Question

Statement I: ${{Buta - 1,3 - diene}}$ is less stable than ${{penta - 1,4 - diene}}$.
Statement II: ${{Buta - 1,3 - diene}}$ has a greater number of resonating structures and the delocalized electron cloud.
A.Statement- ${\rm I}$ is true, Statement -${\rm I}{\rm I}$ is true; Statement ${\rm I}{\rm I}$ is a correct explanation for Statement-${\rm I}$
B.Statement- ${\rm I}$ is true, Statement -${\rm I}{\rm I}$ is true; Statement ${\rm I}{\rm I}$ is not a correct explanation for Statement-${\rm I}$
C.Statement- ${\rm I}$ is true, Statement -${\rm I}{\rm I}$ is false
D.Statement- ${\rm I}$ is false, Statement -${\rm I}{\rm I}$ is true

Answer 1

Hint: The compound having lone pairs, double or triple bond have a maximum chance of having resonance. The compound having a large number of resonating structures is more stable. The conjugate double bond makes the compound more stable as seen in hyperconjugation.

Complete step by step answer:
The structure ${{Buta - 1,3 - diene}}$ is shown below with its all resonating structures.
We can see that there are conjugated double bonds in ${{Buta - 1,3 - diene}}$ which means that the single bond and double bond alternates.
Thus, it leads to resonance structures. It enables the electrons to be delocalized to the whole system. We know that a molecule with more resonance structures is more stable.

The structure ${{penta - 1,4 - diene}}$ is shown below

We could see that there are no conjugated double bonds in ${{penta - 1,4 - diene}}$.
Thus, it does not have resonance structures.
As we can see that ${{Buta - 1,3 - diene}}$ has 4 resonating structures and ${{penta - 1,4 - diene}}$ does not show resonance.
So we can conclude that ${{Buta - 1,3 - diene}}$ is more stable since it shows resonance. The more the resonating structures, the more is the stability.
Hence the statement ${\rm I}$ is false and the statement ${\rm I}{\rm I}$ is true.

Hence, the correct option is D.

Additional information: The stability of carbocation is as follows:- ${{tertiary > secondary > primary}}$. The compound having less energy is more stable. The compound with high energy is less stable.

Note:
To find the stability between two compounds the first focus should be to find the number of resonating structures shown by the compounds. If the compound is having more conjugate bonds then it is more stable. A Conjugate system is a system of bonds having p orbitals with delocalized electrons in a molecule.