A set of chemical transformations starting from benzaldehyde and product analyses revealed the robust benzoyl radical (which had been hypothesized by Lavoisier in 1789).
Wöhler and Liebig, "Studies on the Radical of Benzoic Acid"
Annalen der Pharmacie, 3, 249 (1832)
The paper begins with the following semi-optimistic statement:

Whenever in the murky area of organic nature one comes across a point of light that seems to offer us an entry through which perhaps to gain the true path for investigating and understanding it, one always has cause to count oneself fortunate, even though one is aware of the inexhaustibility of the basic subject.

It then proceeds to describe the following transformations:

Other quotes from the paper:
Why -yl is the radical suffix. The Greek word translitterates as ule which is how -yl sounds in German):
We call it benzoyl (the ending from υλη, substance, matter). The resulting name for pure oil of bitter almonds would be benzoyl hydride and for benzoic acid, benzoyl acid. Naturally we will continue to use the old names oil of bitter almonds and benzoic acid when it is not a question of theoretical explanations.
On pure "Benzoylhydride" [benzaldehyde] from "bittermandelöl" [oil of bitter almonds]:
Its odor is not much different from that of the crude oil; its taste is biting and aromatic.
On benzoyl cyanide:
Its taste is pungent, sweet, weaker than hydrogen cyanide.

Liebig and Wöhler lived full lives (to age 70 and 82, respectively), but of course many 18th and 19th century chemists suffered for their discoveries.

Click here for a lighthearted problem involving Contemporary Relevance of a Traditional Radical

Return to Chem 125 Homepage

Return to Time Line

copyright 1999 J.M.McBride