Given below are two statements. One is labelled as Assertion A an… - Vidyadip

MCQ

Given below are two statements. One is labelled as Assertion A and the other is labelled as Reason $R$.

Assertion $A$ :$[6]$ Annulene.$[8]$ Annulene and cis - $[10]$ Annulene, are respectively aromatic, not-aromatic and aromatic.

Reason $R$ : Planarity is one of the requirements of aromatic systems.

In the light of the above statements, choose the most appropriate answer from the options given below.

A
Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$.
B
Both $A$ and $R$ are correct but $R$ is NOT the correct explanation of $A$.
C
$A$ is correct but $R$ is not correct.
✓
$A$ is not correct but $R$ is correct.

✓

Answer

Correct option: D.

$A$ is not correct but $R$ is correct.

d
If this annulene with five cis double bonds were planar, each internal angle would be $144^{\circ}$. Since a normal double bond has bond angle of $120^{\circ}$, this would be from ideal. This compound can be made but it does not adopt a planar conformation and therefore is not aromatic even though it has ten $\pi$ electrons.

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