Ch_322a_4.015

Ch_322a_4.015 - The Conformations of Cyclohexane Baeyer...

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The Conformations of Cyclohexane Baeyer Strain Theory Cyclohexane Baeyer's theory predicts considerable strain in cyclohexane, which he assumed had the geometry of a hexagon with an internal angle of 120 o . 120 o severe angle strain in planar cyclohexane The prediction is wrong because cyclohexane is not planar . Cyclohexane exists in nonplanar geometries with the most stable being the "chair" with internal bond angles of 109.5 o . In addition, there is no torsional strain in this conformation. In 1885 Adolf von Baeyer (Univ. of Munich) proposed a theory to explain aspects of the chemistry of cycloalkanes. He assumed the structures were plana r, and qualitatively estimated the amount of strain in each according to the difference between the internal angle of the regular polygon, and the idealized bond angle of the recently deduced tetrahedral carbon. This theory became known as the Baeyer strain theory .
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The Chair Conformation of Cyclohexane H H H H H H H H H H H H chair 109.5 o Newman projection view A Newman projection shows that the hydrogens are in a staggered conformation free of torsional strain. H H H H CH 2 CH 2 The most stable conformation of cyclohexane is the chair in which there is neither angle nor torsional strain . The chair has the usual wig wag geometry of an alkane induced by linking a series of tetrahedral carbons.
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Two Types of Hydrogens: Axial and Equatorial There are two types of H in
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This note was uploaded on 07/22/2009 for the course CHEM 322AL taught by Professor Jung during the Summer '07 term at USC.

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Ch_322a_4.015 - The Conformations of Cyclohexane Baeyer...

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