CHE-2201 Lecture Notes - Lecture 9: Rate-Determining Step, Sodium Borohydride, Gibbs Free Energy
Document Summary
A pi bond is converted to two sigma bonds. A pi bond will often act as a lewis base (as a nucleophile or as a bronsted-lowry base) Addition reactions and elimination reactions are often in equilibrium with each other. We use gibbs free energy to assess which side will be favored. We expect the addition reactions to be favored enthalpically. We expect the elimination reactions to be favored entropically. Low temperature favors addition ; high temperatures favor eliminations. Markovnikov"s rule: in general, h atoms tend to add to the c already bearing more. Anti-markovnikov products are observed when reactions are performed in the presence of peroxides (r-o-o-r) Formation of a carbocation is usually always the rate determining step. In many addition reactions, chirality centers are formed. The carbocation is planar, it can be s or r equally. Rearrangements occur for the carbocation if the shift makes it more stable. Increasing the concentration of cl- can help in prohibiting the rearrangement.
