Two elimination products are obtained from the following E2 reaction:

a. What are the elimination products?
b. Which is formed in greater yield?

검증된 단계별 안내

Identify the type of reaction: The problem specifies an E2 elimination reaction. In an E2 reaction, a strong base removes a β-hydrogen (a hydrogen atom on a carbon adjacent to the carbon bearing the leaving group) while the leaving group departs, forming a double bond (alkene).

Analyze the structure of the substrate: The substrate is CH3CH2CHDCH2Br. The β-hydrogens are located on the carbon adjacent to the carbon bonded to the bromine (leaving group). In this case, there are two β-hydrogens: one is a regular hydrogen (H), and the other is a deuterium (D, a heavier isotope of hydrogen).

Determine the possible elimination products: The elimination can occur in two ways, depending on which β-hydrogen is removed. If the regular hydrogen (H) is removed, the product will be CH3CH=CHD. If the deuterium (D) is removed, the product will be CH3CH=CH2. These are the two possible alkenes formed.

Consider the regioselectivity and isotope effect: The E2 reaction typically follows Zaitsev's rule, which states that the more substituted alkene is favored. However, the isotope effect must also be considered. The C-D bond is stronger than the C-H bond, so the removal of the regular hydrogen (H) is kinetically favored over the removal of deuterium (D).

Predict the major product: Based on the isotope effect, the product CH3CH=CHD (formed by removing the regular hydrogen) will be formed in greater yield compared to CH3CH=CH2 (formed by removing deuterium).

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이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

E2 Reaction Mechanism

The E2 (bimolecular elimination) reaction is a concerted mechanism where a base abstracts a proton from a β-carbon while a leaving group departs from the α-carbon, resulting in the formation of a double bond. This reaction typically requires strong bases and is characterized by a single transition state, leading to the simultaneous removal of the leaving group and proton.

Zaitsev's Rule

Zaitsev's Rule states that in elimination reactions, the more substituted alkene is generally the major product. This is due to the stability of alkenes; more substituted alkenes have greater hyperconjugation and lower energy, making them more favorable in terms of yield compared to less substituted alkenes.

Regioselectivity in Elimination Reactions

Regioselectivity refers to the preference of a chemical reaction to yield one structural isomer over others. In E2 reactions, the orientation of the leaving group and the hydrogen being abstracted can lead to different alkene products, and understanding the sterics and electronics of the substrate can help predict which product will be favored.

Two elimination products are obtained from the following E2 reaction: a. What are the elimination products? b. Which is formed in greater yield?