Reactions of nucleophile at saturated carbons

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    Isabelle

    Cards (25)

    • What are key factors influencing the reaction pathway?
      • Substrate structure
      • Leaving group
      • nucleophile and base
      • solvent
      • temperature
    • How does substrate structure reaction pathway?
      • reaction site hindered or not
      • Stabilisation of intermediates or transition states by subtituents
    • How does leaving group ability impact reaction pathway?
      Stabilisation of leaving group (pka)
    • how does nucleophile affect?
      • Steric bulk
      • hard/soft
      • pKa
    • How does solvents affect reaction pathway?
      Stabilises TS or intermediate by solvation
      • polar protic stabilises cationic intermediate
      • Polar aprotic solvates nucleophile counter, increase nucleophile strength
    • how does temperature affect the reaction pathway?
      Entropy factors favour elimination
    • What is an SN1 reaction?
      Unimolecular (first order),
      • two steps
      • formation cation intermediate
    • what is an SN2 reaction?
      Bimolecular (second order)
      • one step
    • what does the rate of reaction depend for an SN1 reaction?
      • ONLY on the concentration of the substrate
    • How many transition states to an SN1?
      2
    • What determines the enantiomers formed from a SN1 reaction?
      Racemization (S/R) chiral centres
    • What is the rate determining step for an SN2 reaction?
      product formation
    • what is the rate of reaction for SN2 reaction?
      depends on concentration of the substrate
      Depends on the concentration of the nucleophile
    • What occurs at the SN2 transition state?
      The filled p orbital at the central carbon atom shares one pair of electrons between the old and new bond (new= nucleophile, old = leaving)
    • What is responsible for the geometry of the transistion state?
      HOMO-LUMO interactions
    • what is a good HOMO-LUMO interaction?
      a large coefficient
    • What is the HOMO of SN2?
      Lone pair on Nucleophile
    • what is the LUMO of SN2?
      C-LG sigma*
    • what is a back-side attack?
      Nucleophilic attack from the back of a molecule.
    • What is the transition state geometry of a SN2 reaction?
      trigonal bipyramidal
    • Does racemisation occur in SN2 reactions?
      No, inversion of configuration instead
    • Can SN1 occur at sp2 centres?
      no
    • Why cant sp2 occur with Sn1?
      no stabilisation from pi orbitals, so no overlap possible as pi orbitals are orthogonal to empty Sp2
    • Does SN2 occur at sp2 centres?
      no
    • why does does no SN2 occur at aromatic rings?
      Approach od nucleophile into a C-LG sigma* is blocked by the rest of the aromatic ring.
      • Inversion of configuration impossible
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