Science Poetry

Flat Confirmation

Cogitate, calculate: 
Dame Kathleen Lonsdale,
Through X-ray spectroscopy,
Compound discerns.
Insight incipient: 
Hex-methyl-ation will 
Benzene’s geometry 
Flatly confirm.

As a new year and new semester are now officially underway, I will return to the weekly routine of these posts.  The 11 April 2022 poem began the 2022 week of “Twitter biographies.”  The first was a pseudo-double-dactyl poem summarizing a key experimental insight in chemistry from Kathleen Lonsdale, who lived from 1903-1971.  

“Cogitate, calculate: /
Dame Kathleen Lonsdale, /
Through X-ray spectroscopy, /
Compound discerns…”

Dame Kathleen Lonsdale was the first woman elected as president of the International Union of Crystallography, in addition to many, many other honors.  

X-ray crystallography is a technique in which, by sending high-energy X-rays at a sample of a compound, a chemist can examine how those X-rays are scattered: a useful analogy might be inferring the shape of an object from the shadow it casts, although X-ray crystallography techniques are far more involved and exacting.  Many compounds’ structures have been discerned through this technique, generalized in the poem as “X-ray spectroscopy” (again, a less precise characterization than is ideal, this time for the sake of the meter).          

“Insight incipient: /
Hex-methyl-ation will / 
Benzene’s geometry /
Flatly confirm.”

The specific experiment commemorated in this poem was Lonsdale’s use of X-ray crystallography to determine the geometry of benzene, a compound which had interested chemists for many years.  Before this insight, it was known that a benzene molecule contained six carbon atoms and six hydrogen atoms and arranged these atoms cyclically, in a ring.  However, scientists had still disagreed for decades as to its planarity: was the ring flat?  (Did it have all of its carbon atoms in the same plane?)    

Lonsdale determined an answer to this question by analyzing a derivative of benzene called hexamethylbenzene, which has a methyl group (-CH3) attached to each carbon in the benzene ring.  She noted that the central benzene ring had to be flat to account for the results seen via her X-ray crystallography experiment.  Thus, the geometry was “flatly confirm[ed]”: benzene was shown to be planar, via significant and convincing evidence.