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A : But-2-ene is more stable than propen...

A : But-2-ene is more stable than propene.
R : Heat of hydrogenation of but-2-ene is lesser than that of propene.

A

If both Assertion & Reason are true and 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 question regarding the stability of but-2-ene compared to propene and the relationship with heat of hydrogenation, we can break it down into clear steps: ### Step-by-Step Solution 1. **Understanding the Structures**: - But-2-ene (C4H8) has the structure: CH3-CH=CH-CH3. - Propene (C3H6) has the structure: CH3-CH=CH2. 2. **Analyzing Stability**: - Stability of alkenes is influenced by hyperconjugation and the number of alkyl groups attached to the double bond. - But-2-ene has more alkyl substituents (2 methyl groups) compared to propene (1 methyl group). - More alkyl groups lead to greater hyperconjugation, which stabilizes the alkene. 3. **Hyperconjugation**: - But-2-ene has 6 possible hyperconjugative structures due to the presence of 2 methyl groups. - Propene has 3 possible hyperconjugative structures due to the presence of only 1 methyl group. - Therefore, but-2-ene is more stable than propene due to increased hyperconjugation. 4. **Heat of Hydrogenation**: - The heat of hydrogenation is the energy released when an alkene is converted to an alkane. - The more stable the alkene, the lower the heat of hydrogenation because it is already at a lower energy state. - Since but-2-ene is more stable than propene, it will have a lower heat of hydrogenation. 5. **Conclusion**: - Assertion (A): But-2-ene is more stable than propene. This is true. - Reason (R): The heat of hydrogenation of but-2-ene is lesser than that of propene. This is also true. - Both statements are correct, but the reason explains the assertion. ### Final Answer Both the assertion and reason are true, and the reason correctly explains the assertion.
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Knowledge Check

  • Assertion : 2,3- dimethyl but -2- ene is more stable than but -2- ene. Reason : 2,3- dimethyl but -2- ene possesses 12 alpha- hydrogen atoms whereas but -2- ene possesses only 6 alph- hydrogen atms and therefore former shows more pronounced hyperconjugation.

    A
    If both assertion and reason are true and the reason is the correct explanation of the assertion.
    B
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  • Assertion : 2,3-Dimethylbut-2-ene is more stable than but-2-ene. Reason : Six hyperconjugation structures can be written for 2, 3-dimethylbut-2- ene while but-2-ene has twelve.

    A
    If both assertion and reason are true and reason is the correct explanation of assertion
    B
    If both assertion and reason are true but reason is not the correct explanation of assertion
    C
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    D
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  • A : N_(2) is more stable than O_(2) . R : Bond order of N_(2) is more than that of O_(2) .

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    B
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    D
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