Talk:Hückel's rule

What is "n"?[edit]

what does 'n' represent in this equation?

Here's an example: for benzene, the ring has 6 carbons, so n = 1. That's because 4(1) + 2 = 6. HTH. --HappyCamper 21:58, 11 March 2007 (UTC)[reply]

I was about to ask the same question.. what exactly does "n" stand for? HappyCamper's explanation, "Six carbons, so n=1" doesn't clarify much. —Preceding unsigned comment added by 131.247.152.4 (talk) 08:09, 29 November 2007 (UTC)[reply]

The article states "n is zero or any positive integer". DMacks (talk) 14:17, 29 November 2007 (UTC)[reply]

The value of n is independent of the organic molecule being examined. Lets look at benzene. Benzene has 6 pi electrons correct? Since there are 6 pi electrons, it follows huckel's rule because when n=1 you obtain a value of six. If a different molecule has 8 pi electrons (4 conjugated double bonds), it will not follow huckel's rule no matter what integer you designate n to be. Therefore, molecules such as Cyclooctatetraene (C₈H₈) are not aromatic, but since they are conjugated they are considered to exhibit Antiaromaticity. Basically Huckel's rule states that any conjugated system with 2, 6, 10, 14...(etc) pi electrons is aromatic. —Preceding unsigned comment added by 199.184.238.211 (talk)

Nit-pick: if cyclooctatetraene were planar it would be conjugated and antiaromatic. DMacks (talk) 17:53, 24 April 2008 (UTC)[reply]

I believe the rule includes non-binding electrons as well as pi bonded electrons too, anyone want to verify this and change it? —Preceding unsigned comment added by 75.45.1.131 (talk) 03:46, 25 May 2008 (UTC)[reply]

If they are involved in resonance, then they aren't "non-bonding". When the resonance-structures are drawn, they actually are pi electrons because they participate in pi-bonds (remember, individual resonance structures do not actually exist). So as a direct answer, electrons drawn as lone-pairs certainly can be involved in resonance and if they are, they are included in the 4n+2 electron count. Hopefully there's information on the aromaticity page about the inclusion/exclusion of various electrons in the aromatic system. DMacks (talk) 05:56, 3 June 2008 (UTC)[reply]

I was going to ask this too. Shouldn't it be made clear that n is an arbitrary integer? People (inc me) assume there is something which determines what n is, not that the result determines it. It's a rather odd rule. 91.111.9.28 (talk) 18:05, 31 August 2008 (UTC)[reply]

The idea is that Hückel aromaticity is possible with any uneven number of electron pairs. FelixP (talk) 22:18, 2 September 2008 (UTC)[reply]

Then there should be added to the article: "The number of pi electrons is equal to twice the number of double bonds" if this is true. That way you can tell the applicability straight from diagrams without having to know what sigma and pi bonds are. 178.38.39.89 (talk) 17:17, 1 November 2014 (UTC)[reply]

As is noted in the above discussion, it's not the number of (electrons in the) double bonds, because any given resonance form could have some of the relevant electrons appearing as nonbonded. Even in something as simple as imidazole, there is no single resonance structure where all the aromatic pi electrons appear as double-bonds. And benzyne makes it clear that saying "double bond" (in appearance according to a diagram) is also not correct, because one of the relevant pi pairs is from a triple-bond instead. DMacks (talk) 20:52, 1 November 2014 (UTC)[reply]

Perhaps more simply: provided that conditions 2 to 4 in the article are met, the overall number of pairs of pi-electrons must be odd. Such number is the sum of double bonds and lone pairs which can participate in pi-bonding system of the ring.--193.206.131.194 (talk) 13:19, 10 November 2020 (UTC)Patrizio[reply]

Should fullerenes be discussed in this article?[edit]

I think the section on fullerenes at the end should be moved to a different article. Huckel never said anything about fullerenes, so they don't follow any kind of "Huckel's rule". Anyone wish to comment? Shalom (Hello • Peace) 02:15, 9 October 2007 (UTC)[reply]

Does this correspond to the Azimuthal quantum number?[edit]

I noticed that the orbital angular momentum quantum number, ℓ has a rule that says any sub-shell can hold a maximum of 4ℓ + 2 electrons. Since 4ℓ + 2 looks quite similar to the 4n + 2 electrons of Hückel's rule, I figure they might be correlated to each other and thus both pages might benefit from this being added. I just would need someone more expert than myself to confirm this before adding it to the page(s). Bush6984 (talk) 22:31, 1 June 2015 (UTC)[reply]

Extension for porphyrins ?[edit]

Does it apply for porphyrins, eg Soret bands, or how are their spectra explained ? - Rod57 (talk) 09:34, 20 November 2020 (UTC)[reply]

Huckel rule extension to fullerenes[edit]

It is not clear if the Hirsch rule and the so called extension had the same purpose in mind. There seems something odd... 193.207.167.19 (talk) 13:57, 17 December 2021 (UTC)[reply]