Phenolic Group Test

Theoretical Background / Context

• Aromatic alcohols are phenols compounds that possess at least one hydroxyl group linked directly to the aromatic ring, forming a phenolic functional group.
• Sometimes, they are also called phenolic compounds. 
• Phenol is the simplest member.

• Phenolic compounds can be classified according to the number of carbon atoms in their structure. 

First: Preparation of Phenols: 

• There are various reported routes for phenolic compounds preparation. 
• For instance, phenols can be prepared through the dealkylation of phenolic ethers and the reduction of quinones. 
• In addition, phenols can be obtained through rearrangement of either corresponding esters or N-Phenolhydroxylamines through Fries and Bamberger rearrangements, respectively.

Second: Phenol Characteristics & General Properties:

• Phenol is a volatile white crystalline solid that is also known as carbolic acid. 
• They are colorless, but they get colored if oxidized.
• Phenols are characterized by being acidic. Their acidity is intermediate between aliphatic alcohols and carboxylic acids. 
• The acidity of phenol is attributed to its ability to lose the hydrogen atom from the hydroxyl group forming a phenoxide or phenolate ion.
• Phenols are characterized by their high reactivity towards oxidation reactions as well as electrophilic substitution reactions.

Third: Uses of Phenols

• Phenolic compounds have been used in different industrial and pharmaceutical applications. For instance, phenol is used as an antiseptic and disincentive agent.
• Phenol has been used in many cosmetics preparations such as sunscreens, hair colorings, and skin formulations. 
• Longer alcohols and fatty alcohols have been used in the industries of plasticizers and detergents.
• Some phenolic compounds are used in food additives.
• Phenolic compounds are used as drugs and prodrugs for treatments of several diseases such as Parkinson’s disease.
• Some phenols are used in chemical synthesis procedures or as indicators.

Principle of Workk

• In this identification test for phenol, aromatic alcohols are tested through detecting their phenolic groups using chemical tests. 
• In addition, these tests can be used to differentiate between phenols and other organic classes, especially those containing hydroxyl groups. 
• This is done through using specific reagents during the phenolic group tests.

Ferric Chloride Test: 

• In this test, ferric chloride is added to a sample containing phenol. 
• Ferric chloride reacts with phenol producing characteristic violet complex according to the following reaction:

C6H5OH + FeCl3 → Fe((OC6H5)6) + 3 HCl

              Violet Complex