1. Tardigrade
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  3. Chemistry
  4. 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. <img class=img-fluid question-image alt=image src=https://cdn.tardigrade.in/img/question/chemistry/1329bc7606946cf3c665edec705d479c-.png /> 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.

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Q. 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.
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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.

JEE MainJEE Main 2022Organic Chemistry – Some Basic Principles and Techniques

Solution:

Assertion A : Not correct , Reason R : correct
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In [10] -Annulene - the hydrogen atoms in the 1 and 6 position interfere with each other and force the molecule out of planarity
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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.