The history behind the discovery of benzene rings

Benzene is considered as one of the fundamental structures in organic chemistry. Benzene has several applications in the manufacturing industry. However, the structure benzene attracted lot of attention when it was first discovered in the 19th century.  Michael Faraday was the scientist who first discovered benzene ring in the year 1825. He had christened it as “bicarburet of hydrogen.” However, Eilhard Mitscherlich was the scientist who named it benzene in 1833. He had distilled this compound from gum benzoin. Benzene gained widespread importance in the paint industry as it could easily remove paint stains from the surfaces of metals.

Because benzene is an important chemical, several efforts were made to elucidate the chemical structure of benzene. At the point of time, scientists knew that benzene contained six atoms of carbon and hydrogen in its chemical structure (C6H6). This baffled chemists because carbon is known to be tetravalent. This means that every carbon atom is capable of chemical bonds with four other atoms. The tetravalency of carbon was proved by Friedrich August Kekule, one of the most reputed scientists of that era. In contrast, the carbon atoms were bonded with only two atoms in the benzene ring. Thus, it did not obey Kekule’s rule.

But, the presence of “unsaturated” carbon atoms was also proposed by Archibald Scott Couper and Joseph Loschmidt at that point of time. Carbon atom is termed to be saturated if it bonded with four atoms in a given molecule. However, it is termed as ‘unsaturated’ if more than one bond exists between two carbon atoms.

The exact structure of benzene was correctly put forth by Friedrich August Kekule. It was quite challenging for him to determine the correct structure of benzene. He was actually solving a chemistry problem and day-dreaming. At that point of time, he saw a snake coiling up and biting its own tail. Looking at the snake, he thought that benzene may be ‘ring’ structure.

He first published an article elucidating the structure of benzene in the year 1865. The article which was published in a leading French journal gained the attention of eminent people in the scientific community. Kekule considered benzene to be a core ring containing six carbon atoms. The ring of carbon atoms was such that it bound carbon atoms through alternating single and double bonds. When he elucidated the structure of benzene ring, it also led to the development of significant pathways in organic chemistry. Now, organic chemists were able to synthesize several derivatives of benzene compounds. These were collectively termed as aromatic compounds. These benzene compounds were extensively used for industrial and medicinal purposes. Most scientists were very elated with the discovery of benzene ring. The German Chemical Society celebrated the 25th anniversary of benzene ring discovery in the year 1890.

Before the commencement of the First World War, one of the primary uses of benzene was gasoline blending. This is because benzene had the capability of increasing the octane number of gasoline. Numerous chemical manufacturers made use of benzene as a solvent. Benzene was also used extensively in the chemical industry during the Second World War. Today, benzene is used as the primary compound for synthesizing different kinds of aromatic compounds, which are used as intermediate compounds in the synthesis of drugs, insecticides and plastics.