Synthesis of Some Azo Disperse Dyes from 1-Substituted 2-Hydroxy-6-pyridone Derivatives and Their Colour Assessment on Polyester Fabric

doi:10.4236/ojapps.2012.21006

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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

Email: [email protected]

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.

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

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.

CNCH

COOC

+ CH

COCH

COOC

(1) (2)

+ RNH

Ethanol

reflux

(3) N

HCl/NaNO

0-5

XN+Cl-

(5) (6)

6 + 40-5oC

XN N

(7 - 9)

R (a) = - H

(b) = - CH

X(a) = - H

(b) = - SO

(d) = - CH

(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.

XXN

(A) (B)

(C)

-O

+ H

-H

(K-2)

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)

ethanol + HCl

λmax (nm)

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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