Today In Science History – July 13


August Kekulé

Friedrich August Kekulé von Stradonitz. (1829-1896) German chemist

July 13 marks the passing of one of the most prominent chemists of the 19th Century, August Kekulé.

Kekulé is credited as the man who discovered the tetravalence of carbon, carbon atoms could bond to other carbon atoms and discovered the bonding order of atoms in a molecule. He was the first to draw chemical structures where atoms were connected by lines to represent the bonds between them.

Kekulé’s theory of molecular bonding would chain together atoms by their valence charges. This allowed chemists to better understand and visualize what the molecule looked like. This in turn allowed chemists to predict what it would take to break apart molecules and synthesize new ones. While this theory was more of a rule of thumb and many exceptions could be found, it’s use greatly advanced organic chemistry in a short amount of time.

Benzene 3D

3D Ball and Stick model of the benzene molecule. Credit: Todd Helmenstine

Kekulé is often credited for discovering the ring structure of the benzene molecule. Benzene consists of six carbon atoms forming a ring, with one hydrogen atom bonded to each carbon. Kekulé wrote about the method of his discovery where he was sitting by the fireplace and started to nod off. He dreamed of atoms arranging themselves in groups of ever increasing size until they became long chains. The chains started to wind and turn like snakes until one snake grabbed its own tail. He woke up suddenly and spent the rest of the night working out the structure. It just goes to show that if you let your mind wander, you may figure out a solution to a problem. That, or it shows chemists can have some strange dreams.


About Todd Helmenstine

Todd Helmenstine is the physicist/mathematician who creates most of the images and PDF files found on sciencenotes.org. Nearly all of the graphics are created in Adobe Illustrator, Fireworks and Photoshop. Todd also writes many of the example problems and general news articles found on the site.