Friedrich August Kekule von Stradonitz –inventor benzene structure

Friedrich August Kekule von Stradonitz –inventor of benzene structure

Category : Personalities
Published by : Data Research Analyst, Worldofchemicals.com

Biography & Contributions

Friedrich August Kekule von Stradonitz was a German organic chemist born on September 07, 1829 – died on July 13, 1896.

Kekule is also famous for having clarified the nature of aromatic compounds, which are compounds based on the benzene molecule.

Kekule’s novel proposal for a cyclic benzene structure theory provided the scientific basis for the dramatic expansion of the German chemical industry in the last third of the 19th century.

Kekule determined the valence of carbon, and was the first scientist to propose that valence could be used to analyze molecules and show how atoms link up with each other in carbon chains or skeletons.

He explained that in substances containing several carbon atoms it must be assumed that some of the affinities of each carbon atom are bound by the affinities of the atoms of other elements contained in the substance, and some by an equal number of the affinities of the other carbon atoms.

Kekule proposed that benzene had a structure in which six carbon atoms formed a ring, with alternating single and double bonds. Kekule suggested in 1872 that there were two forms of benzene, in dynamic equilibrium. Kekule's dynamical theory proved to be partially correct. In 1933 Linus Pauling used quantum mechanics to explain more fully the nature of benzene.

The empirical formula for benzene had been long known, but its highly unsaturated structure was a challenge to determine. Archibald Scott Couper in 1858 and Joseph Loschmidt in 1861 suggested possible structures that contained multiple double bonds or multiple rings.

Kekule also explained every monoderivative of benzene (C6H5X) only one isomer was ever found, implying that all six carbons are equivalent, so that substitution on any carbon gives only a single possible product. For diderivatives such as the toluidines, C6H4(NH2)(CH3), three isomers were observed, for which Kekule proposed structures with the two substituted carbon atoms separated by one, two and three carbon-carbon bonds, later named ortho, meta, and para isomers respectively.

Kekule modified his proposal in 1872 and suggested that the benzene molecule oscillates between two equivalent structures, in such a way that the single and double bonds continually interchange positions.

Kekule also extended his ideas by suggesting that two carbon atoms bonded together in the formation of hydrocarbons such as ethane (C2H6). After some research works he proposed an additional carbon and hydrogen units could be added, extending the carbon atom chain and forming an ordered series.

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