conformations

what is torsional strain?

the difference in energy between staggered and eclipsed conformations

slight: adopts an envelope conformation to avoid angle strain

none: all H bonds are adjacent

what is angle strain?*

very little: bond angles are nearly all 109.5 deg.

none: bond angles are approx. 109.5 deg.

anti

staggered form, lowest energy conformation

groups are 180 deg. apart

gauche

staggered form

steric interaction, degenerate

groups share the same space and are 60 deg. apart

eclipsed

total eclipsed

1,3-diaxial interaction

very steric, high in energy

steric interactions that occur between axial substituents in a chair conformation

numbers describe distance between the substituent and each H

what is the energy ranking of cyclohexane conformations?

half chair, boat, twist boat, chair