Questions tagged [aromaticity]

For questions about the concept of aromaticity. Do not use for reactions of aromatic compounds.

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Is the 9H-fluoren-9-ylium cation aromatic?

In this cation, there are two individual benzene rings which are aromatic. But in the entire π system, there are 12 π-electrons which should make it antiromatic. Which is correct?
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What is jellium aromaticity?

As I understand, if a molecule is cyclic and planar, then every atom in the ring must be $\ce{sp^2}$-hybridized and the molecule must have [4n+2] π electrons, where n∈N (Hückel’s rule). An article in ...
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Is azonine planar?

I came across aza[9]-annulene, which is given to be aromatic. I can clearly see it follows Hückel's rule with 8 π-electrons in the ring and the lone pair of nitrogen. But the thing that concerns me ...
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Is black phosphorous aromatic?

I know that graphite and boron nitride are aromatic in nature. In a similar way, can black phosphorous too exhibit aromaticity? Since it is essentially the same having 6 membered rings with lone ...
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Bond dissociation energy of the trihydrogen cation

Recently, in one of the questions in an assignment on the topic of energetics, we were asked to explain why the bond dissociation energy for the trihydrogen cation is much larger than what we would ...
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Consequences of ortho effect on resonance

Consider any carboxylic acid with any group at ortho position. According to ortho effect, the resonance of the $\ce{C=O}$ with the ring is inhibited. Is this resonance entirely lost? Or some little ...
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Cycloheptatrienyl carbanion aromaticity

Many sources including previous answers on Stack Exchange claim that it is antiaromatic. But in a different yet similar question, I have also seen people saying that a monocyclic ring with 7 or more ...
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378 views

Resonance in a non-planar molecule

I am well aware that the following compound is non-planar and hence, will not be anti-aromatic but non-aromatic. But I wonder whether resonance will occur to some extent i.e. whether any three ...
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Antiaromaticity can be explained by Hückel method?

Pentalene is one of the most famous antiaromatic molecules. But I obtained its energy of $\pi$ system as $8\alpha+10.46\beta$ by Hückel method (with a bit complicated but straightforward calculation). ...
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1answer
354 views

Are p‐xylylene and fulvene aromatic?

Are the following structures aromatic? I have not seen this type of question anywhere so I do not know the answer. This is just a problem that has been roaming around in my head that I may have seen ...
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How come Cyclopropenylhydroxide exists and not cyclopropenol?

I'm currently studying aromatic compounds via online recorded lectures, and my teacher brought up about cyclopropenol and cyclopropenylhydroxide while teaching carbocylic non benzenoid compounds. He ...
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Cross-conjugation and aromaticity in pyrene

I have read about non-huckel double bonds and clar's rule, but what made me confuse is that huckel's perception gives me the feeling that central bonds in polycyclic aromatic hydrocarbons (ex: pyrene) ...
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Clar's rule of polycyclic aromatic hydrocarbons

Clar's rule states that the Kekulé resonance structure with the largest number of disjoint aromatic π-sextets, i.e., benzene-like moieties, is the most important for characterization of properties of ...
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How many π-electrons are there in 2-methylene-2H-pyran?

I thought that the structure will be aromatic and stabilised because one of the lone pairs being delocalised with the help of conjugated double bond system but still only 3 π-bonds will be present at ...
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283 views

What is the Criteria for a Compound Being Non-aromatic vs. Anti-aromatic?

Anti-aromatic compounds are formed with a cyclic system of planar, overlapping p orbitals containing a non-Huckel number of electrons (i.e. not 4n+2 electrons -n being a natural number-). Non-aromatic ...
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170 views

Is cyclo[18]carbon aromatic?

How does this compound even exist? Having such a massive ring strain. Is it even conjugated? As it's resonance structure will have all double bonds. Since it was reported to be found, there must be ...
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118 views

Why is 11-oxabicyclo(4.4.1)undeca-1,3,5,7,9-pentaene aromatic?

I have been told by my instructors that for a compound to be aromatic, it must be planar. In this given molecule the oxygen seems to be out of the plane of the conjugated system: how can it still be ...