251_NSE.txt

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Author:
mish
ID:
48835
Filename:
251_NSE.txt
Updated:
2010-11-11 17:42:42
Tags:
orgo organic chemistry nucleophilic substition elimination
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Description:
Organic chemistry: nucleophilic substition and elimination.
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  1. 4 factors to consider in SN1 vs. SN2:
    • 1. Substrate: SN2 is methyl/primary/secondary, SN1 is secondary/tertiary.
    • 2. Nucleophile: good nucleophile suggests SN2 (since SN1 can use a bad nucleophile).
    • 3. Leaving group: better leaving group suggests SN1, since carbocation forms more easily.
    • 4. Solvent: SN1 prefers polar protic, SN2 prefers polar aprotic.
  2. 2 factors to consider in substitution vs. elimination:
    • 1. Temperature: high temp (>40) favors elimination, low temp (<20) favors substitution.
    • 2. Base/nucleophile size: large/bulky favors elimination, small favors substitution.
  3. Mechanism of SN1 reaction:
    • 1. Leaving group leaves, creating a carbocation.
    • 2. Nucleophile attacks carbocation.
  4. Mechanism of SN2 reaction:
    Leaving group leaves, while nucleophile attacks from opposite side.
  5. Product stereochemistry in SN1 vs. SN2:
    racemic mixture in SN1 vs. inverted in SN2.
  6. Acid-catalyzed dehydration of 1o alcohols (solvent, NSE?, steps):
    • use concentrated H2SO4; E2 process
    • fast protonation of hydroxyl group, slow departure of H20)
  7. Acid-catalyzed dehydration of 2o/3o alcohols (solvent, NSE?, steps):
    • use concentrated H2SO4; E2 process
    • fast protonation of hydroxyl group, slow departure of H20)

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