This document discusses different types of azo dyes. It begins by defining azo dyes as dyes containing an azo (-N=N) group. Azo dyes are then classified into mono azo, bis azo, tris azo and poly azo dyes depending on the number of azo groups. Mono azo dyes containing one azo group are further classified based on their application. Bis azo dyes containing two azo groups are discussed and classified into four types based on their chemical structure. Examples of different types of azo dyes are provided along with brief descriptions of their synthesis.

1. AZO DYES
By
Dr. Dhaval Desai

2. WHAT IS AZO DYES??
The dyes containing azo group (-N=N) in chemical constitution
(nucleous) are known as azo dyes.

3. CLASSIFICATION OF AZO DYES
AZO DYES are further classified according to presence of azo group
(-N=N) in the chemical constitution.
A. Mono Azo Dyes
B. Bis (Dis) Azo Dyes
C. Tris Azo Dyes
D. Tetra Azo Dyes
E. Poly Azo dyes

4. A. Mono Azo Dyes
❖Mono Azo dyes containing one azo groups in its chemical
constitution known as Mono Azo dyes.
❖This class of dyes represented as A→E.
Where, A is the Diazonium component. E is the coupling components.
❖The Mono Azo Dyes could be with or without solubilizing group such
as –SO3H or –COOH group.

5. ❖ Mono Azo Dyes are further classified into the following classes
according to the application on the fibers.
1) Solvent Mono Azo Dyes
2) Pigment Mono Azo Dyes
3) Mordant Mono Azo Dyes
4) Basic (cationic) Mono Azo Dyes
5) Disperse Mono Azo Dyes
6) Reactive Mono Azo Dyes
7) Ingain Mono Azo Dyes

6. 1. Solvent Mono Azo Dyes
❖ A few mono azo dyes find used as a solvent dyes. This class of dyes
not having any solubilizing group.
Ex:- Solvent Red R or Sudan Red R CI-12155
❖ Sudan Red R is prepared by diazotization of cresidine and coupling
with β-Naphthol.
Cresidine → β-naphthol
CH3
O
N
O
H
N
C
H3

7. 2. Pigment Mono Azo Dye
❖ Certain insoluble mono azo dyes are used as pigment following are
the important example of this class.
Ex:-pigments orange 5 CI-12075
❖ 2,4-dinitro aniline → β-naphthol
N
O
H
N
C
H3
NO2

8. ❖ This dyes can not apply directly to the fiber but it require basic
mordant on the fiber.
❖ They are capable of forming complex metallic compound known as
lake.
❖ Mordant azo dyes are characteristics bye the presence of o-hydroxyl
group reactive to the azo linkage allowing metal complex formation.
❖ Importance of mordant dyes is due to there high fastness to light
and washing.
3. Mordant Mono Azo Dyes

9. 4. Basic Mono Azo Dyes
❖ Basic dyes have –NH2 or –NR2 group as the auxochromic group and
chromophore system is –N=N group.
❖ In general the light fastness & washing fastness is vey poor. Due to
these reason basic dyes is generally not used in textile industry.
Ex:- Aniline yellow
Aniline → Aniline
❖ It is used for coloring butter, oil and margarine.
N
N NH2

10. Ex:- chromo tope 2β
p-nitro Aniline → chronotropic acid
OH
OH
SO3H
HO3S
N
N
O2N

11. 5. Disperse Mono Azo Dyes
❖ Disperse Dyes is mainly used for imparting yellow to blue shade on
poly ester fiber. It is also used for natural fiber such as wool & silk.
❖ Disperse Mono Azo Dyes have simple structure and small molecular
size. Thus, it is easily pass into the fiber structure.
Ex:- Disperse Red 13 Or Cellition scanet β
❖ It is prepared diazotization of 2-chloro 4 nitro aniline and couple
with N-ethyl N-hydroxyl ethyl aniline.
NH2
O2N
Diazotization
NaNO2 + HCL
0o
- 5o
C
N
+
O2N N
NH2
NH2
2-chloro-4-nitro aniline
Dizodium salt

12. OH
C2H5
C2H5
N
Coupling with
N -ethyl N -hydroxy ethyl Aniline
OH
C2H5
C2H5
N
ith
ethyl Aniline
N
OH
C2H5
C2H5
N
N
O2N
Disperse Red 13

13. 6) Reactive Mono Azo Dyes
❖ Reactive Mono Azo Dyes having dichloro triazine reactive system.
Ex. Reactive Red B
Aniline H-acid Cyanuric chloride
alk Cond
0-5 °C
So3Na
So3Na
Cl
Cl
N
N
OH N
H
N
N
N

14. 7. Ingain Mono Azo Dyes
❖ These are water insoluble azo dyes which are formed on the fiber.
❖ They are prepare by dipping the fabric in alkaline solution of
coupling component and then immersing in a solution of diazotize
amine.
❖ The most important example of these group is Para Red.
Ex. p-nitro Aniline β-naphthol
N
N
OH
O2N

15. Soluble Mono Azo Dyes
❖ Some azo dyes easily soluble in water due to the presence of water
solubilizing group such as –SO3H and –COOH group.
❖ Following are the important soluble mono azo dyes.
1) Acid dyes
2) Mordant dyes
3) Direct dyes
4) Food color dyes

16. 1. Acid dyes
❖ This class of dyes containing acidic –So3H and –COOH group this
acidic group make the dyes more soluble and it is also used as the
reacting point for fixing the dyes.
❖ In acidic dyes the acidic group act as auxochrome.
❖ Following are the important example of this class.
No. Name of Dye Diazo component Coupler Structure
1. Orange-I Sulphonic Acid 1-Naphthol
2. Orange-II Sulphonic Acid 2-Naphthol
N
N
HO3S OH
N
N
OH
H
O 3S

17. 3. Orange-III
(Methyl Orange)
Sulphonic Acid Dimethyl Aniline
4. Orange-IV Sulphonic Acid Diphethyl Aniline
5. Methyl Red Anthranilic Acid Dimethyl Aniline
N
N
HO3S N(CH3)2
NH
N
N
HO3S
COOH
N
N
HO3S N(CH3)2
Ex. Acid Blue 92
❖ Acid blue 92 is a acidic mono dye. It is used for dyeing cotton and
wool.
❖ It is a prepared by diazotization of H-acid in presence of cold
solution of nitrous acid at low temperature and finally coupling with
N-phenyl peri acid and alkaline medium.
❖ H-acid N-Phenyl Peri Acid

18. H-Acid Diazonium salt
N
SO3H
HO3S
OH N NH
Coupling with N-Phenyl Peri Acid
NaOH
So3Na
HO3S
N
H
Acid Blue 92

19. 2. Mordant dyes
❖ There are also mordant dye containing soluble –SO3H group. They
have –OH group ortho to the azo linkage which is capable for forming
a complex with the mordant.
Ex. Mordant brown 13
2-amino phenol 4-sulphonic acid m-phenylene diamine
N
OH
N
HO3S
NH2
N
H2

20. 3. Direct dyes
❖ This class of dyes used directly for poteineous fiber link wool and silk
leather.
Ex. Acid violet – 1
2-Amino 5- nitro 1- sulphonic acid ϒ-Acid

21. 4. Azo food color
❖ Many azo food color dye which are permitted to used for addition to food
stuff tetrazine is the important example of food dyes.
Ex. Tetrazine
Sulfanilic acid 1-(p-sulphophenyl)-5-payrazolone-3-carboxylic acid
N
N
N
HO3S N N
SO3H
CooH

22. [B] Bisazo Dyes
❖ The dye which is containing two azo group in its chemical are known
as bis-azo dyes.
❖ A large number of azo dyes belong to this group. This method of
preparation are represented by symbol given below.
There are four such classes of bis azo dyes. Each class is assigned a
general formula as follows.
1) A Z A'
2) A M E
E
3) D
E’
4) A Z × Z’ A’

23. Where,
A = Diazo component
Z = Coupling component which can couples with two diazo component.
M = An aromatic amine which after coupling can be diazotized.
E = Coupling component which couples with one molecule of diazo
component.
D = it is an aryl diamine having two diazotize group.
Z×Z’= ‘X’ may be linkage –NH, -NH(CO)NH- other linkage, linkage two
coupling component.

24. 1. Bisazo dyes of the type A Z A'
❖ Most of the dyes in this group are acid and mordant dyes. Dyes of
the class are not vary popular due to their dull shades.
❖ Various coupling component (Z) can be used for the preparation of
this type of dyes. Such as resorcinol, m-phenylene diamine, H-acid, J-
acid, ϒ-acid.
Following are the example of these class.
Ex. Acid Black-I or Naphthol blue black
p-nitro aniline H-Acid Aniline
Acid black-I is dis azo dyes [A Z A’].
Acid Alk

25. ❖It is prepared by dizotization of p-nitro aniline couple with H-acid in
acidic medium. Mono azo dyes is from this mono azo dyes again used
as a coupler and couple with dizonium salt of aniline in alkaline
medium.
P- nitro aniline Diazonium salt
Coupling with H - acid
Acidic medium
O2N N N
NH2 OH
HO3S SO3H
Coupling with Diazonium
salt of Aniline Alkalic medium N
O2N N N
NH2 OH
HO3S SO3H
N
Acid Black-I

26. 2. Bisazo dyes of the type A M E
❖ In this class of dyes the middle component (M) involve on aryl amino
group which is capable of diazotization and further coupling with
suitable end component E.
❖ These are two types of middle component in used.
❖ In the first type on aryl amine used as M coupled with diazonium salt A,
giving a p-amino azo benzene type of dyes such as o-toluidine, aniline, o-
anisidine etc.
❖ The second type of M, has one phenolic group and also containing and
amino group, which after the first coupling can be diazotized and further
couple with an compound E.

27. Ex. Acid Blue 113 or Acid cynine Blue 52
Metanilic Acid 1-naphthyl amine N-phenyl peri acid
Acid blue 113 is a bisazo dye.
❖ It is a prepared by the diazotization of metanilic Acid in presence of
cold solution of nitrous acid low temperature.
❖ A p-amino azo benzene type diazo obtained, which is further
diazotized and coupling with N-phenyl peri acid in acidic medium.
Metanilic Acid Diazonium salt

28. HO3S
N N NH2
Coupling With
1 - naphthyl amino
(i) Diazotization
(ii) Coupling with N - Phenyl Peri Acid
HO3S
N N NH
SO3H
Acid Blue 113

29. 3. Bisazo dyes of the type
❖Many diazo compound having 2- Amino group are used. In such cases
the process of obtaining doubly diazonium group is known as Tetra
azotization.
❖Various aryl diamines (D) are used for the preparation of this class of
dyes.
❖Such as, Benzidine, m-Phenylene diamine, o-dianisidine etc.
❖There are many useful pigments, direct dyes and small number of
acid and mordant dyes are in this class.
❖Following are the important example of this class.

30. Ex:- Direct Blue 15 or Direct Sky Blue – 6B
H-Acid
O-Dianisidine
H-Acid
❖It is prepared by tetra azotization of o-dianisidine and coupling with
two moles of H-acid in alkaline medium.
O-Dianisidine

31. 2 mode coupling
with H - Acid
OH NH2
HO3S SO3H
N
CH3
C
H3
N
OH NH2
HO3S SO3H
N
O O
N
Direct Blue 15

32. 4. Bisazo dyes of the type A Z × Z’ A’
❖Almost, all members of this class of dyes belong to direct dyes.
❖"X" the linking bridge can be made by using a condensing agent like
phosgine and cynuric chloride.
❖This type of bisazo dyes prepared by two ways.
Method : 1
❖The phosgination of two mono azo dyes containing a free amino
group resulting in an urea derivative.
Method : 2
❖In this method J-acid urea is used as a coupling component which is
couple with two diazo component.

33. Ex:1 Direct yellow 49
m- amino benzoic Acid o-amsidine(2-mole)
❖It is prepared by phosgination of two monoazo dyes. Which is
prepared from meta amino benzoic acid and o-anisidine.
CH3
N
HOOC
N NH2
O
C
H3
N
H2
O
N
COOH
N

34. O
CH3
N
HOOC
N NH
O
C
H3
NH
O
N
COOH
N
-2HCL Phosgenation COCl2
Direct Yellow 49

35. Ex:2 Direct Red 23 or chlorazol Scarlet 4 BS
Aniline J-Acid urea p-Amino acetanilide
❖This is the example of bisazo dyes. Which is prepared from J - acid
urea.
OH
NH2
HO 3S
O
OH
SO3H
NH
OH
HO 3S
NH
Phosgenation
COCl2
-HCL
2-mole
J – acid urea
CH3
N
O
OH
SO3H
NH
OH
HO3S
NH
N N N NH
O
Direct Red 23
Coupling With Aniline & p-Amino acetanilide

36. THANK YOU