Question:
Indicate the major product of the following reaction:
\
Indicate the major product of the following reaction:
\
Show Hint
For \( \text{E2} \) elimination in cyclohexanes, stereochemical control (anti-periplanar requirement) completely overrides thermodynamic control (Zaitsev's rule). Always draw the substituents in a chair conformation to verify which H (or D) is trans-diaxial to the leaving group.
Updated On: May 25, 2026
- Fig A
- Fig B
- Fig C
- Fig D
Show Solution
Verified By Collegedunia
The Correct Option is C
Solution and Explanation
Step 1: Understanding the Question:
The problem asks for the major product of an elimination reaction of a substituted cyclohexane ring containing a deuterium (D) and a bromine (Br) atom on adjacent carbons, in the presence of a strong base \( \text{CH}_3\text{ONa} \) in \( \text{CH}_3\text{OH} \). This is an \( \text{E2} \) elimination reaction.
Step 2: Key Formula or Approach:
For an \( \text{E2} \) elimination to occur in cyclohexyl systems, the leaving group (Br) and the hydrogen/deuterium atom being eliminated must be in a trans-diaxial (anti-periplanar) relationship in the chair conformation.
Step 3: Detailed Explanation:
1. In the starting material, the bromine atom (Br) and the adjacent deuterium atom (D) are in a trans relationship (one is wedged, the other is hashed). This allows them to adopt a trans-diaxial conformation upon chair flipping.
2. Conversely, the adjacent hydrogen atom (H) is cis to the bromine, meaning they cannot adopt the anti-periplanar relationship required for \( \text{E2} \) elimination.
3. Consequently, when treated with the strong base \( \text{CH}_3\text{ONa} \), the base selectively abstracts the deuterium atom (D) instead of the hydrogen (H) because only the C-D bond is anti-coplanar to the C-Br bond.
4. The elimination of \( \text{DBr} \) results in the formation of a double bond between C-1 and C-2, leaving the carbon skeleton intact with the methyl group in its original position and the deuterium completely removed. This corresponds to the product shown in option (C).
Step 4: Final Answer:
The major product of the reaction is given in option (C).
The problem asks for the major product of an elimination reaction of a substituted cyclohexane ring containing a deuterium (D) and a bromine (Br) atom on adjacent carbons, in the presence of a strong base \( \text{CH}_3\text{ONa} \) in \( \text{CH}_3\text{OH} \). This is an \( \text{E2} \) elimination reaction.
Step 2: Key Formula or Approach:
For an \( \text{E2} \) elimination to occur in cyclohexyl systems, the leaving group (Br) and the hydrogen/deuterium atom being eliminated must be in a trans-diaxial (anti-periplanar) relationship in the chair conformation.
Step 3: Detailed Explanation:
1. In the starting material, the bromine atom (Br) and the adjacent deuterium atom (D) are in a trans relationship (one is wedged, the other is hashed). This allows them to adopt a trans-diaxial conformation upon chair flipping.
2. Conversely, the adjacent hydrogen atom (H) is cis to the bromine, meaning they cannot adopt the anti-periplanar relationship required for \( \text{E2} \) elimination.
3. Consequently, when treated with the strong base \( \text{CH}_3\text{ONa} \), the base selectively abstracts the deuterium atom (D) instead of the hydrogen (H) because only the C-D bond is anti-coplanar to the C-Br bond.
4. The elimination of \( \text{DBr} \) results in the formation of a double bond between C-1 and C-2, leaving the carbon skeleton intact with the methyl group in its original position and the deuterium completely removed. This corresponds to the product shown in option (C).
Step 4: Final Answer:
The major product of the reaction is given in option (C).
Was this answer helpful?
0
0
Top WBJEE Chemistry Questions
- $20\, mL$ of $0.2\, M \,NaOH$ is added to $50\, mL$ of $0.2\, M$ acetic acid. The pH of this solution after mixing is $(Ka = 1.8 \times 10^{-5})$
- If molecular weight of $ KMn{{O}_{4}} $ is $M$, then its equivalent weight in acidic medium would be
- Which of the following has the smallest number of molecules?
- $ 4.6\times {{10}^{22}} $ atoms of an element weigh $13.8\,g$. The atomic weight of that element is
- The decomposition of hydrogen peroxide can be slowed by the addition of acetamide. The latter acts as a
View More Questions
Top WBJEE Organic Reactions Questions
Increasing order of the nucleophilic substitution of following compounds is
Identify the major product (G) in the following reaction
- Which of the following hydrocarbons reacts easily with MeMgBr to give methane?
The major product (F) in the following reaction is
The major product 'P' and 'Q' in the above reactions are
View More Questions
Top WBJEE Questions
- Let $\vec{\alpha } = \hat{i} + \hat{j} + \hat{k} , \vec{\beta} = \hat{i} - \hat{j} - \hat{k}$ and $\vec{\gamma} = - \hat{i} + \hat{j} - \hat{k}$ be three vectors. A vector $\vec{\delta} $, in the plane of $\vec{\alpha}$ and $\vec{\beta}$, whose projection on $\vec{\gamma}$ is $\frac{1}{\sqrt{3}}$, is given by
- Let a, b, c be real numbers such that $a + b + c < 0$ and the quadratic equation $ax^2 + bx + c = 0$ has imaginary roots. Then
- If the radius of a spherical balloon increases by 0.1%, then its volume increases approximately by
- The velocity of a particle executing a simple harmonic motion is $13\, ms^{-1}$, when its distance from the equilibrium position (Q) is 3 m and its velocity is $12 \, ms^{-1}$, when it is 5 m away from The frequency of the simple harmonic motion is
- By which of the following methods, new and better varieties of plants can be formed?
View More Questions