2-ConformAnalysisHLSF07

2-ConformAnalysisHLSF07 - Sawhorse Newman Sawhorse Newman...

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Conformational Isomers differ by rotation about single bonds. A particular conformation is called a conformer . Isomerism Revisited - Conformational Isomers Conformations of Ethane.
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Eclipsed and Staggered Conformations = torsional angle
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End-on representations for conformations are commonly drawn using a convention called a Newman projection. Step 1. Look directly down the C—C bond (end-on), and draw a circle with a dot in the center to represent the carbons of the C—C bond. Step 2. Draw in the bonds. Step 3. Add the atoms on each bond. Drawing Newman Projections Sawhorse End-on = = Newman Projection
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Conformations of Propane Staggered Eclipsed
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Unformatted text preview: Sawhorse Newman Sawhorse Newman Torsional strain: Relative Stabilities of Eclipsed and Staggered Conformations Potential Energy Vs. Dihedral Angle Butane (and Higher Alkanes) Steric strain = van der Waals repulsion: Relative Energies of Butane Conformations The energy difference between the lowest and highest energy conformations is called a Barrier to Rotation . Alkanes are often drawn in zigzag skeletal structures since the lowest energy conformation has all bonds staggered and all large groups anti. Higher Alkanes Cycloalkanes http://www.cem.msu.edu/~reusch/VirtualText/sterism2.htm#isom7...
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This note was uploaded on 05/13/2010 for the course CHEM 151L taught by Professor Roy,christopher during the Fall '08 term at Duke.

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2-ConformAnalysisHLSF07 - Sawhorse Newman Sawhorse Newman...

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