The compounds are said to be non-aromatic which do not have a continuous overlapping ring of p-orbitals can’t be aromatic or anti-aromatic.
For Example:
In these structures, firstly in the case of cyclohexadiene, there is no conjugation, which indicates clearly that the structure must be non-aromatic. In the case of an open ring structure or acyclic, no planarity shows that the structure is not a planner and it must be non-aromatic.
Stability Order:
Aromatic compounds > Non-Aromatic compounds > Anti-Aromatic compounds
FAQ
What kind of behavior is shown by a given structure aromatic, non-aromatic, or anti-aromatic? Give a suitable reason.
Answer: The given structure indicates that it follows all properties that are found in the aromatic compound as it is planar, cyclic, overlapping λ electrons, and also follows Huckle’s rule
(4n+2 λelectrons).
4n+2 = 4(4)+2= 18
Hence, all such properties clear that that structure is aromatic.
This structure is anti-aromatic. Give reason.
Answer: In this structure, although a lone pair of electrons is present which is considered part of the ring shows its planarity. This structure does not completely fulfill the characteristics of aromatic compounds instead it is cyclic because it does not follow Huckle’s rules.
4n λelectrons = 4(2)= 8λelectrons
Hence; it indicates this structure is anti-aromatic, not aromatic.
Indicate the anti-aromatic, non-aromatic, and aromatic character from the following structures.
Answer:
A) Structure which is indicated by (a) shows it is aromatic. The reason is that it has a lone pair of electrons which must consider the part of the ring. Hence it follows all properties of aromatic character including it has cyclic, planar structure and structure also follows Huckle’s rule.
B) Structure in block (b) shows it is anti-aromatic because here no huckle’s rule is followed.
C) Structure in block (c) shows no planarity, no conjugation, and no huckle rule is followed here. Which indicates it is a non-aromatic structure.
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