1. Stereochemistry in The SN2 Reaction: A Stereospecific Reaction
CH 6-2: SN2 Reaction-II
Stereochemistry in The SN2 Reaction: A Stereospecific Reaction
(S)
(R)
“Inversion of Configuration”……..Why?

2. Example: SN2 Reaction? (R) (S)
What is the configuration at the chiral center in reactant and product?
Is there an “Inversion of Configuration”?
Is this an SN2 reaction?

3. Re-cap: The SN2 Substitution Reaction
A bimolecular, concerted mechanism
Energy Diagram: minimum of one step (one T.S.)
“Pentavalent Carbon” in the T.S.; crowded T.S.
Nuc “grabs” the electrophilic carbon 180o opposite the Lg.
Stereospecific reaction; inversion of configuration

4. Alkyl Halide Structure in SN2 Reactions
What was the significance of the SN2 Transition State?
CROWDED!
How would large “R” groups effect the reaction?
Rank the following substrates in order of SN2 reactivity:
Methyl >>> 1o > o >>>>> o (NR)

5. Alkyl Halide Structure in SN2 Reactions
Methyl >>> 1o > 2o >>>>>>>>>>>>> 3o (NR)

6. Alkyl Halide Structure in SN2 Reactions
Halogens bonded to sp2 carbon (vinyl and phenyl halides) do not undergo substitution:
WHY NOT?