AUGUST KEKULÉ: BIOGRAPHY, THEORY, OTHER CONTRIBUTIONS - ARTE - 2024

Friedrich August Kekulé (1829-1896) was a German chemist who specialized in the organic field and who was best known for having formulated one of the most important points in the theory of chemical structure. This principle allows us to understand the composition, how they are organized and how the different organic elements interact.

He also stood out for discovering that all the elements of carbon have a valence of four. He created the so-called Kekulé ring and gained fame for explaining the constant composition of the benzene molecule.

Portrait of August Kekulé in 1873. Source:, via Wikimedia Commons

His discoveries and studies allowed the creation of materials that today are essential in people's lives, such as plastic.

Biography

Kekulé was born on September 7, 1829, in Darmstadt, Germany. His parents were Karl Ludwig Kekulé and Marie Luise Wilhelmine Kekulé. They were considered as an upper middle class family.

August came from a well-off Czech family based in Prague. The Kekulé came to Germany in the wake of the 30 Years' War.

He was baptized with the name of Friedrich August Kekulé, but in 1895 the Emperor of Germany, Wilhelm II, allowed him to add Von Stradonitz to his name. The German never used or was known by the name Friedrich.

During his first years of life, August showed great aptitudes in the fields of art and languages, as well as in the scientific area. His professional career was very successful, something very different from what happened in his personal life. He was married for the first time on June 24, 1862.

His first wife, Stéphanie Drory, died at just 21, two days after giving birth to their first child, Stephan. She was the daughter of one of his best friends in Gent, Belgium. Kekulé was 32 and Stéphanie Drory was only 19.

This event had a significant impact on the German chemist, who did not return to work until several months after this event.

He had a second marriage, this time with whom he worked as his housekeeper. There are records of this marriage that ensure that it was not very happy.

As he had shown great aptitudes for drawing and his father knew renowned architects, his first inclination was to study architecture.

Studies

Kekulé began studying architecture at the University of Geissen. There he enrolled in 1847 and only lasted one semester in architecture. During his stay in Giessen he attended several of the lectures given by the famous chemist Justus von Liebig.

At that time Kekulé decided to change his area of ​​study to dedicate himself to chemistry. First, with the approval of his family, he attended a vocational school in Darmstadt, where he began his studies in science and mathematics. Then in the summer of 1849 he began his training in chemistry at the University of Geissen.

There, he first learned from Heinrich Will. Then, during the years 1850 and 1851, he studied in the laboratory with Liebig.

Since he began his studies, Kekulé showed great interest in the theoretical part of chemistry. He was less inclined towards the practical aspect of which his tutor, von Liebig, was very passionate.

He followed the advice of von Liebig and went to Paris in 1851 to continue his studies. There he received a scholarship and learned from two important French chemists: Jean-Baptiste Dumas and Charles Gerhardt, who had great influence on Kekulé and with which he maintained a great friendship.

August returned to Germany due to the death of his mother. Back at Giessen, he defended his thesis on amino sulfuric acid and received his doctorate in 1852.

Jobs

After obtaining his doctorate, Kekulé became Adolf von Planta's assistant in Switzerland. He stayed in that country for a year and a half before moving to London, where he worked alongside John Stenhouse on Liebig's recommendation. There he was a laboratory assistant until 1855.

Later, Kekulé worked as a professor at the University of Heidelberg, where he taught organic chemistry until 1858. Later, he moved to Gent, Belgium, and became the professor in charge of chemistry at the age of 29.

In Gent, he succeeded in ensuring that the curriculum of the chemistry career of that University will have a practical subject. Just as he got laboratories to be able to teach classes and carry out research or experiments.

Finally, in 1867 he accepted the post of full professor of chemistry at the University of Bonn. He served in this position until his death in 1896.

Death

Kekulé had some deafness problems, but this did not prevent him from continuing with his work as a teacher or administrative level.

His health was badly affected by a flu attack. He died shortly after, on July 13, 1896, when he was 66 years old. He was buried with the rest of his family in Poppelsdorf Cemetery.

Theory of chemical structure

August Kekulé was the main promoter and founder of the theory of chemical structure, whose ideas he published in two different articles that were made public in 1857 in the Annals of Chemistry. A year later he expanded his proposal with another article.

In these articles he explained that coal had a valence of four, which means that it was tetravalent. Due to this characteristic of carbon, one of the four bonds that this chemical element had could be attached to another carbon atom.

In this way, organic compounds were built as if they were a carbon chain. In addition, other atoms (which also had different valences) could also join, which allowed the creation of inorganic molecules.

All these discoveries were detailed later, when he published the textbook of organic chemistry. He spoke of this theory in the first volume of his work, published in 1859.

Archibald Couper was a Scottish chemist and published a theory very similar to Kekulé's and almost at the same time as the German.

The courses he taught at the University of Heidelberg were based on these proposals. He illustrated many of his lectures with the ideas of individual atoms and molecular bonds.

Problem with Benzene

Aromatic compounds, which were based on the structure of the benzene molecule, did not behave the same as carbon. Benzene was discovered in 1825 by chemist Michael Faraday. It is considered an organic element made up of the union of six carbons and six hydrogens, but its structure was a mystery.

According to Kekulé, the solution to analyze this element came to him through a dream. The German realized that benzene had a ring-shaped structure and that thus its rule of valences could be observed.

Then, in 1865 he presented his studies on benzene substitutions. Here he explained how he considered geometry and determined the derivatives and substitutes for benzene.

Other contributions and discoveries

Kekulé continued to publish studies on chemical elements. For this, he recognized the importance of delegating some of his functions to the University of Bonn, although he never completely disengaged himself.

Isolation of thioacetic acid and synthesis of hydrogen sulfide

He completed studies on the reaction that phosphorus pentasulfide had on acetic acid. Thanks to the results of this research, the German managed to isolate thioacecite acid and created a new type of element, which he called hydrogen sulfide.

This new classification is related to the types of waters and hydrogen chloride that Gerhardt proposed.

These investigations, which were published in 1854, were a step forward in Kekulé's career, with which he began to show greater maturity in the scientific area.

Advances in organic chemistry

Although his passion had to do with the contributions he could make on a theoretical level, his experimental work was also very important and abundant. Thanks to these experiments, he expanded the scope of organic chemistry.

He made studies on unsaturated compounds, organic acids and also on aromatic derivatives. The latter were especially relevant.

One of his contributions was in the industrial production of phenols, which are a type of alcohol. It is widely used in the pharmaceutical and clinical industry, in addition to chemistry. Currently phenol serves as an antiseptic, fungicide or for the creation of resins.

Faculty

His work as a teacher was outstanding. He directed very relevant research groups. He trained highly advanced students in chemistry. He supported postdoctoral work and different colleagues in the area, both in Gent and Bonn.

Three of the first five Nobel laureates in the area of ​​chemistry were his students.

Recognitions

Thanks to his work and contributions to the area of ​​chemistry, he has received several recognitions. In life, he received an honorary master's degree from the University of Bonn, for all his contributions to theoretical chemistry.

There is a lunar crater that was named Kekulé in his honor. Like an asteroid. In 1903 a statue was made in his honor by the sculptor Han Everding. The statue was made in bronze and is located in Bonn, near what was previously the chemistry department of the University.

Postage stamps were also created in Germany in his honor. This happened in 1979 and was to celebrate 150 years of his birth.

References

1. Anschütz, R. (2011). Der Chemiker August Kekulé. Hamburg: Severus.
2. Denning, H. (2006). True hauntings. Woodbury, Minn.: Llewellyn Publications.
3. Göbel, W. (1984). Friedrich August Kekulé. Leipzig: BG Teubner.
4. Hart, H., Craine, L., Hart, D., & Hadad, C. (2007). Organic chemistry. Spain: McGraw-Hill Interamericana.
5. Leicester, H., & Klickstein, H. (1952). A source book in chemistry, 1400-1900. New York: McGraw-Hill.