Talk:Antiaromaticity

Removed the copyvio and npov section, and dumping here. --Rifleman 82 13:10, 25 May 2007 (UTC)

Original url: http://www1.usu.edu/utahstatetoday/archives/may2003/05-02-03/highlights-05-02-03.cfm

Research at Utah State University

Utah State professor Alexander Boldyrev, along with his colleague Lai-Sheng Wang, a professor at Washington State University and a researcher at the Pacific Northwest Lab have discovered aromaticity, a property in chemistry that was initially thought to occur only in organic material. Today, Boldyrev and Wang have made another breakthrough and discovered antiaromaticity, a property that makes materials weak. The study, "All-Metal Antiaromatic Molecule," is featured in the April 24 issue of "Science" magazine. Boldyrev's new findings dealing with antiaromaticity will help chemists understand why certain materials are weaker than others and why they are very reactive to foreign substances. The research gives Boldyrev, an associate professor in the chemistry and biochemistry department, a conceptual breakthrough in understanding chemical bonding in metal clusters.[http://www1.usu.edu/utahstatetoday/archives/may2003/05-02-03/high

Cyclobutadiene

Should cyclobutadiene really be mentioned on the antiaromaticity page? It meets the simple rule for antiaromaticity, but it's been known for some time now that the ring strain associated with a four-carbon ring (especially one containing pi-bonds) is severe enough to make cyclobutadiene asymmetric, and hence, its electrons aren't even delocalized. I suppose it "would" be antiaromatic, but that doesn't really mean anything. I think the cyclobutadiene explanation should be included to clear up the confusion. -134.84.102.237 (talk) 10:49, 28 April 2008 (UTC)

I agree. I just finished reading Deniz et al in Science, Nov 5, 1999. Deniz et al quantified the antiaromaticity of butadiene. It doesn't seem quite right to say in this article that butadiene is neither aromatic NOR antiaromatic. It seems to be clearly anti-aromatic. Abstract at sciencemag.org —Preceding unsigned comment added by 68.19.143.184 (talk) 13:30, 6 March 2009 (UTC)

One of the conditions necessary for antiaromaticity is a continuous planar cloud of pi electrons. In order to avoid becoming antiaromatic cyclobutadiene bends into a rectangular shape so that the two double bonds are isolated from one another. This disrupts the continuous array of pi electrons, and for this reason the compound is non-aromatic. 128.192.230.178 (talk) 23:12, 23 February 2013 (UTC)

• the article already mentions "often antiaromatic compounds distort themselves out of planarity to resolve this instability". All textbooks include cyclobutadiene when discussing antiaromaticity. Cyclobutadiene should be included here V8rik (talk) 23:38, 23 February 2013 (UTC) PS anyone found the expert yet?

Cyclopropenyl anion

Cyclopropenyl anion should no longer be included as an example, as it has recently been demonstrated to be nonaromatic, rather than antiaromatic (DOI: 10.1021/jo401350m). This wikipedia article could probably benefit from a discussion about the history of classification of aromatic/nonaromatic/antiaromatic compounds, and specifically draw attention to the difficulty in applying these terms to compounds like cyclopropenyl anion and cyclobutadiene 128.250.91.230 (talk) 04:05, 10 July 2013 (UTC)MBR

That's an interesting study, and great to see experimental data about it rather than just assuming our theories are correct (yay science!). One interesting feature they seem to report is that the actual molecule is non-planar, which is also consistent with non-aromaticity (rather than just energetic difference of deprotonation), vs the theoretical statement if it were planar it would be antiaromatic (which they don't seem to address). That's not very different from COT, where the "actual molecule" is nonaromatic because it's not planar, and that happens because if it were to be planar it would be electronically less stable. The paper here seems to say that the actual electronic problem is not the same as "antiaromaticity" though. So highlighting cyclopropenyl anion as an actual antiaromatic example is (now:) a problem, and I also agree that we need more discussion of the difficulty of classifying in the absence of experimental results. But we might want to wait a bit before going too far down that road until there are some expert commentaries or followup studies on this just-released primary research. DMacks (talk) 05:03, 10 July 2013 (UTC)

Peer Review 1

Content

The introduction seems to be accessible to non-experts. I would suggest mentioning in your opening sentence that antiaromatic compounds are cyclic. That point becomes obvious later, but I think it would be good to state it at the beginning. The only part of the introduction that seemed like it might be confusing to the general public was the sentence about ring currents and NMR. It might be better to just talk about that later in its own section where you can fully explain the concept.

The sections about the technical definition, NMR spec. and examples of reactivity have contents that justify their length. The aromaticity in reality section doesn’t seem to say enough to justify it having its own section. Those few sentences might be better as an opening to a different section, or a new section on determining antiaromaticity computationally could be created instead, since computational experiments are mentioned in that section but not explained in detail. More of an elaboration on the different computational techniques could be done to really enhance that section. The examples of antiaromaticity section looks a little weird having two examples as two paragraphs and then a third example set off as a new section. The cyclobutadiene part could be set off as its own section instead of a subsection, especially since you are arguing that it isn’t really an example of antiaromaticity. In fact, most of that section seems to be about compounds that aren’t actually antiaromatic. It would be nice to see a couple more examples of compounds that are antiaromatic.

There seemed to be a few places where you could have linked to other wiki pages but didn’t (Diels-Alder reactions and Pauli repulsion for example). I would suggest going back through and double checking that the terms that can be linked back to other pages are.

The examples used throughout the page are appropriate and add to the help explain concepts well, and the content of the page doesn’t seem to duplicate anything already on wiki. There are times when you repeat things stated earlier on your page, but that is sometimes necessary.

Figures

Your figures seem to be of good quality and original. In the reactivity section especially, the figures complement the text nicely. Earlier on the page, the cyclobutadiene is very small and looks a little strange when it’s right under a very large figure. Maybe it could be moved a little. Also, in the very last figure on the page, your text references a blue moiety, but there are only red and green in the figure.

References

The references look complete, and there are a couple non-journal sources. Most of them are journal sources though, and it might be a good idea to try to find some of the same information outside of a journal article, if possible.

Overall

Overall, I think the introduction does a good job of presenting the subject matter to people who may not be familiar with the topic. I think the reactivity examples at the end are a good way to show how this topic is relevant to chemists and how antiaromaticity can affect the outcome of reactions. I think the organization of the middle sections could be worked on a bit to make the whole page flow better. I also think it would be nice to see more examples of actually antiaromatic compounds, preferable ones that are used in chemistry or have interesting properties.

Sjsteiner77 (talk) 18:29, 3 November 2013 (UTC)

Peer Review 2: Terbium4

The sandbox Wikipedia review of antiaromaticity is accurate and corrects the commonly assumed definition of antiaromaticity, a cyclic π electron count of 4n. As described by the writers, antiaromaticity is not only a multiple of 4n π electrons in a ring, but an energetically unfavorable structure that must be stabilized through ring distortion. Antiaromaticity is a driving chemical force for reactivity, and it can be detected through NMR. One alteration they can make to the opening sentence of their introduction is to define antiaromaticity as a “characteristic of cyclic molecules with alternating single and double bonds that have a higher π electron energy than their straight chain counterparts.”

The antiaromaticity sandbox is well written with appropriate length dedicated to the important aspects of antiarmaticity. In particular, noting the detection of antiaromaticity under nuclear magnetic resonance and the effects it has on chemical reactivity are great applications of Huckle’s theory. These figures are drawn well, with no major errors. In most cases, the figures are an improvement on the current page, as they show more relevant examples of antiaromaticity. Specifically, in the introduction section, the current page includes cyclobutadiene, cyclopentadienyl cation, cyclopropenyl anion, all of which explain the Huckle rule (4n electrons). But these molecules are inadequate examples as they do not reflect the antiplanar bending required for antiaromatic molecules to stabilize. In this case, the sandbox figures represent this concept better.

This content is a much needed addition to Wikipedia, as the web linked connections are well documented. Most importantly, link to Huckle Theory and NMR detection of paramagnitism connect the theory back to practice. Lastly, the references used for this page access a range of sources, including a reputable physical organic chemistry text book, web pages and academic articles. This allows readers a variety of sources to use if they desire more background on the subject.

Terbium4 (talk) 19:15, 3 November 2013 (UTC)

Additional Comments

UMChemProfessor (talk) 02:15, 5 November 2013 (UTC) Excellent job on the site. It is easy to follow and understand. The figures enhance the understanding. The peer reviewers made some good suggestions for improvement. The last structure (lactone) is hard to see how it is antiaromatic in the left structure. Maybe draw the resonance form that more clearly shows the antiaromaticity.

Suggestions from ChemLibrarian (talk) 14:52, 5 November 2013 (UTC)

1. Some of the images do not have captions. It's better to add them and refer to the captions in the text.
2. Good job with the table.

Responses to Peer Reviews

Thank you everyone for reviewing! Here are our responses:

We decided to leave the introduction as is, aside from mentioning that antiaromatic compounds must be cyclic. While the sentence regarding NMR may be too technical for some readers, we decided that most people who will be visiting this page will have some background in chemistry and it would be appropriate for them. Using NMR to determine antiaromaticity is an important technique and that justifies the concept being in the introduction. The mention of using NMR to identify antiaromaticity now links to the relevant section of our page where it is explained in more detail.

The "Antiaromaticity in Reality" section was indeed too short. Your recommendations were to either consolidate the section with another or to lengthen it by discussing the computational methods. While we agreed that understanding the computational methods is important, we felt the section would have quickly dissolved into a complex discussion of quantum mechanical principles and methods. We tried to make this article as free from highly technical concepts and jargon as possible, as that was one of the complaints for the current page. In the Examples section, where specific computational methods are mentioned, we put links in to their corresponding Wikipedia pages. Thus, if a reader feels that they need to understand the computational methods, the information is easily accessible.

We completely agree with you that there were more examples of not antiaromatic compounds in the Examples of Antiaromatic Compounds section than antiaromatic compounds. We made a new section and moved those compounds over to it. However, there is a reason that there were so few examples of antiaromatic compounds in the first place. The reason is simple: there are few compounds which scientists are sure are antiaromatic with 100% confidence. Back in the 1980's and 1990's, there was a plethora of papers coming out with titles along the lines of "Synthesis and Application of XYZ Antiaromatic Compounds." However, very few of these scientists did the appropriate structural analysis to the extent needed to confirm with certainty that the molecule is indeed antiaromatic. Even biphenylene, which we listed in the introduction as antiaromatic (and is described as antiaromatic on its own page), may not be truly antiaromatic because literature exists which suggests its bonds might be localized. We added a statement to the Examples section emphasizing that few compounds which are antiaromatic on paper are actually antiaromatic in real life.

We added another resonance structure of the lactone to make the antiaromaticity more apparent and fixed the mislabeled colors.

We also went through and added more links to other Wikipedia articles where appropriate (ie Pauli repulsion) and captioned some of our figures. Figures of reactions are in the text and the norm in other articles appears to be to not caption reaction figures.

P org 2013 (talk) 00:07, 11 November 2013 (UTC)