Where was phenol first isolated from?

Coal tar

The correct answer is option 3. Coal tar.

Here is an explanation of why phenol was first isolated from coal tar:

Coal Tar: A Rich Source of Organic Compounds

Coal Gasification Process: Coal, when heated in the absence of air (a process called coal gasification), decomposes to produce a gaseous mixture called coal gas (used for heating and lighting) and a liquid byproduct called coal tar.

Composition of Coal Tar: This dark, viscous tar is a complex mixture of various organic compounds. These compounds arise from the breakdown of the complex organic molecules present in coal during the high-temperature heating process.

Aromatic Hydrocarbons: Coal tar is a rich source of aromatic hydrocarbons, which are organic compounds characterized by the presence of benzene rings (six-membered carbon rings with alternating single and double bonds). Phenol is one such aromatic hydrocarbon with a hydroxyl group (OH) attached to the benzene ring.

Isolation of Phenol:

Early 19th Century: In 1834, a German chemist named Friedlieb Ferdinand Runge was investigating the properties of coal tar. He employed various techniques like distillation and fractional crystallization to separate the different components present in the tar.

Identification of "Karbolsäure": Through his work, Runge was able to isolate an acidic, white crystalline substance from coal tar. He named it "Karbolsäure," which translates to "coal-oil-acid" in English, reflecting its source and acidic properties. This substance we now recognize as phenol.

Later Developments and Current Production:

Importance of Phenol: Phenol quickly gained recognition for its antiseptic and disinfectant properties. However, the initial extraction methods from coal tar were inefficient and limited large-scale production.

Shift to Petrochemical Industry: With the development of the petrochemical industry in the 20th century, scientists discovered more efficient ways to produce phenol from petroleum-derived feedstocks (raw materials). Today, this remains the primary method for phenol production.

Coal tar played a crucial role in the early discovery and isolation of phenol due to its abundance of aromatic hydrocarbons, including phenol itself. While coal tar is no longer the major source for commercial phenol production, the historical significance of its role in this discovery remains noteworthy.