Synthesis and characterization of Azo dye para red and new derivatives

Article abstract of DOI:10.1155/2012/206076

Azo dyes para red was synthesized. The products were characterized by FTIR and UV-Visible spectrophotometers. The antibacterial activities of the compounds were studied using gram positive and gram negative microorganism.

Full text of DOI:10.1155/2012/206076

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
2012, 9(1), 465-470
http://www.e-journals.net
Synthesis and Characterization of
Azo Dye Para Red and New Derivatives
L ABD-ALREDHA R.AL-RUBAIE* and R. JAMEEL MHESSN,
Department of Pharmaceutical Chemistry,
Pharmacy College, Basrah University, Iraq
leaqaa2000@yahoo.com
Received 5 February 2011; Revised 13 May 2011; Accepted 5 June 2011
Abstract: Azo dyes para red was synthesized. The products were
characterized by FTIR and UV-Visible spectrophotometers. The
antibacterial activities of the compounds were studied using gram
positive and gram negative microorganism.
Keywords: Azo dye, Para red derivatives, Diazonium salts reaction, Synthesis
Introduction
Azo dyes contain at least one nitrogen-nitrogen double bond (N=N); however many different
structures are possible1. Monoazo dyes have only one N=N double bond, while diazo and
triazo dyes contain two and three N=N double bonds, respectively. The azo groups are
generally connected to benzene and naphthalene rings, but can also be attached to aromatic
heterocycles or enolizable aliphatic groups. These side groups are necessary for imparting
the color of the dye, with many different shades and intensities being possible. A common
example of an azo dye is shown in Figure 1. When describing a dye molecule, nucleophiles
are referred to as auxochromes, while the aromatic groups are called chromophores.
Together, the dye molecule is often described as a chromogen. Synthesis of most azo dyes
involves diazotization of a primary aromatic amine, followed by coupling with one or more
nucleophiles. Amino- and hydroxy- groups are commonly used coupling components1.
Because of the diversity of dye components available for synthesis, a large number of
structurally different azo dyes exist and are used in industry2. World wide production of
organic dyes is currently estimated at nearly 450,000 tons, with 50,000 tons being lost in
effluents during application and manufacture3.

466
L. A. R. AL-RUBAIE et al.
Figure 1. Example of an azo dye structure
Azo dyes acquired wide interest in application to biological system and indicator in
complexometric titration of analytical chemistry. Azo dyes are the most important group of
synthetic colorants. They are generally considered as xenobiotic compounds that are very
recalcitrant against biodegradative processes. Aromatic azo compounds especially are used
as acid-base indicators, also used in biological strains and commercial colorants for clothing,
plastics, cosmetics and food beverages. Color changes are caused by change in extent of
delocalization of electrons. More delocalization shifts the absorption max to longer wave
lengths and makes the light absorbed redder, while less delocalization shifts the absorption
max to shorter wavelengths.
In pharmaceutical, azo linkage was used to protect drug from undesirable reaction, such
as prontosil was found to protect against, and cure streptococcal infections in mice.
Interestingly prontosil was inactive on bacterial cultures. Prontosil is totally in active in vitro
but possesses excellent activity in vivo4. Due to the highly variable nature of biological
treatment systems and especially textile effluents, there are a number of factors that may
affect the biodegradation rate of azo dyes. Throughout the literature, researchers have
discussed various problems associated with dye biodegradation that may or may not be
anticipated or remedied. Non-dye related parameters such as temperature, pH, type and
source of reduction equivalents, bacteria consortium, and cell permeability can all affect the
biodegradation of azo dyes and textile effluents. Dye related parameters such as class and type
of azo dye (i.e. reactive-monoazo), reduction metabolites, dye concentration, dye side-groups,
and organic dye additives could also affect the biodegradability of azo dye wastewaters.
The azo dye structure can play a significant role in the dye biodegradation rate.
Depending on the number and placement of the azo linkages, some dyes will biodegrade
more rapidly than others. In general, the more azo linkages that must be broken will cause
the reduction rate to be slower. While there are not a large number of studies that
specifically address this factor, Brown and Laboureur5 observed that two poly-azo dyes
showed only moderate to variable biodegradation as compared to four monoazo and six
diazo dyes. The authors indicate that poly-azo dyes are less likely to degraded than mono- or
diazo dye types5.
The azo dye sulfonamides antibacterial drugs were the first effective chemotherapeutic
agents that could be used systemically for the cure of bacterial infection in humans. A series
of azo dyes containing the sulfonamide functional group were synthesized as potential
antimicrobial agents, sulfonamide was classified into three different types; antibacterials that
are aniline-substituted sulfonamides, prodrug that react to generate active sulfanilamides and
nonanilin sulfonamides. There are also other commonly used drugs that are azo dyes
sulfonamides or sulfanilamides (the diuretic furosemide,the diuretic chlorthlidone and the
oral hypoglycemic drug tolbutamide). Today, there are a few sulfonamides and especially
sulfonamide–trimethoprim combination that are used extensively for opportunistic infection
in the patients with AIDS6.

Synthesis and Characterization of Azo Dye Para Red
467
Experimental
Preparation of azo dye para red (dye I)
Preparation of diazonium salt
Solution of 1 mL of concentrated sulfuric acid in 10 mL of distilled water was added in a
round botton flask. While stirring, 1 g (7 mmol) of p-nitroaniline was added with stirring in
ice bath. Then solution of 0.5 g (7 mmol) of sodium nitrate in 2 mL of distilled water was
added slowly.
Synthesis of para red
Solution of 1 g (7 mmol) of 2-naphthol in 10 mL of 2.5 M sodium hydroxide was added
into the flask with the diazonium salt in an ice bath, with vigorously stirring for a few
minutes. The mixture was acidified with 1 M sulfuric acid. The product was dried under
o
vacuum-oven at 50 C for 2 h. The melting point of product was estimated at 248-252 °C,
the red product was characterized by FTIR and UV spectrophotometer as shows in Figures 2
and 5 respectively.
Preparation of methylsulfonyl para red (dye II)
Methane sulfonyl chloride (0.023 mL) was added drop wise over 15 minutes in an ice cooled
solution of para red (0.461 mmol) and 5 mL tripropylamine. The resulting red suspension
was stirred at 0 °C for 20 minutes, extracted with chloroform, the dye II was dried under
vacuum-oven for 24 h at 50 °C, the melting point was 267 °C, the product was characterized
by FTIR and UV spectrophotometers, as shown in Figures 3 and 5 respectively.
Preparation of dye III
A solution of 1 g (7 mmol) of 4-amino-3-hydroxynaphthalene -1-sulphonic acid in 10 mL of
2.5 M sodium hydroxide was added into the flask with the diazonium salt in an ice bath
(form swelling) with vigorous stirring for 30 minutes. The mixture was acidified with 1 M
sulfuric acid, the product was filtered and washed with distilled water. The dried product
was decomposed at 280 °C . The product was investigated by IR and UV spectrophotometer,
as shown in Figures 4 and 5 respectively.
Results and Discussion
The synthesis of an azo dye requires two organic compounds- a diazonium salt and a
coupling component. The general synthesis of azo dyes is shown below:
The diazonium salt reacts as an electrophile with an electron-rich coupling component,
like a β-naphthol and naphthaline derivative through an electrophilic aromatic substitution
mechanism. The hydroxyl group (such as β-naphthol) direct the aryl diazonium ion to the
para site unless that position is occupied, in which case the ion attaches ortho7.

468
L. A. R. AL-RUBAIE et al.
The prepared products as azo dye were characterized by various available techniques. The
infrared spectroscopy is one of the efficient techniques used in the characterization of organic
compounds. IR spectrophotometers as FTIR which was used in the present study to confirm the
presence of functional groups as following, distinguish stretching vibration band of azo group
(N=N) at 1500.52-1521.73 cm-1 as shown8 in Figures 2 to 4.The stretching vibration appear at
2962.46 cm-1 and 2927.74 cm-1 position was related to methyl group of methylsulfonyl group
(CH3SO2) as shown in Figure 3. The compound III differ from the compound I and II by replace
β-naphthol by 4-amino-3-hydroxy-naphthalene-1-sulphonic acid. The asymmetry stretching
vibration of S-O (SO3-H) group appearance at 1172.6 cm-1 position, while symmetry at 1045.35 cm-1
position.Other peaks of the principle bands are shown in Table 1.
Table 1. Major stretching vibration of absorption bands by FTIR spectroscopy
Compounds
ν
νNO
νO-H str.
νC-H str.
νSO
str.
2
νSO str.
N=N str.
1504.37 1328.86 3390
1500.52 1330.79
str.
3
2
(Phenolic)
Dye I
-
-
1172.6 asy.
1045.35 sym
-
Dye II
-
2962.46 asy. 1400
2927.7 sym
Dye III
1521.73 1344.29 3450
-
-
-
Str. =stretching, asy. = asymmetry , sym. = symmetry , ν = vibration
Figure 2. IR Spectrum for dye I
Figure 3. IR Spectrum for dye II

Synthesis and Characterization of Azo Dye Para Red
469
Figure 4. IR Spectrum fo dye III
The UV-Visible spectrophotometer study was showed the same position of transition
dye I and II in curve, as shown in Figure 5, but differ in intensity. Both dye I and II have a
structure with distinct electron donor and acceptor groups, the so called "Push-Pull" electron
structure. The maximum absorption band is a broad peak that probably embraces the
absorption ascribed either to n → π or n → π* electron transitions, as shown in Table 2.
Wavelength, nm
Figure 5. UV-Visible curves of compounds (I, II and III)
Table 2. Types of UV-Visible transition
Compounds
Dye I
Type of transition Wave length, nm
π → π*
n → π*
π → π*
π → π*
n → π*
π → π*
π → π*
n → π*
285 sharp
325 shoulder
490 tautomerism
290 weak
325 shoulder
490 tautomerism
330 sharp
Dye II
Dye III
490 shoulder

470
L. A. R. AL-RUBAIE et al.
The broader transition may be due to hyperconjugation system of the molecule8.
Figure 6. Represent the hyperconjugation system of para red molecule.
The biological activity against two types of both gram positive and gram negative
microorganism were studied. Azo dye sulfonamide is totally inactive in vitro but possesses
excellent activity in vivo. Trefouel et al.9 performed a structure-activity study on the
sulfonamide azo dyes and concluded that the azo linkage was reductively cleaved to release
the active antibacterial, nocardia, chlamydia trachomatis and some protozoa. Some enteric
bacteria are inhibited some of sulfonamides are drugs of choice for infections such as P(P)
toxoplosmosis, nocardiosis and other bacterial infections. The mechanism of action of
sulfonamide is competitively inhibit the action of dihydropteroate synthase and blocking the
net biosynthesis of folate coenzymes, therefore its bacteriostatic10.
Conclusion
The studies confirm para red was prepared from react diazonium salt of p-nitroanilin with β-
naphthol. The derivatives of para red were prepared. The products; dye I, dye II and dye III were
characterized by FTIR and UV-Visible spectrophotometer. The antibacterial activity was studied
of azo dyes. The in vitro study was shows there is no biological activity of azo dyes.
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Heinrich Z, Color Chemistry, Syntheses, properties and applications of organic dyes
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Paraneswari N, Muthakrishnan J and Guanasekaran P, Indian J Exp Biol., 2006, 44, 618.
Brown D and Laboureur P, Chemosphere, 1983, 12(3), 405.
Wilson and Gisvold′s, Text book of organic medicinal and pharmaceutical chemistry, 11th
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Kucharski S and Janik R, New J Chem., 1999, 23, 765.
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