CH 6-7 Elimination Reactions – Part I

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Elimination Reactions

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Elimination Reactions

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Presentation transcript:

CH 6-7 Elimination Reactions – Part I All SN1 reactions, and some SN2 reactions are accompanied by Elimination Reactions to form alkene products: The Nuc acts as a base, grabbing an acidic b-H. The stronger the base, the more elimination product. +

Keys to Interpreting Elimination Reactions In the substrate, where is the a-carbon (contains Lg), and the b-C’s & b-H’s? Double bond forms between a-C & b-C); Evaluate substrate structure: 1o, 2o, or 3o alkyl halide Is the nucleophile a weak or strong base; small or bulky? Mechanism(s)? (SN1&E1, SN2&E2, only SN2, only E2) Products? For Elimination Reactions: How many alkene products are formed and what is the structure and geometry of the alkene products (cis vs trans)?

The E2 Elimination Mechanism E2: “Elimination….Bimolecular” Rate = k [nucleophile] [substrate] (2nd order reaction) Nucleophile is a strong base “Concerted” Mechanism: E2 may accompany an SN2 reaction (not always).

The E2 Elimination Mechanism – T.S.