Zeolite-assisted regioselective synthesis of dinitronaphthalene

Article abstract of DOI:10.1007/s11164-013-1054-y

The nitration selectivity of naphthalene was studied in different organic solvents with 95 % fuming nitric acid as nitration reagent. The yield of dinitronaphthalene can achieve 78 % in hexane. With nitrogen dioxide as nitration reagent in oxygen, the selectivity of dinitronaphthalene in different types of molecular sieve catalyst was studied. When HBEA zeolite catalyst was used, the yield of dinitronaphthalene was up to 61 %. This method is easy to carry out, environmentally benign, and economical.

Full text of DOI:10.1007/s11164-013-1054-y

Res Chem Intermed
DOI 10.1007/s11164-013-1054-y
Zeolite-assisted regioselective synthesis
of dinitronaphthalene
Haocai Wang
Xiongzi Dong
•
•
Xinhua Peng
Yanfang Tai
•
Chunjie Shi
Hongtao Liu
•
•
Received: 18 November 2012 / Accepted: 15 January 2013
Ó Springer Science+Business Media Dordrecht 2013
Abstract The nitration selectivity of naphthalene was studied in different organic
solvents with 95 % fuming nitric acid as nitration reagent. The yield of dinitro-
naphthalene can achieve 78 % in hexane. With nitrogen dioxide as nitration reagent
in oxygen, the selectivity of dinitronaphthalene in different types of molecular sieve
catalyst was studied. When HBEA zeolite catalyst was used, the yield of dinitro-
naphthalene was up to 61 %. This method is easy to carry out, environmentally
benign, and economical.
Keywords Zeolite Á Dinitronaphthalene Á Nitration Á Regioselective
Introduction
The nitration of aromatic compounds is an important process in both industry and
academic research [1]. However, many traditional processes [2] suffer serious
disadvantages, including low regioselectivity, oxidative degradation byproducts,
and inefficient atomic economy. Selective synthesis of the desired isomer in the
nitration of aromatic compounds is of topical interest to reduce pollution caused by
unwanted isomers and specifically to respond to market demand.
In recent years, various clean nitration approaches have been explored [3–11], and
some progress has been achieved [12–16]. Smith et al. [17] developed a system for clean
and regioselective mononitration of aromatic compounds involving a microporous
solid, dinitrogen tetroxide and air, in which halogeno-benzene and other aromatics got
high yields and significant para selectivities. We have reported [10] zeolite-assisted
nitration of neat toluene and chlorobenzene with a nitrogen dioxide/molecular oxygen
H. Wang Á X. Peng (&) Á C. Shi Á X. Dong Á Y. Tai Á H. Liu
School of Chemical Engineering, Hefei University of Technology, Hefei 230009,
People’s Republic of China
e-mail: orgpeng@gmail.com
123

H. Wang et al.
system and obtained remarkable enhancement of para selectivity. The goal of the
present investigation was to develop a mild, easy to operate and efficient zeolite catalyst
without involving sulfuric acid. In this paper, we report the results of catalytic nitration
of naphthalene with nitric acid (95 %) and 1-nitronaphthalene with nitrogen dioxide/
molecular oxygen in the presence of zeolite catalysts.
Experimental
Reagents and apparatus
1
H NMR spectra were determined in CDCl on a Bruker 400 MHz spectrometer.
3
TLC was performed with silica gel GF254 percolated on glass plates, and spots were
visualized with UV. HPLC (Shimadzu LC-10Avp Plus) was utilized to determine
the compositions of products. IR measurements were made on a Hitachi IR meter
2
60-10 for KBr pellets and only characteristic peaks were recorded. Melting points
were determined on a WRS-2 apparatus and uncorrected. Zeolites were purchased
from New Materials Research Center, Tianjin, China. All other chemicals were
analytical grade without any further purification.
General procedure
Typical experimental procedure for zeolite cation-exchange
The standard procedure for cation-exchange involved stirring a supplied commer-
cial zeolite (5.0 g) in a refluxing aqueous solution of the corresponding metal
chloride (0.2 mol/L, 100 mL) for 24 h. The solid was filtrated, washed with
deionized water until halide-free, dried at 110 °C for 3 h, and then calcined in air at
5
50 °C for 6 h.
Nitration of naphthalene with fuming nitric acid
Naphthalene (0.64 g, 5.0 mmol), nitric acid (2.1 mL, 50 mmol, 95 %), and solvent
(
5.0 mL) were placed in a three-neck flask. The mixture was stirred at refluxing
temperature. The reaction was monitored by TLC. When the reaction was over, the
liquor was washed with water, then a 5 % aqueous solution of sodium bicarbonate
followed by water. The organic layer was separated and dried with anhydrous
Na SO , and concentrated under reduced pressure to give a yellow solid residue.
2
4
The production was analyzed by HPLC.
Nitration of 1-nitronaphthalene with nitrogen dioxide and dioxygen
in the presence of zeolite
1
-Nitronaphthalene (0.17 g, 1 mmol), liquid NO2 (1.0 mL, 30 mmol), zeolite
0.50 g), and acetonitrile (5 mL) were placed in a three-neck flask. Oxygen was
(
1
23

Zeolite-assisted regioselective synthesis
Scheme 1 Nitration of naphthalene
passed into the system to drive away air, and then a balloon filled with oxygen was
connected. The mixture was stirred at refluxing temperature. The reaction was
monitored by TLC. When the reaction was complete, excess NO was expelled by
2
blowing air into the solution. The zeolite was removed by filtration. The mixture
was evaporated under reduced pressure and the residue was extracted with CH Cl
2
2
(
10 mL). The extracts were washed with NaHCO (10 mL 9 3, 10 %) and water
3
(
10 mL 9 3), dried over anhydrous Na SO , and concentrated under reduced
2
4
pressure to give a yellow solid residue, the composition of which was analyzed by
HPLC. The recovered zeolite was reused by washing and calcination.
Table 1 Nitration of naphthalene by nitric acid in various solvents
Runs Solvents
Temperature
°C)
Time
(h)
Conversion
a
(%)
Yield
b
(%)
Isomer 4:5
proportion Ratio
d
(
c
(
%)
4
5
1
2
3
4
5
6
7
8
9
1
1
1
–
90
8
8
C99
C99
C99
Trace
C99
C99
12
28
34
70
–
74
51
65
–
26
49
35
–
2.1
1.0
1.8
–
CH
2
Cl
2
Reflux
Reflux
Reflux
Reflux
CHCl
3
8
THF
12
10
18
24
16
18
12
6
CH
3
3
CN
63
60
88
4
55
58
91
65
–
45
42
9
1.2
1.4
10
CH
COOH 90
C
6
H
5
NO
2
90
DMF
HCONH
AC
90
C99
Trace
C99
C99
C99
35
–
1.9
–
2
90
–
0
1
2
2
O
90
68
78
29
35
59
88
65
41
12
0.53
1.5
7.3
n-Hexane
Reflux
90
DMSO
12
All reactions were carried out in organic solvent (5.0 mL) using substrate 1 (1.0 mmol)
a
Determined by HPLC
b
Combined yield of 4 and 5 based on consumed 1
c
Proportion of starting material consumed that is converter into product
d
Calculated from HPLC peak areas, excluding other isomers and byproducts
123

H. Wang et al.
Table 2 Nitration of 1-nitronaphthalene with nitrogen dioxide and oxygen in the presence of zeolite
a
Runs Nitrating
agents
Catalysts
Time
(h)
Conversion
b
(%)
Yield
c
(%)
Isomer 4:5
proportion Ratio
d
(
%)
4
5
1
2
3
4
NO
NO
NO
NO
2
2
2
2
HZSM-5
HZSM-5
48
48
26
88
85
67
41
37
40
31
78
49
63
44
22
51
37
56
3.51
0.95
1.79
0.79
–O
2
–O
2
–O
2
CuZSM-5 48
MgZSM- 48
5
5
6
7
9
NO
NO
NO
NO
2
–O
2
–O
2
–O
2
–O
2
2
2
2
CoZSM-5 48
LaZSM-5 48
CdZSM-5 48
56
50
43
45
41
38
24
37
45
56
38
41
55
44
62
59
0.82
1.27
0.60
0.69
CuZSM-5
8
All reactions were carried out in acetonitrile (5.0 mL) using substrate 2 (1.0 mmol), liquid NO (1.0 mL)
and catalyst (0.50 g). The reaction was stirred under reflux. Acetonitrile was distilled to eliminate water,
then was dried over 0.4 nm molecular sieves
2
a
Zeolites were calcined at 550 °C for 2 h in air prior to use
Determined by HPLC
b
c
Proportion of starting material consumed that is converted into product
d
Proportions of products as determined by HPLC
Results and discussion
1
,5-Dinitronaphthalene and 1,8-dinitronaphthalene are useful intermediates in the
production of pigments, pharmaceuticals, dyestuffs, and high-energy materials.
These polynitronaphthalenes were synthesized by the classical method involving a
mixture of nitric and sulfuric acids by direct nitration of naphthalene or by further
nitration of 1-nitronaphthalene in industry. 1,5-Dinitronaphthalene is important as
the precursor to high performance polyurethane resins and consequently of greater
market demand than 1,8-dinitronaphthalene.
We attempted to vary the solvents in order to increase the ratio of 4:5 into the
desired product (Scheme 1). The results obtained are given in Table 1.
The effect of different solvents on the reaction was investigated and the results
are summarized in Table 1. The solvent shows a strong influence on the reaction. At
9
0 °C, when nitrobenzene was used as solvent, a low conversion (12 %) was
observed but the highest ratio (10:1) of isomers was obtained. This is possibly
because the naphthalene was freely soluble in nitrobenzene and the reaction was
blocked up with the solvent effect. When the reaction was carried out with n-hexane
and chloroform as solvent, the total yields of products 4 and 5 were obtained at 78
and 70 %, respectively. This could be because, as the reaction proceeds, the
products were precipitated, and it is helpful for the chemical equilibrium moving to
the nitration reaction.
1
23

Zeolite-assisted regioselective synthesis
Table 3 Nitration of 1-nitronaphthalene with nitrogen dioxide and oxygen in the presence of zeolite
a
b
Runs Nitrating
agents
Solvents Catalysts Time
(h)
Conversion
c
(%)
Yield
d
(%)
Isomer 4:5
proportion Ratio
e
(
%)
4
5
1
2
3
4
5
6
7
8
NO
NO
NO
NO
NO
NO
NO
NO
2
–O
2
–O
2
–O
2
–O
2
–O
2
–O
2
–O
2
–O
2
2
2
2
2
2
2
2
CH
CH
CH
CH
CH
CH
CH
CH
3
3
3
3
3
3
3
3
CN
CN
CN
CN
CN
CN
CN
CN
HBEA-
5
48
48
48
48
91
72
59
37
44
29
38
39
65
49
53
28
34
52
22
56
72
28
2.57
1.39
1.27
1.23
0.49
0.64
0.90
0.52
2
HBEA-
80
HBEA-
00
CuBEA-
58
56
55
33
39
47
34
42
44
45
67
61
53
66
2
5
2
5
MgBEA- 48
2
5
CoBEA-
2
48
48
48
5
LaBEA-
2
5
CdBEA-
2
5
All reactions were carried out in organic solvent (5.0 mL) using substrate 2 (1.0 mmol), liquid NO
(1.0 mL) and catalyst (0.50 g). The reaction was stirred under reflux
2
a
Solvent was distilled to eliminate water, then was dried over 0.4 nm molecular sieves
b
c
d
e
Zeolites were calcined at 550 °C for 2 h in air prior to use
Determined by HPLC
Proportion of starting material consumed that was converted into product
Proportions of products were determined by HPLC
Kwok and Jayasuriya [18] applied HZSM-5 zeolite for regioselective monon-
itration of toluene and found that the HZSM-5 zeolite could enhance the
regioselectivity for the para nitrotoluene over the ortho isomer. When naphthalene
was subjected to the combined action of nitrogen dioxide and dioxygen in the
presence of ZSM-5 zeolite (Table 2), the formation of 4 became highly favored,
leading to the reversal of the 1,5-:1,8-dinitronaphthalene isomer ratios. When
dioxygen was used, the conversion was obviously improved (runs 1 and 2 in
Table 2). In this system, dioxygen played an activation role. Several metal ion-
exchanged HZSM-5 zeolites of the same Si/Al ratio were tested, and the results
showed that CuZSM-5 and LaZSM-5 were superior to the Cd and Co forms of
ZSM-5 in selectivity but in lower yields (runs 3–7 in Table 2).
However, when BEA zeolites were used as catalyst and CH CN as solvent, the
3
yield and selectivity of 1,5-dinitronaphthalene were greater than ZSM-5. The results
are shown in Table 3.
BEA zeolites with lower Si/Al ratio showed a better conversion and 1,5-site
selectivity than higher Si/Al ratio (runs 1–3 in Table 3). This may be attributed to
the large pore size structure, which would place less restriction on the transport of a
123

H. Wang et al.
substrate through the pores. H-type BEA-zeolite was superior to the metal-
exchanged ones in the regioselection. This probably due to the interaction of high
density effective sites via the hydrogen bonding (runs 1 and 4–8 in Table 3). In the
five metal-exchanged zeolites, only CuBEA-25 played a positive role in obtaining a
higher 1,5-:1,8-dinitro isomer ratio (run 17). MgBEA-25, CdBEA-25, CoBEA-25,
and LaBEA-25 showed poor regioselection.
Conclusion
For the special structure and acid strength, zeolite HBEA-25 exerted a greater
influence over both the rate and selectivity for 1,5-dinitronaphthalene. However,
cation-exchanged catalysts have less influence on conversion and selectively.
The method with nitrogen dioxide as nitration reagent in oxygen is easy to carry
out, environmentally benign, and economical.
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