Unformatted text preview: SN1 SN 2 Mechanism Two steps: R-L R+ Kinetics 1st order (unimolecular)
Rate = k[R-L]
Ionization is the rate determining
step 2nd order (bimolecular)
Rate = k[R-L][Nu:] Stereochemistry Racemization Inversion Carbon (sp3)
electrophile Favored by electrophiles which can
best stabilize a carbocation.
3° > benzylic ~ allylic ~2° >1° Steric hindrance controlled
CH3 > 1° > 2° (no tertiary) Nucleophile Nature of nucleophile has no effect
on rate Favored by better nucleophiles
RS->NC->I->RO->HO->Cl- Leaving group Favored by better leaving groups:
-N2 > -Otos > -I > -Br > -Cl> -OH2 Favored by better leaving groups:
-N2 > -Otos > -I > -Br > -Cl Solvent effect Favored by polar, ionizing solvents.
Solvolysis: polar protic solvents act
H2O>H2O/ROH (mix)>ROH Favored by polar aprotic solvents.
Disfavored by polar protic
solvents (H-bonding) Competing
reactions E1, rearrangements E2 by strongly basic nucleophiles R-Nu One step: R-L + Nu: R-Nu ...
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- Fall '09
- Solvent, NC, 1°, 2°, 3°, ROH