Synthesis and properties of 172-phenyl-5,10,15,20- tetraazatribenzo[b,g,l]pyrazino[2,3-q]porphyrin-173(17 4H)-one

Article abstract of DOI:10.1134/S1070428013120178

17²-Phenyl-5,10,15,20-tetraazatribenzo[b,g,l]pyrazino[2,3-q] porphyrin-17³(17⁴H)-one was synthesized for the first time by template cyclotetramerization of 5,7-diphenyl-6H-1,4-diazepine-2,3- dicarbonitrile with phthalonitrile. Its complexation with zinc(II) acetate followed a bimolecular mechanism. Acid-base properties of the resulting zinc complex in benzene-acetic acid were studied, and the stability constant of its monoprotonated (at the meso-nitrogen atom) form was determined.

Full text of DOI:10.1134/S1070428013120178

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2013, Vol. 49, No. 12, pp. 1812–1818. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © A.S. Malyasova, E.A. Kokareva, P.A. Tarakanov, V.V. Aleksandriiskii, O.G. Khelevina, O.I. Koifman, 2013, published in Zhurnal
Organicheskoi Khimii, 2013, Vol. 49, No. 12, pp. 1830–1836.
Synthesis and Properties of 172-Phenyl-5,10,15,20-tetraaza-
tribenzo[b,g,l]pyrazino[2,3-q]porphyrin-173(174H)-one
A. S. Malyasova, E. A. Kokareva, P. A. Tarakanov, V. V. Aleksandriiskii,
O. G. Khelevina, and O. I. Koifman
Research Institute of Chemistry of Macroheterocyclic Compounds,
Ivanovo State University of Chemistry and Technology, pr. F. Engel’sa 7, Ivanovo, 153000 Russia
e-mail: helevina@isuct.ru
Received April 30, 2013
Abstract—172-Phenyl-5,10,15,20-tetraazatribenzo[b,g,l]pyrazino[2,3-q]porphyrin-173(174H)-one was synthe-
sized for the first time by template cyclotetramerization of 5,7-diphenyl-6H-1,4-diazepine-2,3-dicarbonitrile
with phthalonitrile. Its complexation with zinc(II) acetate followed a bimolecular mechanism. Acid–base
properties of the resulting zinc complex in benzene–acetic acid were studied, and the stability constant of its
monoprotonated (at the meso-nitrogen atom) form was determined.
DOI: 10.1134/S1070428013120178
Increasing applications of porphyrazines in new
fields, such as semiconducting materials, sensor
devices, and others, requires synthesis of their deriva-
tives with various structures. Fusion of heterorings is
a promising line in structural modification of porphyr-
azines. At present, porphyrazines with fused nitrogen-
containing heterocyclic fragments, including unsym-
metrical derivatives, have attracted much interest
[1–7]. Structural modification of porphyrazine macro-
cycle essentially affects its physicochemical prop-
erties; therefore, synthesis of new porphyrazines and
studies on the structure–reactivity relations in the por-
phyrazine series are important.
of tribenzo(5,7-diphenyl-1,4-diazepino[2,3])porphyr-
azine gives a mixture of tribenzo(5,6-diphenylpyra-
zino[2,3])porphyrazine and tribenzo(2-phenylimid-
azo)porphyrazine [11]. This is especially important for
the synthesis of the latter which cannot be obtained
directly by template cyclotetramerization since 4,5-di-
cyanoimidazole is inactive therein [1]. The ability of
1,4-diazepine ring to undergo rearrangement into imid-
azole derivatives in acid medium was demonstrated
previously [12].
We now report for the first time on the template
condensation of 5,7-diphenyl-6H-1,4-diazepine-2,3-di-
carbonitrile (I) with 10 equiv of phthalodinitrile (II) in
butan-1-ol in the presence of lithium butoxide, which
led to the formation of a mixture of phthalocyanine
(H2Pc, III), 172,174-diphenyl-173H-5,10,15,20-tetra-
azatribenzo[b,g,l][1,4]diazepino[2,3-q]porphyrin
(IV), and previously unknown 172-phenyl-5,10,15,20-
tetraazatribenzo[b,g,l]pyrazino[2,3-q]porphyrin-
173(174H)-one (V) containing no lithium in the coor-
dination center (Scheme 1). The product mixture was
separated by column chromatography on alumina
using methylene chloride–methanol (95:5 by volume)
as eluent. The structure of V was determined on the
basis of its electronic absorption, IR, 1H and 13C NMR,
and mass spectra.
Donzello et al. [8–10] were the first to report on
porphyrazines with peripherally annulated seven-mem-
bered rings, tetrakis(5,7-diphenyl-1,4-diazepino[2,3])-
porphyrazine and its metal complexes. They also syn-
thesized unsymmetrical tribenzo(5,7-diphenyl-1,4-di-
azepino[2,3])porphyrazine and its magnesium complex
and found that fragmentation of the molecular ion of
the magnesium complex under electron impact (43 eV)
is accompanied by elimination of phenylacetylene and
contraction of the diazepine ring with formation of tri-
benzo(2-phenylimidazo)porphyrazine derivative [10].
It was thus demonstrated that the diazepine ring fused
to porphyrazine macrocycle can be modified and that
new porphyrazines can be obtained without resorting
to template cyclotetramerization. Vacuum sublimation
The IR spectrum of V contained an absorption band
at 1711 cm–1 assignable to the carbonyl group. In the
1812

SYNTHESIS AND PROPERTIES OF 172-PHENYL-5,10,15,20-TETRAAZATRIBENZO[b,g,l]...
1813
Scheme 1.
N
Ph
NH
N
N
N
N
CN
CN
NC
NC
LiOBu, reflux, 4 h
N
N
+
10
HN
Ph
N
I
II
Ph
III
Ph
β
α
N
N
O
β
Ph
N
N
N
N
NH
N
α
NH
N
NH
N
N
N
N
N
N
N
+
+
HN
HN
IV
V
(a)
β-H, m-H, p-H
9.0
NH
1.6
α-H, o-H
NH, pyrazine
0.6
8.0
–0.2 –0.6 –1.0
12.8 12.4 12.0
(b)
β-H, m-H, p-H
8.9
NH
1.8
α-H
1.9
α-H
4.1
o-H
1.11.0
0.0 –0.5 –1.0
10.2
9.8
9.4
9.0
8.6
8.2
7.8 δ, ppm
Fig. 1. 1H NMR spectra of porphyrazine V in (a) THF-d8 and (b) benzene-d6.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 12 2013

MALYASOVA et al.
1814
Scheme 2.
Me
Ph
Me
N
N
N
N
N
N
Me
Ph
N
Me
O
O
O
N
H
Ph
1H NMR spectrum of V (tetrahydrofuran-d8) we ob-
served a broadened downfield signal at δ 12.5 ppm
from the amide NH proton and two sets of aromatic
proton signals at δ 9.3–9.7 (α-H, o-H) and 8.0–8.3 ppm
(β-H, m-H, p-H). The inner NH protons in the por-
phyrazine macrocycle gave rise to an upfield signal at
δ –0.6 ppm (Fig. 1a), which was not clearly observed
in benzene-d6, presumably due to its acidity and hence
high lability. The NHCO signal in the spectrum record-
ed in DMSO-d6 was located at δ 12.48–12.56 ppm. We
succeeded in distinguishing signals from α-H (δ 9.90–
9.92, 9.5–9.6 ppm) and o-H (δ 9.48–9.45, 9.36–
9.33 ppm) in the spectrum of V recorded from a solu-
tion in benzene-d6. The carbonyl carbon atom gave
a singlet signal at δC 158.79 ppm in the 13C NMR spec-
trum (DMSO-d6). The mass spectrum of V was also
consistent with the assumed structure.
679
A
1.2
689
653
0.8
The formation of compound V may be rationalized
by high basicity of the reaction medium due to the
presence of lithium butoxide. No compound V was
obtained in the synthesis of magnesium complex of IV
with the use of magnesium alkoxide [10]. Analogous
transformation of the diazepine ring was described in
[13] for 2-methyl-4-phenyl-3H-1,4-benzodiazepine
(Scheme 2).
We then examined the formation of zinc complex
VI from compound V and Zn(OAc)2 in pyridine. Por-
phyrazines react with Zn(OAc)2 in pyridine according
to Eq. (1).
0.4
0.0
400
500
600
700
λ, nm
Fig. 2. Variation of the electronic absorption spectrum of
porphyrazine V during complex formation with zinc(II)
acetate in pyridine.
log(c0/c)
308 K
298 K
H2Pz + Zn(OAc)2(Py)4
ZnPz + 2AcOH + 4Py
(1)
0.8
0.6
0.4
0.2
0.0
Figure 2 shows variation of the electronic absorp-
tion spectrum of porphyrazine V on complexation with
zinc(II) acetate. The electronic absorption spectrum of
the resulting complex is typical of porphyrazine metal
complexes. The complexation was carried out using
a large excess of Zn(OAc)2, i.e., under pseudofirst-
order conditions. The first order of the reaction is con-
firmed by the linear plot of log(c0/c) versus time τ
(Fig. 3). The kinetic equation is given by
288 K
∂c
H2Pz
–
= kef cH Pz
.
(2)
2
∂τ
0
20
40
60
80
100
120
140
The effective rate constants can be calculated by
Eq. 3:
Time, min
Fig. 3. Plots of log(c0/c) versus time for the complex forma-
1
∂cH0 Pz
tion of porphyrazine V with zinc(II) acetate (c0Zn(OAc)
=
2
2
kef =
ln
.
(3)
3.75×10–4 M).
τ
∂cH Pz
2
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 12 2013

SYNTHESIS AND PROPERTIES OF 172-PHENYL-5,10,15,20-TETRAAZATRIBENZO[b,g,l]...
1815
Kinetic parameters of the complexation of porphyrazine V with zinc(II) acetate in pyridine (c0V = 6.72×10–5 M)
c0Zn(OAc) ×104, M
Temperature, K
kef ×104, s–1
kv, l mol–1 s–1
E, kJ/mol
ΔS≠, J mol–1 K–1
2
288
298
308
288
298
308
288
298
308
288
298
308
288
298
308
04.5±0.2
08.0±0.4
17.0±0.5
13.0±0.5
29.0±1.2
48.0±0.9
22.0±1.1
48.0±1.4
78.0±1.6
27.0±1.0
64.0±1.9
110.0±3.30
41.0±1.6
86.0±2.6
150.0±3.00
1.20±0.05
2.11±0.10
4.45±0.13
1.22±0.04
2.90±0.11
4.30±0.08
1.22±0.06
2.61±0.07
4.22±0.09
1.01±0.04
2.43±0.07
4.22±0.13
1.13±0.04
2.31±0.07
4.01±0.08
03.75
11.25
18.75
26.25
37.50
6±1
–280±12
–280±12
–277±10
–278±12
–274±10
6±1
6±1
5±1
6±1
According to the experimental data, the effective
rate constant depends on the concentration of zinc(II)
acetate.
take up protons at the meso-nitrogen atoms and pyra-
zine nitrogen atom. We examined the behavior of com-
pound V and its complex VI in methylene chloride–
trifluoroacetic acid (TFA), as well as of complex VI in
benzene–acetic acid. Porphyrazines are protonated on
acidification of their solutions in a neutral solvent with
a small amount of trifluoroacetic or acetic acid.
n
kef = kv c
.
(4)
Zn(OAc)2
Here, kv is the true reaction rate constant, and n is
the order of the reaction in with respect to zinc(II)
acetate.
Protonation of V in CH2Cl2–CF3COOH is observed
in the range of trifluoroacetic acid concentrations cTFA
from 0.01 to 0.16 M (Fig. 5). Increase in the acidity of
The kinetic parameters for the formation of com-
plex VI are given in table. The order of the reaction
with respect to Zn(OAc)2 (n) was determined by
logkef
308 K
plotting logkef versus logcZn(OAc) (Fig. 4). It turned out
2
–1.8
to be ~1. In keeping with the general concepts of
complex formation with porphyrins and porphyrazines
[14, 15], this means that the reaction follows a bimo-
lecular mechanism. It should also be noted that the
composition of the solvate coordination sphere of
zinc(II) acetate and the structure and properties of the
solvent almost do not change within the examined
range of Zn(OAc)2 concentrations. Then the kinetic
equation for the formation of complex VI looks like
298 K
–2.1
288 K
–2.4
–2.7
–3.0
–3.3
∂cV
–
= kv cV cZn(OAc)
.
(5)
2
∂τ
–3.6
–3.4
–3.2
–3.0
–2.8
–2.6
–2.4
Porphyrazines are weak multicenter bases. Acid–
base interactions with compound V may involve meso-
nitrogen atoms, nitrogen atom in the pyrazine frag-
ment, and inner nitrogen atoms. Zinc complex VI can
0
logc
Zn(OAc)2
Fig. 4. Plots of log kef versus log c0Zn(OAc) for the complex
formation of porphyrazine V with Zn(OAc)2 in pyridine.
2
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 12 2013

MALYASOVA et al.
1816
A
A
675
690
685
1.0
1.6
1.2
0.8
0.4
0.0
646
0.8
0.6
0.4
0.2
0.0
651
719
722
400
500
600
700
800
400
500
600
700
800
λ, nm
λ, nm
Fig. 5. Variation of the electronic absorption spectrum of
porphyrazine V in CH2Cl2–CF3COOH.
Fig. 6. Variation of the electronic absorption spectrum of
complex VI in CH2Cl2–CF3COOH.
A
674
logI
1.0
1.5
0.8
0.6
0.4
0.2
0.0
651
718
689
1.0
0.8
0.0
5.0
5.5
6.0
H0
6.5
7.0
400
500
600
700
800
λ, nm
Fig. 7. Variation of the electronic absorption spectrum of
complex VI in C6H6–AcOH.
Fig. 8. Plot of logI versus H0 for acid–base interaction of
complex VI in C6H6–AcOH.
sume that the red shift of the Q band maxima in the
electronic absorption spectra of porphyrazines in the
first step of acid–base interactions in both CH2Cl2–
CF3COOH and benzene–acetic acid indicates protona-
tion of the meso-nitrogen atoms.
Figure 8 shows the dependence of logI on H0 for
the protonation of VI in benzene–acetic acid.
The thermodynamic stability constant of complex
VI was determined using the Hammett equation,
pK 6.87±0.02 (see Experimental). The number of
donor centers involved in acid–base interactions is
0.95, i.e., it approaches unity. Thus, only one nitrogen
atom is likely to participate in the first step of acid–
base interaction in benzene–acetic acid. A specific
the medium is accompanied by reduction of the inten-
sity of absorption bands at λI 685 and λII 646 nm and
increase of the absorbance at λ 722 nm. Complex VI is
protonated in the cTFA range from 0.01 to 0.13 M.
Addition of TFA leads to reduction of the absorption
intensity at λI 675 and λII 651 nm and increase of the
absorption intensity at λI 719 and λII 690 nm (Fig. 6).
Acid–base interactions of complex VI in benzene–
acetic acid occur at an acetic acid concentration of 2.48
to 15.62 M (H0 6.90–4.85) (Fig. 7). In this case, varia-
tion of the spectral pattern is similar to that observed in
methylene chloride–trifluoroacetic acid. Taking into
account published data and quantum chemical calcula-
tions of protonated porphyrazines [16], we can pre-
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SYNTHESIS AND PROPERTIES OF 172-PHENYL-5,10,15,20-TETRAAZATRIBENZO[b,g,l]...
1817
feature of porphyrazines as multicenter bases is that all
donor centers are simultaneously involved in acid–base
interaction with the medium, but the degree of com-
pleteness is different for different centers. Presumably,
the first step of acid–base interactions of ligand V and
its zinc complex VI at low acid concentration yields
not completely protonated forms but ion–ion associates
like [LM]H+···–OOCCF3 (M = Zn, H2).
phthalodinitrile (II) were added, and the mixture was
stirred for 4 h on heating under reflux. The mixture
changed from light green to dark green. The solvent
was distilled off, and the residue was Soxhlet extracted
with diethyl ether to remove unreacted initial nitriles.
The product mixture was then treated with methylene
chloride to remove phthalocyanine (which is very
poorly soluble in organic solvents) and lithium alkox-
ide. The solvent was removed, and the residue was
subjected to column chromatography on alumina using
methylene chloride–methanol (95:5) as eluent. We
thus isolated phthalocyanine III and porphyrazines IV
(~20%) and V (5%). The absence of metal was proved
by atomic absorption spectroscopy.
EXPERIMENTAL
The electronic absorption spectra of solutions of
porphyrazines and metal complexes were recorded in
the range from λ 380 to 800 nm on a Shimadzu UV-
1800 spectrophotometer using quartz cells. The 1H and
13C NMR spectra were measured on a Bruker Avance
III-500 spectrometer at 500.17 and 125.77 MHz,
respectively, using hexamethyldisiloxane as internal
reference; signals were assigned on the basis of pub-
lished data and chemical shift correlations [17]. The IR
spectra (400–4000 cm–1) were recorded in KBr on
a Thermo Nicolet Avatar 360 FT-IR ESP instrument.
The mass spectra (MALDI-TOF) were obtained on
a Bruker Daltonics Ultraflex mass spectrometer. The
absence of lithium in the macrocycle was confirmed
by atomic absorption spectroscopy using a Saturn
instrument.
Compound IV. Electronic absorption spectrum, λ,
nm (logε): in pyridine: 349 (4.56), 629 (4.33), 678
(4.33), 711 (4.41); in CHCl3: 346 (4.52), 625 (4.23),
676 (4.31), 716 (4.31). IR spectrum, ν, cm–1: 3298 w,
1064 m, 1610 w, 1537 m, 1494 m, 1444 s, 1317 m,
1182 m, 1118 m, 1093 w, 1001 s, 873 s, 734 s, 690 w,
1
655 w, 617 m (NH). H NMR spectrum (THF-d8,
330 K), δ, ppm: –1.33 br.s (2H, NH), 4.61 br (2H,
CH2), 7.50–7.60 (6H, m-H, p-H), 8.03 (4H, β-H), 8.23
(2H), 8.79 d (4H, o-H, J = 6.7 Hz), 9.11 (2H, α-H),
9.16 (2H), 9.32 (2H). Mass spectrum, m/z (Irel, %): 683
(100) [M + H]+, 705 (27) [M + Na]+.
Compound V. Electronic absorption spectrum
(CH2Cl2), λ, nm (logε): 380, 646 (3.96), 685 (4.14). IR
spectrum, ν, cm–1: 3261 w, 3048 w, 2919 m, 2851 m,
1711 m, 1609 w, 1543 w, 1497 w, 1437 m, 1334 m,
1314 m, 1279 w, 1188 w, 1151 w, 1117 m, 1060 m,
1026 s, 950 m, 864 m, 743 s, 715 s, 676 w, 620 w.
1H NMR spectrum (THF-d8, 330 K), δ, ppm: –0.55 to
–0.64 br.s (2H, NH), 8.02–8.23 m (9H, β-H, m-H,
p-H), 9.30–9.43 m (6H, α-H, o-H), 9.57–9.62 d (2H,
Methylene chloride of chemically pure grade was
distilled under atmospheric pressure over 2-amino-
ethanol (bp 40°C). Methanol was dehydrated as fol-
lows. Magnesium turnings, 5 g, were added to 1 L of
methanol. When spontaneous reaction was over, the
mixture was heated for 2–3 h under reflux and distilled
under atmospheric pressure (bp 63–64°C). Benzene
was heated for several hours over P2O5 under reflux
and was then distilled under atmospheric pressure,
a fraction boiling at 80–81°C being collected. Glacial
acetic acid of chemically pure grade was repeatedly
frozen and heated with acetic anhydride under reflux
and was then subjected to fractional distillation
(bp 118°C). Trifluoroacetic acid of chemically pure
grade was distilled over 100% sulfuric acid. Pyridine
of chemically pure grade was dried over potassium
hydroxide and distilled (bp 114°C).
172,174-Diphenyl-173H-5,10,15,20-tetrazatri-
benzo[b,g,l][1,4]diazepino[2,3-q]porphyrin (IV) and
172-phenyl-5,10,15,20-tetrazatribenzo[b,g,l]pyr-
azino[2,3-q]porphyrin-173(174H)-one (V). Metallic
lithium, 0.57 g (0.07 mol), was dissolved in 30 mL of
butan-1-ol, 0.5 g (1.7 mmol) of 5,7-diphenyl-6H-1,4-
diazepine-2,3-dicarbonitrile (I) and 2.6 g (20 mmol) of
3
α-H, J = 7.7 Hz), 12.48–12.56 br.s (1H, NHCO).
13C NMR spectrum (DMSO-d6, 293 K), δC, ppm:
123.38, 129.11, 131.93, 132.21, 133.1, 133.2, 134.05,
134.77, 134.8, 135.26, 136.59, 152.95, 153.95, 153.99,
158.79, 164.50, 167.40, 168.68. Mass spectrum:
m/z 609 (Irel 100%) [M + H]+.
(173-Oxo-172-phenyl-173,174-dihydro-5,10,15,20-
tetrazatribenzo[b,g,l]pyrazino[2,3-q]porphyrinato)-
zinc(II) (VI) was synthesized by heating a mixture of
ligand V and zinc(II) acetate in boiling pyridine for
2 h. The progress of the reaction was monitored by
spectrophotometry. The mixture was poured into water,
and the precipitate was filtered off, thoroughly washed
with water, and purified by column chromatography on
alumina (gradient elution with methylene chloride–
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 12 2013

MALYASOVA et al.
1818
methanol). Electronic absorption spectrum (CH2Cl2),
λ, nm (logε): 350 (4.66), 650 (4.56), 673 (4.70). IR
spectrum, ν, cm–1: 3428, 2924, 2853, 1621, 1573, 1465,
1330, 1165, 1118, 1097, 1060, 881, 771, 725, 694.
This study was performed under financial support
by the President of the Russian Federation (project
no. MK-4171.2012.3).
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Vill, A., and Rizzoli, C., Eur. J. Inorg. Chem., 1999,
p. 2075.
10. Donzello, M.P., Ercolani, C., Mannina, L., Viola, E.,
Bubnova, A., Khelevina, O.G., and Stuzhin, P.A., Aust.
J. Chem., 2008, vol. 61, p. 262.
11. Kokareva, E.A. and Khelevina, O.G., Russ. J. Org.
Chem., 2012, vol. 48, p. 1484.
The kinetics of the complex formation of porphyr-
azine V with zinc(II) acetate were studied as follows.
A spectrophotometric cell was charged at a required
temperature with a solution of V and Zn(OAc)2 with
known concentrations, and the optical density at
λ 679 nm (absorption maximum of complex VI) was
measured at definite time intervals. The current and
final concentrations of the ligand were calculated using
formula (7):
12. Lloyd, D., McDougall, R.H., and Marshall, D.R.,
J. Chem. Soc., 1965, p. 3785.
13. Matsumoto, M., Matsumura, Y., Iio, A., and Yone-
zawa, T., Bull. Chem. Soc. Jpn., 1970, vol. 43, p. 1496.
c = c0 (Aτ – A∞)/(A0 – A∞),
(7)
14. Berezin, B.D., Koordinatsionnye soedineniya porfirinov
i ftalotsianina (Coordination Compounds of Porphyrins
and Phthalocyanine), Moscow: Nauka, 1978.
15. Stuzhin, P.A. and Khelevina, O.G., Uspekhi khimii porfi-
rinov (Advances in the Chemistry of Porphyrins), Go-
lubchikov, O.A., Ed., St. Petersburg: Nauch.-Issled. Inst.
Khimii Sankt-Peterb. Gos. Univ., 1997, vol. 1, p. 150.
16. Stuzhin, P.A., Khelevina, O.G., and Berezin, B.D.,
Phthalocyanines. Properties and Applications, Lez-
noff, C.C. and Lever, A.B.P., Eds., New York: VCH,
1996, vol. 4, p. 19.
where A0, Aτ, and A∞ are, respectively, the optical
densities at the initial moment, at a time τ, and after
reaction completion, and c0 and c are, respectively, the
initial and current concentrations of porphyrazine.
The energy of activation (J/mol) was calculated by
the Arrhenius equation:
T1 T2
k2
k1
Ea = 8.314
ln
.
(8)
T1 – T2
17. Balci, M., Basic 1H- and 13C-NMR Spectroscopy,
The entropy of activation ∆S≠ (J mol–1 K–1) was
Amsterdam: Elsevier, 2005.
calculated by Eq. (9):
18. Stuzhin, P.A., Ul’-Khak, A., Chizhova, N.V., Semei-
kin, A.S., and Khelevina, O.G., Zh. Fiz. Khim., 1998,
vol. 72, p. 1585.
∆S≠ = 8.314lnk298 + Ea/298 – 253.22.
(9)
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 49 No. 12 2013