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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.
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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.
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Mechanism of SN1 reaction:
- 1. Leaving group leaves, creating a carbocation.
- 2. Nucleophile attacks carbocation.
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Mechanism of SN2 reaction:
Leaving group leaves, while nucleophile attacks from opposite side.
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Product stereochemistry in SN1 vs. SN2:
racemic mixture in SN1 vs. inverted in SN2.
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Acid-catalyzed dehydration of 1o alcohols (solvent, NSE?, steps):
- use concentrated H2SO4; E2 process
- fast protonation of hydroxyl group, slow departure of H20)
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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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