Reactions

Question 1

Meerwein-Ponndorf-Verley Oxidation

(with AlCl₃)

Answer 1

This reaction is typically run using an alcohol solvent such as ethanol or isopropanol.

When AlCl3 is added, the solvent replaces the chloro groups

Question 2

S_N1 Reactions

Answer 2

• 3^o (bulky) substrates are favored
• Weaker nuc^-
• Polar Protic Solvent
• Nuc^- is in the solvent (they are the same, common for S_N1 rxn’s)
• The substrate that can make the more stable carbocation will be faster (resonance!)
• Always form carbocation

Question 3

S_N1 Rate Law

Answer 3

Rate = k•[substrate]

1^st order rxn

Question 4

Substrate Effect

S_N1

Answer 4

• 3^o ideal
• 2^o acceptable but not always good
• 1^o never

Question 5

S_N1 Stereochemistry

Answer 5

• form a C+ intermediate, so nucleophile can attack to produce products with both inversion and retention of configuration.
• Expect a racemic mixture

Question 6

S_N2 Reactions

Answer 6

• 1^o (less bulky) substrates are favored
• Me groups
• Stronger nuc^-
• Polar aprotic solvents
• Nuc^- comes and directly attacks the carbon adjacent to LG

Question 7

S_N2 Stereochemistry

Answer 7

• Reaction proceeds with inversion of configuration—the nucleophile must “hit it from the back”
• Mechanism is concerted: Attacks with simultaneous loss of LG

Question 8

S_N2 Rate Law

Answer 8

Rate = k•[substrate][Nuc^-]

2^nd order rxn

Question 9

Substrate Effect

S_N2

Answer 9

• 1^o and 2^o substrates ideal
• 3^o are too sterically hindered

Question 10

E1 Reactions

Answer 10

• If the leaving group is OH and the solvents is H₂O and some kind of acid- dehydration reaction, E1 is favored
• 2^o or 3^o
• 2+ step rxn:
  
  • 1: kick off LG
  • 2: pull off a proton (i.e. H on CH3)
  • 3: leftover electrons form a double bond
• Always form carbocation
• typically involve water, acid, or alcohol

Question 11

E2 Reactions

Answer 11

• Pull off L.G. and Proton (H)
• Strong bases
• Think about substrate as being the acid and your nuc^- as being the base.
• Reaction Steps:
  
  • 1: draw out base formation, then put your LG and H in that configuration (anti-periplanar)
  • 2: rotate
    
    • Dashes end up on the same side of alkene, wedges end up on same side of alkene.
  • Pull off group that’s anti-periplanar. Both need to be axial

Question 12

Substrate Effect

E2

Answer 12

• With a 3^o substrate, steric hindrance prevents the reagent from functioning as a nuc^- at an appreciable rate, but the reagent can still function as a base without encountering much steric hindrance.
• Works best with 3^o and 2^o substrates

Question 13

Reaction Rate

Answer 13

• Carbocation formation is rate determining!
• The ideal geometry for a carbocation is planar with 120° angles.

Question 14

E2 Stereoselectivity

Answer 14

Substrate produces two stereoisomers of unequal amounts