOC4H9),
4.320 (t, 2H, COOAC4H9); mass spectrum M+ 365.
IIIg–IVg
IIIh–IVh
2.38 (s, 3H, PhCH3), 4.24 (s, 3H, NOCH3), 4.379 (q, 2H, COOC2H5),
4.383 (q, 2H, COOC2H5); mass spectrum M+ 309.
2.1.9. 3,5-Di(butoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, ethyl ether (IVh)
2.1.5. 3,5-Di(ethoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, ethyl ether (IVd)
Yellow crystals, yield 47%, m.p. 68–70 °C. NMR 1H (CDCl3): d
0.960 (t, 3H, COOC4H9), 0.965 (t, 3H, COOAC4H9), 1.41–1.42 (m,
4H, 2COOC4H9), 1.43 (t, 3H, NOC2H5), 1.71–1.76 (m, 4H,
2COOC4H9), 2.23 (s, 3H, PhCH3), 2.39 (s, 3H, PhCH3), 4.310 (t, 2H,
Yellow crystals, yield 80%, m.p. 95–96 °C. NMR 1H (CDCl3): d
1.367 (t, 3H, COOC2H5), 1.373 (t, 3H, COOC2H5), 1.42 (t, 3H,
NOC2H5), 2.24 (s, 3H, PhCH3), 2.40 (s, 3H, PhCH3), 4.375 (q, 2H,
Fig. 7. The calculated electron density map of the 2,6-diethoxycarbonyl-3,5-dimethyl 4-nitrosophenolate anion.

178
D.G. Slaschinin et al. / Journal of Molecular Structure 1015 (2012) 173–180
Table 4
Table 5
The most important interatomic distances in 3,5-di(ethoxycarbonyl)-2,6-dimethyl-
1,4-benzoquinone-1-oxime methyl ether.
The most important angles between bonds in 3,5-di(ethoxycarbonyl)-2,6-dimethyl-
1,4-benzoquinone-1-oxime methyl ether structure.
0
Atom A
Atom B
Atom A
Atom B
Atom C
Angle (ABC)
d(A–B), (AÅ)
C8
O14
O16
O17
C2
C2
C2
C3
C3
C3
C4
C4
C4
C5
C5
C5
C6
C6
C6
C7
C7
C7
C8
C8
C8
C12
C12
C12
C18
C20
N10
C20
C18
C22
C3
C7
C7
C2
C8
C8
C5
C9
C9
C6
C4
C4
C5
C11
C11
C2
C12
C12
O14
C3
C3
O16
C7
121.06
123.01
107.43
120.30
119.96
119.69
120.52
120.74
118.69
119.67
116.09
124.22
124.11
115.93
119.94
120.12
121.87
117.94
119.90
120.26
119.64
119.98
121.45
118.56
119.89
120.86
119.23
102.37
107.59
122.28
O14
O14
O15
O13
O1
O16
O16
O17
O17
C2
C2
C2
C3
C3
C3
C4
C4
C4
C5
C5
C5
C6
C6
C6
C7
C7
C7
C8
C8
C8
C8
1.338
1.464
1.220
1.211
1.199
1.342
1.451
1.399
1.430
1.199
1.445
1.451
1.351
1.445
1.497
1.351
1.452
1.506
1.300
1.446
1.452
1.355
1.446
1.514
1.355
1.451
1.502
1.211
1.338
1.497
1.506
1.514
1.220
1.342
1.502
1.451
1.476
1.476
1.464
1.481
1.481
1.430
1.300
1.399
C12
N10
O1
O1
C3
C4
C4
C2
C3
C3
C5
N10
N10
C6
C7
C7
C5
C6
C20
C12
C8
C2
C12
C18
N10
C22
O1
C3
C7
C4
C2
C8
C3
C5
C9
N10
C6
C4
C7
C5
C11
C6
C2
C12
O13
O14
C3
C4
C6
O15
O16
C7
O16
C19
C18
O14
C21
C20
O17
C5
C6
C2
O13
O13
O14
O15
O15
O16
O16
O14
C5
C7
C19
C21
O17
C9
C11
C12
C12
C12
C18
C18
C19
C20
C20
C21
C22
N10
N10
4H, 2COO-i-C5H11), 1.74 (m, 2H, 2COO-i-C5H11), 2.23 (s, 3H,
PhCH3), 2.37 (s, 3H, PhCH3), 4.346 (t, 2H, COO-i-C5H11), 4.349 (t,
2H, COO-i-C5H11), 4.23 (s, 3H, NOCH3); mass spectrum M+ 393.
2.1.13. 3,5-Di(isoamoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, ethyl ether (IV l)
Yellow crystals, yield 83%, m.p. 60–61 °C. NMR 1H (CDCl3): d
0.956 (d, 6H, COO-i-C5H11), 0.959 (d, 6H, COO-i-C5H11), 1.43 (t,
3H, NOC2H5), 1.63 (m, 4H, 2COO-i-C5H11), 1.75 (m, 2H, 2COO-i-
C5H11), 2.23 (s, 3H, PhCH3), 2.39 (s, 3H, PhCH3), 4.35 (t, 4H,
2COO-i-C5H11), 4.48 (q, 2H, NOC2H5); mass spectrum M+ 407.
O17
COOC4H9), 4.317 (t, 2H, COOC4H9), 4.48 (q, 2H, NOC2H5); mass
spectrum M+ 379.
2.2. Acquisition of 1H NMR and mass spectra
2.1.10. 3,5-Di(isobutoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, methyl ether (IV i)
The1H NMR spectra were obtained using Bruker Avance III 600
in deuterochloroform medium. The mass spectra were acquired
with a Finnigan MAT 8200.
Yellow crystals, yield 49%, m.p. 86–87 °C. NMR 1H (CDCl3): d
0.988 (d, 6H, COO-i-C4H9), 0.995 (d, 6H, COO-i-C4H9), 2.043 (m,
2H, 2COO-i-C4H9), 2.24 (s, 3H, PhCH3), 2.39 (s, 3H, PhCH3), 4.106
(d, 2H, COO-i-C4H9), 4.110 (d, 2H, COO-i-C4H9), 4.24 (s, 3H,
NOCH3); mass spectrum M+ 365.
2.3. Methods of quantum-chemical calculations
The quantum chemical optimizations were made with the soft-
ware package FireFly [11] using the Hartree–Fock method with the
6-31G basis set and Muller–Plesset second order electron correla-
tion corrections [12–15].
2.1.11. 3,5-Di(isobutoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, ethyl ether (IV j)
Yellow crystals, yield 52%, m.p. 55–56 °C. NMR 1H (CDCl3): d
0.986 (d, 6H, COO-i-C4H9), 0.992 (d, 6H, COO-i-C4H9), 1.43 (t, 3H,
NOC2H5), 2.04 (m, 2H, 2COO-i-C4H9), 2.24 (s, 3H, PhCH3), 2.40 (s,
3H, PhCH3), 4.12 (d, 4H, 2COO-i-C4H9), 4.48 (q, 2H, NOC2H5); mass
spectrum M+ 379.
2.4. X-ray diffraction method of determining the structure of the
methyl ether of 3,5-di(ethoxycarbonyl)-2,6-dimethyl-1,4-
benzoquinone-1-oxime
2.1.12. 3,5-Di(isoamoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-
oxime, methyl ether (IV k)
The X-ray powder diffraction data were obtained using CuK
radiation on a PANalytical X’Pert Pro diffractometer equipped with
a PIXcel detector and a graphite monochromator.
a
Yellow crystals, yield 86%, m.p. 74–75 °C. NMR 1H (CDCl3): d
0.953 (d, 6H, COO-i-C5H11), 0.958 (d, 6H, COO-i-C5H11), 1.63 (m,

D.G. Slaschinin et al. / Journal of Molecular Structure 1015 (2012) 173–180
179
Fig. 8. NMR 1H spectrum of 3,5-di(ethoxycarbonyl)-2,6-dimethyl-1,4-benzoquinone-1-oxime methyl ether. Duplication signals of Methyl and methylene groups of ester
substituents are caused by syn- or anti-position with methyloxime group.
The sample was ground in an agate mortar and the holder was
front loaded. The acquisition ranged from 3° to 90° in 2h, with a
gen atom of the hydroxyl group seems more preferable. On the
average, the charge excess amounts to 0.17 e. The calculated elec-
tron density map of the 2,6-diethoxycarbonyl-3,5-dimethyl-4-
nitrosophenolate anion presented in Fig. 7. The substitution of
the alkoxycarbonyl groups in the series (Me, . . ., Am) leads only
to a slight decrease of the charge difference in the considered
groups which is apparently connected with the absence of the con-
step of 0.013°,
Dt – 50 s.
The unit lattice parameters were determined and refined with
the help of the software described in [16,17]. The search of the
structure model was implemented by the Monte-Carlo method
[22,23] using the software FOX [18]. The structure of the anion
C
14H17NO6 was used as the initial model [2,3,20]. The refining pro-
jugation of their p-systems with the benzene ring. A possible
cedure of the chosen structure variants was carried out with the
help of the full-profile analysis using the program FullProf [19].
During refinement, both interatomic distances and angles were
subjected to weighted restraints. The dihedral angles were not re-
strained. The restraints were relaxed gradually during refinement
[21]. At the last stage of the refinement the hydrogen atoms rigidly
attached to the corresponding carbon atoms were added into the
structure model using the program XP [24]. The displacement coef-
ficients of the atoms were specified in the isotropic approximation.
Fig. 4 shows the result of the agreement between the simulated
and experimental X-ray diffraction patterns for the final structure
model. Table 1 presents the crystallographic structure characteris-
tics of the methyl ether of 3,5-di(ethoxycarbonyl)-2,6-dimethyl-
1,4-benzoquinone-1-oxime, while Figs. 5 and 6 show the crystal
structure. More detailed data concerning present investigation
can be found in [25]. Cif-file is deposited in CSD (#CCDC 846074).
obstacle for implementing the interaction on the oxygen atom of
the hydroxyl group can be the increasing steric effect of the alkoxy
groups.
Side by side with the difference in the charge density the
HOMO’s of oxygen of hydroxyl and nitroso groups have significant
difference too. It means that the discussed chemical reaction may
follows via different mechanisms: SN1 and SN2. The oxygen of hy-
droxyl group interacts with a carbocation via SN1 while the oxygen
of nitroso group follows SN2 mechanism in the reaction with halo-
gen alkane. The calculation carried out counts in favor of the sec-
ond way. The difference HOMO of the oxygen hydroxyl group
and LUMO of the carbocation is very large while HOMO of oxygen
nitroso group and LUMO of halogenalkans are nearly equal.
On the other hand, the structure optimization of the possible
nitrosophenol alkylation products and the comparison of the total
energies of the molecules alkylated on the oxygen atoms of the hy-
droxyl or nitroso groups (Table 3) evidences a higher energy ben-
efit of the alkylation products on nitroso groups which would
result in the formation of the ethers of persubstituted para-benzo-
quinone monoximes.
The course of the alkylation reactions was experimentally re-
vealed by the reaction of persubstituted nitrosophenol potassium
salts with alkyl iodides in the absolute ether. In all the cases the
crystalline alkylation products of yellow color were obtained. The
product composition was confirmed by the mass-spectrometry
measurements presented in the experimental part. In each mass-
spectrum there was a molecular ion exactly corresponding to the
molecular weight of the alkyl ether and the remaining molecule
3. Results and discussion
Taking into account the fact that in the anions of persubstituted
nitrosophenols there are two nucleophilic centers – the oxygen
atoms of the hydroxy group and nitroso group – quantum chemical
optimizations of the nitrosophenolate anions were made to carry
out an analysis of their reactivity.
Table 2 shows the charge density values on the oxygen atoms of
the hydroxy and nitroso groups obtained as a result of the anion
structure optimization. From the point of view of the charge values
on the nucleophilic centers the course of the reaction on the oxy-

180
D.G. Slaschinin et al. / Journal of Molecular Structure 1015 (2012) 173–180
fragments formed as a result of the electron impact. The crystal
structure of the methyl ether of 3,5-di(ethoxycarbonyl)-2,6-di-
methyl-1,4-benzoquinon-1-oxime (C15H19NO6) was determined by
the X-ray structure analysis using a polycrystalline sample. The
substance has a molecular structure (Fig. 4). In the unit cell there
are 4 identical formula units, with the molecule being asymmetri-
cal. The planes of the ethoxycarboxyl groups are turned almost per-
syn- or anti-location with respect to the methyloxime group and
give signals as singlets of the same intensity with the chemical
shifts of 2.24 ppm and 2.38 ppm. Likewise, the signals of the ethyl
ether groups for the same reason give «double» signals: triplets
with the chemical shifts of 1371 ppm and 1378 ppm as well as
quartets with 4379 ppm and 4383 ppm. The signal of the methyl
group of oxime is a singlet with the chemical shift of 4.24 ppm.
Thus, it was established that (in spite of the high charge locali-
zation on the oxygen atom of the hydroxyl group) the alkylation
reaction of persubstituted nitrosophenols occurred on the oxygen
atom of the nitroso group with the formation of alkyl ethers of
hexasubstituted quinine oximes which are more beneficial from
the energy point of view.
o
pendicular to the ring, forming dihedral angles of 79.89 and
76.84o. The ethoxy groups are oriented on different sides of the ring
plane. Other substitutes (@O, ACH3, ACH3, @NO(CH3)) are located
in the ring plane. The methyloxime group is likely to have p-conju-
gation with the carbonyl group which is revealed by the presence of
the quinoid distortion of the benzene ring, (d(C3AC2) = 1.44(1) Å,
d(C3AC2) = 1.35(1) Å). The shortened distances C2AO1 (1.20(1) Å)
and C5AN10 (1.30(1) Å) are also indicative of the appearance of
double bonds with the oxygen atoms of the carbonyl and meth-
yloxime groups. Other interatomic distances and angles are pre-
sented in Tables 4 and 5.
The investigation was carried out at the financial support of the
Ministry of Education and Science of the Russian Federation (State
Contracts No. 02.740.11.0629 and No. G2263), and the Interna-
tional Center of Diffraction Data (ICDD, Grant No. 93-10).
References
The crystal structure is a column packing of molecules along the
axis a. (Fig. 6). In the column the molecules are located in pairs re-
lated by the symmetry center. The distance between the planes of
the benzene rings in the pairs is about 3.63 Å. Hydrogen bonds are
absent, thus, the observed packing is a result of the most dense
molecule packing taking into account their own geometry.
Important information on the ether structure was obtained by
analyzing the 1H NMR spectra. The examination of the 1H NMR
spectra of the products showed that in all the cases the alkyl ethers
of the hexasubstituted quinine-oximes were formed (Fig. 3, reac-
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one triplet in the strong one. Such a picture vividly confirms that
the alkylation in all the cases occurred on the oxygen atom of
the nitroso group.
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Fig. 8. The methyl groups of the ring are non-equivalent due to