Azo dyes are contain azo function group (N=N). azo dye are synthetic class type dyes. it is bound to aromatic ring and it is easy to dissolve in water. this dyes are mostly used for dyeing of textile cloths.
We will discuss about test for amines such as azo dye test, carbylamine test, hinsbarge test, solubility test, litmus test.
By the end of this article You can properly understand about test for amines. first off all, we will discuss about azo dyes.
What is an azo dye?
Azo dyes are chemical class of dyes. this dye are highly organic compound. this dyes are contain azo function group (N=N). azo dye are properly bound to aromatic ring.
Azo dyes are soluble in water. azo dyes are easily dissolve in water. Its broken down with the help of high temperature. and Some important dyes are based on arylamines.
Azo dyes are windly used for the dyeing of cellulose materials as well as polyester materials. this dyes are produced strong colour with good depth of shade on to the materials. Different popular azo dyes are also be used in textile industries, for example Acid orange 7, (2- naphthol or orange-2).
Direct blue 15, and methyl yellow, acid red 13. these are the important class of azo dyes which is windly used in textile industry. and alos these types of dyes gives good effect on cellulosic materials. this dyes also have some important colouring Function property. this is the reason it gives good colour (shade) on materials.
But some azo dyes is harmful for skin but not all. when this dyes are contect on skin then it may increase chances of skin cancer. Azo dyes could be banned from contact because azo dyes have highly solubility tendency in water. but it is easy to absorb on to skin.
This dye are easily observed on the skin of body during dyeing process. this dyes are easily accumulated and absorb in the body. when azo dye are contect on skin. it may increase chances to damage of skin.
Also increase the chances of exposure when wearing garments. so, some company are banned of some class of azo dyes. and Azo coupling reaction is carried out with phenol and naphthol. (reaction with coupling components process with phenol and naphthol). After this, it is given an azo dyes. this way, you can prepared of an azo dyes.
But if we are talking about other dyes, such as, Basic dye, Reactive dye, Acid dye. different dyes have different property. different dyes have ability to colouration for different materials. This mean, Basic dye are used for colouration of reactive dyes have capability to colouration for cellulose materials.
Where as Acid dye are used to colouration of proteins fibre, such as silk, wool and proteins fibre. Azo dye are more complex. it difficult to dyeing processing. but it is easy to done dyeing processing with the other dyes, such as, Reactive dyes, Acid dyes, Basic dyes.
Azo Dye Structure
Azo dye is a one type of organic compound. it contains function group such as (N=N).
This is also known as azo compound and this is also called an azo dyes. it is used for treatment of textile materials.
It is also be used as a azo pigment. but it is insoluble in water. it is made from phenol, aniline and amines.
Preparation of an Azo Dye From Aniline;
Preparation of an azo dyes from aniline is, first aniline is react in the presence of NaNO2/HCl at temperature 0-5°C.
After this reaction, as a results, it is given benzene diazonium chloride. and then, after this coupling reaction is carried out with phenol. As a result (coloring compound ) azo dyes is formed as a product.
Now, we will also discuss about preparation of an azo dye with the help of flow chart/process sequence.
First of all aromatic amines (aniline) taken then after reaction, it is transferred to diazonium component.
After this, azo coupling reaction is carried out with phenol and naphthol. (reaction with coupling components process with phenol and naphthol).
After this, it is given an azo dyes. this way, preparation of an azo dye will be completed.
Lets know, preparation of an azo dyes with flow chart.
Azo dye preparation flow chart/ process sequence;
Take Aromatic Amines (aniline), it react with the presence of Nano2/HCl at 0-5°C.
| After reaction (transformed)
Diazonium component (benzene diazonium chloride)
Cuppling reaction with cuppling component process with phenol or nepthole
Azo dye (red, yellow, orange) is formed.
these are the following steps for making an azo dyes. this way, Azo dyes are prepared.
Azo C – Coupling reaction with phenol
1. When benzene diazonium chloride react with phenol then it make azo component, it is orange product, this is called orange azo dyes.
2. Aniline solution is react with same benzene diazonium chloride then it is given yellow product. this product is called yellow azo color or yellow azo dyes. azo dye test is carried out for produced aromatic amines (aniline). Aniline is an aromatic amine and after reaction with aniline it gives yellowish azo dye.
3. In this reaction, beta nephthol (napthelene+alcohol = beta nephthol) is react with benzene diazonium chloride then it make azo component. this is called red colour azo dyes.
Azo N – Coupling reaction with aniline
In this coupling reaction, aniline is directly reacted with benzene diazonium chloride and with maintain pH – > 7. then it make an azo Component or azo dye.
What is azo dye test?
Azo dye test is simple quantitative test. the main role of this test is to determine the value of amines. azo dyes test are given value of amines. In this process, different colourant dye and pigments are used for colouration of textile apparel or accessories. this colourant are based on azo dyes and Anthraquinone dyes.
Test for Amines
these are the important test for aromatic amines. now, lets go to know, how to done these test.
1. Azo dye test
2. Hinsberg test
3. Carblymine test
4. Solubility test
5. Litmus test
6. Nitrous acid test
7. Mustard oil test
Azo dye test
Aromatic primary amines can be determine by an azo dye test.
In this case, aromatic amines for example: (aniline) is reacts with nitrous acid with HCl at 0-5°C to produce diazonium salt.
this solution is reacts with beta-nepthol to produce red colour solution. this red colour solution is known as red azo dye. It is sparingly soluble in water.
Here, we will also provide Process sequence of azo dye test.
Materials required for “azo dye test“
• test tube
• p glass
• glass rod
• gas burner
• bekar with ice
In case of azo dye test process, some important chemicals is required such as,…
• Aromatic amine (aniline)
• Beta Nepthole
Azo dye test is carried out with two steps. it is given below.
In case of azo dye test, first of all take aniline solutions in Test tube then add hcl. Heat for few seconds then cool, and again add NaNO2 and mix properly then keep the solution in ice bath. it is given diazonium salt or diazonium component.
In second steps, again take beta-napthol solution in second test tube. then add sodium hydroxide (NaOH) then heat for few seconds then keep in the ice bath. then it is given beta-napthol solution.
Then add both solutions, for example.(Diazonium solution+ beta-napthol solution). Then it is given red colour solution. It is known as red azo dyes.
For better understanding we are providing process sequence of azo dye test.
First Take Aromatic amine (aniline) C6H5NH2 solution
Heat (10- 15 sec)
Again add NaNO2
Keep the test tube in ice cold bekar
Diazonium salt is formed
Take beta napthol in second test tube
Heat (for few seconds)
Keep the second test tube in ice bekar
Beta- Nepthol solution is formed.
Add both solutions
diazonium salt + Beta – Nepthol solution
Azo dyes is formed (red colour)
We know that hinsberg test is performed with the help of hinsberg reagent.
benzene sulphanyl chloride reagent is windly use for this test.
The structure of hinsberg reagent is,
C6H5SO2Cl – benzene sulphanyl chloride
it is also called hinsberg reagent.
Now, first of all,
Take 1°anine (for hinsberg test)
also take – R-NH2 – primary amine
Where, (R-NH2 is a primary amine)
When primary amine is react with benzene sulphanyl chloride then it give N-alkyl benzene sulphonamide chloride as shown in reaction.
R-NH2 + C6H5 – SO2- Cl – C6H5-SO2-NHR
You know that, in this reaction, Nitrogen have loan pair. it is easy to donate loan pair.
Nitrogen is electron donating group, so during reaction first of all Nitrogen is donate electron for sulphur.
Then after donating electron for sulphur then it make bond (or compound) and living group Cl will remove.
Where, Cl – living group and after reaction finally N-alkyl benzene sulphonamide is formed.
Now, acetic hydrogen is present in primary amine. so, it is easy to soluble in sodium hydroxide NaOH.
When C6H5-SO2-NHR is react with NaOH then it give sodium salt.
C6H5-SO2-NHR + NaOH
In this reaction, one hydrogen is attack on OH or react with each other.
then it make H2O water molecule and one nitrogen have – charge (N-) and Na have positive charge (Na+) then it finally make sodium salt as a product.
R-NH2 – primary amine.
C6H5-SO2-Cl – Benzene sulphanyl chloride.
C6H5-SO2-NHR – N alkyl benzene sulphonamide.
and finally Sodium salt is formed as shown in the reaction.
Carbylamine Test / Carbylamine Reactions
It is very important test for primary amine. In this test, some important chemical is required. it is given as follow,
1. Aniline (primary amine)
3. Alcoholic potassium hydroxide
these are very important chemical for carbylamine test.
In this test, first of all
Take test tube – (take two test tube)
take 5-6 drop of aniline in first test tube.
After this, take 1 mil alcoholic potassium hydroxide in second test tube.
after this, mixed both solution properly.
after this, add few drop of chloroform.
then heat at boil for few second.
after this, add concentration sulphuric acid in the solution and mixed properly.
after few time it produce carbylamine solution as a product (this hole test is called carbylamine test).
Check Also – What is Carbylamine reactions?
We know that amines are basic in nature, and it is properly soluble in minral acid. If it is soluble in minral acid then it may be amines. Lets get to check solubility in minral acid.
Now, we will discuss about some steps for solubility test;
First : add water and sample of lipid to the test tube. lipid is insoluble in water. So, it forms emulsion if it will be shaken properly.
Second: add ethanol and sample of lipid to the test tube. Again, lipid is insoluble in ethanol so, it forms emulsion if it will be shaken well.
Third: add diethyl ether and sample of lipid to the test tube. lipid is insoluble in diethyl ether. It is forms emulsion.
Fourth: add chloroform and sample of lipid to the test tube. lipid is properly soluble in chloroform.
If it is soluble it may be amines.
This test is also be used for identify amines,
Now, let’s get to check some following steps,
First: take red and blue litmus paper.
Second: take some chemical such as,
1. Soap solution
2. Acitic acid
3. Lime solution
first off all, take three red litmus paper and three blue litmus paper.
(a) add few drop of lime solution on first both paper (red and blue paper).
(b) add few drop of soap solution on second both paper (red and blue paper).
(c) add few drop of acitic acid on third both sample (red and blue paper).
After few minutes, you can see that,
Conclusion + result;
Acid substance turns blue litmus to red.
Base substance turns red litmus to blue.
Nitrous Acid Test
test for amines,
Amines react with nitrous acid
Amines + NaNO2 (sodium nitrite) + HCl,
in other words, we can write of this reaction,
R – NH2 + NaNO2 + HCl = ?
If final product is alcohol then it is called primery amines.
If final product is nitroso amines then it is called secondary amines.
But if reaction is not done (not react) then it is called Tertioery amines.
Mustard oil test
In this test, first off all,
– primary amine react with alcoholic, corbon dioxide (cl2) + HgCl2 (take excess amount) then it is given isothiocyanates.
after reaction if pangent smell is occurred (it is same as mustard oil smell) then it will be primary amines.
– secondary amines react with CS2 (carbon di sulphide) then it is given Dithocarbamic acid but secondary amines not react with HgCl2. then it will be secondary amines.
– tertiary amines not react with CS2 as well as hgcl2 then it will be tertiary amines.
secondary amines and tertiary amines
Azo dye test for phenol, Aniline, bita nepthol
Azo dyes test is used for detarmine the value of aromatic amines.
Azo dye test is given aromatic amines. such as, aniline. it is an aromatic amine.
Aniline is easily diazotized on coupling reaction gives azo dyes.
This test is given yellow colour azo dyes but it turn red brown with contact of air or light.
Azo dye test for phenol
azo dye is properly solublized in NaOH sodium hydroxide. after reaction it is given sodium phenoxide solution.
In this reaction, first phenol is react with NaOH then it is given sodium phenoxide. and then keep in ice bath.
Then add cooling benzene diazonium chloride solution then it is reaction between both component such as, Sodium phenoxide and benzene diazonium chloride. In other words;
“Sodium phenoxide+benzene diazonium chloride.”
then it is given azo component it is known as yellow – orange azo dye.
• Azo dye test for aniline
In this reaction, first of all some liquid of phenylalanine (aniline) is add in cooling solutions of benzene diazonium chloride.
and then mixed properly of both solutions. A yellow solid will produce. and yellow colour is formed.
This strong color is azo compound. this is used as a azo dyes.
• Azo dye test for beta nepthol
beta naphthalene is dissolved in NaOH (sodium hydroxide). this solution will keep in ice bath for few time.
And then mixed properly with benzene diazonium chloride solution. and it gives Orange-red color. this product is also called red azo dyes.
Azo dye test for phenol (reaction)
- Azo dye tes for phenol
- Azo dye test for aniline
- Azo dye test for Bita napthole
- Azo dye test for phenol
When phenol is react with benzene diazonium chloride, at pH 10-11, then it gives azo dyes. For example; orange colour azo dyes is formed.
2. Azo dye test for aniline
When aniline is react with benzene diazonium chloride then it gives azo dyes. For example; yellow colour azo dyes is formed.
3. Azo dye test for bita-napthols
When bita-napthols is react with benzene diazonium then it make azo dyes. such as, red azo dyes is formed.
bita-napthol = napthelene +alcohols.
The Carbylamine reaction is one of type of reaction which is synthesis of an isocyanide with the help of primary amine, chloroform, and base.
Also synthesis of tert-butyl isocyanide from tert-butylamine in the presence of catalytic amount of the phase transfer catalyst.
Such as, benzyltriethylammonium chloride
Me3CNH2 + CHCl3 + 3NaOH – Me3CNC + 3NaCl + 3H2O
Similarly, it is used to make secondary amine.
Mechanism of Carbylamine
The mechanism involves the addition of amine to dichlorocarbene.
The mechanism created or generation of intermediate with the help of dehydrohalogenation of chloroform.
In this case, two base – mediated dehydrochlorination steps is done to form isocyanide.
Properly, dehydrochlorinarion is done to form isocyanide.
Question and Answer
1. What is difference between azo dye test and back azo dye test?
- azo dye test :- In azo dye test, the main role of azo dye test is given by aromatic primary amine. it react with nitrous acid to form diazonium salts. and these diazonium salts undergo coupling reaction with phenol, aniline, and Beta naphthol. and it is given red, yellow, orange colour azo dyes.
2. back azo dye test – it is windly uses in textile industry. It is one type of synthetic dyes. In this case some azo dyes is given carcinogenic and allergenic aromatic mines.
2. How azo dye test is done for aromatic amines?
If (aromatic amine) aniline solution is react with same benzene diazonium chloride then it is given yellow product and this product is called yellow azo color or yellow azo dyes.
3. How will you get azo dye from phenol?
First of all, in this reaction first phenol is react with NaOH then it gives sodium phenoxide. and then keep in ice bath and then add cooling benzene diazonium chloride solution. then it react between sodium phenoxide and benzene diazonium chloride. and then its make yellow – orange azo dyes.
4. Why azo dyes are banned?
azo dyes having “aminogroup” but some amines are careinogenic in nature. and some amines present in azo dyes but this amines are highly effected for skin. And because When dyes are contect on skin then this amines are easy to absorb or accumulated in the body and easy to absorb by the skin then thet cause skin cancer.
This is the reason some azo dyes are banned. this dyes are very harmful for skin if you are not use properly.
5. What is azo dye test?
Azo dyes test is carried out for finding about aromatic amines. the main purpose of Azo dyes test is identifing about aromatic amines. Azo dyes test from phenol, aniline and amine is carried out for making an Azo dyes. Azo dyes is produce different colours such as, red, yellow and orange.
In this process diffrent colour, dye, pigment are used for colouration of apparel or accessories.
This is done with the help of azo or Anthraquinone.
6. Why do you need to test for azo dyes?
Mainly, azo dyes are used as for colourant in textile material and lather materials. azo dyes can under reactive conditions to produce primary aromatic mines. this is called Carcingeous and classified as skin sensitigers.
7. Azo dyes in textile?
Azo dyes are windly used in textile industries for the dyeing of cellulose materials as well as polyester materials. Azo dyes are produced strong colour with good depth of shade on to the materials. Different popular azo dyes are windly used in textile industries. Such as, Acid orange 7, direct blue 15, methyl yellow, acid red 13 and more.
8. What types of products are azo dyes usually found in?
Azo dyes can be more use in wind range of materials such as
9. How long does azo dyes testing take?
3 – 5 days (working days).
10. When dyeing with your azo dye which fibers seemed to interact best with the dye?
Azo dyes are soluble in water therefore, azo dyes are easily dissolve in water. Azo dyes are contain azo function group (N=N). azo dye are synthetic class type dyes.
This dyes have some important colouring Function property. this is the reason it gives good colour (shade) on materials. this dye gives good effect on cellulosic materials as well as wool fibers. In case of azo dye, the best interact with azo dye is 3 amino benzene sulfonic acid.
11. Azo dye test is given by?
(a) Primery amines
(b) Primery aliphatic amines
(c) Primery aromatic amines
(d) None of these
In azo dye test, azo dye test is given by primary aromatic amine. it react with nitrous acid to form diazonium salts. and these diazonium salts undergo coupling reaction with phenol, aniline, and Beta naphthol. and it is given red, yellow, orange colour azo dyes.
As a result, we can say that primery aromatic amines is correct.
So, option C is correct.