Novel sulphoarylazo 4-pyrazolone-based tartrazine dye analogues

Article abstract of DOI:10.1080/10426500490459858

In a multistep synthesis, a novel series of 4-pyrazolone-based tartrazine dye analogues were prepared benzimidazol -5-yl acetoacetamide derivative I. Chemical structure of the hitherto prepared dyestuffs were confirmed on the basis of correct elemental an

Full text of DOI:10.1080/10426500490459858

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Phosphorus, Sulfur, and Silicon and the Related
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NOVEL SULPHOARYLAZO 4-PYRAZOLONE-BASED
TARTRAZINE DYE ANALOGUES
M. A. Hanna a , A. A. Al-Sarawy a , I. G. Rashed a & F. K. M. Wali a
a University of Mansoura, Mansoura, Egypt
Published online: 16 Aug 2010.
To cite this article: M. A. Hanna , A. A. Al-Sarawy , I. G. Rashed & F. K. M. Wali (2004): NOVEL SULPHOARYLAZO 4-
PYRAZOLONE-BASED TARTRAZINE DYE ANALOGUES, Phosphorus, Sulfur, and Silicon and the Related Elements, 179:6, 1209-1226
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Phosphorus, Sulfur, and Silicon, 179:1209–1226, 2004
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Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490459858
NOVEL SULPHOARYLAZO 4-PYRAZOLONE-BASED
TARTRAZINE DYE ANALOGUES
M. A. Hanna, A. A. Al-Sarawy, I. G. Rashed, and F. K. M. Wali
University of Mansoura, Mansoura, Egypt
(Received September 4, 2003; accepted October 15, 2003)
In a multistep synthesis, a novel series of 4-pyrazolone–based tartrazine
dye analogues were prepared benzimidazol -5-yl acetoacetamide deriva-
tive I. Chemical structure of the hitherto prepared dyestuffs were con-
firmed on the basis of correct elemental analysis as well as spectral data.
The degree of exhaustion of the hitherto synthesized 3-[2-(oxoimidazo-5-
yl) carboxamido] tartrazine dye analogues was determined and found
to be in the range of 92.6–97.8%. The latter high ratios might be as-
cribed to the presence of the cyclic amide function in structure of these
dyestuffs.
Keywords: Degree of exhaustion; synthesis; tartrazine dye analogues
Since Ludwig Knorr’s report1 in 1883 for preparation of Devel-
oper Z (3-methyl-1-phenyl-5-pyrazolone) and Ziegler’s discovery2 in
1887 of the yellow dyestuff tartrazine i.e., 1-(p-sulphophenyl)-4-(p-
sulphophenylazo)pyrazol-5-one 3-carboxylic acid, numerous pyrazol-4-
or -5-one derivatives have been synthesized3,4 and widely used in the
fields of photography and textile dyeing.5–7 Such compounds provide a
fairly full range of hues, especially yellows, oranges, and and reds. They
also have very high all-round fastness properties, in particular toward
light, heat, water, acids, and alkalies.
In view of these findings and the current interest in utilizing the
arylazo-4-pyrazolone dyestuffs of type (A) for dyeing different types of
fibers, the present investigation describes the synthesis of a novel group
of tartrazine dyes analogous of type (B).
EXPERIMENTAL
All melting points are uncorrected and measured on a Griffin & George
MBF 010T apparatus. Recorded yields correspond to the pure products.
Address correspondence to M. A. Hanna, POB 48, Mansoura University, 35516
Mansoura, Egypt. E-mail: mahanna69@hotmail.com
1209

1210
M. A. Hanna et al.
IR (KBr) spectra were recorded on a Perkin Elmer SP-880 spectropho-
1
tometer and H NMR spectra were measured on a Varian 270 MHz
spectrometer using CDCl3 as a solvent and trimethylsilane (TMS) as
an internal standard (chemical shifts are given as δ in ppm). Microanal-
yses were carried out in the Microanalytical Data Unit in Cairo and at
El-Mansoura University.
Synthesis of 4-Bromo-2,3-dioxo-N-(2ꢀ-oxobenzimidazol-
5ꢀ-yl)butyramide (II)
Benzimidazol-5-yl acetoacetamide derivative I8 (0.05 mmol, 11.66 g)
was dissolved in 40 ml of chloroform, and the solution was gradually
treated, with occasional shaking, with bromine (0.05 mmol, 2.60 ml) in
20 ml of chloroform. The mixture was left overnight. The precipitated
product was filtered off and recrystallized from petroleum ether (60/80)
to give yellowish orange crystals of melting point 178◦C (46%).
Analysis for C11H10N3O3Br (312.15)
Calcd: C, 42.32%, H, 3.24%, and N, 13.47%.
Found: C, 42.46%, H, 3.11%, and N, 13.26%.
IR Spectra (ν/ cm−1): 3310 (intramolecular hydrogen bonded NH),
3180 (free NH), 3060 (CH stretching), 2965–2905 (CH2 grouping), 1765
(bromoacetyl CO), 1680 (cyclic amide I band) and 1645 (acyclic amide
band).
1
The H-NMR spectrum of this compound (CDCl3/δ in ppm): 8.10–
7.20 (multiplet, 3H, aromatic protons), 5.80–5.20 (broad, 3H, cyclic &
acyclic amidic NH), 4.00 (singlet, 2H, CO CH2 CO), and 3.94 (singlet,
2H, Br CH2 CO).
Synthesis of 4-Bromo-2,3-dioxo-N-(2ꢀ-oxobenzimidazol-
5ꢀ-yl)butyramide 2-sulphoarylhydrazone derivatives
(IIIa–e)
An aryl sulphonic acid (0.05 mmol, 10.5 g) was mixed, in a 250 ml
conical flask, with anhydrous sodium carbonate (2.65 g) and water

Tartrazine Dye Analogues
1211
(100 ml), and the whole mixture was warmed until a clear solution
was obtained and then it was cooled to about 15◦C. A solution of
sodium nitrite (0.052 mmol, 3.6 g) in water (10 ml) was added. The
resulting solution was slowly added with stirring into a 600 ml beaker
containing concentrated hydrochloric acid (10.5 ml) and crushed ice
(60 gm). The solution was tested for the presence of free nitrous acid
and kept stirred for 15 min whereupon fine crystals of the diazoaryl-
sulphonate soon separated. The suspension was kept in an ice wa-
ter bath for 10 min and then poured, with stirring, into a solution
of the bromo-acetoacetamide derivative (II) (0.05 mmol, 15.60 g) in
cold 10% sodium hydroxide solution (50 ml). The whole mixture was
cooled to 0–3◦C. Coupling takes place readily and the dyestuff sep-
arates as a paste. The whole mixture was stirred well for 10 min
and warmed until the paste was dissolved completely, and concen-
trated sodium chloride solution (20 ml) was added to that mixture.
The solution was allowed to cool spontaneously for 1 h in air and
then was cooled in an ice bath until complete precipitation of the
product occured. The salt was collected by filtration, washed with
a little saturated sodium chloride solution and dried at 80◦C. Acid-
ification of aqueous solution of the salt gave the pure 4-bromro-
2,3dioxbuteranilide 2-sulphoaryl hydrazone derivatives (IIIa–e) as yel-
lowish white to yellow colored crystals which were recrystallized from
ethanol in good yield. Physical properties of the isolated 4-bromo-2,3-
dioxobutyramide 2-sulphoaryl hydrazone derivatives (IIIa–e) are listed
in Table I.
The IR spectrum (ν-/ cm−1) of compound (IIIa), as a representative
example for this series, showed characteristic bands at: 3360 (OH of sul-
phonic acid moiety), 3230, 3095 (amide and hydrazone NH), 1680 (cyclic
amide I band), 1635 (acyclic amide I band), 1630 (bromoacetyl CO), 1600
(C C of phenyl ring), 1525 (amide II band), and 1345, 1155 (asymmetric
and symmetric stretching vibrations of sulphonic acid moiety).
The 1H-NMR spectrum (CDCl3/δ in ppm) of the same compound re-
vealed signals at: 13.40 (broad hump, 1H, NH of hydrazone moiety),
12.35 (broad, 1H, SO3H proton), 8.10–7.65 (multiplet, 7H, aromatic pro-
tons), 5.80 (broad hump, 3H, amidic NH protons), and 4.75 (singlet, 2H,
bromoacetyl protons).
Synthesis of 4-Hydroxy-1-sulphoarylpyrazole 3-[N(2ꢀ-
oxo-benzimidazol-5ꢀ-yl)]carboxamide Derivatives (IVa–e)
To a mixture of III (0.003 mmol in each case) in n-propanol (15 ml)
was added sodium acetate trihydrate (1.5 g) in water (20 ml), and the
mixture was refluxed for 3 h and left to cool. During the reflux time, the

1212

Tartrazine Dye Analogues
1213
color of the reaction mixture changed from yellow to brownish green.
The colored solid that separated was collected, washed several times
with water, and finally recrystallized from ethanol or acetic acid to give
the pure product (69–81%). Physical data of the isolated 4-hydroxy-
1-sulphoarylpyrazole 3-carboxamide derivatives (IVa–e) are listed in
Table II.
The IR spectrum (ν/ cm−1) of compound (IVa), as a representa-
tive example for this series, revealed characteristic bands at: 3355
(OH of sulphonic acid function), 3325 (enolic OH function), 3195
(amidic NH), 1675 (cyclic amide I band), 1650 (acyclic amide I
band), 1615 (C N),1595 (C C), 1530 (amide II band), and 1350, 1145
(asymmetric and symmetric stretching vibrations of sulphonic acid
moiety).
Synthesis of 4-Hydroxy-1-sulphoaryl-5-sulphoarylazo-
pyrazole 3-[N-(2ꢀ-oxo-benzimidazol-5ꢀ-yl)]carboxamide
Derivatives V–IX(a–e)
An aryl sulphonic acid derivative (0.03 mmol in each case), was dis-
solved with stirring in sodium hydroxide solution (100 ml, 0.03 M). To
this solution was added sodium nitrite solution (7.5 ml, 4 M), and the
whole mixture was slowly poured into a mixture of hydrochloric acid (12
ml, 30%) and ice (50 g) and kept stirred for 3 h at 0–5◦C. The produced
diazonium salt solution was added slowly (over 30 min), with stirring,
to a mixture of the 4-hydroxy-1-sulphophenylpyrazole derivative (IVa)
(0.03 mmol) and sodium carbonate (6.5 g) in water (140 ml) and left with
continuous stirring for further 3 h. The precipitated solid material was
collected by filtration, washed several times with concentrated sodium
chloride solution, filtered off, and allowed to dry in air. Acidification with
dilute acetic acid afforded the crude product which was recrystallized
from acetic acid to give highly colored crystals of the required dyestuffs
Va–e in high yield. Similarly, the other four series of 5-sulphoarylazo-
1-sulphoaryl pyrazole derivatives were prepared. These dyes together
with their physical data are listed in Tables III–VII.
The IR spectrum of compound Va (ν-/cm−1), as a representative ex-
ample for these dyes, showed characteristic bands at: 1680 (cyclic amide
I band), 1635 (acyclic amide I band), 1530 (amide II band), 1455 (N N
azo function), 1340 and 1150 (asymmetric and symmetric stretching
vibrations of SO3H group).
1
The H-NMR spectrum (CDCl3/δ in ppm) of compound Vc revealed
signals at: 5.75 (broad hump, 3H, amidic NH protons), 8.20–7.10 (mul-
tiplet, 11 H, aromatic protons), 9.45 (broad, 1H, enolic OH), and 12.50
(broad, 2H, of the two sulphonic acid mieties).

1214

1215

1216

1217

1218

1219

1220
M. A. Hanna et al.
RESULTS AND DISCUSSION
Synthesis of the prepared sulphoarylazo dyestuffs was accomplished
according to the sequence of reactions that are given in Scheme 1. Ace-
toacetanilides were reported3 to show the carbonyl bands near 1725 and
1660 cm−1. These bands were assigned to the acetyl and amidic carbonyl
groups respectively. By analogy, the strong band at 1765 cm−1 in the IR
spectrum of the hitherto prepared amide derivative II is assigned to the
carbonyl group of the bromoacetyl function, whereas, the band at 1680
and 1645 cm−1 are assigned to the cyclic and acyclic amide I bands.
The higher frequency of the CO stretching vibrations of compound II as
compared to that of acetoacetanilide might be attributed to the induc-
tive effect of the bromine atom. The appearance of the ketonic CO band
as well as the absence of any enolic OH stretching vibrations indicate
that 4-bromo-N-(2ꢁ-oxobenzimidazol-5ꢁ-yl)-3-oxobutyramide (II), under
the condition of measurements, exists almost entirely in the keto form.
This is also substantiated from its 1H-NMR spectrum where the signals
due to vinylic OH and CH protons were not observed.
The produced 4-bromo-3-oxobutyranilide (II) reacted with diazo-
tized sulpho-aryl amines to yield the corresponding 4-bromo-2,3-
dioxobutyramide 2-sulphoarylhydrazone derivatives (IIIa–e) in an
overall good yield. Each of these products exhibited a strong band in
the region of 1595–1610 cm−1 which was assigned to the skeletal C C
in plane vibrations of phenyl moieties.9
Solid 2,3-dioxobutyranilide 2-sulphophenyl hydrazone and ethyl 2,3-
dioxobutyrate 2-sulphophenylhydrazone were found to exhibit their
acetyl CO stretching near 1623 and 1620 cm−1 respectively.10 As to
the diazonium coupling products in this study, each exhibits three CO
bands: two strong bands near 1680 abd 1635 and a relatively weak
one near 1630 cm−1. These were assigned to the cyclic, acyclic amide,
and bromoacetyl carbonyl functions, respectively, in agreement with
those reported for 2,3-dioxobutyranilide-2-phenylhydrazone.10 The ex-
tremely low value of 1630 cm−1 for the bromoacetyl CO indicates the
presence of α,β-unsaturation. It also indicates that the acetyl CO group
of such coupling product is hydrogen bonded, since the value of 1630
cm−1 is still lower than the normal conjugated carbonyl compounds.
Both factors, conjugation with C C or C N and intramolecular hydro-
gen bonding, were reported to diminish considerably the force constant
of CO groups.11 Such IR data eliminate the possibility of the presence
of compounds IIIa–e in the azo forms. However, it highly substantiate
the hydrazone structure for such products.
Furthermore, the spectra of compounds (IIIa–e), show strong and
well defined absorption bands near 1345 and 1155 cm−1 (for asymmetric

Tartrazine Dye Analogues
1221
SCHEME 1 Ar & Arꢁ = Sulphoaryl moieties (For Ar & Arꢁ see Tables I–VII).

1222
M. A. Hanna et al.
and symmetric stretching vibrations of sulphonic acid moiety). More-
over the spectra revealed a strong band near 1560 cm−1, which was
not observed in the spectrum of the parent 4-bromo-3-oxobutyramide.
Though probably it represents an aromatic ring absorption, the 1560
cm−1 band was assigned to the C N double bond. The fact that the
latter does sometimes fall below 1600 cm−1 has been reported12 previ-
ously. The low frequency position for the C N bands of the compound
(IIa–e), may be attributed to its conjugation with CO group.13
Refluxing ethanolic solution of 4-bromo-2,3-dioxo-N-(2ꢁ-oxobenzi-
midazol-5ꢁ-yl)butyramide-2-sulphoaryl hydrazone (IIIa–e) in pres-
ence of sodium acetate, afforded the pure crystalline 4-hydroxy-
1-sulphoaryl-3-[N-(2ꢁ-oxobenzimidazol-5ꢁyl)] carboxamide pyrazole
derivatives (IVa–e) (Scheme 1).
The IR spectra of compounds (IV) in potassium bromide possessed an
absorption band typical of a sulphonic OH function near 3355 cm−1 and
an intra-molecularly bonded enolic OH near 3325 cm−1. This suggests
that the cyclized products exist in the hydroxy form rather than in the
tautomeric keto structure.
The assignment of the hydroxy structure is further substantiated
by the fact that each of the compounds IVa–e shows two absorption
bands near 1675 and 1650 cm−1, typical of cyclic and acyclic amidic CO
functions respectively. As for the 4-oxo structure, if it were present one
would expect to find, in the spectra of such compound, three CO absorp-
tion bands corresponding to the cyclic, acyclic amide, and ketonic CO
groups. In no case could the keto CO band be identified. The complete
absence of a cyclic ketonic CO band apparently is compatible with the
hydroxy structure.
1
The H-NMR spectral data, in deutereochloroform, are consistent
with the assigned 4-hydroxy form of the prepared compounds IVa–e. For
1
example the H-NMR spectra of compound (IVa) in CDCl3 showed no
signal due to the methylene proton resonance of the keto structure. This
1
result finds support from the previously reported work,14 on the H-
NMR spectra of 1-p-tolyl-2-pyrazolin-4-one-3-carboxanilide derivative
in trifluoro-acetic acid (TFA) which is known to favor the keto form. The
latter spectra revealed two signals at δ = 8.30 and δ = 2.30, assignable
to vinylic C CH and methylene CH2 proton at C5 of the hydroxy and
the keto forms, respectively. On the basis of their integrated areas, the
percentage of the hydroxy form was calculated to be 75%.
Treatment of the pyrazole derivatives IVa–e with sulphoaryl di-
azonium salts in alkaline medium afforded the corresponding 5-
sulphoarylazo derivatives. The resulting coupling products V–IX(a–e)
can exist in three tautomeric forms: the azo-keto form (A), the hydrazo-
keto form (B) and the hydroxy-azo form (C) (Scheme 2). In the present

Tartrazine Dye Analogues
1223
SCHEME 2
investigation, the latter hydroxy-azo tautomeric structure (C) has been
found to represent the actual structure of these compounds. The spec-
tral evidence on which such a conclusion is based involved IR and
1H-NMR spectra.
Concerning IR spectra, it has been showed that 3-carboxy deriva-
tives of 4-arylazo-2-pyrazolin-5-ones have the hydrazone struc-
ture. For example, 1-phenyl-3-methoxycarbonyl-4-phenylhydrazono-2-
pyrazolin-5-one derivative (VI) exhibits two carbonyl absorption bands
at 1735 and 1665 cm−1. These were assigned to the ester and lactam
CO groups respectively.15
In our case, the carbonyl region of IR spectra of each of the prepared
dyestuffs (V–IX), however, revealed only two sharp and well defined
carbonyl peaks near 1680 5 and 1635 cm−1. If the hydrazo-keto form
(B) represented the actual structure of these coupling products, one

1224
M. A. Hanna et al.
would expect three carbonyl bands to appear, the absence of acyclic
ketonic band in this region thus exclude the possibility of structures of
type A or B.
In the spectra of each of the examined 4-pyrazolone dyestuffs (V–
IX), two other absorption bands were noted, one intense band in the
region 1530 cm−1 and the second in the region of 1460-1440 cm−1. As
the former band was observed in the spectra of both 1-sulphoaryl-4-
hydroxypyrazole-3-carboxamides (IVa–e) and the coupling products of
4-bromo-3-oxobutyramides (IIIa–e), it was not assigned to an azo, but
to the amidic group (amide II band) which is common in all the three
series of compounds. Such an assignment is reinforced by the fact that
in the spectra of 1,3-diphenyl-4-ethyl-4-arylazo-2-pyrazolin-5-one (VII),
which does contain an azo group,16 the band near 1530 cm−1 definitely
vanished in the solid state and in chloroform solution. On the other
hand, amides are known to exhibit their CONH band (amide II) in the
region 1570–1555 cm−1 regions.17
Regarding the 1460-1440 cm−1 band, it was absent in the spectra
of both the parent 4-pyrazolones (IVa–e) and in the coupling prod-
ucts of 4-bromo-3-oxobutyranilide IIIa–e. It was therefore assigned to
an azo group. Since the coupling products of 5-pyrazolone, which are
known to exist in the hydrazone form, do not exhibit such a band, it
is not unreasonable to conclude, therefore, that the hitherto prepared
4-sulphoarylazo-pyrazolone dyestuffs do exist in the azo forms (A or C).
As the 1H-NMR spectrum provides strong evidence against the presence
of methine (CH) proton, it would not be unreasonable to exclude struc-
ture (A). This elimination is compatible with the absence of a ketonic CO
band. In consequence the tautomeric structure (C) of 5-sulphoarylazo
derivatives of the 4-hydroxy-1-sulphoarylpyrazole 3-carboxamides,
under investigation, is the only one which accommodates these IR
observations.

Tartrazine Dye Analogues
1225
The1H-NMR spectra of the prepared dyestuffs in CDCl3, showed the
usual phenyl pattern, a multiplet at δ 7.10–8.20 and two broad acidic
proton peaks at δ 9.40 0.20 and at δ 12.30 0.30, assignable to an in-
tramolecularly hydrogen bonded hydroxy proton and the acidic protons
of sulphonic acid moieties in these compounds. Another small hump
near δ 5.70 0.20 was observed in the spectra and was attributed to the
amidic NH protons. Judging from these results, it could be concluded
that the diazonium coupling products (V–IX) exist predominantly in
hydroxy-azo form.
DYEING PERFORMANCE
The degree of exhaustion of the hitherto synthesized 3-[2-(oxoimidazo-
5-yl) carboxamido] tartrazine dye analogues was determined colorimet-
rically and found to be in the range of 92.6–97.8%. The latter high ratios
might be ascribed to the presence of the cyclic amide function in struc-
ture of these dyestuffs.
The importance of the cyclic amide function might be explained on
the basis of the fact that in the process of bonding of the dye with the
FIGURE 1 Tartrazine Dye Analogues.

1226
M. A. Hanna et al.
fiber, two different bonds via NH or oxygen moieties play a significant
role. They probably form the dimers of the dye as well as dye-fiber bonds.
A highly probable mode of binding with cellulose molecules of the
fiber comprises the formation of a dimer by one of the NH groups, while
the second NH group shared in the formation of the bond between the
dimer and cellulose fiber (Figure 1). Such a proposition makes it pos-
sible to explain the particularly good affinity of these dyestuffs to the
fiber, which ensures an uninterrupted interaction of the two NH groups,
forming various types of association. Further binding of the previously
mentioned dimers might be ascribed to the presence of the hydroxy
azo moiety in these dyestuffs (Figure 1). The behavior of the hitherto
prepared dyestuffs (V–IX) toward cellulosic fibers finds support from
previous reports in literature.18
Assessment of the dyeing performance together with evaluation of
the percentage reflectance of the dyed fiber, at different wavelengths
in the visible region, and application of Kubelka-Munk equation for
calculation of K/S function of the dyed materials are, for the time being,
under investigation and will be published separately.
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[6] J. Kraska and K. Blus, Dyes and Pigments, 5, 415 (1984).
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