객관식
Which of the following is the most reactive substrate in an E reaction?
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8. Elimination Reactions
E1 Reaction
객관식
Consider the reaction of the tertiary halide shown. Which of the following statements best describes the rate-determining step of this reaction?
A
The rate-determining step is the deprotonation of the hydrogen by the base.
B
The rate-determining step is the nucleophilic attack on the carbocation intermediate.
C
The rate-determining step is the simultaneous removal of the leaving group and a proton in a concerted process.
D
The rate-determining step is the loss of the leaving group to form a carbocation intermediate.
검증된 단계별 안내1
Identify the type of reaction: An E1 reaction involves two main steps—a slow, rate-determining step where the leaving group departs forming a carbocation intermediate, followed by a fast deprotonation step.
Understand the rate-determining step: In E1 mechanisms, the rate depends only on the concentration of the substrate because the first step (loss of the leaving group) is the slowest and controls the reaction rate.
Analyze the options: The deprotonation of the β-hydrogen by the base is a fast step that occurs after the carbocation forms, so it is not rate-determining.
Recognize that nucleophilic attack is not involved in E1 elimination; instead, the base removes a proton after carbocation formation, so nucleophilic attack on the carbocation is not the rate-determining step.
Conclude that the rate-determining step is the formation of the carbocation intermediate by loss of the leaving group, which is a unimolecular process characteristic of E1 reactions.
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