CHM136H1 Lecture Notes - Lecture 4: Cyclohexane Conformation, Tetrahedron, Ring Strain

• School: UTSG
• Department: Chemistry
• Course: CHM136H1
• Professor: Andrew( Andy) Dicks

Document Summary

You cannot just rotate when you have a ring structure. Stereoisomers: compounds having the same atom connectivity but different 3d atomic arrangements in space. Cis two groups on the same face of the ring. Trans one group on top, one on the bottom. Rings 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. It was known that the tetrahedral angle was important for carbon. Cyclohexane is considered to be a strain free molecule (thus, why it is so abundant in biological compounds) Ri(cid:374)gs fro(cid:373) 3 to 30 c"s do e(cid:454)ist (cid:271)ut are strai(cid:374)ed due to (cid:271)o(cid:374)d (cid:271)e(cid:374)di(cid:374)g distortio(cid:374)s a(cid:374)d steri(cid:272) interactions. Angle strain: expansion or compression of bond angles away from most stable. Mainly compressed away from the ideal tetrahedral angle for a singly bonded carbon atom. Torsional strain: eclipsing of bonds on neighbouring atoms (eclipsing strain)