10-18 - Which SN2 reaction is faster? If the atom type (row...

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1 Which S N 2 reaction is faster? + CH 3 CO 2 Na Br O O A 37 + Br Br + NaOH OH + Br - B Why? stronger conjugate acid weaker base weaker conjugate acid stronger base If the atom type (row of periodic table) changes, then nucleophilicity may not be determined by basicity. OH CH 3 C O O HO H basicity nucleophilicity 38 SH pK a = 16 7 H H CH 3 C O O H basicity nucleophilicity If the atom type (row of periodic table) changes, then nucleophilicity may not be determined by basicity. 39 basicity nucleophilicity Why are some species, such as H-S and I weak bases and strong nucleophiles? 40 basicity nucleophilicity Sulfur has more polarizable electrons (3s/p) and can form strong bonds at long distances. O H X C R R R HO C R R R X weak bond in transition state b l f i lib l 41 S H X C R R R HS C R R R X because sulfur is more polarizable a stronger bond is formed in the transition state O H HO C R R R Cl Cl C R R R 42 HS C R R R Cl Cl C R R R S H
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2 HO C R R R Cl Cl C R R R O H 43 The S N 2 Reaction is very sensitive to steric effects. S H HS C R R R Cl Cl C R R R Predict, with an explanation, which one of the following reactions will occur at a faster rate. CH 3 CH CH 2 Br CH 3 + O CH 3 CH 3 CH CH 2 CH 3 OCH 3 A 44 + CH 3 CH CH 2 Br CH 3 S CH 3 CH 3 CH CH 2 CH 3 SCH 3 more polarizable nucleophile Any solvent, but the same for both B Predict, with an explanation, which one of the following reactions will occur at a faster rate. CH 3 CH CH 2 CH 3 I + CH 3 SO 3 - more polarizable nucleophile A 45 CH 3 CH CH 2 CH 3 Cl + CH 3 SO 3 - Any solvent, but the same for both B Halide Nucleophilicity SH OH basicity nucleophilicity 46 IB rC lF >>> nucleophilicity (H-bonding solvent) basicity Factors affecting S N 2 reaction rate CX Nu 1. nucleophilicity of the nucleophile.
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10-18 - Which SN2 reaction is faster? If the atom type (row...

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