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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: darkdevil on July 16, 2016, 06:09:24 AM

Title: Can Frost Circle (Huckle Rule) be applied to fused aromatic ring systems?
Post by: darkdevil on July 16, 2016, 06:09:24 AM

According to Hückel's rule, an aromatic compound must have (4n + 2) π electrons
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However, most examples showed in textbooks only demonstrated simple aromatic compounds such as benzene. I wonder if the Frost Circle rule can be applied to heterocyclics such as indoles or other fused ring systems? and how do you draw the Frost Circle of them? which vertex to choose as the bottom orbital?

Thanks!!!

Title: Re: Can Frost Circle (Huckle Rule) be applied to fused aromatic ring systems?
Post by: sjb on July 16, 2016, 08:20:20 AM

I think probably not, at least not simply. One of the simplifications I think Frost Muslin(?) diagrams imply is that the molecule in question is fairly highly symmetric, so would not work for e.g. indole, let alone things like thiophene or imidazole.