CHEM 211 Lecture Notes - Lecture 12: Ring Strain, Ethane, Cyclopentane
6 Oct 2016
School
Department
Course
Professor
Document Summary
Ethane (c2h6: has degrees of rotation. Pi bonds limit degrees of rotation, but sp3 has no pi bonds: as your rotate the molecules because of the bonds, you create conformational isomers. Ethane has two different kinds of conformational isomers: one where the hydrogens are aligned (eclipsed), one where the hydrogens are spaced (staggered). The higher energy conformational isomers are more ordered: you can draw out an energy diagram using rotations, you can draw out projections on paper. Butane (c4h10: anti = staggered, gauche = intermediate between staggered and eclipsed, gauche is higher energy then antis, but but as high energy as eclipsed groups. More stable = lower, less stable = higher energy. Cyclopropane = 3 c 6 h. unstable: angle strain. wants to be 109. 5, but angles are around 60. Cyclobutane = 4 c 8 h. unstable, but not as unstable as cyclopropane: angle strain. wants to be 109. 5, but angles are around 90, a pucker exists.
