Arsole Yes, believe it or not, there is actually a molecule called Arsole... and it's a ring! It is the arsenic equivalent of pyrrole, and although it is rarely found in its pure form, it is occasionally seen as a sidegroup in the form of organic arsolyls. For more information, see the paper with probably the best title of any scientific paper I've ever come across: "Studies on the Chemistry of the Arsoles", G. Markl and H. Hauptmann, J. Organomet. Chem., 248 (1983) 269. Although the class of molecules with this general structure are called 'arsoles', the specific molecule shown on the right is actually called 'arsenole' (not to be confused with the London football club, Arsenal). Contrary to popular belief, new research (see reference below) shows that arsoles are only moderately aromatic... Incidentally US patent number US 3 412 119 by the Dow Chemical Company is entitled 'Substituted Stannoles, Phospholes, Arsoles, and Stiboles' - I didn't know there was a substitute for an arsole...

Furthermore, if six of them are bonded together we can apply the prefix 'sexi', to get 'sexiarsole'. And the structure where arsole is fused to a benzene ring is called 'benzarsole'; 6 of these bonded together would be called 'sexibenzarsole' (although neither of those sexi- molecules have been synthesised yet). Another well known poisonous arsenic molecule is the simple hydride, called 'arsine', with formula AsH 3 .

And on a related theme, I've been told of an Aryl Selenide compound with the superb shorthand of ArSe, which is both toxic and smelly. The paper it comes from in J. Am. Chem. Soc. was published by authors from, of course, the University of Aarhus! I've been told that it's possible to make molecules with Se-Se bonds, so if ArSe is bonded to a selenium halide (with X representing Br, Cl, etc), then it's possible to make ArSe-SeX. I'll leave this as a challenge to synthetic chemists to first try to make this compound, and then to try to get its name in the title of a paper!

Also, the related molecule phosphole (which just replaces As with P) is quite amusing if you are a French speaker, since it's pronounced the same as 'fausse folle'. Fausse means 'fake' or 'false', and folle means both a 'crazy woman' and a 'drag-queen' or 'ladyboy'. Thanks to Neil Brookes, Nicholas Welham, Andy Shipway, Lloyd Evans, Peter Sims, John Perkins, Bob Buntrock and Ben Mills for some of the info and details about these molecules. This article inspired Mikael Johansson from Helsinki University to do a scientific study into the aromaticity of arsoles, which has been published: Letts. Org. Chem. 2 (2005) 469. Another intriguing reference supplied by Patrick Wallace is: G. Märkl and H. Hauptmann, "Unusual Substitution in an Arsole Ring", Angew. Chem. Int. Ed. . 11, (1972) 441, and another one supplied by Simon Cotton is: "Arsole metal complexes", E.W. Abel, I.W. Nowell, A.G.J. Modinos, C. Towers, J. Chem. Soc., Chem. Commun., (1973) (7), 258-259. Thanks also to Thomas Jeanmaire and Alan Parker for the info and translation about phosphole.