L07 Chem 261 Lecture Notes - Lecture 5: Gene Bilbrew, Hyperconjugation, Butane
13 Dec 2016
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Both will have the same keq and are identical: keq = products/reactants. For anti gauche, keq = gauche/anti, so we can derive gauche : anti : gauche ratio. % anti = 1 / (1 + 2keq), % gauche = 2keq/(1 + 2keq) Ie- -oh is smaller than ch3: look at sterics. Fewer carbons reduce sterics: for straight chains, there is about the same g (from butane to pentane) since there are the same kinds of bonds. Ie- steric interaction of ethyl (et) and methyl (me) is very similar to me-me interaction since the extra carbon can get out of the way on et: as there is more branching, there are much larger steric interactions. Ie- 2-methylpentane has sterics between a me and ipr group (larger than butane me- This *(c-f) orbital has a larger contribution from c and when in phase with the c-h bond, can have a very weak pi-like interaction.
