Some areas of science progressed via very famous predictions that were subsequently verified by experiments. Think of Einstein and gravitational waves or of Dirac and the positron. There are fewer well-known examples in chemistry; perhaps Watson and Crick’s prediction of the structure of DNA, albeit based on the interpretation of an existing experimental result. Here I take a look at a what if, that of John Kirkwood’s prediction of the absolute configuration of a small molecule based entirely on matching up the sign of a measured optical rotation with that predicted by (his) theory.
Archive for November, 2019
Prediction preceding experiment in chemistry – how unlucky was John Kirkwood?
Saturday, November 30th, 2019The Structure of Tetrodotoxin as a free base – with a better solvation model.
Tuesday, November 26th, 2019In the previous post, I discussed the structure of the free base form of tetrodotoxin, often represented as originally suggested by Woodward[1] below in an ionic form:
References
- R.B. Woodward, "The structure of tetrodotoxin", Pure and Applied Chemistry, vol. 9, pp. 49-74, 1964. http://dx.doi.org/10.1351/pac196409010049
The Structure of Tetrodotoxin as a free base.
Saturday, November 9th, 2019The notorious neurotoxin Tetrodotoxin is often chemically represented as a zwitterion, shown below as 1. This idea seems to originate from a famous article written in 1964 by the legendary organic chemist, Robert Burns Woodward.[1] This structure has propagated on to Wikipedia and is found in many other sources. 
With the elegance and the unique style that is typical Woodward, his article is a tour de force because of the way in which he deploys a large armoury of spectroscopic (X-ray crystal,† NMR, IR) as well as physicochemical (pKa) tools to infer this structure; an approach that has been subsequently widely emulated. The article a well worth a read for the elegant logic that slowly builds to a climax on page 73 (sic!) of the article, when he unveils his final structure (XXXVIII, or 38). The lecture(s) from which the article is apparently derived must have been one hell of an occasion.‡
References
- R.B. Woodward, "The structure of tetrodotoxin", Pure and Applied Chemistry, vol. 9, pp. 49-74, 1964. http://dx.doi.org/10.1351/pac196409010049