Kinetics and mechanism of 1-phenyl-5-methyltetrazole nitration in HNO3–H2SO4system

Article abstract of DOI:10.1134/S107042801611021X

At nitration of 1-phenyl-5-methyltetrazole with nitric acid in aqueous solutions of sulfuric acid of 84–96% concentration a mixture forms of 1-(4-nitrophenyl)- and 1-(3-nitrophenyl)-5-methyltetrazoles in a ratio 60: 40. According to kinetic data, the tetrazole ring in the substrate is present in a protonated form. The protonation constants of 1-(4-carboxyphenyl)-5-methyltetrazole at the tetrazole ring and the carboxy group were determined. The Hammet’s electronic constant of the protonated tetrazole ring was calculated.

Full text of DOI:10.1134/S107042801611021X

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2016, Vol. 52, No. 11, pp. 1674–1680. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © V.А. Ostrovskii, А.S. Enin, L.N. Boiko, R.Е. Trifonov, E.А. Popova, Yu.N. Pavlyukova, V.Yu. Dolmatov, 2016, published in Zhurnal
Organicheskoi Khimii, 2016, Vol. 52, No. 11, pp. 1679–1685.
Kinetics and Mechanism of 1-Phenyl-5-methyltetrazole Nitration
in HNO3–H2SO4 System
V. А. Ostrovskiia,* А. S. Enina, L. N. Boikoa, R. Е. Trifonova,b,
E. А. Popovab, Yu. N. Pavlyukovaa, V. Yu. Dolmatovc
a St. Petersburg State Technological Institute (Technical University), Moskovskii pr. 26, St. Petersburg, 190013 Russia
*e-mail: va_ostrovskii@mail.ru
b St. Petersburg State University, St. Petersburg, 119034 Russia
c Special Design – Technological Bureau “Technolog,” St. Petersburg, Russia
Received July 27, 2016
Abstract—At nitration of 1-phenyl-5-methyltetrazole with nitric acid in aqueous solutions of sulfuric acid of
84–96% concentration a mixture forms of 1-(4-nitrophenyl)- and 1-(3-nitrophenyl)-5-methyltetrazoles in a ratio
60 : 40. According to kinetic data, the tetrazole ring in the substrate is present in a protonated form. The
protonation constants of 1-(4-carboxyphenyl)-5-methyltetrazole at the tetrazole ring and the carboxy group
were determined. The Hammet’s electronic constant of the protonated tetrazole ring was calculated.
DOI: 10.1134/S107042801611021X
Tetrazoles are used as energy rich substances, as
active pharmaceutical ingredients for drugs [1, 2], and
also components of materials of various application,
for example, promising modifiers for detonative nano
diamonds surfaces [3].
the interpretation of nitration of N-phenyltetrazoles is
still on the same level.
Aiming to supplement this gap in the tetrazole
chemistry we investigated in the present study the
kinetics of nitration of 1-phenyl-5-methyltetrazole 5
with nitric acid in aqueous solutions of sulfuric acid of
various concentrations. Electrophilic aromatic nitration
of 1-phenyl-5-methyltetrazole 5 may result in three
isomeric nitro compounds 6–8 (Scheme 2).
Unsubstituted tetrazole was first obtained by Bladin
in 1885 in keeping with Scheme 1 [4].
One of the stages of this synthesis is the nitration of
the corresponding N-phenyltetrazole 2, which was
assumed to give nitro derivative 3. It has been already
130 years since the study was published [4], however
According to NMR data and HPLC, the nitration of
tetrazole 5 resulted mostly in the formation of para-
Scheme 1.
Ph
NH
N
N
N
N
NC
HNO2
KOH
N
N
N
Ph
NC
Ph
HO2C
N
N
NH2
2
1
N
N
N
N
N
N
KMnO4
HNO3
SnCl2
N
N
N
N
HO2C
HO2C
N
N
NO2
H
NH2
3
4
1674

KINETICS AND MECHANISM OF 1-PHENYL-5-METHYLTETRAZOLE NITRATION
1675
Scheme 2.
NO2
NO2
HNO3_H2SO4
H3C
H3C
H3C
H3C
NO2
N
N
N
+
N
+
N
N
N
N
N
N
N
N
N
N
N
N
5
6
7
8
and meta-nitro derivatives 6 and 7, and the content of
ortho-isomer 8 in the reaction product did not exceed
1%. The kinetics of nitration were investigated by UV
spectroscopy that allowed monitoring the process
without isolating the initial substrate and reaction
products. UV spectra were recorded in sulfuric acid
(с ≥ 84.1 wt %), for in this case tetrazoles 5–8 are in
the form protonated at the N4 atom of the heteroring
[5]. In UV spectrum of nitration products the
maximum of ortho-nitro derivative 8 (λmax 250 nm, ε
5608) is not observed within the limits of accuracy of
determination of optical density. Further it was
assumed that as a result of tetrazole 5 nitration only the
corresponding para- and meta-nitro derivatives 6 and 7
are formed (Fig. 1).
mechanism of nitration may be assumed also for 1-
phenyl-5-methyltetrazole 5. In this case the formation
of ortho-isomer 8 is connected with spatial hindrances
that is probably the reason of negligible fraction of this
isomer.
The rate of nitration of 1-phenyl-5-methyltetrazole
5 was monitored by increasing of the optical density at
40°C at the analytical wavelength λ 271 nm. The
kinetics was investigated in conditions of pseudo-first
order reaction [c(HNO3) >> cТ], where c(HNO3) is the
concentration of nitric acid generated in situ from
sodium nitrate; cТ is the concentration of substrate,
tetrazole 5. The rate constants of pseudo-first order are
ε×10–3
The ratio of 1-(4-nitrophenyl)- (6) and 1-(3-
nitrophenyl)-5-methyltetrazoles (7) was calculated by
Vierordt method [6]. The obtained data are compiled
in Table 1.
12
As seen from Table 1, the ratio of para- and meta-
nitroisomers 6 and 7 changes with concentration of
sulfuric acid insignificantly and in the investigated
interval of acidity is on the average 62 : 38. The
constant value of the isomer ratio in the environment
of various acidity allows the application of the
kinetic method to determine the values of the
observed (effective) rate constants and their
subsequent analysis.
10
3
8
6
2
4
Kinetics of nitration of 1-phenyl-5-methyltetrazole
5 with nitric acid, obtained in situ from sodium nitrate
in sulfuric acid (с 81.1–98.7 wt %), was investigated
by the spectrophotometric method. According to
classic concepts, the nitrating agent in processes of
electrophilic nitration of aromatic substrates is
nitronium cation that forms a π-complex with
phenyl ring in the limiting stage [7]. This complex
undergoes a fast rearrangement into cationic σ-
complex that further loses a proton to give the
corresponding isomeric nitro derivatives [7]. A similar
2
1
0
240
260
280
300
320
220
λ, nm
Fig. 1. UV spectra of [c(H2SO4) 84.1 wt %]: 1, 1-phenyl-5-
methyltetrazole 5; 2, 1-(4-nitrophenyl)-5-methyltetrazole 6;
3, 1-(3-nitrophenyl)-5-methyltetrazole 7.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 11 2016

OSTROVSKII et al.
1676
Table 1. Ratio of para- and meta-nitroisomers 6 and 7
formed at nitration with nitric acid of 1-phenyl-5-
methyltetrazole 5 in aqueous solutions of sulfuric acid of
various concentrations at 25oC. In parentheses are shown the
values of Hammet’s acidity function.
Table 2. Values of logarithms of effective second order rate
2
constants kef, L min–1 mol–1, of 1-phenyl-5-methyltetrazole
5 nitration at various concentration of sulfuric acid
(Hammet’s acidity functions Ho) at 40°C
H2SO4, wt %
81.1
–Ho
7.70
8.15
8.54
9.09
9.34
9.62
9.90
10.05
log2kef
–1.650
–0.72
–0.04
0.83
H2SO4, wt % (–Ho) p-Isomer 6, %
m-Isomer 7, %
84.1
84.1 (8.1)
86.5 (8.5)
90.4 (9.1)
92.2 (9.4)
94.2 (9.7)
96.1 (9.9)
64.4
59.2
62.1
60.0
59.9
62.8
38.6
40.8
37.9
40.0
40.1
37.2
86.6
90.4
92.2
0.780
0.594
0.458
0.209
94.2
96.1
98.7
calculated from relations log kef = 2.303/τ·log (D∞
̶
Do)/
1-Phenyl-5-methyltetrazole 5 is a weak base
(pKBH+ –1.96) [5]. It may be expected that in acid
environment where kinetic investigations were realized
(Table 2) this compound is present mostly in the
protonated form. Evidently, the nitration of positively
charged protonated form would be difficult in
comparison to neutral substrate. In conditions of
kinetic experiment the presence of neutral form of
tetrazole should be negligible. To answer the question
on prototropic substrate form of nitration we applied
method [8], in keeping with which the identification of
the form of the substrate existence was based on the
analysis of kinetic acidic profiles (Martinsen curves).
Following the recommendation of [8], we considered
in combination the dependences on Hammet’s acidity
function of logarithms of effective second order rate
constants of nitration with sulfuric-nitric acids
nitrating mixture of 1-methyl-5-phenyltetrazole 5,
trimethyl-anilinium cation, 2,6-dimethoxy-3-nitropyri-
dine (Fig. 2).
(D∞ Dτ) where Do, Dτ are optical densities in the initial
̶
and in the current moment (τ) correspondigly, D∞ is
the optical density of reaction products at the analytic
wave length. The linearity of semilog relationships
[dependences log (D∞ ̶ Dτ) on time τ] was observed to a
high degree of conversion (higher than 80%). The
second order effective rate constants of nitration of 1-
phenyl-5-methyltetrazole 5, found by dividing the
values of effective rate constant of pseudo-first order
on the concentration of nitric acid (sodium nitrate), are
presented in Table 2.
log kef
3
0.6
0.2
1
–0.2
As follows from the dependence of log kef on Ho
(Fig. 2) effective rate constants of nitration for 2,6-
dimethoxy-3-nitropyridine, reacting in nonprotonated
form, quickly decrease with raising the environment
acidity after passing the “Martinsen peak.” It is due to
the decrease in the substrate reactivity caused by the
protonation at the nitrogen atom of “pyridine” type. On
the opposite, at nitration of positively charged
substrate, trimethylanilinium cation (Fig. 2), the
decrease in the reaction rate with raising environment
acidity is not so sharp. The analysis of the kinetic
profile of 1-phenyl-5-methyltetrazole 5 (Fig. 2) allows
2
–0.6
–1.0
8.1
8.6
9.1
9.6
10.1
10.6
–Ho
Fig. 2. Dependences on the acidity function of environment
of logarithms of effective second order rate constants of
nitration with sulfuric-nitric acids nitrating system: 1, 1-
methyl-5-phenyltetrazole 5; 2, trimethylanilinium cation; 3,
2,6-dimethoxy-3-nitropyridine.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 11 2016

KINETICS AND MECHANISM OF 1-PHENYL-5-METHYLTETRAZOLE NITRATION
1677
Scheme 3.
N
N
+
N
N
N
H
N
N
N
1
2
+
N
N
+
+
pKBH
pKBH
H
N
N
CH3
HO
+
CH3
CH3
HO
HO2C
HO2C
9a
9b
9c
an assumption that this substrate enters the process in
protonated form. It is evident from practically fully
parallel dependences of log kef on Hammet’s acidity
function (Fig. 2) after passing the “Martinsen peak.”
analyzing the dependence of the chemical shift of
protons of methyl group in the position 5 of the
tetrazole ring on the environment acidity. Tetrame-
thylammonium bromide (δ 3.33 ppm) was used as
internal reference. Chemical shifts corresponding to
protonated and nonprotonated forms are determined by
Arnett-Wu method [9], in keeping with equation
Considering the fact that just the protonated from of
1-phenyl-5-methyltetrazole 5 undergoes nitration, we
tried to evaluate the character of electronic effect of
tetrazole cation on the phenyl ring. To this end
we investigated protonation of a model compound,
1-(4-carboxyphenyl)-5-methyltetrazole 9a in aqueous
solutions of H2SO4. It is important that this model
compound may be protonated both at the tetrazole
ring with the formation of cation 9b and at the
carboxy group with the formation of dication 9c
(Scheme 3).
½
½
δef (ho + ho) = δBH+·ho + ho ·δB.
where δB, δBH+ are chemical shifts of nonprotonated
and protonated forms of the base; δef are the observed
values of chemical shifts; ho are values of the
environment acidity, at which are determined δef; ho1/2
are values of acidity in the inflection point of sigmoid
dependence of chemical shift on Ho. Chemical shifts of
nonprotonated (9a) and protonated (9b) forms
determined by this method were used to calculate
ionization ratios I = [BH+]/[B]. The dependence of
logarithm of ionization ratio on Hammet’s acidity
The protonation of the tetrazole ring of compound
9a was investigated by 1H NMR spectroscopy,
ε×10–3
ε×10–3
20
10
9
20
16
12
8
18
16
14
12
10
8
8
7
1
5
2
6
3
4
4
0
220
240
260
280
300
λ, nm
6
8
12
–H+
10
Fig. 3. UV spectra of 1-(4-carboxyphenyl)-5-methyltet-
razole 9 in aqueous solutions of sulfuric acid, с, wt %: 1,
71.4; 2, 79.2; 3, 82.5; 4, 86.5; 5, 90.5; 6, 94.8; 7, 95.7; 8,
98.4; 9, 100.3; 10, 104.3.
Fig. 4. Dependence of molar extinction coefficient ε (λanal
260 nm) on acidity H+ for protonation of 1-(4-
carboxyphenyl)-5-methyltetrazolium 9b in concentrated
solutions of sulfuric acid and oleum.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 11 2016

OSTROVSKII et al.
1678
function for protonation of 1-(4-carboxyphenyl)-5-
methyltetrazole 9a is presented as an equation: log I =
0.95Ho – 2.74. The value of pK1BH+ was determined by
division of free term of this dependence by the slope
[10]. The value of pK1BH+ –2.9 is quite expectable
(Scheme 3). Also using the spectrophotometry method
in concentrated aqueous solutions of sulfuric acid and
oleum we determined the value of protonation constant
of 1-(4-carboxyphenyl)-5-methyltetrazolium 9b by the
carboxy group.
nitroisomer. Such specific effect of protonated
tetrazole fragment may be due to conjugation effects.
Further we are planning to check this hypothesis by
quantum-chemical analysis of electron structure of
intermediate sigma-complexes.
EXPERIMENTAL
UV spectra were recorded on a spectrophotometer
Shimadzu UV-2401PC. 1H NMR spectra were
recorded on a spectrometer Bruker Avance III at
working frequency 400.13 MHz in DMSO-d6, and also
in aqueous solutions of H2SO4 (Me4NBr was used as
internal reference). IR spectra were recorded in tablets
of KBr on a spectrometer Shimadzu FTIR-8400.
Elemental analysis was carried out on an elemental
analyzer Leco CHNS-932. HPLC analysis was
performed on chromatograph Shimadzu LC-10Avp
with UV detector; elution system acetonitrile – 0.1%
aqueous solution of orthophosphoric acid, 90 : 10, at
30°С; chromatographic column Supelco C18; λdetect
220, 250 nm. For electrochemical titration of solutions
of sulfuric acid and oleum ionometer Cyberscan-510
was applied. 1-Phenyl-5-methyltetrazole 5, 1-(4-
nitrophenyl)-5-methyltetrazole 6, 1-(3-nitrophenyl)-5-
methyltetrazole 7, 1-(2-nitrophenyl)-5-methyltetrazole
8 were obtained by known methods [17]. All
compounds were purified by crystallization from
glacial acetic acid with following three-fold
recrystallization from ethanol. Properties of
compounds were consistent with the published data.
Sodium nitrate of “chemically pure” grade was
purified by five-fold crystallization from water. All
measurements were performed with sodium nitrate
from the same batch. To prepare solutions we used
concentrated sulfuric acid of a “very pure” grade and
also oleum of “chemically pure” grade. For dilution of
acidic solutions double-distilled water was used.
With increase in the concentration of sulfuric acid
at the value of acidity function of environment lower
than Ho –8 in UV spectra of compound 9 a noticeable
red shift and hyperchromic effect are observed (Fig. 3).
The character of changes in molar extinction
coefficients indicates that these changes are due to the
secondary protonation of 9b form (Scheme 3).
Dependences of values of molar extinction coefficients
of compound 9 on Brandt-Bonner acidity function H+
[11, 12] describing the protonation of unicharged
cations (Scheme 3) in the considered range of acidity
are typical sigmoid curves (Fig. 4).
The value of pK2BH+ (Scheme 3) was determined
from equation: log I = –mH+ + pK2BH+, whose
parameters were calculated basing on spectral data
obtained at three analytic wavelengths: λanal 255, 260
and 265 nm. Slopes m of this linear dependences in all
three cases insignificantly differ from 1 and, according
to Yates and McClelland recommendations [9], for the
pK2BH+ value was taken the free term of the above
dependence divided by the slope m. For three analytic
wave lengths mentioned above close values were
obtained: pK2BH+ –9.5, –9.7, –9.6 correspondingly.
Average value of this quantity for 1-(4-carboxyphenyl)-
5-methyltetrazole 9 is pK2BH+ –9.6; it turned out to be
close to the base constant of 4-nitrobenzoic acid
(pKBH+ –9.54 [13]). Hence, the tetrazol-1-yl fragment
protonated at atom N4 demonstrates a strong electron-
acceptor effect on the center of protonation (group
CO2H), approximately equal to effect of a nitro group
(σ 0.78) [14–16]. The value of Hammet’s σ-constant of
the protonated tetrazole ring mentioned above, first
determined in this study, explains the failures at
attempts of introducing a second nitro group into the
phenyl ring of mononitro-substituted derivatives of 1-
phenyl-5-methyltetrazole 5. At the same time it is not
clear, why at nitration of 1-phenyl-5-methyltetrazole 5
forms mostly para-nitroderivative 6 (Table 1). It is
known [7] that, on the opposite, the electron-acceptor
substituents favor the formation of mostly meta-
1-(4-Carboxyphenyl)-5-methyltetrazole (9). 7 g
(0.04 mol) of 1-(4-methylphenyl)-5-methyltetrazole
was added to a solution of 18 g (0.06 mol) of finely
ground sodium bichromate (dihydrate) in 39 mL of
water. To the obtained mixture while vigorously
stirring at 30–40°C within 2 h was added dropwise
concentrated sulfuric acid (96 wt %). Then the mixture
was stirred for 30 min at 90°C, cooled, and poured into
200 mL of water. The precipitate was filtered off and
washed with water on the filter, then dissolved at
heating in 5% aqueous solution of sodium hydroxide,
the solution was filtered, then aqueous solution of
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 11 2016

KINETICS AND MECHANISM OF 1-PHENYL-5-METHYLTETRAZOLE NITRATION
1679
Table 3. Logarithms of ionization ratios at different values
of Hammet’s acidity function for protonation of 1-(4-
carboxyphenyl)-5-methyltetrazole 9 at the tetrazole ring
determined from 1H NMR data.
H2SO4 (7 g conc. H2SO4 in 100 mL H2O) was added.
The precipitate was filtered off, washed with water on
the filter. The reaction product was purified by three-
fold recrystallization from ethanol. Yield 6.7 g (82%),
mp 259–260°C. IR spectrum, ν, cm–1: 1720 (CO2H).
1H NMR spectrum (DMSO-d6) δ, ppm: 2.52 s (3H,
CH3), 7.80–7.85 m (2H, Ph), 8.18–8.25 m (2H, Ph).
Found, %: С 53.37; H 4.40; N 27.33. С9H8N4O2.
Calculated, %: C 52.94; H 3.95; N 27.44.
–Ho
2.54
2.94
3.14
log I
–0.33
0.14
–Ho
3.58
3.84
–
log I
0.59
0.98
–
0.18
Determination of content of nitroisomers 6–8 by
HPLC method. The reaction mixture (10 mL),
obtained as a result of nitration of 1-phenyl-5-me-
thyltetrazole 5 in sulfuric-nitric acids nitrating mixture
[c(H2SO4) 85.7 wt %], was poured in 200 mL of ice
cold water. The mixture was extracted with chloroform
(3 × 50 mL). The organic layer was washed with
water, 5% solution of NaHCO3, dried with anhydrous
MgSO4, evaporated till dryness. The residue was
dissolved in acetonitrile, diluted, and applied to HPLC
analysis. Relative content of isomers was determined
as the ratio of reaction products peaks area.
the same concentration as in the working cell. For
solutions of all compounds the validity of the law of
Burger–Lambert–Beer was checked in the investigated
concentration range.
Protonation of 1-(4-carboxyphenyl)-5-methyltet-
razole (9). A weighed sample of compound 9 was
placed into a vial, then aqueous solution of sulfuric
acid of certain concentration was added in such
amount as to make the compounds concentration of
~0.1 mol/L. Dependence was determined of chemical
shift of proton singlet of methyl group in the position 5
of the ring on Hammet’s acidity funcion. Tetramethyl-
ammonium bromide (δ 3.33 ppm) was used as internal
reference. From analysis by Arnett and Wu [9]
dependences of chemical shifts on the environment
acidity values were found of chemical shifts of
protonated (δBH+) and nonprotonated (δB) forms of
weak base that were used to calculate logarithms of
ionization ratios (I = [BH+]/[B]) (Table 3).
Determination of nitroisomers ratio (7 and 8) by
UV spectroscopy method. 0.02–0.03 g of tetrazole 5
and ~0.3 g of sodium nitrate were weighed on analytic
balance in a quartz vial. The vial with the weighed
sample placed into a funnel, inserted into a volumetric
flask (25 cm3), then the sample was washed away into
the flask with a solution of sulfuric acid of a known
concentration. Liquid level in flask was brought to the
mark and the solution was thoroughly stirred. After
36–40 h (25°C), 1 mL of solution was brought into
another volumetric flask (250 cm3) and the liquid level
was brought to the mark with bidistilled water. After
dilution the analytic concentration of nitration products
was 4–5×10–5 mol/L, and the concentration of sulfuric
acid was 2–3 wt %. UV spectra were recorded at
temperature in working cell and comparison cell
controlled at 25±0.1°C. Into comparison cell was
placed a solution of sodium nitrate in sulfuric acid at
Protonation of the carboxy group of 1-(4-
carboxyphenyl)-5-methyltetrazole (9). 0.03 g of com-
pound 9 was placed into a volumetric flask (100 cm3),
then dissolved in a solution of sulfuric acid of a certain
concentration. Liquid level in flask was brought to the
mark and solution was thoroughly stirred. 0.5 mL of
prepared solution was brought into a volumetric flask
(25 cm3) and liquid level was brought to the mark. The
solution was thoroughly stirred. Analytic concentration
was made of 2–3×10–5 mol/L. UV spectra of
Table 4. Acidity functions, molar coefficients of extinction, and logarithms of ionization ratios for protination of 1-(4-
carboxyphenyl)-5-methyltetrazole 9 at carboxy group, determined by UV spectroscopy method at different wavelengths.
λ, nm
–Ho
ε
log I
λ, nm
–Ho
ε
log I
λ, nm
–Ho
ε
log I
255
9.10
9.40
9.70
9.83
10.4
–
12185
12800
14050
14770
16415
–
̶
̶
0.34
0.10
0.19
0.37
0.99
–
260
9.10
9.38
9.52
9.70
9.83
10.2
8830
9600
10200
10790
11610
12800
̶
̶
̶
̶
0.49
0.30
0.18
0.07
0.08
0.39
265
9.10
9.38
9.70
9.83
10.1
–
5850
6600
7650
8290
9130
–
̶
̶
0.40
0.21
0.06
0.22
0.46
–
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 11 2016

OSTROVSKII et al.
1680
3. Dolmatov, V.Yu., Russ. Chem. Rev., 2007, vol. 76,
compound 9 in solutions of sulfuric acid were recorded
as described above. The obtained data are compiled in
Table 4.
p. 339.
4. Bladin, J.A., Chem. Ber., 1885, vol. 18, p. 1544.
5. Trifonov, R.E. and Ostrovskii, V.A., Russ. J. Org.
Chem., 2006, vol. 42, p. 1585.
Kinetics of nitration of 1-phenyl-5-methyltet-
razole (5) in HNO3–H2SO4 system. ~0.05 mL of
solution of compound 5 in sulfuric acid was added into
volumetric flask (25 cm3) kept at controlled
temperature with solution of sodium nitrate in sulfuric
acid of certain concentration. Analytic concentration
for tetrazole 5 was made at ~5×10–5 mol/L, for sodium
nitrate, at 2×10–2 mol/L. Into comparison cell was
placed a solution of sodium nitrate with the same
concentration in sulfuric acid. The reaction was
performed in conditions of pseudo-first order. The
second order rate constant was calculated as described
above. The second order rate constants were calculated
by dividing the rate constant of pseudo-first order by
the concentration of HNO3. The reaction order was
independently confirmed by Van’t Hoff differential
method [18]. In all cases the second order rate constant
of was determined from results of no less than two
parallel experiments. Inaccuracy in determination of
second order rate constants did not exceed 5%.
6. Berstein, I.Ya. and Kaminskii, Yu.L., Spektrofoto-
metricheskii analiz
v
organicheskoi khimii
(Spectrophotometric Analysis in Organic Chemistry),
Leningrad: Khimiya, 1986.
7. Ingold, K., Teoreticheskie osnovy organicheskoi khimii
(The Theoretical Foundations of Organic Chemistry),
Beletskaya, I.P., Ed., Moscow: Mir, 1973.
8. Johnson, C.D. and Katritzky, A., J. Chem. Soc. B, 1967,
p. 1204.
9. Ostrovskii, V.A. and Koldobskii, G.I., Slabye
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Leningrad: Izd. LGU, 1990.
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The study was realized under a financial support of
the project no. 10.1264.2014/К in the frame of the
project part of State contract in the area of scientific
activity for 2015, and also by agreement of a grant
contribution from 05 June 2014 no. 14.579.21.0001
between Special Design – Technological Bureau
“Technolog” (Russia) and Russian Ministry of
Education and Science.
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 11 2016