How the Misuse of Symmetry Can Obscure the Underlying Science: Furan, Pyrrole and Formamide Case Studies

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 15 (2010) pp 268-271

How the Misuse of Symmetry Can Obscure the Underlying Science: Furan, Pyrrole and Formamide Case Studies

Shannon G. Lieb

Department of Chemistry, Butler University, Indianapolis, IN 46208, slieb@butler.edu
Received September 9, 2009. Accepted April 9, 2010.

Published: 20 July 2010

Abstract. Hybridization and Valence Shell Electron Pair Repulsion (VSEPR) theory, and its underlying symmetry, are invaluable aids to quickly assign bond angles around individual second row atoms within a molecule. In the cases of oxygen and nitrogen atoms, this can lead to false conclusions as to an appropriate atomic orbital hybridization and local symmetry of those orbitals when compared to experimental finding. This becomes most evident when an extended conjugation of a lone pair of electrons on nitrogen or oxygen creates a situation that “breaks the rules” of hybridization. A method of introducing hybridization other than sp3 for nitrogens and oxygens, which are “neighbors” to a double bond is presented.

Key Words: In the Classroom; general chemistry; organic chemistry; physical chemistry; quantum mechanics; lewis structures; valence shell electron pair repulsion; hybridization; huckel’s rule of aromaticity; symmetry and group theory

(*) Corresponding author. (E-mail: slieb@butler.edu)

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