CHM136H1 Lecture Notes - Lecture 10: Cyclopentane, Cyclopropane, Ring Strain
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CHM136H1 Full Course Notes
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Document Summary
Cyclic compounds include: proteins, lipids, carbohydrates, nucleic acids, steroids. *substituents group are given the lowest possible number. Cycloalkanes: are less flexible than open chain alkanes. Compounds having the same atom connectivity but different 3d. Cis: when the substituent groups are on the same side. Trans: when the groups are on opposite sides. The different cis and trans conformations cannot interconvert. Ring larger than three atoms are not flat. Cyclic molecules assume non planar conformations to minimize angle strain and torsional strain by ring puckering. Larger rings have: many possible conformations difficult to analyze. Rings from 3 to 30 c"s do exist but are stained due to bond bending distortions and steric interactions. Strain summary: angle strain: expansion or compression of bond angles away from the most stable (tetrahedral, torsional strain: eclipsing strain, were bonds are lined up, steric strain: repulsive interactions between non bonded atoms in close proximity. Requires that sp3-sp3 or sigma bonds are bent and weakened.
