CHEM266 Study Guide - Substituent, Conformational Change, Chemical Formula
2 Dec 2012
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Document Summary
Conformations (rotamers) temporary molecular shapes resulting from rotation around single bonds. Dihedral angle = angle between 2 groups can range anywhere from 0 to 180 . Staggered conformation lowest in energy: everything is furthest from each other (little steric interaction) Eclipsed conformation highest in energy: steric interaction. Anti conformation = dihedral angle of 180 lowest energy conformation: maximum separation of methyl groups (furthest apart) Angle strain = in cycloalkanes, having bond angle different than 109. 5 . Conformations of cyclohexane chair: no angle strain all bonds are ~109. 5 , no torsional strain (all h"s are staggered; none eclipsed) Boat conformation is much higher in energy than the chair conformation of cyclohexane. Axial = bonds that go straight up and straight down. Equatorial = bonds at obtuse angles (>90 ) from axial substituent. If axial bond is up, the equatorial bond will be below the horizontal plane.
