CHEM266 Chapter Notes - Chapter 5: Van Der Waals Strain, Eclipsed Conformation, Staggered Conformation
4 Oct 2016
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Document Summary
Bonds are free to rotate, allowing molecules to adopt different orientations in space. Conformations (or rotamers): temporary molecular shapes caused from rotation about single bonds. Conformational analysis: study of energy changes due to a molecule rotating around bonds. Dihedral angle: separates a bond on one atom from a bond on a nearby atom. Eclipsed conformation: occurs when the dihedral angle is 0 . Staggered conformation is 12 kj/mol more stable than the eclipsed conformation because of the e- repulsion between c-h bonds between adjacent carbons. Torsional strain: difference in energy between the two conformations (staggered and eclipsed) Bond rotates and the potential energy of the molecule changes eclipsed is 12 kj/mol less stable and has a higher potential energy. 2 staggered conformations of butane anti and gauche. 2 eclipsing conformations of butane one with eclipsing hydrogens and eclipsing hydrogen-methyls, and the other eclipsing methyls and eclipsing hydrogens.
