Talk:Aromatization

Expansion

Something I noticed while I was looking over the article for its class assessment: it doesn't contain anything about either history or real-world applications. If these could be added, the article would be a lot better. –Compassionate727 ^(T·C) 17:38, 28 May 2016 (UTC)

@Compassionate727: I plan to add a section explaining aromaticity. Also to make a separate biochemical section on the enzyme aromatase / cancer treatment and aromatization in biochemistry (in shikimate and purine paths, for example). I think some applications in synthesis should be pretty evident, though. How would you suggest I make that clearer? EdChem (talk) 09:51, 29 May 2016 (UTC)

@EdChem: I was just thinking of a separate section explaining what can be done with aromatization. –Compassionate727 ^(T·C) 14:46, 29 May 2016 (UTC)

@Compassionate727: there is now a proper discussion of what aromaticity is and where aromatic systems appear, does that explain sufficiently why we care about how to make aromatic systems? EdChem (talk) 08:13, 5 June 2016 (UTC)

@EdChem: Yes, thank you! –Compassionate727 ^(T·C) 13:02, 5 June 2016 (UTC)

• I am not happy with this expansion The article should be about aromatization reactions. In biology are aromatic rings recycled or formed in aromatization processes? V8rik (talk) 20:38, 6 June 2016 (UTC)

I am also not entirely happy with the article. The discussion of aromatization reactions is desirable, and this article is the proper place for them. However, I think this article contains or duplicates content that belongs in Aromaticity. The section on the elucidation of the structure of benzene, for example, deals primarily with electrophilic aromatic substitution reactions, not aromatizations.

Aromatization is a powerful force in synthesis and in biochemistry; this article should address primarily those reactions in which aromatic systems are formed. The above question, for example, should be readily answered by the lead of the article: in vivo both recycling of aromatic rings and their formation de novo are important.

The DYK nomination is appreciated, though. Roches (talk) 03:29, 7 June 2016 (UTC)

@V8rik and Roches:: Firstly, the section on biochemistry is completely missing at present, but I agree that it is major area. Purine synthesis and the shikimate pathway are two critical areas of biochemical aromatization that are needed before I could offer this for GA. The lede will need a proper re-write, too, so I agree that there is a balance issue and missing content. Regarding the introductory material, I added it in part to address the question above, essentially "who cares?" To me, the importance of aromatization likes in the importance of aromatic systems, so I set out to briefly explain what aromatic systems are and what they are used for, before turning to how they are made. The detail is far more than needed for a discipline expert (if you look at the article history), I started with nothing on it. My past GA / FA experiences, though, led me to explain enough for a non-chemist to appreciate / understand. Maybe I have too much, and I'm open to others making changes (obviously) but that was my thinking. Like when I write the abstract of a paper last, I meant to come back to the lede once the body was largely complete. Thoughts? EdChem (talk) 06:17, 7 June 2016 (UTC)

It's difficult to judge how well a non-chemist would understand the article. There's a certain amount of assumed knowledge about bonding and skeletal structures, and later in the discussion about aromaticity the NMR shift to higher frequency is mentioned. The ring current effect and the NMR evidence for aromaticity is important, but can it be understood by someone who does not know how alkenes undergo addition reactions?

If the goal is GA status, then Aromaticity should be a GA before Aromatization. The issue there is that I think this article does a better job at introducing the concept than the main article does. I'm a chemist, but I don't usually edit chemistry articles. In general they seem to be convoluted messes. I suspect most of the edits, like the multitude of uninteresting chemistry blogs... and everything except a tiny portion of the primary literature... are meant to promote authors, rather than chemistry itself. That is probably why I prefer the freshly written explanation here.

I don't think you should remove content from the article. When this article is further developed, it may prove best to migrate some of it to Aromaticity in place of existing text. Roches (talk) 08:10, 7 June 2016 (UTC)

@Roches: if you want to copy materials across to the aromaticity article, you are free to - the content I have written is all freely licensed. If you look at the rhodocene article (an FA I wrote), you will find lots of introductory material early on, which I added during the GA and FA reviewing processes to make the article more accessible, and I am applying that same philosophy here. Were I writing for students or a text book, that material would not be here. I think a balance of intro explanation and necessarily more advanced concepts (like ring current) are both needed. Having said that, thanks for the compliment on my writing - that the intro materials here are better written than those in aromaticity - that was appreciated and made me feel better. Ironically, I recently got described as someone claiming some knowledge of science, and so a chemist liking some of my work is affirming. Unfortunately, WP is often unfriendly to the genuine expert - especially in cases where a complete re-write is desirable. EdChem (talk) 11:49, 12 June 2016 (UTC)

Further: We could include images of 2H-pyrole and pyran as examples of systems which are non-aromatic due to the lack of a conjugated system, or azete as having only 4 electrons and hence being antiaromatic? EdChem (talk) 12:34, 12 June 2016 (UTC)

Is thiophene an aromatic compound?

I am puzzled as to how molecules like thiophene can be classed as aromatic. I would class thiophene as a conjugated diene. It does not have the aromatic sextet which I was taught is the defining characteristic of an aromatic compound. Yes, there is delocalization in the conjugated double bond part of the molecule, but delocalization does not extend over the whole ring, as it does in "true" aromatic compounds. Petergans (talk) 08:22, 11 June 2016 (UTC)

I'm sure EdChem could give a more thorough answer but I'll have a quick go... In addition to the 2 × double bonds there is also the lone pair of electrons on the sulphur which sit in a pi orbital giving the 4n + 2 pi electrons (6 in this case) required for aromaticity - Basement12 (T.C) 08:39, 7 June 2016 (UTC)

@Petergans: Basement12 is correct, thiophene is aromatic courtesy of one of the lone pairs on the sulfur atom, and there is discussion of aromaticity on the thiophene page. It undergoes electrophilic aromatic substitution rather than addition, for example. It is not as aromatic as benzene, though. EdChem (talk) 13:34, 8 June 2016 (UTC)

@Petergans: Also, your signature needs to contain a link to your user or usertalk page. In this case, I believe going to your preferences and unchecking the box that says "Treat the above as wiki markup" should fix this. –Compassionate727 ^(T·C) 22:03, 8 June 2016 (UTC)

The question has been answered but it raised a point for me. Taking imidazole as an example: the nitrogen with two formal single bonds requires its lone pair to participate in the pi system, while the nitrogen with a double and a single bond has its lone pair in the plane of the molecule and the nitrogen is basic. There are also few counterexamples of non-aromatic compounds that look like they "should" be aromatic. I think it's safe to conclude that a large proportion of the readership will be students of organic chemistry, and both those concepts are classic test questions.

@EdChem: The synthesis section presents electrocyclic cyclization reactions before it discusses condensation reactions, and it discusses condensation reactions in less detail. Can you comment on the reason? It's the opposite of the traditional introductory course, and most of the in vivo cyclizations with acyclic substrates are condensations. However, I'm an idealist rather than a realist with respect to teaching organic chemistry, so I would support this order of presentation if you think it is better than the traditional one. Roches (talk) 05:10, 9 June 2016 (UTC)

@Roches: I agree with you on the classic test questions, and I have included some examples that might not look aromatic to some, but are. The difficulty with looks like it might be aromatic but is not, which does turn up in tests, is difficult to include in an encyclopaedia. Happy for you to include something if you think it is appropriate.

Re the sequence, this is how the article was when I started - trimerisations at the start, no condensations. I did not give much thought to whether the condensations come first. My background is organometallics so cyclotrimerisations occur to me first, but I have no objection to reorganisation. I don't own the article, so if you want to make changes, go for it! I do plan to add a biochemical section (shikimate, etc), but if anyone else starts first, that's fine too. EdChem (talk) 11:40, 12 June 2016 (UTC)

Thiophene behaves as an aromatic compound in many ways, and most thiophene chemists would classify it as such. Here are some aspects:

• undergoes electrophilic substitution (greedily). Acetylation, chloromethylation, etc. Mainly at 2,5 positions but it undergoes full iodination.
• smells aromatic, no organoS odor (samples must be pure).
• forms metal complexes as an h5-ligand often, many h6-benzene complexes have been replicated with thiophene.
• very reluctant to form S-bonded complexes with metals. So it is a poor thioether.
• oxidized at S reluctantly as well, again indicating that S is nonbasic. Situation is slightly easier for dibenzothiophene but even that one is less basic than diphenylsulfide.
• and by the way, it has a sextet satisfying the Huckel rule.

Of course I should find a ref. The go-to sources are things like Adv. Heterocyclic Chem and Comprehensive Heterocyclic Chem. --Smokefoot (talk) 02:37, 15 June 2016 (UTC)

Article might be off-topic?

Aromatization (IMHO) is the conversion of a molecule into one that is aromatic. Aromatization is a kind of reaction. It is not aromaticity. Here are a few of the most highly cited reviews on aromatization:

1. Gunanathan, C.; Milstein, D. Metal-Ligand Cooperation by Aromatization-Dearomatization: A New Paradigm in Bond Activation and "Green" Catalysis. Acc. Chem. Res. 2011, 44, 588-602.
2. Lephart, E. D. (1996). "A review of brain aromatase cytochrome P450". Brain Res. Rev. 22: 1-26. doi:10.1016/0165-0173(96)00002-1.
3. Navarro, R. M.; Pena, M. A.; Fierro, J. L. G. (2007). "Hydrogen Production Reactions from Carbon Feedstocks: Fossil Fuels and Biomass". Chem. Rev. 107: 3952-3991. {{cite journal}}: Cite has empty unknown parameter: |1= (help)CS1 maint: multiple names: authors list (link)
4. Ono, Y. (1992). "Transformation of lower alkanes into aromatic hydrocarbons over ZSM-5 zeolites". Catal. Rev. - Sci. Eng. 34: 179-226. doi:10.1080/01614949208020306.

$Pape, A. R.; Kaliappan, K. P.; Kuendig, E. P. Transition-Metal-Mediated Dearomatization Reactions. Chem. Rev. (Washington, D. C.) 2000, 100, 2917-2940

So I am going to remove the off-topic matter, and we will have an article of about 5% of the current size. As always comments and suggestions are welcome.--Smokefoot (talk) 00:57, 7 May 2019 (UTC)