CHEM 212 Lecture Notes - Lecture 8: Ethylene, Atomic Number, Geminal
17 Jun 2015
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Chem 212: introductory organic chemistry 1 lecture 8: ionic reaction (part 2)& Factors that affect the rate of e1 and e2 reactions (cont) E1--no effect on rate, therefore, weak base is ok. Base is not involved in rate determining step. Solvolysis competition--substitution by solvent molecule always joint with. E2--has strong effect on rate, therefore must be good bronsted base and concentration matters a lot. Base is involved in rate determining step; therefore e2 reaction needs a strong base, which is a conjugate acid with high pka--need to possess very weakly acidic c-h bond. Polar protic > pola aprotic>>>non-polar (just like sn!) Polar protic solvent--best cation solvation -- carbocations are stabilized when solvated more effectively. Protic solvent surrounds strand base and therefore reduce reactivity of it. Aprotic solvents has low anion solvation--improve base reactivity. Protic solvents has stronger anion solvation --lower base reactivity. The weaker base the leaving group is, the better the leaving group (more stable)
