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An amino group is a type of nitrogen group that belongs to the class of organic synthesis. It plays an important role in the synthesis of proteins and metabolism.
- In an amino group, a nitrogen atom is connected by a single bond with either carbon or hydrogen.
- Amine is a compound in which nitrogen atoms are directly connected with the lone pair.
- The functional group in amine compounds is NH2.
- In amine compounds, ammonia derivatives are replaced with the alkyl or aryl groups.
- The structural formula of amine is R-NH2, where R is an alkyl or aryl group.
- The most common example of amine includes polymers, vitamins and drugs.
Read More: NCERT Solutions For Class 12 Chemistry Chapter 13 Amines
Key Terms: Amine, Amino Group, Nitrogen, Polymers, Ammonia, Alkyl Groups, Litmus, Solubility test
Test for Amino Groups: Theory
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The aim of the experiment is to determine different tests and their results for amino groups of ammonia.
- The test will help determine the presence of an amine group in the required organic compound.
- Amines are derivatives of nitrogen in which one or more hydrogen atoms are replaced by substituent groups.
- It is divided into three categories namely primary, secondary and tertiary amines.
- The class of amine in which the substituent atom is attached to only one nitrogen atom are called alkyl arylamines.
Read More: Hofmann bromamide reaction
Types of Amine
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Amines are divided into three broad categories depending upon the number of substituents on the nitrogen atom.
- Primary Amine: It is a type of amine in which one atom of nitrogen is replaced by the alkyl or aryl groups.
- Secondary Amine: It is a type of amine in which two atoms of nitrogen are replaced by the alkyl or aryl groups.
- Tertiary Amine: It is a type of amine in which three atoms of nitrogen are replaced by the alkyl or aryl groups.
Read More: Uses of Amines
Types of Test for Amino Groups
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The different types of tests that can be used to identify amino groups in organic compounds are as follows:
Solubility Test
The Solubility Test is the most commonly used test to determine the presence of an amino group in an organic compound. The nature of amines is basic thus making them completely dissolve in acid like hydrochloric acid.
The chemical reaction for the solubility test is as follows: C6H5NH2 + HCl → C6H5NH3 + Cl–
Litmus Test
The most simple test to determine the presence of amine in a compound is the litmus test. The nature of amine is basic thus it will change the colour of litmus paper blue but it is not a confirmed test as the compound might be amine.
The chemical reaction for the litmus test is as follows: CH3-CH2-NH2 + H2O → CH3-CH2-NH3+ + OH–
Oxidation with Caro Acid
The third method to determine the presence of amine is the Caro acid test. This test helps in the determination of aromatic amine groups. Aromatic amine groups are quickly oxidised in the presence of air thus forming a coloured coloured compound.
The chemical reaction is as follows: C6H5NH2 + K2Cr2O7 + H2SO4 → Black Coloured Compound
Carbylamine Test
In this test, amines are made to react with chloroform in the presence of an alkali. The final compound formed is called isocyanide. This is the reason the carbylamine test is also famous with the name isocyanide test.
The chemical reaction is as follows: R-NH2 + 3KOH + CHCl3 → RNC(isocyanide) + 3KCl + 3H2O
Halogenation Test
Another test that can be conducted to determine the presence of an amine group is the halogenation test. This test is used to check for aromatic amine compounds. In this aniline reacts with bromine water to form a white-coloured compound called 2,4,6 tribromoaniline.
Read More: Haloalkanes and Haloarenes
Apparatus Required for the Experiment
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Here is the list of apparatus required for the experiment:
- Test Tubes
- Aniline
- Test Tube Holder
- Beaker
- Sodium Nitrite
- Aniline
- Chloroform
- Potassium Hydroxide
- Dilute and Concentrated Hydrochloric Acid
- Bromine water
- Sodium Hydroxide Solution
- Burner
- Ethanol Solution
Procedure of the Experiment
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The procedure for conducting the experiment is as follows:
Solubility Test
The process of carrying out solubility test is as follows:
- First, take a clean test tube.
- Next, put a small amount of organic compound in the test tube.
- In the test tube add two to three drops of concentrated hydrochloric acid solution.
- Shake the mixture properly and then check its solubility in the required acid.
Litmus Test
The process to carry out the litmus test is as follows:
- Take a simple litmus paper.
- Put a drop of the required organic compound on the paper.
- Wait for the litmus paper to change its colour and check the final result.
Oxidation with Caro Acid
The process to carry out the Caro Acid test is as follows:
- Firstly, take a small amount of organic compound in a clean test tube.
- Place the test tube in the test tube holder and allow it to rest for a few times.
- Check for the colour of the solution.
Carbylamine Test
The process to carry out the Carbylamine test is as follows:
- Take a small amount of potassium hydroxide solution in a clean test tube.
- Add two ml of ethanol solution to the test tube.
- Turn the burner on and warm the test tube until the mixture completely dissolves.
- Next place the test tube in the holder to allow the mixture to cool down.
- Lastly, check the odour of the mixture.
Halogenation Test
The following are the steps for the halogenation test:
- Take a clean test tube and a small amount of organic compound in it.
- Add a small amount of bromine water in the mixture.
- Warm the test tube with the help of a burner so that the compound gets completely dissociated.
- Place the test tube in the holder to cool the mixture.
Read More: Method of Preparation of Diazonium Salts
Observation Table of the Experiment
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The observation table of the experiment is as follows:
| S.No | Test | Observation |
|---|---|---|
| 1 | Solubility Test | If the compound dissolves in the acid then it is an amine |
| 2 | Litmus Test | It will turn the litmus paper blue |
| 3 | Oxidation with Caro Acid | It will produce black colour aniline |
| 4 | Carbylamine Test | The smell of unpleasant odour indicates the presence of amine |
| 5 | Halogenation Test | Produce a white colour solution |
Inference Drawn from the Experiment
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The inference drawn from the experiment is as follows:
- The required organic compound contains aromatic or aliphatic amine.
- The amine can be classified as primary, secondary and tertiary.
Precautions while doing the Experiment
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The things to keep in mind while performing the experiment is as follows:
- Always use a clean test tube for the experiments.
- Use burners under the guidance of senior authority.
- Do not smell any chemicals or compounds.
- Wash your hands properly after handling any chemicals.
- Maintain the required temperature for the experiment.
Check More:
| Related Topics | ||
|---|---|---|
| Allylic Carbon | Nomenclature of Organic Compounds | Stereoisomerism |
| Adsorption Chromatography | Carbanions | Organic Solvent |
Things to Remember
- Amines are organic compounds that are made of NH2 amino groups.
- They are divided into primary, secondary and tertiary amines.
- The presence of an amine group can be determined with the help of tests like litmus test, solubility test and halogenation test.
- Amines are used as reagents in the organic compound synthesis.
- Aromatic amines are used in the dye and rubber industry.
Previous Year Questions
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Sample Questions
Ques. In which colour will litmus paper when a drop of amine is placed over it? (1 mark)
Ans. The colour of the litmus paper will turn blue when a basic organic compound is added to it.
Ques. How to carry out the halogenation test to determine the presence of amine in the organic compound? (3 marks)
Ans. The steps to carry out the halogenation test are as follows:
- First, take a clean test tube from the holder.
- Put a small amount of the required organic compound in the test tube.
- Next, add a small amount of bromine water to the test tube.
- Heat the test tube over the burner to allow the mixture to dissolve completely.
- Allow the test tube to cool down and check the colour of the solution.
Ques. What is the solubility test conducted for the identification of amine compounds? (3 marks)
Ans. The Solubility Test is the most famous method to determine the presence of an amino group in the required compound. In this test, the required organic compound is placed in the mixture of hydrochloric acid. If the compound dissolves completely then an amino group is present in the compound.
The reaction for the test is as follows: C6H5NH2 + HCl → C6H5NH3 + Cl–
Ques. Name some tests to determine the presence of an amino group in an organic compound. (2 marks)
Ans. The tests which can be conducted to determine the presence of amino groups in an organic compound are as follows:
- Solubility Test
- Litmus Test
- Carbylamine Test
- Halogenation Test
- Oxidation of Caro Acid Test
Ques. What materials are required to conduct the list of tests? (2 marks)
Ans. The list of material required to conduct the list of test are as follows:
- Test Tubes
- Aniline
- Test Tube Holder
- Beaker
- Sodium Nitrite
- Aniline
- Chloroform
- Potassium Hydroxide
- Dilute and Concentrated Hydrochloric Acid
- Bromine water
- Sodium Hydroxide Solution
- Burner
- Ethanol Solution
Ques. How carbylamine test determines the required amine in the organic compound? (3 marks)
Ans. The steps to carry out carbylamine test to determine the required amine in the organic compound are as follows:
- First, take a clean test tube and add a small amount of potassium hydroxide solution.
- In the test tube add at least 2 ml of ethanol solution.
- Next turn on the burner and place the test tube over it.
- Allow the mixture to dissolve completely in the solution.
- Next, keep the test tube in the holder to allow the mixture to cool down.
- Check the smell of the required solution.
Ques. What precautions should be taken while conducting the test? (3 marks)
Ans. The list of precautions taken while conducting the test is as follows:
- Wear gloves while conducting the test.
- Avoid touching your eyes and nose during the test.
- Wash your hands on a regular basis while touching any chemical.
- Take only a clean test tube for conducting the test.
- Perform the test under the supervision of a senior.
- Do not throw the test tubes directly into the sink.
Ques. What is the result of the oxidation with the Caro Acid test? (1 mark)
Ans. The result of the oxidation of the Caro Acid test will produce a black colour aniline mixture.
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