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34 Cards in this Set
- Front
- Back
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SN2 rxn - mechanism
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one step - rate determining step
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SN2 rxn - stereochemistry
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Inversion
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SN2 rxn - favored substrate
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Methyl/Primary
Will go SN2 with secondary and weak bases Won't react with tertiary |
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SN2 rxn - big obstacle
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steric hindrance
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SN2 rxn - nucleophile
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Requires good, unhindered nucleophile/strong base
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SN2 rxn - preferred solvent
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polar aprotic
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SN2 rxn - leaving group
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requires good leaving group (because leaving group is in RDS)
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SN1 and SN2 - 5S
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Nucleophile
Substrate Solvent Speed Stereochemistry Skeleton |
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Nucleophiles for SN1/SN2
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SN2 requires a strong nucleophile
SN1 doesn't care about nucleophile strength (not in rate) |
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Substrates for SN1/SN2
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SN2 favors methyl, primary. Will occur with secondary.
SN1 favors tertiary. Will occur with secondary. |
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Solvents for SN1/SN2
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SN1 favors polar protic solvents
SN2 favors polar aprotic solvents |
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Speed for SN1/SN2
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SN2 depends on concentration of substrate and nucleophile
SN1 depends only on concentration of substrate |
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Stereochemistry for SN1/SN2
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SN2 inverts stereochemistry
SN1 creates racemic mixture |
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Skeleton for SN1/SN2
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SN1 can undergo rearrangement
SN2 will never undergo rearrangement |
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SN1 rxn - mechanism
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two steps:
- formation of carbocation - nucleophilic attack |
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SN1 rxn - stereochemistry
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Creates racemic mixture
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SN1 rxn - favored substrate
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Tertiary
Will react with secondary with H2O or MeOH as nucleophile |
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SN1 rxn - big obstacle
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stabilizing carbocation
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SN1 rxn - nucleophile
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doesn't matter (can work with poor/weak Nu)
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SN1 rxn - preferred solvent
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polar protic
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SN1 rxn - leaving group
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requires good leaving group
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Methyl halides - rxn
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SN2
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Primary alkyl halides
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SN2 with strong unhindered base/weak base
E2 with bulky base |
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Secondary alkyl halides
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SN2 with weak bases
E2 with strong bases |
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Tertiary alkyl halides
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E2 with strong base
SN1 (major) with weak base E1 (minor) with weak base |
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Nucleophilicity - same element
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Negative charge -> better Nu
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Basicity - same element
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Negative charge -> stronger base
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Leaving group - same element
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Positive charge -> better leaving group
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Nucleophilicity - different elements (same row)
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Less electronegative -> better Nu
more willing to donate electrons |
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Basicity - different elements (same row)
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Less electronegative -> stronger base
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Leaving group - different elements (same row)
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More electronegative -> better leaving group
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Nucleophilicity - different elements (same column)
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bigger -> better Nu (usually)
(big Nu’s are less hindered by solvent, more polarizable) |
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Basicity - different elements (same column)
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bigger -> weaker base
(large base can spread out and stabilize electron density) |
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Leaving group - different elements (same column)
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bigger -> better leaving group
(big LG’s can spread out and stabilize electron density) |
