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In the following questions, a statement ...

In the following questions, a statement of assertion (A) is following by a statement of reason (R )
A : Meso -2, 3 - dibromobutane on reaction with Zn/ether gives trans but -2 ene .
R : Zn/ether gives anti elimination .

A

If both Assertion & Reason are the reason is the correct explanation of the assertion, then mark (1).

B

If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark(2).

C

If Assertion is true statement but Reason is false , then mark (3)

D

If both Assertion and Reason are false statements, then mark (4)

Text Solution

AI Generated Solution

The correct Answer is:
To solve the given question regarding the assertion (A) and reason (R), we will analyze both statements step by step. ### Step-by-Step Solution: 1. **Understanding the Assertion (A)**: - The assertion states that meso-2,3-dibromobutane reacts with Zn in the presence of ether to yield trans-but-2-ene. - Meso-2,3-dibromobutane is a compound that contains two bromine atoms at the 2nd and 3rd carbon of a butane chain and has a plane of symmetry, making it optically inactive. 2. **Structure of Meso-2,3-dibromobutane**: - The structure can be represented as follows: ``` CH3-CH(Br)-CH(Br)-CH3 ``` - This compound has two stereocenters, but due to its symmetry, it does not exhibit optical activity. 3. **Reaction with Zn/Ether**: - When meso-2,3-dibromobutane is treated with zinc (Zn) in the presence of ether, an elimination reaction occurs. - The mechanism of this reaction involves the formation of a double bond through the elimination of bromine atoms. 4. **Anti Elimination Mechanism**: - The reason states that Zn in the presence of ether leads to anti elimination. - In anti elimination, the leaving groups (in this case, bromine atoms) must be on opposite sides of the molecule. This results in the formation of a double bond between the two carbon atoms from which the bromines were removed. 5. **Formation of Trans-But-2-ene**: - As the bromine atoms are eliminated anti to each other, the resulting product is trans-but-2-ene, which has the following structure: ``` CH3-CH=CH-CH3 ``` - This structure is indeed the trans isomer, confirming the assertion. 6. **Conclusion**: - Both the assertion (A) and the reason (R) are correct. The reaction of meso-2,3-dibromobutane with Zn in ether does yield trans-but-2-ene, and this occurs via an anti elimination mechanism. ### Final Answer: - **Assertion (A)**: True - **Reason (R)**: True - **Explanation**: The reason correctly explains the assertion.
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