Efficient and facile method for the nitration of aromatic compounds by nitric acid in micellar media

Article abstract of DOI:10.1080/00397910802711318

Aromatic compounds were efficiently nitrated under mild reaction conditions by employing HNO3 in the presence of anionic (sodium dodecyl sulfate, SDS), cationic (cetyl trimethyl ammonium bromide, CTAB), and nonionic (Triton-X 100) micelles. The reaction rapidly afforded corresponding mononitro derivatives in fair to good yields with high regioselectivity. This new method offers an environmentally safe reaction condition to minimize the waste products.

Full text of DOI:10.1080/00397910802711318

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Efficient and Facile Method
for the Nitration of Aromatic
Compounds by Nitric Acid in
Micellar Media
a
a
a
S. Sana , Tasneem , M. Moazzam Ali , K. C.
a
b
Rajanna & P. K. Saiprakash
a
Osmania University Postgraduate College, Mirzapur,
India
b
Department of Chemistry, Osmania University,
Hyderabad, India
Available online: 14 Jul 2009
To cite this article: S. Sana, Tasneem, M. Moazzam Ali, K. C. Rajanna & P. K.
Saiprakash (2009): Efficient and Facile Method for the Nitration of Aromatic
Compounds by Nitric Acid in Micellar Media, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 39:16,
2949-2953
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1
Synthetic Communications , 39: 2949–2953, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802711318
Efficient and Facile Method for the Nitration
of Aromatic Compounds by Nitric Acid
in Micellar Media
1
S. Sana, Tasneem, M. Moazzam Ali, K. C. Rajanna,
1
1
1
2
and P. K. Saiprakash
Osmania University Postgraduate College, Mirzapur, India
Department of Chemistry, Osmania University, Hyderabad, India
1
2
Abstract: Aromatic compounds were efficiently nitrated under mild reaction
conditions by employing HNO in the presence of anionic (sodium dodecyl
sulfate, SDS), cationic (cetyl trimethyl ammonium bromide, CTAB), and nonionic
Triton-X 100) micelles. The reaction rapidly afforded corresponding mononitro
3
(
derivatives in fair to good yields with high regioselectivity. This new method
offers an environmentally safe reaction condition to minimize the waste products.
Keywords: CTAB, efficient nitration of aromatic compounds, micellar media,
SDS, Triton-X 100
INTRODUCTION
Aromatic nitro compounds are particularly versatile chemical feedstock
for a wide range of industrial products, such as pharmaceuticals,
agrochemicals, dyestuffs, and explosives. Traditionally, it is a common
practice to use a mixture of nitric and sulfuric acids to perform the nitra-
tion reaction (mixed-acid method). However, the method is notoriously
unselective for nitration of substituted aromatic compounds, and the dis-
posal of the spent acid reagents presents a serious environmental issue.
To overcome these problems, several alternative methods for aromatic
Received August 22, 2008.
Address correspondence to K. C. Rajanna, Osmania University Postgraduate
College, Mirzapur (B) 502249, India. E-mail: kcrajannaou@rediffmail.com
2
949

2950
S. Sana et al.
Scheme 1. Reaction conditions: (i) 69% HNO , CTAB, CH CN=rt=2–3 h; (ii)
3
3
69% HNO
rt=2–3 h.
3
, SDS, CH
3
CN=rt=2–3 h; (iii) 69% HNO
3
3
, Triton-X 100, CH CN=
[1]
nitration have been developed recently. Thus, development of new
catalyst systems that facilitate aromatic nitration in this manner should
be of great importance. In continuation of our work on environmentally
friendly organic synthesis, we tested the combination of nitric acid with
[2]
micelles for the purpose of nitration. Our preliminary results encour-
aged us to use micelles in combination with nitric acid to explore the
nitrating properties in a nitration reaction of aromatic compounds. We
hoped (a) to increase the rate and yield of the reaction and (b) to improve
ortho=para ratio of the nitrated aromatic compounds under mild
reaction conditions (Scheme 1).
RESULTS AND DISCUSSION
While optimizing the reaction conditions for the proposed micelle-
mediated nitration, cetyl trimethyl ammonium bromide (CTAB), sodium
dodecyl sulfate (SDS), and Triton-X 100 were selected as the most pro-
mising candidates. Accordingly, a range of aromatic compounds were
treated with 1 equivalent of 69% nitric acid in acetonitrile at room tem-
perature (rt) in the presence of 0.05 M solution (5.0 mL) of CTAB, SDS
and Triton-X 100. All the products were characterized by infrared(IR),
1
H-NMR, mass spectra (MS), and physical data compared with authentic
samples, and found to be satisfactory.
The nitration of aromatic compounds proceeded rapidly at room
temperature in the presence of anionic (SDS), cationic (CTAB), and also
nonionic (Triton-X 100) micelles, affording good yields of corresponding
mono-nitro derivatives with good regioselectivity (Table 1). When the
reaction was conducted in the absence of micelles, the reaction was too
sluggish even under reflux conditions, with a prolonged reaction time
and poor product yield. However, there was a dramatic reduction in
reaction times when the same reaction was conducted in micellar media,
from several hours (in nonmicellar media) to 2.0 to 3.0 h at room

2
951

2952
S. Sana et al.
temperatures (in micellar media), as shown in Table 1. The reactions are
dramatically enhanced in micellar media. Even the sluggish reactions
yielded quantitative yields Even though electron-withdrawing and
electron-donating groups on the benzene ring had significant influence
on the reaction times and yields of products in nonmicellar reactions,
such variations are not seen in micelle-mediated reactions. Irrespective of
the nature of the aromatic compound and the nature of the substituents,
all the compounds underwent nitration. There was remarkable improve-
ment in the yields and selectivity of the products formed via nitration
reaction in the presence of micelles (i.e., CTAB, SDS, and Triton-X
1
00). The nitration took place smoothly in a short time to give desired
products in good yields. These observations probably indicate that
micelles function as microreactors and are capable of increasing the reac-
tant concentration within the hydrophobic or hydrophilic areas; they
[
2]
cause a favorable orientation of the reactants by the polarity gradient.
Thus, it is assumed that the CTAB, SDS, and Triton-X 100 micelles act
as nitronium ion carriers in the nitration reaction. Progress of the reac-
tion is monitored by a visible change in the color of reaction mixture
and also by thin-layer chromatography (TLC) during the course of the
reaction. After completion of the reaction as indicated by TLC, the sol-
vent was evaporated, diluted with dichloromethane, and washed with
water. The organic layer was evaporated to afford the nitrated products.
CONCLUSION
In summary, we have developed a new, mild, and efficient method for the
nitration of aromatic compounds using nitric acid in the presence of
CTAB, SDS, and Triton-X 100 micelles, resulting in mono-nitro deriva-
tives in fair to good yields with good regioselectivity. Furthermore, the
present method also is environmentally safe, uses readily available and
inexpensive laboratory benchtop reagents, and needs mild reaction
conditions with simple workup. Thus, the present method is a major step
forward in the area of clean technology for aromatic nitration under
environmentally friendly conditions.
EXPERIMENTAL
Typical Procedure
HNO (69%, 1 mmol) was added to a solution of phenol (1 mmol) in
3
CH CN, followed by the addition of
3
a
solution of CTAB

Nitration of Aromatic Compounds
2953
(5 ml of 0.05 M) in CH CN, and reaction mixture was stirred at room
3
temperature for 2 h. After completion of the reaction as indicated by
TLC, the CH CN evaporated, and the reaction mixture was diluted with
3
dichloromethane and washed with water. The organic layer was sepa-
rated out, dried over sodium sulfate, and evaporated under vacuum.
The crude product was purified by silica-gel chromatography with ethyl
ꢀ
acetate–hexane (3:7) as eluent to get p-nitrophenol. Mp 113 C (lit. mp
ꢀ
1
14 C). Yield: 85% as major product.
ACKNOWLEDGMENTS
The authors thank Prof. T. Navaneeth Rao (former vice-chancellor,
Osmania University, Hyderabad), and Nawab Shah Alam Khan,
chairman, and Nawab Mahboob Alam Khan, secretary of Nawab Shah
Alam Khan Center for Postgraduate Studies and Research, Mallepally,
Hyderabad, for their constant encouragement.
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