Nitration of aromatic compounds by Zn(NO3)2· 2N2O4 and its charcoal-supported system

Article abstract of DOI:10.1081/SCC-200048450

Zn(NO₃)₂·N₂O₄ and its charcoal supported system were found to be efficient nitrating agents. Mononitration of aromatic compounds such as benzene, alkyl benzenes, halobenzenes, nitrobenzene, anisol, and the highly selective mono-, di-, and trinitration of phenol, and dinitraion of substituted phenols were also performed in the presence of these reagents.

Full text of DOI:10.1081/SCC-200048450

This article was downloaded by: [North Dakota State University]
On: 03 July 2014, At: 00:10
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Synthetic Communications: An
International Journal for Rapid
Communication of Synthetic
Organic Chemistry
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/lsyc20
Nitration of Aromatic
Compounds by
Zn(NO3)2 · 2N2O4 and Its
Charcoal‐Supported System
Nasser Iranpoor a , Habib Firouzabadi a , Reza
Heydari a & Morteza Shiri a
a Department of Chemistry, College of Sciences ,
Shiraz University , Shiraz, 71454, Iran
Published online: 28 Jul 2007.
To cite this article: Nasser Iranpoor , Habib Firouzabadi , Reza Heydari &
Morteza Shiri (2005) Nitration of Aromatic Compounds by Zn(NO3)2 · 2N2O4 and Its
Charcoal‐Supported System, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 35:2, 263-270, DOI: 10.1081/
SCC-200048450
To link to this article: http://dx.doi.org/10.1081/SCC-200048450
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the
information (the “Content”) contained in the publications on our platform.
However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness,
or suitability for any purpose of the Content. Any opinions and views
expressed in this publication are the opinions and views of the authors, and

are not the views of or endorsed by Taylor & Francis. The accuracy of the
Content should not be relied upon and should be independently verified with
primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages,
and other liabilities whatsoever or howsoever caused arising directly or
indirectly in connection with, in relation to or arising out of the use of the
Content.
This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden. Terms & Conditions of access and use can be found at
http://www.tandfonline.com/page/terms-and-conditions

Synthetic Communicationsw, 35: 263–270, 2005
Copyright # Taylor & Francis, Inc.
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1081/SCC-200048450
Nitration of Aromatic Compounds by
.
Zn(NO3)2 2N2O4 and Its
Charcoal-Supported System
Nasser Iranpoor, Habib Firouzabadi,
Reza Heydari, and Morteza Shiri
Department of Chemistry, College of Sciences, Shiraz University,
Shiraz, Iran
.
Abstract: Zn(NO3)2 N2O4 and its charcoal supported system were found to be
efficient nitrating agents. Mononitration of aromatic compounds such as benzene,
alkyl benzenes, halobenzenes, nitrobenzene, anisol, and the highly selective mono-,
di-, and trinitration of phenol, and dinitraion of substituted phenols were also
performed in the presence of these reagents.
Keywords: Zinc nitrate, charcoal, dinitrogen tetroxide, nitration, aromatic compounds
INTRODUCTION
Aromatic nitration is among the organic reactions, which have been exten-
sively studied. This reaction can be carried out by verities of nitrating
agents such as HNO3/H2SO4,[1,2] NaNO2/HNO3,[3,4] N-nitropyrazole/
BF3.Et2O/CH2Cl2,[5] metallic nitrates,[6–8] NaNO3/H2SO4/NaNO2,[9–11]
[12]
AgNO3/BF3/CH3CN,[13] tetra-
.
NaNO3/HCl/La(NO3)3/Et2O H2O,
nitromethane,[14] clay-supported nitrates,[15,16] AcONO2,[17] BzONO2,[18,19]
TfONO2,[20] HNO3/SiO2,[21] pyridine derivatives carrying transferable nitro
groups,[22] and montmorillonite impregnated with bismuth nitrate.[23]
Received in the UK March 8, 2004
Address correspondence to Nasser Iranpoor and Habib Firouzabadi, Department of
Chemistry, College of Sciences, Shiraz University, Shiraz 71454, Iran. E-mail:
iranpoor@chem.susc.ac.ir or firouzabadi@chem.susc.ac.ir

264
N. Iranpoor et al.
Dinitrogen tetroxide is also considered as a highly reactive nitrating agent,
which its reactions are usually carried out at low temperatures and does not
show selectivity for mono- or dinitartions (e.g., nitration of alkyl substituted
phenols produces mono- and dinitrated isomers together with considerable
amounts of nitrocyclohexadienones).[24] Very recently, NO2/O2 in the
presence of Zeolite has been used for the nitration of moderately deactivated
arenes.[25] In organic solvents such as ethyl acetate, N2O4 can react with
metals in atomic, oxide, or salt forms to give metal nitrate complexes.[26,27]
Recently, we have reported on the nitration and oxidation abilities of some
.
of these adducts, such as Cu(NO3)2 N2O4, Fe(NO3)3 2N2O4, and
.
[28–31]
.
Cr(NO3)3 2N2O4.
These complexes are capable to nitrate only
phenolic compounds and even activated aromatic rings such as anisole
cannot be nitrated by these metal nitrate/N2O4 complexes. In this article,
.
we report on the use of Zn(NO3)2 2N2O4 as a homogeneous reagent and its
charcoal-supported system as a heterogeneous nitrating gent for the
selective mono-, di-, and trinitration of phenol, dinitration of substituted
phenols, and mononitration of benzene and arenes substituted with activated
and moderately deactivated groups.
RESULTS AND DISCUSSION
.
Zn(NO3)2 2 N2O4 was prepared by complexation of zinc nitrate with dinitro-
gen tetroxide[23] in ethyl acetate. This compound, similar to other reported
metal nitrate N2O4 complexes, is a delicant solid and soluble in organic
solvents. When it was supported on charcoal, we obtained a heterogeneous
.
reagent, which is easy to handle. The reactions of both Zn(NO3)2 2N2O4
and its charcoal-supported system with phenol were found to be very
selective and dependent on the molar ratio of nitrating agent/phenol and
also the reaction temperature. The reaction with 0.75 molar equivalents of
either reagent in ethyl acetate at room temperature produced a mixture of
.
2- and 4-nitrophenols in high yields. The reaction with Zn(NO3)2 2N2O4
.
completes immediately, but the reaction with Zn(NO3)2 2N2O4/charcoal
requires 1 hr. Treatment of phenol with two molar equivalents of either of
these reagents produced 2,4-dinitrophenol in 83–85% yield. When the
reaction of phenol was performed with three equimolar amounts of
.
Zn(NO3)2 2N2O4 in refluxing ethyl acetate, the corresponding trinitrophenol
was produced in 86% yield (Table 1). Similar to the reactions of phenol
with N2O4 or N2O4-metal nitrate complexes,[28–31] the formation of some
minor amounts of 1,4-benzoquinone (5–8%) in the reaction of phenol with
.
.
Zn(NO3)2 2N2O4 or Zn(NO3)2 2N2O4/charcoal was also observed. The
results of Table 1 show that the yields of the products with both reagents
.
are very similar, but the reaction times for Zn(NO3)2 2N2O4/charcoal
are higher. However, handling of the reagent and workup of the reactions

Nitration of Aromatic Compounds
265

266
N. Iranpoor et al.
.
using Zn(NO3)2 2N2O4/charcoal is much simpler than those for
.
Zn(NO3)2 2N2O4. We then used both reagents for mononitration of
different substituted phenolic compounds. The results obtained for this
study are shown in Table 2. Using the molar ratio of the reagent/phenolic
compound (2 : 1), the selective dinitration of phenols was obtained
(Table 3). This study showed that phenol can be nitrated to 2,4,6-trinitro-
.
.
phenol with Zn(NO3)2 2N2O4, but the reaction with Zn(NO3)2 2N2O4/
charcoal does not occur (Table 1).
In comparison with the reactions of metal nitrate N2O4 complexes, which
were found to nitrate only phenolic compounds,[28–31] these two reagents
showed to be effective nitrating agents for phenols as well as benzene,
naphthalene, and benzenes carrying activating and moderately deactivating
groups. The results are shown in Table 4.
.
In conclusion, Zn(NO3)2 2N2O4 and its charcoal-supported system are
cheap and easily prepared reagents for nitration reactions. These reagents
are selective for nitration of the phenolic compounds and can also be
applied for the nitration of aromatic rings having activating and moderately
deactivating groups.
Table 2. Mononitration of substituted phenols with one molar equivalent of
.
.
Zn(NO3)2 2 N2O4/charcoal and Zn(NO3)2 2 N2O4 in CH2Cl2 at room temperature
Entry
Substrate
Timea
Product (% yield)a,b
1
2
3
4
5
6
7
4-Fluorophenol
4-Bromophenol
4-Chlorophenol
4-Methylphenol
4-Nitrophenol
(5 min) 2 hr
4-Fluoro-2-nitrophenol (98) 97
4-Bromo-2-nitrophenol (95) 95
4-Chloro-2-nitrophenol (98) 96
4-Methyl-2-nitrophenol (86) 81
2,4-Dinitrophenol (93) 95
2,4-Dinitrophenol (78) 82
2,6-Dichloro-4-nitrophenol
(98) 96
(5 min) 2.5 hr
(5 min) 2.5 hr
(5 min) 1.5 h
(15 min) 5 hr
(20 min) 4 hrc
(5 min) 4.25 hr
2-Nitrophenol
2,6-Dichlorophenol
8
9
2,6-Dimethylphenol
Salicylic acid
(5 min) 2 hr
(5 min) 4 hr
2,6-Dimethyl-4-nitrophenol
(75)83
2-Hydroxy-5-nitro benzoic acid
(80)73
2-Hydroxy-3-nitro benzoic acid
(15)20
10
Vanillin
(5 min) 0.5 hr
4-Hydroxy-3-methoxy-5-nitro
benzaldehyde (80)75
aData in the parentheses refer to the use of Zn(NO3)2 2 N2O4 and those out of the
.
.
parentheses refer to the reactions with Zn(NO3)2 2N2O4/charcoal.
bIsolated yield.
cReflux condition.

Nitration of Aromatic Compounds
267
Table 3. Dinitration of substituted phenols with two molar equivalents of either
reagenta in CH2Cl2 at room temperature
Entry
Substrate
Time
Product (% yield)b
1
2
3
4
5
6
7
4-Fluorophenol
4-Bromophenol
4-Chlorophenol
4-Methylphenol
4-Nitrophenol
2-Nitrophenol
Salicylic acid
(5 min) 2 hr
4-Fluoro-2,6-dinitro (91) 97
4-Bromo-2,6-dinitro (81) 86c
4-Chloro-2,6-dinitro (93) 87c
4-Methyl-2,6-dinitro (85) 80
2,4,6-Trinitro (90) tracec
2,4,6-Trinitro (86) tracec
2-Hydroxy-3,5-dinitro
(10 min) 4 hr
(10 min) 3 hr
(10 min) 1.25 hr
(35 min) 12 hr
(90 min) 12 hr
(20 min) 10 hr
benzoic acid (88) 60c
8
2-Methoxyphenol
(10 min) 1 hr
2-Methoxy-4,6-dinitro (85) 80
aData in the parentheses refer to the use of Zn(NO3)2 2N2O4 and those out of the
.
.
parentheses refer to the reactions with Zn(NO3)2 2N2O4/charcoal.
bIsolated yield.
cUnder reflux condition.
EXPERIMENTAL
Thin-layer chromatography on commercial plates of silica gel 60 F254 was
used to monitor the progress of the reactions. Column chromatography
was carried out by using silica gel 60. Yields refer to isolated pure products
after column chromatography. Products were characterized by comparison
of their physical and spectral data with those of authentic samples. Infrared
spectra were recorded on a Perkin Elmer 781 spectrometer. The NMR
spectra were recorded on a Bruker Avance DPX 250. Mass spectra were
recorded on a Shimadzu GCMS-QP 1000EX.
.
Preparation of Zn(NO3)2 2N2O4
A solution of ZnCl2 (34 g, 0.25 mol) in EtOAc (150 mL) was cooled to 2108C
in an ice-salt bath while being stirred. Generated N2O4 gas[28–32] was bubbled
through this solution for about 1 hr. The solvent was evaporated under reduced
pressure to give Zn(NO3)2 2N2O4 complex[27] as a pale yellowish deliquescent
.
compound (79 g, 85%).
.
Preparation of Zn(NO3)2 2N2O4 Complex/Charcoal
.
To a vigorously stirring solution of Zn(NO3)2 2N2O4 (10 g) in dry CH2Cl2
(25 mL) at 08C was added active charcoal (5 g). After 2 hr, the solvent was
.
evaporated, and the residue was dried under vacuum. Zn(NO3)2 2N2O4/
charcoal powder (15 g) was obtained.

268
N. Iranpoor et al.

Nitration of Aromatic Compounds
269
.
Mononitration of Phenol with Zn(NO3)2 2N2O4/Charcoal
.
A mixture of phenol (0.094 g, 1 mmol) and Zn(NO3)2 2N2O4 complex/
charcoal (0.44 g, 0.75 mmol) in ethyl acetate (5 mL) was stirred for 1.5 hr at
room temperature. The mixture was filtrated, and the residue was washed
with ethyl acetate (2 Â 15 mL). H2O (15 mL) was added to the filtrate
and organic layer was separated and dried over MgSO4. Ethyl acetate was
evaporated under vacuum. After plate chromatography on silica gel
eluted with petroleum ether:acetone (8 : 2), 4-nitrophenol (0.075 g, 56%),
mp 111–1138C [Lit.[33] mp 112–1148C], 2-nitrophenol (0.047 g, 34%),
mp 45–468C, [Lit.[33] mp 45–468C] and benzoquinone (0.008 g, 5%) mp
113–1148C [Lit.[33] mp 112.5–113.58C] were obtained.
.
Dinitration of Phenol with Zn(NO3)2 2N2O4/Charcoal
.
A mixture of phenol (0.094 g, 1 mmol) and Zn(NO3)2 2 N2O4 complex/
charcoal (1.11 g, 2 mmol) in ethyl acetate (5 mL) was stirred vigorously
for 4 hr at room temperature. The workup was performed similar to the
above-mentioned experiment. After column chromatography on silica gel
eluted with petroleum ether:acetone (3 : 1), 2,4-dinitrophenol (0.156 g, 85%)
mp 111–1128C [Lit.[33] 111–1138C] was obtained.
.
Mononitration of 4-Chlorophenol with Zn(NO3)2 2N2O4
.
A mixture of 4-chlorophenol (0.129 g, 1 mmol) and Zn(NO3)2 2N2O4
complex (0.28 g, 0.75 mmol) in CH2Cl2 (4 mL) was stirred vigorously at
room temperature. The reaction was competed immediately. After column
chromatography on silica gel using petroleum ether/acetone (8 : 2) as
eluent, 4-chloro-2-nitrophenol (0.169 g, 98%) mp 90–918C [Lit.[33] 918C]
was obtained as yellow needle crystals.
.
Dinitration of 4-Chlorophenol with Zn(NO3)2 2N2O4
To a solution of 4-chlorophenol (0.129 g, 1 mmol) in CH2Cl2 (5 mL),
.
Zn(NO3)2 2N2O4 complex (0.75 g, 2 mmol) was added. The mixture was
stirred for 10 min at room temperature. The mixture was chromatographed
on a column of silica gel and eluted with petroleum ether/acetone (8 : 2) to
give 4-chloro-2,6-dinitrphenol (0.2 g, 93%) mp 80–818C [Lit.[33] 818C].
.
Nitration of Chlorobenzene with Zn(NO3)2 2N2O4/charcoal
.
A mixture of chlorobenzene (0.17 g, 1.5 mmol) and Zn(NO3)2 2 N2O4
complex/charcoal (0.55 g, 1 mmol) was stirred vigorously at room tempera-
ture for 30 min. The progress of the reaction was followed by GC. After

270
N. Iranpoor et al.
completion of the reaction, the resulting mixture was dissolved in acetone
(3 mL) and was presorbed on silica gel (5 g). The resulting silica gel
mixture was applied on a silica gel column and eluted with petroleum
ether/acetone (7 : 3) to afford 0.135 g (84%)of 2-nitro-chlorobenzene,
mp 318C [Lit.[33] 31–338C] and 4-nitrochlorobenzene mp 808C [Lit.[33]
81–828C] with ratio of 47 : 53, respectively.
REFERENCES
1. Schofield, K. Aromatic Nitration; Cambridge University Press, 1980.
2. Vogel’s. Textbook of Practical Organic Chemistry, 4th Ed.; Lonman: New York,
1987.
3. Germain, A. J. Chem. Soc. Chem. Commun. 1990, 1697.
4. Thompson, M. J.; Zeegers, P. J. Tetrahedron 1991, 47, 8787.
5. Santaniello, E.; Ravasi, M.; Ferraboschi, P. J. Org. Chem. 1983, 48, 739.
6. Bisarya, S. C.; Joshi, S. K.; Holkar, A. G. Synth. Commun. 1993, 23, 1125.
7. Crivello, J. V. J. Org. Chem. 1981, 46, 3056.
8. Poirier, J. M.; Vottero, C. Tetrahedron 1989, 45, 1415.
9. McCullough, T. J. Chem. Ed. 1990, 67, 801.
10. Thompson, M. J.; Zeegers, P. J. Tetrahedron Lett. 1988, 29, 2471.
11. Zeegers, P. J. J. Chem. Ed. 1993, 70, 1036.
12. Ouertani, G.; Girard, P.; Kagan, H. B. Tetrahedron Lett. 1982, 23, 4315.
13. Olah, G. A.; Narang, S. C.; Olah, J. A.; Lammertsma, K. Proc. Natl. Acad. Sci.
USA 1982, 4487.
14. Alazard, J. P.; Kagan, H. B.; Seeton, R. Bull. Soc. Chem. Fr. 1977, 499.
15. Cornelis, A.; Laszlo, P. Synthesis 1985, 909.
16. Cornelis, A.; Laszlo, P. Synlett 1994, 155.
17. Knowles, J. R.; Norman, R. O.C. J. Chem. Soc. 1961, 3888.
18. Kurz, M. E.; Yang, L. T.A.; Zahora, E. P.; Adams, R. C. J. Org. Chem. 1973, 38,
2271.
19. Nagy, S. M.; Yarovoy, K. A.; Shakirov, M. M.; Shubin, V. G.; Votrikova, L. A.;
Ione, K. G. J. Mol. Catal. 1991, 64, 31.
20. Masci, B. Tetrahedron 1989, 45, 2719.
21. Topia, R.; Torres, G.; Valderrama, J. A. Synth. Commun. 1986, 16, 681.
22. Pervez, H.; Onyisiuka, S. O.; Rees, L.; Rooney, J. R.; Sukling, C. J. Tetrahedron
1988, 44, 4555.
23. Samajdar, S.; Becker, F. F.; Banik, B. K. Tetrahedron Lett. 2000, 41, 8017.
24. Fisher, A.; Mathivanan, N. Tetrahedron Lett. 1988, 29, 1869.
25. Peng, X.; Fukui; Mizutu, M.; Suzuki, H. Org. Biomol. Chem. 2003, 1, 2326.
26. Addison, C. C.; Lewis, J. J. Chem. Soc. 1951, 2843.
27. Addison, C. C. Chem. Rev. 1980, 21, 80.
28. Iranpoor, N.; Firouzabadi, H.; Zolfigol, M. A. Synth. Commun. 1998a, 28, 367.
29. Iranpoor, N.; Firouzabadi, H.; Zolfigol, M. A. Synth. Commun. 1998b, 28, 377.
30. Iranpoor, N.; Firouzabadi, H.; Zolfigol, M. A. Synth. Commun. 1997, 27, 3301.
31. Iranpoor, N.; Firouzabadi, H.; Zolfigol, M. A. Synth. Commun. 1998c, 28, 2773.
32. Mallakpour, S. E.J. Chem. Ed. 1992, 69, 238.
33. Fluka. Chemica-Biochemical; 1993/94.