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Hückel's rule
In organic chemistry, Hückel's rule estimates whether a planar ring molecule will have aromatic properties. It was formulated by physical chemist Erich Hückel in 1931. A cyclic ring molecule follows Hückel's rule when the number of its pi electrons equals 4n + 2 where n is zero or any positive integer.
Hückel's rule is not valid for many compounds containing more than three fused aromatic nuclei in a cyclic fashion like in pyrene or coronene.
The Pariser-Parr-Pople method is a more precise method of estimating whether a cyclic ring molecule is aromatic.
Last updated: 05-26-2005 04:53:08
10-26-2009 08:16:03
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The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details