Nanosilica/NaNO2: Novel heterogeneous system for synthesis of Azo compounds

Article abstract of DOI:10.1080/15533174.2011.555872

Various azo compounds are synthesized by electrophonic substitution reaction in the presence of Nanosilica/NaNO₂as a catalyst. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2011.555872

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Synthesis and Reactivity in Inorganic, Metal-Organic,
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Nanosilica/NaNO2: Novel Heterogeneous System for
Synthesis of Azo Compounds
Hassan Fathinejad Jirandehi a , Marjan Mirzaeian a & Mojtaba Mirzaeian b
a Chemistry Department , Islamic Azad University , Farahan Branch, Farahan, Arak, I. R.
Iran
b Department of Chemical and Process Engineering , University of Strathclyde , Glasgow,
UK
Published online: 22 Apr 2011.
To cite this article: Hassan Fathinejad Jirandehi , Marjan Mirzaeian & Mojtaba Mirzaeian (2011) Nanosilica/NaNO2: Novel
Heterogeneous System for Synthesis of Azo Compounds, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-
Metal Chemistry, 41:4, 376-377, DOI: 10.1080/15533174.2011.555872
To link to this article: http://dx.doi.org/10.1080/15533174.2011.555872
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:376–377, 2011
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.555872
Nanosilica/NaNO2: Novel Heterogeneous System for
Synthesis of Azo Compounds
Hassan Fathinejad Jirandehi,1 Marjan Mirzaeian,1 and Mojtaba Mirzaeian2
1Chemistry Department, Islamic Azad University, Farahan Branch, Farahan, Arak, I. R. Iran
2Department of Chemical and Process Engineering, University of Strathclyde, Glasgow, UK
are sized between 1 and 100 nanometers. Nanoparticles may or
may not exhibit size-related properties that differ significantly
from those observed in fine particles or bulk materials.[8]
Nanosilica (fumed SiO2) as a stable acidic reagent (solid
acid) effectively plays the role of HCl in the reaction, assist-
ing the formation of diazonium species. Protection of transi-
tion compounds is a key factor in multi-step synthesis process;
hence, due to the decomposition of diazonium salts at tempera-
tures above 5◦C, synthesis must take place in solution near ice
temperatures. In addition to the elimination of HCl as a haz-
ardous substance, using nanosilica as catalyst for synthesis of
azo compounds possess many advantages such as mild reaction
conditions; low energy consumption; high efficiency; and high
selectivity.
Various azo compounds are synthesized by electrophonic sub-
stitution reaction in the presence of Nanosilica/NaNO2 as a catalyst.
Keywords azo compound, fumed SiO2, nanomaterials, sodium ni-
trite, solid acids
INTRODUCTION
Azo compounds are chemical compounds that contain R-
N=N-Rꢀ as a functional group. Derivatives containing aryl
groups are more stable. Oxidation of hydrazine (R-NH-NH-Rꢀ)
is a method for the synthesizing of azo compounds. Aromatic
azo compounds are more common and can be synthesized by
azo coupling reaction, which is an electrophilic substitution re-
action of diazonium salt on aromatic ring.[1]
Because of the electron delocalization, many azo com-
pounds are colored and have been utilized as the oldest and
largest class of industrial organic dyes and analytical reagents.[2]
These compounds have more recently attracted increased atten-
tion by finding potential applications in various fields such as
biomedicine;[2,3] organic synthesis;[4−6] and as materials with
excellent optical and photoelectric properties.[7]
Many methods for the synthesis of these compounds have
been described in literature; however, most of them have dis-
advantages such as low productivity, insensitive reaction condi-
tions, expensive reagents, and undesirable side reactions. Most
of the processes for the large scale production of azo compounds
use liquid acids, such as HCl, as catalyst,[2] resulting in the
generation of large amount of wastes that are environmentally
hazardous and costly to treat.[3]
In order to reduce or eliminate the use or generation of haz-
ardous materials during the synthesis, and simplify the handling
procedures in the production process, viable alternative man-
ufacturing processes that use eco-friendly catalysts with lower
toxicity and higher stability are under attention. Nanoparticles
EXPERIMENTAL
All chemicals were reagent grade quality obtained from
Merck company and used as received. Melting points were
measured by a MODEL digital melting point measurement ap-
paratus. IR spectrometry was performed on a Galaxy FT-IR
1
500 spectrophotometer. H NMR spectra were recorded on a
Brucker 300 MHz spectrometer. Chemical shifts (ppm) were
referenced to the internal standards tetramethylsilane (TMS).
The reactions were monitored by thin layer chromatography
using silicagel F254 aluminum sheets (Merck).
General Producer
Azo compounds were synthesized as follows: The required
amounts of corresponding aniline or p-amino benzoic acid
(0.054 mol), nanosilica (0.054 mole), water (15–20 mL), and
NaNO2 (0.054 mol) were mixed in a flask. After gentle grinding
of the resultant mixture for 15 min, a basic solution of phenol
(0.054 mol in sodium hydroxide) was added drop wise to the
flask (in a period of 15–20 min), and the mixture was stirred
vigorously for 20 minutes. It was then filtered, and the resul-
tant solid was washed with diethyl ether and then air dried. The
crude product was recrystallized from acetic acid (or ethanol).
Received 23 August 2010; accepted 31 October 2010.
Address correspondence to Hassan Fathinejad Jirandehi, Chem-
istry Department, Islamic Azad University, Farahan Branch, Farmahin,
Arak, I. R. Iran. E-mail: h.fathinejad@iau-farahan.ac.ir
4-Ethyl-2(p-carboxyl azophenyl) phenol (2a)
mp: 171–173◦C, yield% 92. IR (KBr): 3225 (OH), 3078 (CH
aroma), 2962 (CHaliph), 3300–2500 (COOH), 1683 (C=O),
376

SYNTHESIS OF AZO COMPOUNDS WITH NANOSILICA/NaNO2
377
TABLE 1
Azo compounds
Entrance
Ar
Arꢀ
4a
4b
4c
4d
4e
4f
4-ethyl phenol
1-naphthol
4-flourophenol
2,3-dichlorophenol
2, 6-dichlorophenol
2-hydroxybenzaldehyde
4-chlorophenol
p-carboxyl phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
phenyl
Phenyl
SCH. 1. Synthesis of Azo compounds
1
1593 (C=C) cm−1. H NMR (DMSO-d6): δ = 1.02 (t, 3H,
4g
4h
CH3), 2.66 (q, 2H, CH2), 7.07–7.99 (m, 7H, CHarom), 8.01 (d,
1H, OH), 10.61 (bs, 1H, COOH).
1, 3-dihydroxy benzene
4-(Azopheny◦l)-1-naphthol (2b)
RESULTS AND DISCUSSION
m.p:165-168 C, yield %95, IR (KBr): 3225.58 (OH), 3078
(CHarom), 3300-2500 (COOH), 1683 (C=O), 1593 (C=C)
cm−1. 1H NMR (DMSO-d6): δ = 5.62–6.73 (m, 11H, CHarom),
8.4 (s, 1H, OH).
Scheme 1 shows the reaction between a phenol derivative and
an appropriate aniline compound in the presence of nanosilica as
catalyst. The reaction takes place at mild condition with suitable
yield.
The authors’ studies on nanomaterials for finding appropriate
solid acids led to nanosilica, which is exhibited. Nanosilicas
have different properties based on their size. Nanosilica (fumed
silica), also known as pyrogenic silica, is a non-crystalline, fine-
grain, low density, and high surface area. Silica is also known
as microsilica. Fumed silica (10–15 nm) has acidic properties
with pH = 4.2.
4-Flouro-2-(Azophenyl) Phenol (2c)
m.p:101–103◦C, yield %85. IR (KBr):3205.89 (OH), 3159.58
1
(CHarom), 1610.25 (C=C) cm−1. H NMR (DMSO-d6): δ =
7.07–7.99 (m, 8H, CHarom), 8.01 (d, 1H, OH).
2,3-Dichloro-4-(Azophenyl) Phenol (2d)
m.p: 230–233◦C, yield %65. IR (KBr): 3213 (OH), 3061
(CHarom), 1591 (C=C) cm−1. 1H NMR (DMSO-d6): δ = 6.33–
6.51 (m, 2H, CHarom), 7.43–7.68 (m, 5H, CHarom), 7.85(d, 2H,
OH).
As shown in Table 1, the substitutes in the phenol compounds
of the reaction have an effective role. Electron-withdrawing
group on phenol compounds decreased the yield of reaction
compared to the electron-releasing groups and the substitute
group; its position on phenol ring affects the color of the final
azo compounds.
The 1H NMR data of the synthesized compounds are shown
2, 6-Dichloro-4-(Azophenyl) Phenol (2e)
1
as follows. The H NMR data of all synthesized compounds
m.p: 142–144◦C, yield %90. IR (KBr): 3508 (OH), 3084
(CHarom), 1570 (C=C).1H NMR (DMSO-d6): δ = 6.33-6.51 (m,
2H, CHarom), 7.43–7.68 (m, 5H, CHarom), 7.85(d, 2H, OH).
are consistent with the expected structures. The 1H-NMR spec-
tra of 2a shows two broad singles at 10.61 ppm, which is at-
tributed to the resonance of the carboxylic group. Seven aro-
matic protons related to two aromatic rings appeared as a mul-
tiple at the 7.07–7.99 ppm range. Protons of CH2 and CH3
groups appeared as quartet and triplet at 2.66 and 1.02 ppm,
respectively.
2-Hydroxy-3-(Azophenyl) Benzaldehyde (2f)
m.p: 151–153◦C, yield %95. IR (KBr): 3207 (OH), 3040
(CHarom), 1591 (C=C) cm−1. 1H NMR (DMSO-d6): 6.89-6.96
(m, 3H, CHarom), 7.48–7.53 (m, 2H, CHarom), 7.77–7.85 (m, 2H,
CHarom), 11.31 (bs, 2H, OH, CHO).
REFERENCES
1. Zollinger, H. Azo and Diazo Chemistry, Aliphatic and Aromatic Com-
pounds; Interscience: New York, 1961.
2. Singh, A. K.; Das, J.; Majumdar, N. J. Am. Chem. Soc. 1996, 118, 6185–
6191.
3. Bondock, S.; Khalifa, W.; Fadda, A. A. Eur. J. Med. Chem. 2007, 42,
948–954.
4. Qiao, R. Z.; Zhang, Y.; Hui, X. P.; Xu, P. F.; Zhang, Z. Y.; Wang, X.Y.;
Wang, Y. L. Green Chemistry 2001, 3, 186–188.
4-Chloro-2-(Azophenyl) Phenol (2g)
m.p:161–163◦C, yield %72. IR (KBr): 3311 (OH), 3057
1
(CHarom), 1591. (C=C) cm−1. H NMR (DMSO-d6): 7.10 (d,
1H, CHarom), 7.43–7.64 (m, 5H, CHarom), 7.99 (s, 2H, CHarom),
10.85 (bs, 1H, OH).
5. Little, R. D.; Venegas, M. G. J. Org. Chem. 1978, 43, 2921–2923.
6. Hashim, A. B.; Elie, A. J.; Noel, C. Tetrahedron Lett. 1996, 37, 2951–2954.
7. Liu, Z. F.; Hashimoto, K.; Fujishima, A. Nature, 1990, 347, 658.
8. Garrett, P.R. Defoaming, Theory and Industrial Applications; USA: CRC
Press. 1992, pp. 239–240.
2, 6-Dihydroxy-1-(Azo Phenyl) Benzene (2h)
m.p:152–155◦C, yield %95. IR (KBr): 3213.61 (OH), 3061
(CHarom), 1591 (C=C) cm−1. 1H NMR (DMSO-d6): 6.08–6.11
(m, 2H, CHarom), 6.32–6.73(m, 6H, CHarom), 8.79 (s, 2H, OH).