Archibald Scott Couper Scottish chemist Date of Birth: 31.03.1831 Country: Great Britain

1. Early Life and Education
2. Contributions and Controversies
3. Differences from Kekulé's Ideas

Archibald Scott Couper: A Scottish Chemist and Pioneer in Chemical Structure and Bonding Theories

Archibald Scott Couper was a Scottish chemist who proposed one of the earliest theories on chemical structure and bonding. He introduced the concept of tetravalent carbon atoms, which are bonded together to form larger molecules. He also demonstrated that the order of bonding between atoms in a molecule can determine its chemical properties.

Early Life and Education

Archibald Scott Couper was born into a wealthy family near Glasgow as the sole surviving son of a textile factory owner. He studied at the University of Glasgow and the University of Edinburgh, with intermittent periods in Germany between 1851 and 1854. In late 1854, he formally began his chemical research at the University of Berlin, and in 1856, he joined the private laboratory of Adolphe Wurtz at the Faculty of Medicine in Paris (now Paris Descartes University).

Contributions and Controversies

Couper published his "New Chemical Theory" in French on June 14, 1858, in a condensed form. He then published a more detailed version simultaneously in French and English in August of the same year. Couper's idea that carbon atoms can bond with each other according to the rules of valency was independently proposed by August Kekulé, who discussed the concept of tetravalent carbon earlier in 1857. However, due to disagreements with Wurtz, Couper's article appeared in print later than Kekulé's work (the latter published in May 1858), which is why Kekulé is considered the first to propose the possibility of carbon atoms bonding with each other.

When Couper expressed his discontent with Wurtz, he was expelled from his laboratory. In December 1858, Couper received an offer for an assistant position at the University of Edinburgh. However, his health deteriorated after a stroke. In May 1859, he suffered a nervous breakdown and was admitted to a private clinic. After his discharge in July of the same year, he immediately experienced a relapse, likely due to sunstroke, and underwent treatment until November 1862. His health was undermined, and he could no longer engage in serious scientific work. The last 30 years of his life were dedicated to caring for his mother.

Differences from Kekulé's Ideas

Couper's research differed from Kekulé's ideas in several aspects. Couper proposed the idea of divalent carbon, which Kekulé did not consider. He provided more accurate formulas than Kekulé in his article and even suggested heterocyclic formulas, which may have influenced Kekulé's future work on the benzene ring. Couper assumed the atomic weight of oxygen to be 8, not 16, which resulted in twice as many oxygen atoms in his formulas compared to Kekulé's. Finally, Couper used dotted lines or dashes between atoms in his formulas, which resembles the style of later structures. In this respect, his work likely influenced the early structures proposed by theorist Alexander Mikhailovich Butlerov and Alexander Crum Brown.