What is Carbolic Acid?

Phenol is the chemical name of carbolic acid. It has the molecular formula $C_6H_5OH$ and is an aromatic organic compound. It is a flammable white crystalline solid. A phenyl group $(C_6H_5)$ is bonded to a hydroxyl group $(OH)$ in this molecule. It's mildly acidic and should be treated with caution because it can cause chemical burns.


Carbolic acid was originally derived from coal tar, but it is now made on a large scale (approximately 7 billion kg/year) from petroleum-derived feedstocks. It's a crucial manufacturing product because it's used to make a variety of products and compounds. It is mainly used in the manufacture of plastics and other materials. Polycarbonates, epoxies, Bakelite, nylon, detergents, herbicides like phenoxy herbicides, and a variety of prescription drugs all include phenol and its chemical derivatives.


Properties of Carbolic Acid (Phenol)

Physical Properties of Carbolic Acid

  • Carbolic acid is an organic compound.

  • Carbolic acid is soluble in water.

  • Carbolic acid is weakly acidic in nature.

  • In an aqueous medium, the carbolic acid gets converted into a phenolate ion.

  • Carbolic acid exhibits resonance phenomena.

  • Carbolic acid forms hydrogen bonding.

  • Carbolic acid exhibits tautomerism phenomena.

Chemical Properties of Carbolic Acid

Since the oxygen atom's pi electrons donate electron density to the ring, phenol is highly reactive against electrophilic aromatic substitution. Many groups can be appended to the ring using this general method, including halogenation, acylation, sulfonation, and other methods.

  1. Addition of base to the phenol 

$C_6H_5OH + NaOH \to C_6H_5ONa + H_2O$

  1. Addition of Acyl Group

$C_6H_5OH + C_6H_5COCl \to C_6H_5OCOC_6H_5 + HCl$

  1. Reduction under zinc dust

$C_6H_5OH + Zn \to C_6H_6 + ZnO$

  1. Oxidation of phenol

$C_6H_5OH + CH_2N_2 \to C_6H_5OCH_3 + N_2$


Synthesis of Carbolic Acid

1. Hock Process

The Hock rearrangement is used to partially oxidise cumene (isopropylbenzene). The cumene process, in comparison to most others, uses relatively mild conditions and low-cost raw materials. Both phenol and the acetone by-product must be in high demand for the process to be cost-effective.

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2. Oxidation of Benzene to Toluene

While direct benzene to phenol oxidation is theoretically possible and of great interest, it has yet to be commercialised.

$C_6H_6 + O \to C_6H_5OH$

An alternating current electrosynthesis produces phenol from benzene.


3. Dow Chemical Produced a Copper

catalyzed reaction of molten sodium benzoate with air for the oxidation of toluene

$C_6H_5CH_3 + 2O_2 \to C_6H_5OH + CO_2 + H_2O$    


4. Hydrolysis of Benzenesulfonate

The reaction of a strong base with benzenesulfonate is the first commercial method, produced by Bayer and Monsanto in the early 1900s. This idealised equation represents the conversion.

$C_6H_5SO_3H + 2NaOH \to C_6H_5OH + Na_2SO_3 + H_2O$    


5. Hydrolysis of Chlorobenzene

Chlorobenzene is hydrolyzed to phenol using alkali or steam. This process is known as the Dow process (Raschig–Hooker process).

$C_6H_5Cl + NaOH \to C_6H_5OH + NaCl \\  C_6H_5Cl + H_2O \to C_6H_5OH + HCl$ These methods suffer from the cost of chlorobenzene and the need to dispose of the chloride by-product.


6. Coal Pyrolysis

Pyrolysis of coal produces phenol, which can be recovered. The oxidation of toluene to benzoic acid is achieved separately in the Lummus Process.


Carbolic Acid Uses

Let us discuss the carbolic acid uses:

The most common use of phenol is to make plastics precursors, which accounts for two-thirds of its overall use. Condensation of bisphenol-A with acetone produces bisphenol-A, a key precursor to polycarbonates and epoxide resins. Bakelite is a well-known example of phenolic resins, which are formed when phenol, alkylphenols, or diphenols react with formaldehyde to form phenolic resins. Cyclohexanone, a precursor to nylon, is formed when phenol is partially hydrogenated. Alkylation of phenol yields alkylphenols including nonylphenol, which are then ethoxylated to yield nonionic detergents.

When phenol is partially hydrogenated, cyclohexanone is formed, which is a precursor to nylon. Alkylation of phenol produces alkylphenols, such as nonylphenol, which are then ethoxylated to produce nonionic detergents.


What is the Carbolic Acid Price?

Let us discuss the carbolic acid price:

The carbolic acid price is Carbolic Acid at Rs 600/bottle. This price is the average price for carbolic acid.


Did You Know

  • Carbolism is a phenomenon of poisoning with carbolic acid.

  • Carbolic acid is used to sterilize surgical instruments.

  • Carbolic acid is used as an antiseptic.

FAQs (Frequently Asked Questions)

Question: What is Phenol Carbolic Acid?

Answer:  It has the molecular formula C6H5OH and is an aromatic organic compound. It is a flammable white crystalline solid. A phenyl group (C6H5) is bonded to a hydroxyl group (OH) in this molecule. It's mildly acidic and should be treated with caution because it can cause chemical burns.

Question: What is the Use of Carbolic Acid?

Answer: The uses of carbolic acid are given below:

The conversion of phenol to plastics precursors is the most important use of phenol, accounting for two-thirds of its usage. Bisphenol-A, a primary precursor to polycarbonates and epoxide resins, is generated by condensation with acetone. Bakelite is a well-known example of phenolic resins, which are formed by condensation of phenol, alkylphenols, or diphenols with formaldehyde. When phenol is partially hydrogenated, cyclohexanone is formed, which is a precursor to nylon. Alkylation of phenol produces alkylphenols, such as nonylphenol, which are then ethoxylated to produce nonionic detergents.

Question: What are the Different Types of Synthesis Reaction for Phenol?

Answer: 

Hock Process

The Hock rearrangement is used to partially oxidise cumene (isopropylbenzene). The cumene process, in comparison to most others, uses relatively mild conditions and low-cost raw materials. Both phenol and the acetone by-product must be in high demand for the process to be cost-effective.


Oxidation of Benzene to Toluene

While direct benzene to phenol oxidation is theoretically possible and of great interest, it has yet to be commercialised.

C6H6  +  O  →  C6H5OH

An electrosynthesis employing alternating current gives phenol from benzene.

Dow Chemical produced a copper-catalyzed reaction of molten sodium benzoate with air for the oxidation of toluene:

C6H5CH3  +  2O2  →  C6H5OH  +  CO2  +  H2O


Hydrolysis of Benzenesulfonate

The reaction of a strong base with benzenesulfonate is the first commercial method, produced by Bayer and Monsanto in the early 1900s. This idealised equation represents the conversion.

C6H5SO3H  +  2NaOH  →   C6H5OH  +  Na2SO3  +  H2O

Chlorobenzene can be hydrolyzed into phenol using either a base (Dow process) or steam (Raschig–Hooker process).

C6H5Cl  +  NaOH  →  C6H5OH  +  NaCl

C6H5Cl  +  H2O  →  C6H5OH  +  HCl

The cost of chlorobenzene and the need to dispose of the chloride by-product are also drawbacks of these approaches.


Coal Pyrolysis:

Pyrolysis of coal produces phenol, which can be recovered. The oxidation of toluene to benzoic acid is achieved separately in the Lummus Process.