Test for Phenolic Group

Phenol is an aromatic chemical compound with the hydroxyl (-OH) functional group. A group of aromatic carbon compounds generated from alcohol is known as phenols. Aryl alcohols are what they’re called. Essentially, the phenol group is a hydroxyl group attached to a carbon atom in a benzene ring. Phenols can be found in plants and animals. 

Phenol structure and formula:

The alcohol functional group is bound to a carbon atom in a cyclic configuration in phenols. The double and single bonds in the ring structure alternate. 

Formula of phenol: C6H5OH

It’s a six-carbon-atom hexagonal ring with alternate single and double bonds. In benzene, each carbon atom is linked to a hydrogen atom. A hydroxyl group replaces one of the hydrogen atoms in phenol. 

Properties of phenol:

1. At normal temperature, phenol is a white crystalline solid. The stones, on the other hand, turn pink with time. Oxidation is responsible for the colouring.

2. The odour of phenol is distinct.

3. The molecular mass of phenol is 94.11 g/mol.

4. Phenol has a melting point of 40 degrees Celsius.

5. Because of intramolecular hydrogen bonding, its boiling point is higher than that of other organic compounds of comparable mass. At 181.75 degrees Celsius, it boils.

6. It is slightly acidic, with a pH between 5 and 6. The highly electronegative oxygen draws the electrons it shares with hydrogen to itself, resulting in the acidic nature. The oxygen’s electron removal is stabilised by conjugation in the benzene ring. 

7. When phenol comes into touch with the skin, it causes burns. The result isn’t immediately apparent. As a result, it’s even more harmful. 

Tests for phenol group:

Litmus test:

To determine whether a solution is acidic or basic, scientists use litmus paper. In the presence of a base, red litmus paper turns blue and blue litmus paper stays the same. 

Phenol causes the blue litmus paper to turn crimson. This demonstrates the acidic nature of phenol. This is also a test for carboxylic acid. In comparison to carboxylic acid, phenol is mildly acidic and does not effervesce when dissolved in water. 

Procedure:

1. On moist blue litmus paper, place a drop of the provided organic solution or a tiny crystal.

2. If the colour shifts to red, the presence of a phenolic group is suspected. 

Observations:

Phenol causes the blue litmus paper to turn crimson. 

Ferric chloride test:

When aqueous phenol combines with freshly prepared ferric chloride solution, a coloured complex is formed. The majority of phenols produce a dark-colored solution. 

The following is a chemical reaction:

6C6H5OH + FeCl3 → [Fe(C6H5O)6]3– (violet colour complex)+ 3HCl + 3H+ 

Procedure:

1. Dissolve the organic components in water as directed.

2. Slowly drizzle in a neutral ferric chloride solution.

3. Take note of the colour shift.

4. The presence of phenol is indicated by a red, blue, green, or purple coloration. 

Observations:

The presence of phenol is indicated by a violet or blue coloration. 

Libermann’s test:

A yellow colour quinone monoxime complex is formed when phenol interacts with intense sulfuric acid and sodium nitrite. A deep blue indophenol complex is generated when phenol and sulfuric acid are used in excess. Dilution produces a red indophenol, which when treated with sodium hydroxide transforms into a deep blue sodium salt solution of indophenol.  

Procedure:

1. In a clean, dry test tube, place the sodium nitrite crystals.

2. To the sodium nitrite solution, add 1 mL of phenol.

3. Allow the mixture to cool after gently heating it.

4. 1 mL concentrated sulfuric acid + 1 mL water + 1 mL concentrated sulfuric acid + 1 mL water + 1 mL concentrated sulfuric acid +

5. Keep an eye on the colour of the solution as it changes.

6. If a phenolic group is present, dilute the solution with water until the supplied chemical turns red.

7. When you add sodium hydroxide solution, you’ll get a blue or green colour solution. 

Observations:

The presence of phenol is indicated by the deep blue colour of the solution. 

Conclusion:

Phenol is used in pharmaceuticals as a precursor. It’s a type of antiseptic. It’s used in the manufacture of nylon. It’s used to keep immunizations fresh. Oral analgesics contain it. Phenol derivatives are utilised in cosmetics such as hair colour and sunscreen. It’s used in the manufacture of polymers. Detergents and carbonates are made from it.