Steric hindrance at the electrophilic carbon slows the

Steric hindrance at the electrophilic carbon slows the

Steric hindrance at the electrophilic carbon slows the SN2 reaction. no SN2

polar solvents especially good for SN1 (OK for some SN2)

aprotic solvents (no H on O or N) cannot H-bond to Nu especially good for SN2

Intramolecular Reactions (within one molecule) forms ring

Intramolecular reactions that form 3, 5, and 6 membered rings are faster. (favorable entropy)

E1 has the same first step as SN1 (carbocation formation). Some E1 always accompanies SN1.

Fig. 9-8, p. 368 Table 9-11, p. 368

The Competition between Elimination and Substitution Methyl Substrates: CH3L SN2 only

Primary Substrates: RCH2L good for SN2 with almost any nucleophile no SN1/E1 can cause E2 with a sterically hindered strong base

potassium tert-butoxide (KOt-Bu) Secondary Substrates: R2CHL SN2 favored with good Nu that is not too basic

(especially in aprotic solvents) CH3CO2, RCO2, CN , RS E2 favored with strong bases HO , RO (NaOH, NaOEt)

SN1 favored by absence of good Nu in polar solvent often neutral or acidic conditions some E1 product is usually formed

a solvolysis reaction Tertiary Substrates no SN2 (too hindered)

E2 favored with strong bases HO , RO (NaOH, NaOEt) SN1 favored by absence of good Nu in polar solvent often neutral or acidic conditions

some E1 occurs SN2 and E2 favored over SN1 and E1 by a strong base/Nu

SN2 is slowed by steric hindrance, but E2 is not strong base, strong Nu strong base means E2, not SN1

SN2 and E2 Stronger bases favor E2 over SN2

stronger base weaker base SN2 and E2

higher temperatures favor elimination G = H - TS SN2

weaker bases less steric hindrance lower temperature

E2 stronger bases more steric hindrance higher temperature

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