Chapter 7 SN2 & E1 Reactions Flashcards
Substitution Reaction
When an alkyl halide group is treated with a nucleophile, the halogen will be substituted by the nucleophile
Elimination Reaction
When an alkyl halide is treated with a base, an alkyl halide will undergo elimination, in which a pie bond (alkene) is formed.
What are 2 conditions for SN1 reactions?
- The leaving group must be a very weak base (conjugate acid must be strong, pka <0)
- Carbocation is highly stabilized
What are considered strong leaving groups?
- H20
- R-OH (CH3OH)
- Diphosphate (Mg2+ makes it more stabilized and a weaker base so conjugate acid pka is < 1
- Cl-, Br-, I-
What are 2 types of solution that readily facilitates ionic dissociation of substrates? Why do these solutions work?
Water and methanol. These 2 medium of high dielectric constant greatly diminish the attractive forces between ions, facilitating separation.
Rate-Determing Step
The overall rate of a multistep reaction is identical to the rate of its slowest step (RDS)
What is the rate-determine step in SN1 reactions?
The dissociative formation of a carbocation
What type of reaction is SN1 and E1?
The probability that a molecule of substrate will undergo ionic dissociation is a function of the total number of molecules present in the medium; the concentration of substrate.
SN1 reactions are First-Order Reactions.
Rate = k [S]
In SN1 reactions, what is “Retention of Configuration?”
The nucleophile enters in the same orientation as the leaving group.
In SN1 reactions, what is “Inversion of Configuration?”
The nucleophile enters in the opposite orientation as the leaving group.
In SN1 reactions, what is “Loss of Configuration?”
The nucleophile enters partly with retention and inversion of configuration
Will SN1 reactions result in Loss of Configuration?
Yes. However, in enzymes there might be more selectivity resulting in specific orientation of the nucleophile.
What is an important aspect of E1 reactions
E1 reactions result in the most substituted alkene. The favoured alkene isomer happens to be more thermodynamically stable (hyperconjugation)
Do SN1 and E1 reactions compete with each other?
Yes.
What is Acetyl CoA?
A molecule that participates in many biological reactions in proteins, carbohydrates, and lipid metabolism. It’s main function is to deliver the acetyl group to the citric acid cycle to be oxidized for energy production.
