Open Journal of Applied Sciences, 2012, 2, 54-59
doi:10.4236/ojapps.2012.21006 Published Online March 2012 (http://www.SciRP.org/journal/ojapps)
Synthesis of Some Azo Disperse Dyes from 1-Substituted
2-Hydroxy-6-pyridone Derivatives and Their Colour
Assessment on Polyester Fabric
Kurenkaka Johnson Sakoma, Kasali Ademola Bello, Mohammed Kabir Yakubu
Department of Textile Science and Technology, Ahmadu Bello University, Zaria, Nigeria
Received January 3, 2012; revised February 1, 2012; accepted February 15, 2012
ABSTRACT
The synthesis of a series of 3-(p-substituted phenylazo)-6-pyridone dyes which is suitable for the dyeing of polyester
fabrics, is described. Visible absorption spectra of the dyes were examined in various solvents and the compounds in
solution exhibited hydrazone-common anion equilibrium. The electronic absorption spectra cover a λmax range of 404 -
464 nm in DMF at uniformly high absorption intensity between 5.33 × 104 - 8.55 × 104 l·mol–1·cm–1 and gave bright
intense hues of yellow to orange on polyester fabrics. The colour parameters of the dyed fabrics were measured and the
dyes have excellent exhaustion between 72% - 79% for polyester fabrics, more intense and of very good fastness prop-
erties on polyester fabrics. The remarkable degree of levelness and brightness after washing is indicative of good pene-
tration and excellent affinity of these dyes for the polyester fabric.
Keywords: Pyridone; Disperse Dye; Exhaustion; Carrier; Polyester; Fastness
1. Introduction
Pyridone derivatives are relatively recent heterocyclic
intermediates for the preparation of dyes. The azo pyri-
done dyes give bright hues and are therefore of investiga-
tive interest. In our previous investigations, we reported
the use of pyridone as an active methylene compounds for
the production of methine dyes [1-5]. In this paper some
3-(p-substituted phenylazo)-6-pyridone dyes were pre-
pared by coupling the diazonium salts of p-substituted
phenylamines with a 1-substituted 2-hydroxy-4-methyl-
5-cyano-6-pyridone coupling components. The spectral
characteristics of the dyes and also a colorimetric evalua-
tion of the dyes on polyester fabrics were investigated in
order to examine the influence of substituent on the
colour of the prepared dyes.
2. Materials and Methods
2.1. General Information
All the chemicals used in the synthesis of the dyes and
intermediates were of analytical grade and were used
without purification. Melting points were determined by
the open capillary method. The visible absorption spectra
were measured using HEX10SY UV-visible spectropho-
tometer. IR spectra were recorded on a Nicolet FTIR-100
Thermoelectron spectrophotometer and the Mass spectra
were determined on an Agilent 6890 Mass spectrometer.
2.2. Synthesis of 3-Cyano-4-methyl-6-hydroxyl-
1-amino-2-pyridone (4a)
A mixture of ethyl acetoacetate (65.07 g, 0.5 mol), ethyl
cyanoacetate (56.56 g, 0.5 mol), ethanol (50 ml) and
ammonia (70 ml, 0.5 mol) was stirred and refluxed until
the reaction was completed (about 7 - 8 h). During the
reaction, the white product precipitated. The crude prod-
uct was filtered, dried and recrystallised from ethanol to
give white crystals (91%), m.p. 303.1˚C (P+ at m/e 150).
2.3. Synthesis of 3-Cyano-4-methyl-6-hydroxyl-
1-methyl-2-pyridone (4b)
The pyridone (4b) was prepared in a manner similar to 4a,
except methylamine was used instead of ammonia, and
after completion of the reaction, the alcohol was removed
by evaporation and the viscous residue poured slowly
into ice-cold 10% aqueous hydrochloric acid (600 ml) to
precipitate the product. The crude product was recrystal-
lised from ethanol as white crystals (86%), m.p. 296.5˚C
(P+ at m/e 164).
2.4. Synthesis of 3-Cyano-4-methyl-6-hydroxyl-
1-ethyl-2-pyridone (4c)
Compound 4c was prepared in a similar manner to that
described above for 4b, except ethylamine was used in-
stead of methylamine, and was recystallised from ethanol

K. J. SAKOMA ET AL. 55
as white crystals (90%), m.p 178˚C (P+ at m/e 177).
2.5. Synthesis of 3-Phenylazo-2-hydroxy-4-
methyl-5-cyano-6-pyridone (7a)
Aniline (9.3 ml, 0.1 mol) was dissolved in aqueous hy-
drochloric acid (26.7 m, 0.3 mol), the solution was cooled
with stirring to 0˚C - 5˚C and sodium nitrite (7.04 g, 0.102
mol) was added to it. The mixture was stirred for 40 - 45
min at 0˚C - 5˚C and excess nitrous acid was destroyed by
the addition of urea. The clear diazonium salt solution
was slowly poured into a solution of 2-hydroxy-4-methyl-
5-cyano-6-pyridone (15 g, 0.1 mol) in water-acetone (1:1,
300 ml), keeping the pH at 3 - 4, and the liquor was stirred
for 4 - 5 h at 0˚C - 5˚C. The yellow dye was filtered off,
washed with water, dried and recrystallised from acetone
to yield yellow crystals. Yield, melting point and appea-
rance of the crystals are summarized in Table 1.
The other dyes 7b, 8 and 9 were prepared in a similar
manner to that described for 7a. Absorption spectra, IR
are summarized in Table 1 and Table 2.
2.6. Dyeing and Fastness Properties Measurement
The dye baths were prepared from the dye (1.0% weight
of fibre) with a dispersol-levelling agent (1 g·litre–1) and
5% phenol as carrier to a final liquor of 30:1, w/w. The
pH value of the bath was adjusted to 4 - 5 with acetic
acid (10%). The polyester fabrics, previously wetted,
were placed into the liquor at 25˚C - 30˚C. The tempera-
ture was raised to 100˚C at the rate of 2˚C/min, and dye-
ing continued for 60 min. After cooling, the dyed fabrics
were reduction cleared in sodium hydroxide (6 g·litre–1),
soap (1 g·litre–1) and hydrosulphite (2 g·litre–1) at 75˚C
and then washed and dried. The percentage exhaustion
was determined by the usual method [6], washfastness
and lightfastness were determined by the standard pro-
cedure [7]. The results are summarized in Table 4.
3. Results and Discussion
3.1. Synthesis of Dyes and Intermediates
1-Substituted-2-hydroxy-4-methyl-5-cyano-6-pyridones
(4a - 4c) were prepared from a mixture of ethyl cyanoace-
tate (1), ethyl acetoacetate (2) and amines (3a - 3c) in etha-
nol under reflux. The p-substituted anilines (5a - 5f) were
diazotized using hydrochloric acid and sodium nitrite at
0˚C - 5˚C and the diazonium salts (6a - 6f) were coupled
with pyridone compounds (4a - 4c) at pH 3 - 4 to give the
1-substituted 3-(p-substituted phenylazo)-6-pyridone dyes
(7 - 9). The dyes were purified by recrystallisation from
acetone and their purity examined by thin-layer chroma-
tography. The structures of the pyridones were confirmed
by mass spectrometry and IR while the structures of the
dyes were confirmed by IR. The physical characteristics of
the dyes are summarized in Table 1.
3.2. Infrared Spectra of the Dyes
As can be seen from the infra-red spectra results in Table
2, all the dyes gave absorption peaks due to azo group,
N=N stretching vibration at 1428 - 1376 cm–1; aromatic
C-H stretching vibration bands appeared in the region of
2953 - 2923 cm–1; aromatic C-H bending vibration bands
appeared in the region of 892 - 721 cm–1; C≡N stretching
vibration bands appeared in the region of 2260 - 2220
cm–1; C=C stretching vibration band appeared in the re-
gion of 1675 - 1600 cm–1; C=O stretching vibration bands
appeared in the region of 1850 - 1550 cm–1; C-H stretch-
ing vibration bands appeared in the region of 1292 - 757
cm–1, N-H stretching vibration bands appeared in the re-
gion of 3443 - 2953 cm–1; N-H bending vibration bands
appeared in the region of 1631 - 1513 cm–1; O-H stretch-
ing vibration bands appeared in the region of 3520 - 3139
cm–1; OH bending vibration bands appeared in the region
f 1498 - 1457 cm–1; C-Cl stretching vibration appeared in o
Table 1. Physical characteristics of the dyes.
Dye No Molar Mass M. Pt ˚C Wt of Dye (g) % Yield Colour of Crystals
7a 255 200-203 1.12 60.83 Yellow
7b 335 198-201 2.27 74.62 Deep yellow
7d 285 158-161 1.71 62.33 Orange
7e 289 218-221 1.79 64.68 Light yellow
7f 271 207-210 2.01 75.57 Orange
8a 270 199-201 0.79 42.03 Yellow
8b 359 158-160 2.83 90.46 Deep yellow
8c 314 158-160 1.49 74.03 Light yellow
8d 300 143-145 2.34 82.54 Orange
8e 304 172-173 1.86 65.05 Light yellow
8f 286 178-180 0.99 35.88 Orange
9a 284 116-117 0.87 45.54 Yellow
9b 364 159-161 1.96 60.84 Deep yellow
9c 328 195-198 1.68 82.07 Light yellow
9d 314 119-120 2.79 95.71 Orange
9f 300 157-160 1.35 47.76 Orange
9e 318 160-162 1.50 50.75 Light yellow

K. J. SAKOMA ET AL.
56
Fun c ti on
group
Azo
N=N
Ar om a t ic
C-H
Ar om a t ic
C-H C≡NC=CC=O Aliphatic
C-H C-HN-HN-H COOHC-ClC-So
3
HO-H O-H
Typeof
vibrati on
Stretching
vibration
Stretching
vibration BendingStretching Stretching StretchingBendingStretching Stretching Bending Stretching Stretching Stretching Stretching Bending
DYE
NO. ---------------
7a1377 29237232220 1663 16312853 75731271543--33781465
7b1377 29238882224 1603 169028531275-1518--1222 34321457
7c1428 29238532231 1670 158228531292344315823210 2359-35201465
7d1399 29248922222 1649 160328531246 31391513---31391460
7e1383 29238252223 1672 16352852825-1534-2358-33901465
8a1376 29247662231 1643 158828531276-1588-2362-34101459
8b1377 29537212231 1645 159028531277----1223-1465
8c13782924852223116171721285312293214 1520 3210---1458
8d1377 29548192220 1628 157628531257-1576----1462
8e1377 29257212231 1635 167628531272-1585-2231--1464
8f1402 29548192221 1631 167528531219 29531631----1498
9a1377 29248782223 1672 162928531277-1576----1462
9b1376 29238242224 1671 162828531281-1522--1223-1465
9c1376 29238242224 1642 163528531281-15223210---1465
9d1377 29238342222 1628 163028531249-1515----1459
9e1378 29238772229 1675 163528531276-1584-2361-34201464
9f1376 29247212223 1654 162428531272 29541624----1462
Table 2. Infra-red spectra for the dyes.

K. J. SAKOMA ET AL.
57
CNCH
2
COOC
2
H
5
+ CH
3
COCH
2
COOC
2
H
5
(1) (2)
+ RNH
2
Ethanol
reflux
(3) N
CH
3
C
N
O
R
HO
4
NH
2
HCl/NaNO
2
0-5
oC
XN+Cl-
N
X
(5) (6)
6 + 40-5oC
XN N
R
O
CN
CH
3
N HO
(7 - 9)
R (a) = - H
(b) = - CH
3
(c) = - C
2
H
5
X(a) = - H
(b) = - SO
3
H
(c) = - COOH
(d) = - CH
3
O
(e) = - Cl
(f) = - OH
˚C
0 - 5˚C
Scheme 1. Synthetic route for intermediates and dye s.
the region 2363 - 2231 cm–1; COOH and C-SO3H stretch-
ing vibration bands appeared at the peak of 3210 cm–1 and
1222 cm–1 respectively.
The dyes may exist in two tautomeric forms, namely
the azohydroxypyridone form A and the diketohydrazone
form B. The deprotonation of the two tautomers leads to
a common anion C, as shown in Scheme 2.
The infrared spectra of all the compounds (in KBr)
showed two intense carbonyl bands at 1700 and 1600 cm–1;
intensities of the two bands were very similar, and the lat-
ter band is related to intramolecularly hydrogen-bonded
carbonyl. It was therefore assigned to the diketohydrazone
form B. In the infrared spectra of the compounds in CHCl3,
two carbonyl bands were also observed, with the 1600
cm–1 band having lower intensity. This suggests that the
dyes exits in the hydrazone form in the solid state and
predominantly in the hydrazone form in CHCl3. These
conclusions are in accord with those of Ertan [8] and
Cheng [9].
3.3. Visible Absorption Spectra of the Dyes
Visible absorption maxima of the dyes in various sol-
vents are given in Table 3. The visible absorption spectra
of the dyes were found to exhibit a strong solvent de-
pendence which did not show a regular variation with the
dielectric constants of the solvent. It was observed that in
DMF, ethanol and ethanol plus a drop of HCl the absorp-
tion spectra of the dyes did not change significantly. λmax
of the dyes shifted considerably in acetone for example
dye 7a, λmax is 404.0 nm in DMF and 467.0 nm in ace-
tone. The absorption maxima of most of the dyes also
showed bathochromic shifts when a small amount of HCl
was added to dye solutions in ethanol. A typical example
is 7d with λmax of 400.00 nm in ethanol and 459.50 when
a drop of HCl was added to the solution in ethanol.
Dye 7a was obtained by diazotising aniline and coupling
to 3-cyano-4-methyl-6-hydroxy-2-pyridone and absorbed
at 467.0 nm in acetone and when sulphonic acid group was
introduced into para-position of the diazo component (ani-
line) the resulting dye 7b absorbed at 460.0 nm in the same
solvent and thus the dye 7b was hypsochromic by 7 nm
when compared with dye 7a. Replacement of the sul-
phonic acid group in dye 7b by carboxylic group gave dye
7c which absorbed at 468.0 nm and showed a bathochro-
mic shift of 8 nm and 1 nm respectively when compared
with dye 7b and 7a. Substitution of methoxy group into the
para-position of aniline gave dye 7d with maximum ab-
sorption wavelength of 445.0 nm in the same solvent. This
is highly hypsochromic when compared with all the other
dyes in this series. This may be due to the fact that meth-
oxy group is an electron donating group compared with all
the other substituents that are electron withdrawing groups.
Replacement of the methoxy group by chlorine gave dye
7e with λmax of 480.0 nm in acetone and this is bathochro-
mic when compared with dyes 7a - 7d with enhanced ex-
tinction coefficient. Dye 7f was obtained by replacing the
chlorine group in dye 7e by the hydroxyl group with λmax
of 502.0 nm in the same solvent. When methyl group was

K. J. SAKOMA ET AL.
58
N
CH
3
CN
O
R
N
N
XXN
N
R
O
CN
CH
3
N
K1
O
H
O
H
(A) (B)
(C)
O
XN
N
R
O
CN
CH
3
N
-O
N
CH
3
CN
O
R
N
N
_ X
K
2
K
3
+ H
+
-H
+
(K-2)
1
Scheme 2. Hydrazone-common anion equilibrium.
Table 3. The UV Spectroscopic properties of dyes.
Dye No.
εmax in
acetone x
104 lmol1cm–1
Acetone
λmax (nm)
Dimethylformamide
λmax (nm)
Ethanol
λmax (nm)
a
ethanol + HCl
λmax (nm)
b
Change in
λmax (nm)
(b-a)
7a 5.57 467.0 404.00 433.50 433.00 –0.5
7b 5.33 460.0 439.50 460.00 400.00 –60.0
7c 5.50 468.0 414.00 431.00 434.50 +3.5
7d 4.98 445.0 447.50 400.00 459.50 +59.50
7e 6.65 480.0 412.50 459.00 436.00 –23.0
7f 6.64 502.0 434.50 458.50 462.50 +4.0
8a 6.52 472.0 412.50 429.50 434.50 +5.0
8b 6.13 479.0 420.00 436.50 433.00 –3.5
8c 6.07 473.0 428.50 438.50 433.50 –5.0
8d 6.16 536.0 453.00 423.50 430.50 +7.0
8e 6.76 472.0 412.50 432.00 462.00 +30.0
8f 5.56 531.0 464.00 458.50 457.50 –1.0
9a 6.93 452.0 410.00 454.50 432.50 –22.0
9b 8.55 470.0 418.00 458.00 415.50 –42.5
9c 7.90 499.0 433.50 438.00 432.50 –5.5
9d 7.85 510.0 414.00 434.00 444.00 +10.0
9e 7.24 480.0 417.50 438.00 476.00 +38.0
9f 7.11 493.0 460.00 438.00 458.00 +20.0
introduced into the coupling component to produce 3-
cyano-4-methyl-6-hydroxyl-1-methyl-2-pyridone (4b) and
then coupled to aniline and substituted anilines, this gave
dyes in series 8. The introduction of the various substituent
groups gave slight changes in the visible absorption wave-
length. With the exception of dyes 8d and 8f which ab-
sorbed at 536 nm and 531 nm that are highly bathochro-
mic when compared with all the dyes in series 7 and 8.
When the alkyl chain length was increased by replac-
ing the methy group by ethyl group to give 3-cyano-4-
methyl-6-hydroxyl-1-ethyl-2-pyridone 4c and then cou-
pled to aniline and substituted anilines, this gave dyes in
series 9. From the results summarized in Table 3, the
introduction of different substituent into the coupling
component did not show any specific pattern in the visi-
ble absorption spectra. Similarly, the introduction of dif-
ferent substituent into the diazo component did not fol-
low a specific pattern.
The effects of solvent polarity on the visible absorp-
tion spectra were also studied and from the results sum-
marized in Table 3, there is no specific pattern in the
results. For example, dye 7a absorbed at 467.0 nm in
acetone and gave λmax of 404.0 nm in DMF which is
hypsochromic by 63 nm. Most of the dyes showed nega-
tive solvatochromism when the solvent was changed to
more polar solvents. Similarly, the effects of few drops

K. J. SAKOMA ET AL. 59
of HCl on ethanolic solution of the dyes showed positive
and negative halocromism as can be seen in the results
summarized in Table 3. This means that the dyes can be
used as indicator in acid-base titration. The extinction
coefficients of the dyes are very high, ranging from 4.98
× 104 - 7.90 × 104 lmol–1cm–1 which are very good for
textile application.
3.4. Dyeing and Fastness Properties
The dyes were applied to polyester fabric using carrier
dyeing method and the wash fastness property was ex-
amined using I.S.O. 3 procedure. The results of the wash
fastness rating are summarized in Table 4. The dyes
gave very good levelness and fibre penetration on poly-
ester. The exhaustion was good ranging from 73% - 79%
and the wash fastness rating is very good with rating of 4
and 5 in most cases. The staining of the adjacent white
fabric is also limited with rating of 4 - 5 indicating slight
staining in most cases. The excellent wash fastness ob-
tained on polyester is due to the crystalline structure of
the polyester which disallowed the migration of dye out
of the fabric when this has entered the fabric. The light
fastness of the dyes is similarly studied and the results
are summarized in Table 4. From these results the light
fastness are good with rating of 5 in all cases. This is also
good for commercial applications.
4. Conclusion
The synthesize of azo-disperse dyes based on pyridone as
coupling component was undertaken. The relative mo-
Table 4. % Exhaustion and fastness proper tie s of the dye s.
Wash Fastness Rating
Dye No %
Exhaustion Change in
Shade
Staining of
White
Light Fastness
Rating
7a 74 5 4-5 5
7b 77 4 4-5 5
7d 76 4 4 5
7e 77 5 4-5 5
7f 72 4 4-5 5
8a 75 5 4-5 5
8b 79 4 4-5 5
8c 76 4 5 5
8d 73 4 4 5
8e 75 4 5 5
8f 75 4 4-5 5
9a 75 5 4 5
9b 75 4 4-5 5
9c 78 4 4-5 5
9d 74 5 4 5
9e 74 5 5 5
9f 74 4 4-5 5
lecular mass of 3-cyano-4-methyl-6-hydroxyl-1-methyl-
2-pyridone and 3-cyano-4-methyl-6-hydroxyl-1-ethyl-2-
pyridone were confirmed using mass spectrophotometer.
Generally, the exhaustion of the dyes was very good on
polyester fabric with excellent wash and light fastness
properties. These dyes, however, are noteworthy in their
excellent affinity and intensity of colour. Other outstand-
ing characteristics of these dyes are that they give deep
and bright hues with level dyeings. The bright hue might
be attributed to the greater planarity of the pyridone ring,
because of the lower steric interaction of a five mem-
bered ring. The remarkable degree of levelness and
brightness after washing is indicative of good penetration
and the excellent exhaustion of these dyes for the poly-
ester fabric due to the accumulation of polar groups.
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