August Kekulé

August Kekulé born Friedrich August Kekulé ( since 1895 Kekule von Stradonitz, born September 7, 1829 in Darmstadt, † July 13, 1896 in Bonn ) was a German chemist and scientist who laid the foundations for the modern structural theory of organic chemistry.

Life

Was born August Kekulé (since the recognition of the old Bohemian nobility in 1895 Kekule von Stradonitz ), the son of a family of civil servants Darmstadt with noble Bohemian ancestors. His father Karl Ludwig Kekule was Oberkriegsrat and rose growers.

With the marriage of the Englishwoman Stephanie Drory 1862 in Ghent and the birth of the son, the later genealogists and lawyers Stephan, the spelling Kekulé was officially certified in order to clarify legally speaking after French grammar pronunciation of the final - e. Only a year later Drory died. From Kekulé in 1876 closed the second marriage three more children were born.

Youth

In his youth, his hobbies were hiking, botany, collecting butterflies and drawing. He began his schooling at the grammar Ludwig George's School in Darmstadt and was a good student with an aptitude for languages ​​, so that he spoke in German, French, Italian and English.

Although Kekulé was a frail teenager, he developed into a robust and healthy adults, who was very active in sports until the end of his school days in 1847. He loved to juggle and dance and was a talented and entertaining imitator.

Finding

Since he was a gifted artist and his father was a close friend of the famous architect, he began to study at the University of Giessen Architecture in Hugo von Ritgen. He then turned but the chemistry when he attended lectures by Justus von Liebig. For one semester he was at the Polytechnic Institute in Darmstadt, as his relatives imposed on him for reflection regarding his career. Temporarily, he attended the University of Paris, where he was a pupil of Jean Baptiste Dumas and Charles Frédéric Gerhardt. In 1852 he received his doctorate in Liebig with the paper "On the Amyloxydschwefelsäure and some of its salts." He was then assistant at Liebig pupil Adolph von Planta (1820-1895) in Schloss Reichenau, Graubünden ( Switzerland ).

Research

His creative phase began when he held until 1855 as an assistant to John Stenhouse in St Bartholomew's Hospital in London, worked in 1854. He had there made ​​friends with Alexander William Williamson. In England, he was the first chemist to sulfur in organic compounds by replacing one oxygen a. He synthesized thiocarboxylic and mercaptans from diphosphorus. Even in England preferred Kekulé the spelling of Charles Gerhardt, to indicate in a formula that sulfur and oxygen dibasic ( bivalent), hydrogen and chlorine are monobasic.

In 1856 he qualified as a professor in Heidelberg, was there from 1856 to 1858 lecturer and delivered during this time heated debates with Adolf von Baeyer. In 1858 he was among other things, Liebigs intercession Professor of Chemistry at the University of Ghent in Belgium in 1867 and was followed by a call from the University of Bonn.

As Kekulé was appointed in 1867 to Bonn, the new chemical institute in Poppelsdorfer castle was completed in the shell. He was a major influence on the establishment and the interior of the large building, which made it one of the best equipped institutions across Germany. He pulled by many German and foreign students to the Rhine, so that the building soon bursting at the seams. An extension was approved only as Kekulé rejected a call to Munich as successor by Justus von Liebig.

Kekulé was less practical chemists as more of a theorist, his contributions were sometimes very speculative. His main work was in the representation of organic molecules by structural formulas. In front of him was known only the carbon-hydrogen - oxygen ratio of the organic compounds and has the connections to empirical formulas ( accurate than radicals) in the literature as indicated. His field was the carbon chemistry and the elucidation of the constitution of aromatic compounds.

He realized simultaneously with AS Couper 1858, the four valence of the carbon and the presence of carbon-carbon bonds. For the number x of the binding partners of an atom Kekulé used the terms " x - atomig ", " x - basic", later introduced by Erlenmeyer term " valent " and the concept of valence, the Hermann Wichelhaus had introduced. From the number of atoms and their chemical valences structures could now be derived which could easily write on a sheet of paper. Alexander Butlerov suggested in Speyer in 1861 the concept of chemical structure for the representation of a molecule with its valences ago. Even in Kekulé textbook of organic chemistry from the year 1859, the ideas have been developed for structural chemistry. Only in his textbook of 1864 cars Kekulé structural formulas to represent organic molecules. By the structural formula, each chemist could quickly identify how the molecule of a substance is composed.

The structures of aromatic compounds to him at this stage were still unknown.

He published his proposal for the structure of the benzene ring for the first time in 1865 in a French magazine, and published it in 1866 in German in Liebigs Annalen under the title ' Investigations on aromatic compounds '. Since the molecules of many compounds of Steinkohleteers, the main raw material for organic chemists at this time, of one or more benzene rings passed, the knowledge of the structure of benzene was particularly important. Chemists now able to derive the structural formulas and synthesis of novel compounds on the basis of these formulas for all aromatic compounds from the elemental analysis, and the chemical reactions. The structural formulas formed the basis for progress in chemistry.

In the years 1878, 1886 and 1891, he was elected to the board of the German Chemical Society of Berlin. Many of his students were also professors or were successful in the chemical industry. Significant students were Richard Anschütz, Otto Wallach, Ludwig Claisen.

After a measles disease in the same year, which had significantly affected his health, he increasingly turned to the publication of his work. Many of his works appeared in the Annalen der Chemie and Pharmacie. His most influential work was the unfinished book of organic chemistry, whose four volumes in 1859 (reprinted in 1861 and 1867), 1866, 1882 and 1887 appeared.

Afterlife

Kekulé died in 1896 in Bonn and was buried in a grave of honor Poppelsdorf cemetery, where you can visit his grave today. Its a created by Hans Ever thing and 1903 built monument is similar to the famous Manneken Pis in Brussels before the old Chemical Institute of the University of Bonn in Meckenheimer Allee 168 is decked with various seasonal utensils statue from time to time; In contrast to the Manneken Pis but not from official, established tradition, but rather sporadically and spontaneously. The University Institute of Organic Chemistry and Biochemistry (now based in Bonn- Endenich ) him " Kekulé Institute " was named in honor.

Kekulé estate is owned by the Deutsches Museum in Munich.

Kekulé was an honorary member of the Gymnastics Association in VC Cimbria Bonn ( Bonn today Turnerschaft in CC Cimbria Istaevonia ).

Attachment Theory

Before Kekulé theory there were only vague notions of how the atoms in a molecule linked to one another. Bonds between individual atoms and structural formulas were not known. Kekulé used nor the terms " atomig " or "basic" for specifying the number of binding partners of an atom. Erlenmeyer used the designations of one-, two - three - and tetravalent for the number of binding partners of a Atoms.Viele chemists thought in his time that the structures of molecules that could not be seen as reactions indeed altered the structure unpredictable. Kekulé examined various carbon compounds, especially benzene.

Already in 1858 postulated Kekulé:

• Carbon atoms can combine to form chains of any length and complexity.
• Carbon atoms are always 4 -valued, ie, four bonds with one (Note: Kekulé was the first chemist who formulated this ).
• The number of the monovalent binding partner on a linear carbon chain having n carbon atoms (2 * n 2).
• The investigation of reactions makes it possible to gain information about the arrangement of the atoms.

When Kekulé celebration in March 1890 Kekulé described his findings as follows:

" It has been said. Benzene theory had appeared like a meteor in the sky, she was absolutely come again and suddenly Gentlemen Thus the human mind is not thinking something totally new has never been thought of, certainly not in the chemistry!. . "

As a result of the lecture, he spoke about the other researchers for structural chemistry: Auguste Laurent, Jean Baptiste Dumas, Jöns Jacob Berzelius, Frankland.

Kekulé reported further from his reverie in a bus:

I sank into a reverie. Since the atoms flitted before my eyes. I had always seen them in motion, those little creatures, but I was never able to overhear the nature of their movement. Today I saw how often two smaller came together into pairs; as larger two small included, even larger three and even four small clung, and how everything in a whirling dance turned. I watched as a series were larger and smaller mitschleppten still only at the ends of the chain. The reputation of the ... Conducteurs, Clapham Road, awakened me from my reverie.

He continues:

With express trains do you not research trips and the study of even the best textbooks will not be an explorer. Those who want to train as researchers, original works of travelers must studying; so thoroughly that not only did he read between the lines, but is able to guess the self as unexpressed thoughts. He must follow the paths of the Boy Scouts; on each foot track on every bent twig, on every fallen leaf need it to be.

Surprisingly simple as he made the wide variety of carbon compounds understandable and brought order to the prevailing confusion. However, the structure of benzene remained an open question. Kekulé reported in 1890 by a waking dream. He was sitting at his desk in the night of his discovery in the winter of 1861 and have been looking at the radio play of the fire half asleep. All at once, who told me he had a dream the long-sought solution brought: He saw the carbon and hydrogen atoms danced before his eyes. In this dream the old alchemical symbol of Ourobourosschlange appeared to him, biting its head in its own tail. Also in 1861 used Loschmidt in his little-noticed publication " Constitutions formulas of organic chemistry a graph of " a ring as a symbol of benzene.

1865 Kekulé published in French (he was a professor since 1858 in Ghent ), the first version of his benzene theory. This theory was based on the principle that the molecule of benzene consists of a ring of six carbon atoms. In 1866 he published a lengthy German article ( in Liebigs Annalen der Chemie ) on the same subject.

In 1870, he discovered the azo coupling; In 1872 he completed his benzene theory by Oszillationshypothese on the alternating single and double bonds to explain the properties of benzene.

Kekulé work contributed significantly to the development of organic chemistry and led to a boom in the German chemical industry, led by the dye manufacturer.