Statement I : 2, 3-dibromo butane with Zn-dust gives frans-2-butene as...
Zn reacts with 2,3 - dibromobutane to give alkene. As trans 2-butene is more stable than cis 2-butene(owing tosterric hinderancce), former is major product.
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Statement I : 2, 3-dibromo butane with Zn-dust gives frans-2-butene as...
Statement I: 2, 3-dibromo butane with Zn-dust gives frans-2-butene as the major product.
Statement II: frans-2-butene is more stable than c/s-2-butene.
Explanation:
To understand the given statements, let's analyze the reaction and the stability of the isomers.
1. Reaction of 2, 3-dibromo butane with Zn-dust:
When 2, 3-dibromo butane reacts with Zn-dust, it undergoes a dehydrohalogenation reaction to form an alkene. The reaction mechanism involves the elimination of two bromine atoms from the adjacent carbon atoms, resulting in the formation of a double bond.
2. Formation of frans-2-butene:
In the given reaction, frans-2-butene is formed as the major product. This is because the Zn-dust mediated dehydrohalogenation reaction follows the anti-elimination mechanism, which leads to the formation of the trans-alkene (frans-2-butene) as the major product.
3. Stability of frans-2-butene:
In general, trans-alkenes are more stable than cis-alkenes. This is due to the absence of steric hindrance between the substituents present on the double bond in the trans-configuration. In the case of frans-2-butene, the substituents (methyl groups) are present on opposite sides of the double bond, resulting in less steric hindrance and greater stability.
Now, let's analyze the given statements:
Statement I: 2, 3-dibromo butane with Zn-dust gives frans-2-butene as the major product.
This statement is correct. The Zn-dust mediated dehydrohalogenation reaction of 2, 3-dibromo butane indeed results in the formation of frans-2-butene as the major product.
Statement II: frans-2-butene is more stable than c/s-2-butene.
This statement is also correct. The trans-configuration of frans-2-butene makes it more stable compared to the cis-configuration of c/s-2-butene.
Explanation of the relationship between the two statements:
Statement II provides the correct explanation for Statement I. The stability of frans-2-butene, due to its trans-configuration, is the reason why it is the major product in the given reaction. The absence of steric hindrance in the trans-configuration allows for a more favorable transition state during the elimination reaction, leading to the formation of frans-2-butene as the major product.
Therefore, both Statement I and Statement II are correct, and Statement II is the correct explanation for Statement I.
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