Page 31 Flashcards
What determines whether a reaction follows the E1 or E2 mechanism?
A: The strength of the base. Strong bases like -OH and -OR favor E2 reactions, while weaker bases like H_2O and ROH favor E1 reactions.
How does the rate of an E1 reaction depend on the structure of the alkyl halide?
A: The rate of an E1 reaction increases as the number of R groups on the carbon with the leaving group increases due to increased carbocation stability.
What is the key feature of the energy diagram for an E1 reaction?
A: The diagram shows two steps with two energy barriers. Step 1, involving carbocation formation, is rate-determining.
What happens in the first step of the E1 mechanism?
A: The leaving group departs, forming a carbocation intermediate.
What is the effect of polar aprotic solvents on the E2 reaction?
A: Polar aprotic solvents increase the rate of E2 reactions.
What role does the leaving group play in E2 reactions?
A: The bond to the leaving group is partially broken in the transition state, and a better leaving group increases the rate of the reaction.
How does the Zaitsev (Saytzeff) rule apply to elimination reactions?
A: The major product in \beta-elimination has the more substituted double bond, which is more stable.
What does it mean for an E2 reaction to be stereoselective?
A: It forms predominantly one stereoisomer when two or more are possible, favoring the more stable trans-isomer.
How does the substitution level of the alkyl halide affect E2 reactions?
A: More highly substituted alkyl halides react faster due to the increased stability of the resulting alkene.
How does the transition state of E2 reactions affect the reaction rate?
A: The double bond is partially formed in the transition state, and increased stability of the transition state lowers activation energy, increasing the reaction rate.
How does Zaitsev’s rule apply to E1 reactions?
A: E1 reactions are regioselective, favoring the formation of the more substituted, more stable alkene as the major product.
