Kinetics of the reaction of 1-R-3,5-dinitrobenzenes with 4-chlorophenol in DMF in the presence of potassium carbonate

Article abstract of DOI:10.1134/S1070428010120079

The effect of substituent in 1-R-3,5-dinitrobenzenes on the rate and activation parameters of their reactions with 4-chlorophenol in dimethylformamide in the presence of potassium carbonate was studied by the competing reactions technique. Analysis of the activation parameters revealed predominant contribution of the enthalpy factor to variation of the Gibbs energy of activation. Pleiades Publishing, Ltd., 2010.

Full text of DOI:10.1134/S1070428010120079

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 12, pp. 1817–1821. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © I.A. Os’kina, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46, No. 12, pp. 1808–1811.
Kinetics of the Reaction of 1-R-3,5-Dinitrobenzenes
with 4-Chlorophenol in DMF in the Presence
of Potassium Carbonate
I. A. Os’kina
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 9, Novosibirsk, 630090 Russia
e-mail: oi@nioch.nsc.ru
Received May 28, 2010
Abstract—The effect of substituent in 1-R-3,5-dinitrobenzenes on the rate and activation parameters of their
reactions with 4-chlorophenol in dimethylformamide in the presence of potassium carbonate was studied by the
competing reactions technique. Analysis of the activation parameters revealed predominant contribution of the
enthalpy factor to variation of the Gibbs energy of activation.
DOI: 10.1134/S1070428010120079
Diaryl ethers are extensively used in various fields
of synthetic chemistry, in particular in the synthesis of
herbicides [1], antibiotics [2], and other biologically
active compounds [3]. Therefore, development of new
methods for the synthesis of diaryl ethers and improve-
ment of known procedures [4], as well as studies on
the mechanisms of these processes, seem to be im-
portant.
It is known that the rate of bimolecular SNAr reac-
tions is determined by the nature of nucleophile, sub-
strate, departing group, and solvent and that it is usual-
ly controlled by the enthalpy factor [5, 6]. Variation of
the departing group in 1-nitro-3-X-arenes could result
in entropy control over SNAr reactions with phenols in
the presence of potassium carbonate in DMF [7]. With
a view to estimate the effect of substituent on the
reactivity in bimolecular SNAr processes, the kinetics
of reactions of 1-R-3,5-dinitrobenzenes with 4-chloro-
phenol in the presence of potassium carbonate
(Scheme 1) were studied by the competing reactions
technique in dimethylformamide in the temperature
range from 60 to 80°C.
The reactions resulted in replacement of one nitro
group in the substrate by 4-chlorophenoxy group, and
the products were characterized using NMR spectros-
copy and mass spectrometry. From the relative reaction
rates (Table 1) it follows that the reactivity of the nitro
group in I–III decreases in the series NO2 > CN > CF3
and that the difference in the relative reaction rates
decreases as the temperature rises.
The Hammett ρ values for the reactions of dinitro-
benzenes I–III with 4-chlorophenol (IV) in DMF in
Scheme 1.
a
Table 1. Relative rate constants krel for the reactions of
R
1-R-3,5-dinitrobenzenes I–III with 4-chlorophenol in DMF
in the presence of K2CO3
OH
+
krel
O2N
NO2
Cl
R
Σσm [8]
I–III
IV
60°C
70°C
80°C
R
NO2
CN
1.42
1.27
1.14
19.4±1.1
03.4±0.2
1
17.3±1.5
03.3±0.1
1
15.1±1.6
03.1±0.3
1
Cl
K2CO3, DMF, 60–80°C
O2N
O
CF3
V–VII
a
The relative rate constant krel was calculated assuming krel = 1 for
compound III on the basis of the data in Table 5.
I, V, R = NO2; II, VI, R = CN; III, VII, R = CF3.
1817

OS’KINA
tron-acceptor power of the substituent in the substrate
1818
logkrel
increases. Insofar as the latter factor implies accelera-
tion of nucleophilic attack due to enhancement of the
electrophilicity of the carbon atom linked to the nitro
group but the stage involving abstraction of the leaving
group is thus decelerated, the observed large positive ρ
values suggest that the rate-determining step is forma-
tion of transition state (cf. [9]).
NO2/CF3
1.2
1.0
0.8
0.6
0.4
Temperature dependences of the logarithms of the
relative rate constants were determined for each elec-
trophile (Fig. 1), and they were used to estimate the
differences in the activation parameters ∆∆H≠, ∆∆S≠,
and ∆∆G≠, depending on the substituent in the sub-
strate, according to the modified Eyring equation [10]
(Table 2).
CN/CF3
3.0
2.8
2.9
1/T×10–3, K
Fig. 1. Semilog plots of the relative rate constants versus
reciprocal temperature for the reactions of 1-R-3,5-dinitro-
benzenes I–III with 4-chlorophenol in DMF in the presence
of K2CO3.
logk(NO2/CF3) = 652.3/T – 0.7;
r = 0.998, s = 0.004, n = 3;
logk(CN/CF3) = 269.1/T – 0.3;
r = 0.992, s = 0.004, n = 3.
the presence of K2CO3 were determined from the
logkrel—∑σm dependences [8]:
Analysis of the activation parameters of the ex-
amined reaction showed that increase in the substrate
electrophilicity is accompanied by reduction of the en-
thalpy, entropy, and Gibbs energy of activation. Here,
the contribution of the enthalpy factor to variation of
the Gibbs energy of activation predominates (Table 2).
logkrel(60°C) = 4.61(∑σm) – 5.28;
r = 0.998, s = 0.05, n = 3;
logkrel(70°C) = 4.43(∑σm) – 5.07,
r = 0.998, s = 0.05, n = 3;
Correlations between the enthalpy and entropy of
activation (ΔΔH≠ = 0.98ΔΔS≠ – 0.01; r = 0.999, s =
0.02, n = 3) and between the enthalpy and Gibbs
energy of activation (∆∆H≠ = 1.54∆∆G≠ – 0.01; r =
0.999, s = 0.01, n = 3) were found for the reactions of
compounds I–III with 4-chlorophenol. The existence
of such correlations suggests enthalpy–entropy com-
pensation effect [11, 12]. The calculated compensation
(isokinetic) temperature (976 K) considerably exceeds
the experimental temperature (333–353 K), which may
be regarded as an evidence in support of the chemical
nature of the observed compensation effect.
logkrel(80°C) = 4.22(∑σm) – 4.83,
r = 0.998, s = 0.05, n = 3.
The ρ values are linearly related to temperature, and
they decrease as the temperature rises. The absolute
values of ρ are fairly high, which is typical of stepwise
processes; they also suggest considerable electron
density redistribution in the transition state. Positive ρ
values indicate acceleration of the process as the elec-
Table 2. Variation of the activation parameters for the reac-
tions of 1-R-3,5-dinitrobenzenes I–III with 4-chlorophenol
in DMF in the presence of K2CO3
Correlations were also found between the enthalpy,
entropy, and Gibbs energy of activation, on the one
hand, and Hammett substituent constants ∑σm for 1-R-
3,5-dinitrobenzenes (Table 3, Fig. 2). The slopes of the
corresponding linear dependences are negative, for in-
crease in electron-withdrawing power of the R substit-
uent is accompanied by reduction of the activation
parameters. The absolute values of the slopes (Table 3)
characterize the sensitivity of the activation parameters
to variation of substituent in the electrophile [13]. It
is seen that the enthalpy and entropy of activation are
ΔΔH≠,a
ΔΔS≠,a
TΔΔS≠,a,b ΔΔG≠,a,b
R
kJ/mol J mol–1 K–1
kJ/mol
kJ/mol
NO2 –12.5±0.7 –12.8±0.05
–4.4
–8.1
CN
0–5.1±0.6 0–5.2±0.04
–1.8
–3.3
CF3
0
0
–0.0
–0.0
The differences in the activation parameters ΔΔH≠ = ΔH≠(NO2 or
CN) – ΔH≠(CF3), ΔΔS≠ = ΔS≠(NO2 or CN) – ΔS≠(CF3), and
ΔΔG≠ = ΔG≠(NO2 or CN) – ΔG≠(CF3) were calculated by the
Eyring equation: logkrel = (–ΔΔH≠/T + ΔΔS≠)/4.576 [10].
a
b
At 70°C.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 12 2010

KINETICS OF THE REACTION OF 1-R-3,5-DINITROBENZENES
1819
Table 3. Absolute values of the slopes |b| of the dependences
of activation parameters a upon Hammett substituent con-
stants ∑σm for the reactions of 1-R-3,5-dinitrobenzenes
I–III with 4-chlorophenol in DMF in the presence of
K2CO3; a = b ∑σm + c
more sensitive to variation of substituent in the electro-
phile than the Gibbs energy of activation.
The activation parameters ∆H≠, ∆S≠, and ∆G≠ were
calculated from those found for the reaction with com-
pound III [7] and the corresponding differences for
compounds I–III (Table 4). The dependences of ∆H≠,
∆S≠, and ∆G≠ upon ∑σm were also determined:
Activation
parameter a
|b|
c
r
s
n
∆∆H≠
44.8
45.8
15.8
29.0
51.3
52.5
18.1
33.2
0.998
0.998
0.998
0.998
0.6
0.6
0.2
0.4
3
3
3
3
ΔH≠ = –44.8∑σm + 241.3;
r = 0.997, s = 0.6, n = 3;
∆S≠ = –45.8∑σm + 230.5;
r = 0.998, s = 0.6, n = 3;
T∆S≠ = –15.8∑σm + 79.1;
r = 0.996, s = 0.3, n = 3;
∆∆S≠
T∆∆S≠ a
∆∆G≠ a
a
At 70°C.
ΔG≠ = –29.0∑σm + 162.2;
r = 0.999, s = 0.3, n = 3.
Table 4. Activation parameters of the reactions of 1-R-3,5-
dinitrobenzenes I–III with 4-chlorophenol in DMF in the
presence of K2CO3
These dependences made it possible to estimate the
activation parameters for the reaction of 1,3-dinitro-
benzene with 4-chlorophenol in the presence of potas-
sium carbonate in DMF (Table 4; cf. [7]).
ΔH≠,a
ΔS≠,a
TΔS≠,a,b
kJ/mol
ΔG≠,a,b
kJ/mol
R
kJ/mol J mol–1 K–1
NO2 177.5±9.90 165.2±0.9
56.6
59.3
61.0
67.9
120.9
125.6
129.0
141.6
CN
CF3
Hd
184.9±22.2 172.8±1.3
Thus the results of the present study have shown
that nucleophilic replacement of one nitro group in
1-R-3,5-dinitrobenzenes by 4-chlorophenoxy group in
DMF in the presence of K2CO3 is characterized by
predominant contribution of the enthalpy factor to
variation of the Gibbs energy of activation.
c
190.0
209.5
178
198
The activation parameters ∆H≠, ∆S≠, and ∆G≠ were determined
from those found for compound III and the corresponding dif-
ferences given in Table 2.
a
b
c
d
At 70°C.
Data of [7].
EXPERIMENTAL
Calculated from the dependences of the activation parameters
upon ∑σm for σm = 0.71: ΔH≠ = –44.8∑σm + 241.3 (r = 0.997, s =
0.6, n = 3), ∆S≠ = –45.8∑σm + 230.5 (r = 0.998, s = 0.6, n = 3),
T ∆S≠ = –15.8∑σm + 79.1 (r = 0.996, s = 0.3, n = 3), ΔG≠ =
–29.0∑σm + 162.2 (r = 0.999, s = 0.3, n = 3).
1
The H and 19F NMR spectra were recorded on
a Bruker AC-200 spectrometer using hexamethyldisil-
oxane and trifluoroacetic acid, respectively, as internal
references. The mass spectra (electron impact, 70 eV)
were obtained on a Finnigan MAT 8200 instrument.
The reaction mixtures were analyzed by GLC on
Hewlett–Packard HP 5890 and LKhM-7A instruments
(thermal conductivity detector; linear oven tempera-
ture programming from 50 to 270°C at a rate of
10 deg/min; stationary phase 15% of SKTFT-803,
SE-30, or VS-1 on Chromaton W; carrier gas helium,
flow rate 60 ml/min). Quantitative analysis was per-
formed by the internal normalization method, and the
components were identified by adding the correspond-
ing authentic samples.
Table 5. Relative rate constants of competing reactions of
1-R-3,5-dinitrobenzenes I–III with 4-chlorophenol in DMF
in the presence of K2CO3
a
krel
R1/R2
60°C
70°C
80°C
NO2/CN
CN/CF3
5.66±2%
3.43±6%
5.26±9%
3.29±5%
4.89±2%0
3.09±11%
a
Average values from at least three measurements.
benzotrifluoride (III) were synthesized by known
methods, and their physical constants were consistent
with those given in [14, 15].
Dimethylformamide was distilled under reduced
pressure over calcium hydride. Potassium carbonate
was calcined in a muffle furnace and ground prior to
use. Commercial 1,3,5-trinitrobenzene (I) and 4-chloro-
phenol (IV) were purified according to standard proce-
dures. 3,5-Dinitrobenzonitrile (II) and 3,5-dinitro-
Diphenyl ethers V–VII (general procedure).
A flask maintained at a constant temperature was
purged with argon and charged with required amounts
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 12 2010

OS’KINA
1820
Variation of activation parameter a, kJ/mol
1-(4-Chlorophenoxy)-3-nitro-5-trifluoromethyl-
benzene (VII) was synthesized from 0.24 g
(1.02 mmol) of 3,5-dinitrobenzotrifluoride (III) and
0.12 g (0.94 mmol) of 4-chlorophenol in the presence
of 0.28 g (2.03 mmol) of K2CO3 in 2 ml of DMF. Yield
of the crude product 0.26 g. Purification by column
chromatography (silica gel, CHCl3) gave 0.17 g (54%)
of compound VII with mp 39–40.5°C; published data
0
–2
–4
T∆∆S≠
∆∆G≠
–6
1
[13]: mp 47–48°C. H NMR spectrum (CDCl3), δ,
–8
ppm: 7.25 m (2H, o′-H, J = 9.0 Hz), 7.45 m (2H, m′-H,
J = 9.0 Hz), 7.52 m (1H, 6-H), 7.90 m (1H, 2-H),
8.65 m (1H, 4-H). 19F NMR spectrum (CDCl3):
δF 98.78 ppm, s (3F, CF3).
–10
–12
∆∆H≠
Determination of the relative rate constants of
the reactions of dinitrobenzenes I–III with 4-chloro-
phenol in DMF in the presence of K2CO3. A flask
maintained at a constant temperature was purged with
argon and charged with substrate couple I/II or II/III,
4-chlorophenol, and K2CO3 at a ratio of 5:5:1:2, and
dimethylformamide was added so that the substrate
concentration cI = cII be equal to ~10–1 M. The mixture
was stirred as long as necessary (up to 90 min) at
a required temperature (60, 70, or 80°C), and the
process was terminated by adding a mixture of 5 ml of
chloroform and 5 ml of 5% hydrochloric acid. The
organic phase was separated, washed with 10 ml of
water, and dried over anhydrous calcium(II) chloride.
The solvent was removed, and the residue was
weighed and analyzed by GLC. The relative rate con-
stants were calculated by the following formula [16]:
1.2
1.3
1.4
Σσm
Fig. 2. Dependence of the activation parameters (a) on the
Hammett substituent constants ∑σm for the reactions of 1-R-
3,5-dinitrobenzenes I–III with 4-chlorophenol in DMF in the
presence of K2CO3; a = b∑σm + c; σm values were taken
from [8].
of substrate I–III, 4-chlorophenol, potassium carbon-
ate, and dimethylformamide. The mixture was stirred
for 3 h at 60°C, cooled to room temperature, diluted
with 10 ml of water, and neutralized with 10% hydro-
chloric acid. The precipitate was filtered off, washed
with water, and dried.
4′-Chloro-3,5-dinitrodiphenyl ether (V) was syn-
thesized from 2.13 g (10 mmol) of 1,3,5-trinitroben-
zene (I) and 1.28 g (10 mmol) of 4-chlorophenol in the
presence of 2.76 g (20 mmol) of K2CO3 in 10 ml of
DMF. Yield of the crude product 2.68 g. Purification
by column chromatography (silica gel, CHCl3) gave
2.41 g (82%) of compound V with mp 133–134°C.
1H NMR spectrum (CDCl3), δ, ppm: 7.05 m (2H,
o′-H), 7.44 m (2H, m′-H, J = 9.0 Hz), 7.52 m (1H,
6-H), 8.06 m (1H, 2-H), 8.72 m (1H, 4-H). Found:
m/z 294.00402 [M]+. C12H7ClN2O5. Calculated:
M 294.00434.
kI/kII = (log[A0I] – log[AτI])/(log[A0II] – log[AτII]),
where A0I and A0II are the initial concentrations (mol/l)
of compounds I and II, respectively; and AτI and AτII are
the concentrations (mol/l) of the same compounds at
a moment of time τ. The relative rate constants cal-
culated from the results of at least three measurements
are collected in Table 5.
3-(4-Chlorophenoxy)-5-nitrobenzonitrile (VI)
was synthesized from 0.17 g (0.88 mmol) of 3,5-di-
nitrobenzonitrile (II) and 0.11 g (0.86 mmol) of
4-chlorophenol in the presence of 0.3 g (2.2 mmol) of
K2CO3 in 2 ml of DMF. Yield of the crude product
0.2 g. Purification by column chromatography (silica
gel, CHCl3) gave 0.14 g (59%) of compound VI with
REFERENCES
1. Page, M.J., Ma, J., Qi, H., Healy, E., and Trolinger, J.,
J. Agric. Food Chem., 1997, vol. 45, p. 3095; Hayashi, Y.
and Kouji, H., J. Agric. Food Chem., 1990, vol. 38,
p. 845.
1
mp 78–79.5°C. H NMR spectrum (CDCl3), δ, ppm:
2. Pearson, A.J. and Belmont, P.O., Tetrahedron Lett., 2000,
7.03 m (2H, o′-H), 7.40 m (2H, m′-H, J = 9.0 Hz),
7.51 m (1H, 2-H), 7.94 m (1H, 4-H), 8.15 m (1H, 6-H).
Found: m/z 274.01508 [M]+. C13H7ClN2O3. Calculated:
M 274.01452.
vol. 41, p. 1671.
3. Nakamura, K., Nishiya, H., and Nishiyama, S., Tetra-
hedron Lett., 2001, vol. 42, p. 6311.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 12 2010

KINETICS OF THE REACTION OF 1-R-3,5-DINITROBENZENES
1821
11. Liu, L. and Guo, Q.X., Chem. Rev., 2001, vol. 101,
4. Sawyer, J.S., Tetrahedron, 2000, vol. 56, p. 5045.
p. 673.
5. Terrier, F., Nucleophilic Aromatic Displacement: the
Influence of the Nitro Group, New York: VCH, p. 1991.
12. Kulikov, O.V., Lapshev, P.V., and Terekhova, I.V.,
Zh. Fiz. Khim., 1998, vol. 72, p. 725; Krug, R.R.,
Hunter, W.G., and Grieger, R.A., J. Phys. Chem., 1976,
vol. 80, p. 2341.
6. Miller, J., Aromatic Nucleophilic Substitution, Amster-
dam: Elsevier, p. 1968.
7. Khalfina, I.A. and Vlasov, V.M., Russ. J. Org. Chem.,
13. Ruff, F., Internet Electr. J. Mol. Des., 2004, vol. 3,
2005, vol. 41, p. 978.
p. 474.
8. Hansch, C., Leo, A., and Taft, R.W., Chem. Rev., 1991,
14. Nakajima, N. and Ubukata, M., Tetrahedron Lett., 1997,
vol. 91, p. 165.
vol. 38, p. 2099.
9. Khalfina, I.A. and Vlasov, V.M., Russ. J. Org. Chem.,
15. Khalfina, I.A., Rogozhnikova, O.Yu., and Vlasov, V.M.,
2002, vol. 38, p. 47.
Russ. J. Org. Chem., 1996, vol. 32, p. 1328.
10. Gordon, A.J. and Ford, R.A., The Chemist’s Com-
panion, New York: Wiley, 1972. Translated under the
title Sputnik khimika, Moscow: Mir, 1976, p. 159.
16. Investigation of Rates and Mechanisms of Reactions,
Bernasconi, C.F., Ed., New York: Wiley, 1986, 4th ed.,
p. 203.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 12 2010