Steric hindrance at the electrophilic carbon slows the S N 2 reaction.

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

8. Hammond Postulate: the structure of the transition state for a reaction step is closer to that of the species (reactant or product of the step) to which it is closer in energy. SN1 reaction transition state resembles the carbocation

9. Effect of Substituents on the Rate of the SN1 Reaction A more stable carbocation intermediate results in a faster rate for the SN1 reaction. No SN1 for CH3Cl or CH3CH2Cl (primary)

10. Hyperconjugation works for any sigma bond on the adjacent C secondary can do 2x, tertiary can do 3x

12. 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

13. Competition Between SN1 and SN2 Reactions SN1 SN2 stabilized C+ tertiary, resonance secondary OK low steric hindrance -CH3, primary secondary OK polar solvent aprotic solvent poor Nu good Nu

14. Intramolecular Reactions (within one molecule) Intramolecular reactions that form 3, 5, and 6 membered rings are faster. forms ring (favorable entropy)

15. Carbocation Rearrangement (SN1 only) migration of H as :H – (hydride shift) or alkyl group as :R – from adjacent C to give a more stable carbocation

17. Stereoelectronic Requirement orbitals that are going to form the pi bond must overlap from the beginning (coplanar) Syn Elimination syn-periplanar conformation eclipsed

18. Anti Elimination anti-periplanar conformation Anti elimination is preferred less steric hindrance in the transition state staggered

20. Direction of Elimination regiochemistry: which constitutional isomer is formed 81% 19% two C’s on the C=C one C on the C=C Zaitsev’s Rule: The major alkene product is the one with more alkyl groups on the carbons of the double bond (the more highly substituted product).

22. Hofmann elimination Hofmann’s rule: The major alkene product has fewer alkyl groups bonded to the carbons of the double bond (the less highly substituted product).

23. Formation of the less substituted product is favored by removal of the more acidic H and steric hindrance.

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

26. The Competition between Elimination and Substitution 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

27. SN2 and E2 Stronger bases favor E2 over SN2 stronger base weaker base

28. SN2 and E2 higher temperatures favor elimination G = H - TS E2 SN2 weaker bases less steric hindrance lower temperature stronger bases more steric hindrance higher temperature

29. SN1 and E1 favored over SN2/E2 by absence of strong base/Nu often neutral or acidic conditions tertiary or secondary substrates in polar solvents SN1 is usually major, but some E1 always occurs also

30. 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)

31. 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

32. 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