Commons talk:WikiProject Chemistry

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Wrong geometry[edit]

There are many images which are disputed with the reason "Wrong geometry". What does that mean? Samulili (talk) 08:07, 21 August 2008 (UTC)

It means an image implies a molecule has a certain shape, which is not the real shape of the molecule. The majority of '"wrong geometry" tags seem to concern azo compounds. These molecules are (conceptual) derivatives of diazene, and the NNH or NNR angle is about 120°, not the 180° angle depicted in many structural formulae of azo compounds.
Ben (talk) 10:04, 21 August 2008 (UTC)

Category:Chemistry diagrams[edit]

Hi, I noitce the Category:Chemistry diagrams has over 400 diagrams listed. I think this subcategory could require some diffusion. I am however no expert in this field, and wonder if you could give some suggestions. I had an idea for:

  • 3d Chemistry diagrams
  • and soemthing like "structure formula diagrams"

But maybe you have some better ideas to retrieve some diffusion there. Thanks. -- Marcel Douwe Dekker (talk) 13:59, 26 August 2008 (UTC)

Even these proposed subcategories would, if properly populated, contain tens of thousands of images each.
I suggest chemistry diagrams (2D or 3D) are simply located in the category for the chemical they depict.
Ben (talk) 19:01, 26 August 2008 (UTC)


Ok thanks. I guess the {{categorize}} in the Category:Chemistry diagrams is in the right place. Good luck. -- Marcel Douwe Dekker (talk) 00:10, 28 August 2008 (UTC)

Category:Teaching illustrations of chemistry[edit]

One other thing is the Category:Teaching illustrations of chemistry. At the moment there is no content and the subcategory listed Chemical processes seems rather odd to me. What is your opinion here? -- Marcel Douwe Dekker (talk) 14:03, 26 August 2008 (UTC)

Chemistry diagram[edit]

I nominated this gallery page for deletion. --Leyo 13:03, 6 March 2009 (UTC)

Category:Chemistry (unsorted)[edit]

The catgory was first moved and than made a redirect, which I consider to be wrong. Diskussion here: Commons:Categories for discussion/Current requests/2009/03/Category:Chemistry (unsorted). --Cwbm (commons) (talk) 09:18, 9 March 2009 (UTC)

Subpage for deletion requests on chemistry-related files[edit]

What about a subpage, where current deletion requests on chemistry-related files are transcluded? In this way, it would be facilitated to us joining these discussions.
BTW: IFAIK, there are currently two open DRs: here and here. --Leyo 18:07, 10 June 2009 (UTC)

Great idea, do it!
Ben (talk) 20:02, 10 June 2009 (UTC)
Commons:WikiProject Chemistry/Deletion requests
Any improvements or corrections are welcomed. --Leyo 20:38, 10 June 2009 (UTC)

I checked the images in some subcategories of Category:Deletion requests. I haven't done it for January–April 2009 yet, but for the rest. --Leyo 14:59, 11 June 2009 (UTC)

bad font rendering in chemical SVGs[edit]

It is really annoying and effects most of the text-based (not converted to path using Inkscape) chemical SVGs. I noted it at Bug 16368 [SVG Rendering] Worsening of font rendering quality, but no developer responded there yet. Anyway you can vote for the bug to enhance it's priority. It would also be interesting to discuss ways to fix it (which fonts work, which don't and where to fix it in librsvg). Matt (talk) 17:38, 24 September 2009 (UTC)

Yes, it is. However, there have been no such problem for chemical structures recently uploaded by de-WP users using ChemBioDraw (e.g. NEUROtiker, Yikrazuul or me). The new version even offers direct SVG export. There is a fully working trial version (two weeks). --Leyo 20:24, 24 September 2009 (UTC)
Yes, but the SVGs of three of us (and others, of course) don't contain letters embedded as text, but instead as vectors. I think what Matthias meant are SVGs, where the text has not been converted to vectors. With those there are often displaying issues ranging from alternating fonts to mis-scaled letters. --NEUROtiker  21:20, 24 September 2009 (UTC)
Thanks for stating it more precisely. BTW: There are currently several SVG images not rendering correctly in Category:Low quality chemical diagrams. --Leyo 21:57, 24 September 2009 (UTC)
Note: some fonts seem to render better than others. Nimbus Sans L seems to render fine at File:Acetic acid.svg. Matt (talk) 21:38, 30 September 2009 (UTC)
True, but I wouldn't rely on that. With the next update of the librsvg version this could change dramatically as it already has in the past. I can't really see, why text in SVGs – and particularly in chemical images – shouldn't be converted to paths. --NEUROtiker  19:50, 3 October 2009 (UTC)

Tools for making SVG files[edit]

I know that there are tools for making SVG files. But does anyone know a simple converter, that is make svg files from png or jpg? It is not easy with most good drawing programs do not make svgs yet. -- Chemist62 (talk) 13:30, 26 October 2009 (UTC)

Have you already read en:Wikipedia:Manual of Style (chemistry)/Structure drawing#Generating SVG files? --Leyo 13:39, 26 October 2009 (UTC)

Internationalization of “Upload a chemical structure”[edit]

Hi everyone! Whenever I use the Upload a chemical structure link to upload a structural formula to Commons, the section headings == Summary == and == Licensing == are used instead of == {{int:filedesc}} == and == {{int:license}} ==. Would it be possible to internationalize these heading when using the “Upload a chemical structure” link? Or does anyone know whom to address for this suggestion? Thanks in advance and best wishes, --Sponk (talk) 08:24, 11 April 2010 (UTC)

Strange. When I use the upload link on my user page (that is more or less similar), no section headings at all are included (example). --Leyo 19:30, 11 April 2010 (UTC)
Hi Leyo, now this is sort of weird, 'cos, the structures I have uploaded 10 min ago, have no section headings at all, too (see [1] or [2] for instance)!? Would be nice to recognize any pattern behind that… maybe someone's currently working on that issue? Best wishes, --Sponk (talk) 04:55, 18 April 2010 (UTC)
In my opinion, this should be the normal case using this upload link. The section headings could be added to the link if you like. IMHO they are not so important in the case of chemical structures, because the description page is also easily comprehensible without them. --Leyo 09:12, 18 April 2010 (UTC)

Category talk:Mesomerism[edit]

Should Category talk:Mesomerism be renamed to to Category:Chemical resonance? Mesomerism is rather an outdated term. -Bduke (talk) 09:57, 18 April 2010 (UTC)

Pictogram voting info.svg Info We have a special page for category relation discussions, but it is OK for now. --Leyo 10:44, 18 April 2010 (UTC)
According to IUPAC it is not outdated.[3] I read it the other way round it P. Bruice: Organic Chemistry, that resonance should be avoided because it confuses as it has nothing to do with resonance in classical physics. Matt (talk) 20:30, 27 April 2010 (UTC)
The main IUPAC page is here. That looks primary to me. It only mentions mesmerism under "See also". It is not a mirror of the mesonerim page The English wikipedia page is at w:Resonance (chemistry). I suggest Bruice is an old man out. He may be formally correct, but nobody is listening to him. The only two organic books I have to hand, McMurry and Morrison and Boyd do not seem to even mention mesomerism. First year texts such as Zumdahl are the same. I have never seen it used in a paper on valence bond theory, while resonance is widely used there. I work in valence bond theory where the term resonance originated with Linus Pauling. Resonance, like it or not, is the term in English that chemists use. Mesomerism is hardly ever used in English, although it is used in other languages such as French and German. Category:Resonance (chemistry) would be better to reflect the article titles. --Bduke (talk) 22:58, 27 April 2010 (UTC)
Clayden has this to say on pp. 154–155:
"What words should be used to describe delocalization is a vexed question. Terms such as resonance, mesomerism, conjugation, and delocalization are only a few of the ones you will find in books. You will already have notices that we don't like 'resonance' because it suggests that the structure vibrates rapidly between localized structures. We shall use conjugation and delocalization: conjugation focuses on the sequence of alternating double and single bonds while delocalization focuses on the molecular orbitals covering the whole system. Electrons are delocalized over the whole of a conjugated system."
As for March, I'll just direct you to the full text at Google Books.
Ben (talk) 01:24, 28 April 2010 (UTC)

This is a bit off point. I have not looked at all the images, but those I did deal with resonance structures. That is they were displaying the diagrams that represent individual valence bond structures. That means that anything to do with molecular orbital theory is not relevant and should not be in this category. So the issue is not just what we call this category, but what criteria we use to add this category to images. If we are covering everything then conjugation might be a better term as it is not as wedded to MO theory as resonance is to VB theory. I will leave it all with you, as I am taking a wikibreak while travelling for the next 5 weeks. --Bduke (talk) 22:39, 28 April 2010 (UTC)

Fair comment about being off topic.
I've created Category:Delocalized chemical bonding and branched off the discussion at Category talk:Delocalized chemical bonding#Relevant IUPAC Gold Book entries.
I think "resonance structures" is probably a better name for the category than "mesomerism".
Enjoy your voyage!
Ben (talk) 14:42, 29 April 2010 (UTC)

Template:Molecule[edit]

There is Template:Molecule, but it is not transcluded many times. Would it be a good idea to use it more often? Could it be optimized? --Leyo 22:47, 4 July 2010 (UTC)

That's a lot of work to do. But I assume that bots can optimize it, by checking info on big wikis that use these images and use templates (chembox, drugbox) with appropriate fields (name, CAS, formula, SMILES). Rhadamante (talk) 22:00, 6 July 2010 (UTC)
Hello Leyo, do you have an example, where the template is in use?. --Roland1952 (talk) 15:00, 8 July 2010 (UTC)
Special:WhatLinksHere/Template:Molecule :-) --Leyo 15:06, 8 July 2010 (UTC)
Symbol support vote.svg Support It makes sense to add some database information and put it here instead of Wikipedia. One could also add the INCHI and EC-number. Please note that there is also Template:Chemical structure verified and we should have only one template of that kind. Matt (talk) 16:26, 10 July 2010 (UTC)
I think that these templates should be merged. The only case where keeping both would make sense is when one is used for file description pages, whereas the other is used in category or gallery pages. --Leyo 16:10, 27 December 2010 (UTC)

I added the template to Commons:Upload/Chemistry. Matt (talk) 12:46, 24 December 2010 (UTC)

Maybe Leyo is right and putting Template:Molecule into category or gallery/data pages here on commons and not on every file description page is a better idea to avoid redundancy. Matt (talk) 13:16, 9 January 2011 (UTC)

I asked the RSC if they would support Template:Molecule for their Wikibox-feature at http://www.chemspider.com if we link back to them with an Chemspider ID in exchange, so we get more data more quickly to Commons. Matt (talk) 13:16, 9 January 2011 (UTC)

The RSC answered (7 days ago, but they went to my spam folder, sorry): "I would think that adding InChIKey, StdInChI and StdInChIKey would also be appropriate. In general most sites are starting to use StdInChI and StdInChIKeys by default and that is likely the best way to go for linking to online databases etc. Also, for the template I assume you want isomeric SMILES?" Maybe we need categories like Category:D-Glucose instead of just Category:Glucose if we want to put Template:Molecule on category pages. Matt (talk) 18:53, 18 January 2011 (UTC)

Berzelius[edit]

Is anybody recognising these symbols:

Berzelius Bref 8.djvu

? -- Lavallen (talk) 05:26, 29 July 2010 (UTC)

Image Question[edit]

The image in File:DewarBenzeneSynthesis.png is incorrect in that the startiing material shows phthalic anhydride but it should be the cis-1,2-dihydro derivative. This was recognised at the en:wp Dewar benzene page. User:Dissolution has generously provided a new image at File:Dewar benzene synthesis.svg. My questions:

  1. should the other wikipedias be notified that the image they are using has an error?
  2. should the error be noted somewhere for future users who might consider using the image with a mistake?
  3. are images with errors generally deleted?
  4. is this an appropriate place for me to ask about this, or should I have gone somewhere else?

Thanks. EdChem (talk) 10:03, 13 September 2010 (UTC)

  1. You might do it, but you can also replace the incorrect file with the correct version.
  2. Place Template:Disputed chem on the file description page.
  3. There are exeptions such as historic errors.
  4. Yes.
--Leyo 16:59, 13 September 2010 (UTC)

Ok, thanks... I have tagged the original image and notified the uploader. I have not altered the other language wikipedia using the image as it appears to be in Chinese, and I have no clue what I'd be doing. EdChem (talk) 13:04, 15 September 2010 (UTC)

Category:Wikibooks:de:chemistry[edit]

I think we should get rid of that category. It is not helpful at all and does not follow any category naming convention. The German Chemistry Wikitextbook also has it's own site to collect those images at b:de:Anorganische Chemie für Schüler: Projektkoordination: Bilder so it is redundant. Anyone want to help categorizing? Matt (talk) 01:23, 2 January 2011 (UTC)

duplicates[edit]

Recently a number of my structural formulae (e.g. this or this) have been tagged as duplicates though most of them are not identical to the other version but rather differed to a small extent. Since I haven't been very active in quite some time now I was wondering whether I have missed out on a consensus regarding multiple, similar versions of chemical compounds. In my opinion there's no disadvantage of having multiple high quality pictures for the same compound, even if they're only slightly different. Usually, my formulae are drawn in a special way according to the guidelines of the german wikipedia and in some cases in order to fit to a set of structures (e.g. for this wikibook). I'd be happy to hear your thoughts on this topic. Regards --NEURO  12:14, 12 August 2011 (UTC)

I'm not aware of any change in consensus regarding multiple, similar versions of chemical compounds. Chemical images that are similar, but not exact duplicates should not be tagged as duplicates (and definitely should not be deleted if there are no quality/accuracy issues). As for images such as File:Weinsäure.svg and File:Tartaric acid.svg, I would have to say they are nearly indistinguishable. I would not see any advantage in either keeping both or in deleting one of them. Ed (Edgar181) 13:17, 12 August 2011 (UTC)
The fact that the width of the margin is different can matter in some uses. --Leyo 13:29, 12 August 2011 (UTC)
I'm certainly happy to go with whatever consensus develops regarding multiple quite-similars (and will now lean towards deletion-discussion rather than dup-tagging, now that there is not a clear consensus). However, I don't see a need to default to keep multiple in the same format them without a reason. By policy, we are told not to have images in same-format that differ only by size, so the only "keep"able differences would be actual layout/formatting. Regarding layout issues, a few years ago, en.wp put together some standards based on de.wp. If there are differences, that really needs to be ironed out so we don't waste time generating lots of duplicates (contrary to the ideas of having layout standards and of having a shared pool of image-files) or overwriting each other's revision of a shared file in the name of making it "right" for one or another use-base. If the only difference is overall margin-size, I disagree with keeping for that reason--I can't think off-hand of a use-case where that can't be fixed using wiki markup or similar controls with an underlying "close-cropped" image (that's one of the layout-standards I think?). If a file does have a specific non-standard styling or margin or background for a particular case, everyone benefits if that situation is noted in the description page. One of the problems with having multiple images of the same thing is that each one tends to accumulate different category and other tags, making it harder to find information and associated content. I try to remember to copy these metadata from things I mark as dup to the other one so that the retained one has everything. DMacks (talk) 06:29, 14 August 2011 (UTC)

While I can understand that you want to delete low quality gifs and jpegs most of the time the reason to delete these svgs escapes me. No category is overcrowded enough so that one additional svg would hurt. No hard drive space is freed up and even if it was the amount with svgs is ridiculously small and overcompensated by the space that the deletion discussions take up. All you achive is that you piss of uploader who took the time and drew svgs only to find them deleted because somebody else drew something _half way_ similar. --Cwbm (commons) (talk) 06:56, 20 August 2011 (UTC)

In that specific, the svg I flagged has a quality problem. Then you found another quality problem in both that one and my proposed replacement. So which is a cleaner approach: scrapping one deficient image and fixing the other, or fixing both which will make them *literal* {{duplicate}} and then deleting one on that basis? As to your uploader-centric concern, "hurt feelings" isn't a keepable criterion/saving-grace for commons:scope, and the public-domain nature of the image and explicit "anyone can edit" nature means he has to accept that these things can happen. Or are you proposing I don't fix the problem you see in his (if I did, it would be no more "his" any more than if it were deleted and recreated from scratch) again so we don't hurt feelings? DMacks (talk) 12:46, 20 August 2011 (UTC)
I'm proposing having one super high quality svg and marking the other little less quality one as superseded and leaving it at that. --Cwbm (commons) (talk) 13:02, 20 August 2011 (UTC)
Okay, right there sounds like the kernel of your position (and matches your recent del-discussion comments). I disagree with keeping less-good images and think this position is in keeping with commons:scope#Must be realistically useful for an educational purpose, and hope here now that others will help get some consensus on this point. DMacks (talk) 03:10, 26 August 2011 (UTC)
When I say little less quality I'm simply parroting what you say. Since y'all (a lot of you) define a low quality simply as everything you don't like and not all of that is actually low quality. --Cwbm (commons) (talk) 05:53, 26 August 2011 (UTC)
The drawing standards for chemical diagrams are objective and explicit, and many del-discussions point to specific aspects of them. Other discussions point to more general commons image-quality guidelines and/or the actual educational usefulness. Isn't that why we're all here, to help make and organize a reusable collection of images to the best of our collective ability? You obviously don't agree with the approach many of us have been taking here for a while, which is fine (and you're welcome to have the last word here if there something that hasn't been said). But if you don't dispute that some quality is low, then all you can dispute is how to handle that situation. DMacks (talk) 18:06, 27 August 2011 (UTC)

Allene diagram geometry[edit]

File:Allene.png has the central carbon bent slightly, which is not correct. That image-name is widely used. File:丙二烯.png is the geometrically correct equivalent but with few uses. What's the better fix, migrate the pages pointing to the poor one to use the correct and then DR (incorrect, then-unused, and replaceable by the correct one), or just set the poor as a redirect to the improved? DMacks (talk) 01:28, 28 September 2011 (UTC)

IMHO File:Allene.png should be redrawn with (exactly) correct geometry, a hashed wedged bond and a higher resolution. --Leyo 07:18, 28 September 2011 (UTC)
We also have File:Propyl allene.png in current use, which has correct geometry at the central carbon, the proper hashed-wedged bond, and high resolution. DMacks (talk) 16:37, 28 September 2011 (UTC)

Sortkey in Category:Organometallic compounds by metal[edit]

The order of the subcategories seems to be a mess, currently. I suggest using sortkeys as follows:

[[Category:Organometallic compounds by metal|Zinc]]

for Category:Organozinc compounds. Thoughts? --Leyo 10:40, 26 November 2012 (UTC)

That looks like a good idea to me. Ed (Edgar181) 14:41, 26 November 2012 (UTC)
The same might be done in Category:Organotransition metal compounds. --Leyo 16:43, 26 November 2012 (UTC)
✓ Done Ed (Edgar181) 14:11, 28 November 2012 (UTC)

Drawing methoxy groups[edit]

This discussion was originally in Commons:Village pump and was brought here per suggestion

What is the best way to draw methoxy groups in chemical compounds, when the image shows the group in the order H-(CH2)-O-? I've seen many ways, and I'm uncertain which one is the "best":

I've drawn a lot of compounds recently, and I fear I have added to the confusion. Albmont (talk) 17:21, 4 March 2013 (UTC)

–OCH3, H3CO–, –O–CH3 and H3C–O– are all fine, but e.g. CH3O– is not. --Leyo 22:35, 4 March 2013 (UTC)
File:5-hydroxyferulic acid.svg also shows the group as CH3O-. Is there any place where the Collective discussed standards for the drawing of compounds? Some of the compounds I drew look awful, like File:Perchloropropene.svg or File:1,1-diphenylethane.svg. Albmont (talk) 18:46, 12 March 2013 (UTC)
The two Wikipedias with the most active uploaders of chemical structures have such a page: de:WP:WEIS, en:WP:CSDG. --Leyo 23:46, 12 March 2013 (UTC)
I read the English rules (my German skills are rudimentary, enough to do some minor editing in wiki.de but not for reading rules!) and it seems that both forms, as explicit CH3 or by implicit bonds are accepted. There are no rules about H3C, but it seems that the text suggests that methyl groups at the extreme of chains, if the uploader wishes to show them explicitly, should be CH3. Albmont (talk) 11:08, 13 March 2013 (UTC)
I agree that –OCH3, H3CO–, –O–CH3 and H3C–O– are all acceptable, but I wouldn't say that CH3O– is not. It is widely used in the chemical literature and is readily understood by anyone who knows chemical structures. I don't think it is a good idea to mark structures that contain CH3O– with the {{disputed chem}} template. The accuracy of those chemical structures is not really in question. They may use a non-preferred style, but they are not wrong in my opinion. Ed (Edgar181) 16:56, 13 March 2013 (UTC)
You may call it sloppy style or bad practice. I can tag them with {{low quality chem}} instead. --Leyo 17:05, 13 March 2013 (UTC)
I agree that it's more of a quality issue. It might be misleading to those who don't really know how to read "condensed" structure fragments, but its meaning is pretty obvious if you do and it's correct in that system (does anyone write butane H3CCH2CH2CH3?). DMacks (talk) 17:32, 13 March 2013 (UTC)
You cannot compare a Halbstrukturformel (I don't know the translation) that is always read from left to right with a group that sticks out towards left. --Leyo 18:49, 13 March 2013 (UTC)
And what about CH3-O- in the structure? It seems more natural than drawing H3C-O-. Also, other groups are shown the same way, like NO2- (specially because whenever I try to draw the nitro group with the artificial N+ and O-, BKChem or Inkscape always do a mess and it never shows right). Albmont (talk) 12:39, 15 March 2013 (UTC)
Just turn the molecule that the relevant group sticks out towards right. ;-) --Leyo 00:02, 20 March 2013 (UTC)

Help!![edit]

Hi, I make a big miskate between 1-benzooxepine and 3-benzooxepine about the position of oxygen atome- I confused 1-benzooxepine with 3-benzooxepine and reciprocally. It concerns two couples photos I create today :

I need this photos quikly because I work on the poor french article fr:wp:Benzoxépine! I already ask for te rename at 10:52 but the situation hasn't changed... Help ! I put too this message in french on Commons:Bistro because nobody here since --Leyo 00:02, 20 March 2013 (UTC)

My highest consideration to the first sysop will solve this case!--The Titou (talk) 13:18, 16 November 2013 (UTC)

All moves were done. --Leyo 00:56, 17 November 2013 (UTC)

Drawing polymers[edit]

Does anyone know how to draw polymers in BKchem? I would like to draw File:poly(propyl methacrylate).svg to include in article pt:Polimetacrilato de propila, but I don't know if there's a way to draw the elipsis or open dashes like in www.polymerprocessing.com. Albmont (talk) 16:58, 19 November 2013 (UTC)

Its, as far as I see impossibel. Onyl bracked are possible. Her there isn't a need for this because the formular is pretty simple and all carbons can be written in a C-Chain. --Codc (talk) 19:53, 19 November 2013 (UTC)

Antifungals/fungicides[edit]

We currently have two categories for the same topic: Category:Fungicides and Category:Antifungals. Or maybe they aren't quite the same. The fungicides category includes mostly those for agricultural use, and the antifungals category includes mostly pharmaceuticals. Should there be two categories, or just one? Ed (Edgar181) 13:41, 27 March 2014 (UTC)

Normally, an antifungal is a medication to treat mycoses, while an fungicide is a substance to kill a fungi specie. Antifungals are fungicides, but not the opposite. Rhadamante (talk) 01:20, 30 March 2014 (UTC)
That sounds reasonable to me. If no one objects, I will check the two categories and consolidate all the pharmaceuticals into Category:Antifungals and all the others into Category:Fungicides. Ed (Edgar181) 13:41, 17 April 2014 (UTC)
I've added a small explanation in both categories. Albmont (talk) 16:37, 18 May 2014 (UTC)

Category:Benzene derivatives/Category:Phenyl compounds[edit]

Hi, usually, I always hesitate between these two categories when I have to classify a molecule containing a benzene ring, and cannot be classified in a sub-category (by the way, the problem is the same for the sub-categories, in which of these two should we put them?). Is there a strong difference between what should be in each of these two categories? Is there even a proper definition of what should be in each of these two categories?

I see that, french version excepted (and it seems I've created the two corresponding categories on fr:, a long time ago, probably in accordance on what was on commons), not a single Wikipedia version has these two categories. Actually, it's even worse, Category:Benzene derivatives only exist on fr: and nl: (where it is pretty well developed), and Category:Phenyl compounds only exists on English, French, Farsi, Chinese, Serb and Serbo-Croatian versions. And for the English version, it only contains 7 articles (why these 7?), and one subcategory, the vast majority of benzene derivatives been directly classified in "Aromatics compounds". I'm not a big fan of the latest, but without going that far, do we really need 2 of these categories? Rhadamante (talk) 15:57, 22 May 2014 (UTC)

I think these two categories have the same meaning, too, so we can move all the files in one category only. Between the two ones, the name "Phenyl compounds" it looks to me more precise, because it means that the molecule contains at least one phenyl group, instead the name "Benzene derivatives" looks to me like a more commercial and less chemical definition, because it means "everything that can be produced from benzene". --Daniele Pugliesi (talk) 22:31, 27 June 2014 (UTC)

Category:Chemical structures by substance[edit]

The subcategory Category:Chemical structure of methane was created today by User:Daniele Pugliesi. I am skeptical whether this is a good idea, because I would not like to see this being done for many chemicals. Any thoughts? --Leyo 20:32, 27 June 2014 (UTC)

I agree that this would not normally be a good thing for many chemicals. In almost every case, structure is all we have, and we usually only have one or a very few such images .Even for drugs and many other chemicals, we often only have a handful total (including structures and dose/packaging or simple photographs). It's only a useful subcat of a chemical when there are many other images, such as methane production/storage facilities and data/graphs etc. But having such a full subcat suggests that maybe we really do have many redundant images (13 VDW-like space-filling? 2 different SVGs of the plain-text "CH4" formula?)--there are really very few different ways to represent especially such a simple chemical. OTOH, for such a prototypical molecule of such a well-known compound among the general public, it's important to keep Category:Methane it organized and have multiple different representations available. DMacks (talk) 20:51, 27 June 2014 (UTC)
I created the category just for the cases like methane and water where we have a lot of pictures related to the representation of the molecule and a lot of other pictures related to other aspects of the compound, in order to facility the navigation, so I agree that we don't have to create such categories when we have a few of pictures.
Also after the creation of Category:Chemical structure of methane my intention was to identify which pictures are redundant or not useful in order to propose them for deletion. At this regard, I indicate here below the groups of images that are duplicated, so we can decide to maintain just one or two of them for each group, for example one png and one svg (if you think he have to discuss about this in another page, you can move this discussion):
Lewis formula
Space-filling model
Ball-and-stick model
Natta projection (view 1)
Natta projection (view 1 + bond lenght)
Natta projection (view 2)
Fischer projection

Furthermore, these representations looks to me not standard (or maybe someone of them follow a standard that I don't know - for example a sawhorse projection?), so I think they can be deleted, also:

If my considerations are correct, it means that about 30 pictures of 67 have to be deleted because they are duplicated.

Also I think we have to create a Category:Natta projection. --Daniele Pugliesi 22:19, 27 June 2014 (UTC)

en:Natta projection is just a standard tetrahedral geometry representation for tetrahedral geometry. It's probably the standard. But now that we're in a cat with just structure-diagrams, it's not so special, and it's certainly not a name that non-experts would be able to follow if the goal is easily navigable organization. Unless there is actually lots of stereochemistry or other geometric detail, I don't know too many even specialists who distinguish between Natta and Fisher style diagrams. 05:52, 28 June 2014 (UTC)
In the case they are not sure a representation is a Natta projection or a Fisher projection or something else, they can just do not categorize the file with these categories and eventually the experts will do it. We could also create a Category:Chemical formulas with stereo bonds. --Daniele Pugliesi 14:50, 28 June 2014 (UTC)
What would be the purpose of such a category? --Leyo 15:12, 28 June 2014 (UTC)
I think that every chemical structure has to included in (at least) two categories: one related to the nature of the chemical species (e.g.: water, methanol, etc.) and the other one related to the type of visualization used (e.g.: Fisher projection, Natta projection, Ball-and-stick model, etc.). --Daniele Pugliesi (talk) 18:56, 28 June 2014 (UTC)
I think that's not a generally-useful way of categorizing, especially for standard skeletal ones (not special 3D graphical renderings). I can't think of a time I have ever said "I'd like a chemical diagram that is a natta projection. What chemical? Eh, don't care, let's see what's available." Or "Here's a nice image of a chemical; what other chemicals use this same universal diagram standard?". Those are the ways I think categories are generally helpful--finding something from a lead idea or jumping to related images once I'm looking at a starting point. DMacks (talk) 19:00, 28 June 2014 (UTC)
Such a categorization can be useful for example for students which want to exercise in the representation of molecules in a particular way: they don't care the nature of the molecule; instead they are looking for a collection of a lot of molecules represented in a particular way. --Daniele Pugliesi (talk) 19:10, 29 June 2014 (UTC)

As anticipated, I proposed for deletion some of the pictures above. I will propose the other ones later, first I want to see the outcomes of these proposals to be sure that I am following the rules of en.wikipedia. --Daniele Pugliesi (talk) 23:03, 13 July 2014 (UTC)

Thanks for working on this curation! In addition to tagging the files and starting the deletion-discussion page, be sure to add a link to the discussion page on the dated discussion list (step III of Commons:Deletion requests/listing a request manually). For chemical files, please also list them at Commons:WikiProject Chemistry/Deletion requests. Other editors have handled the listings of your recent batch of noms. DMacks (talk) 02:28, 14 July 2014 (UTC)

Allura Red AC Formula V.1.svg[edit]

I think File:Allura Red AC Formula V.1.svg is wrong. The image does not match the chemical description, the coupling should be in the C-1 position (C-2 being the hydroxy group). Albmont (talk) 19:08, 11 July 2014 (UTC)

The image is exactly taken from The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 14. Auflage (Merck & Co., Inc.), Whitehouse Station, NJ, USA, 2006; S. 284, ISBN 978-0-911910-00-1. I have also checked the formula in the SciFinder. The same structure is shown in the SciFinder. The structural formula is in my opinion correct. Best regards --Jue (talk) 10:54, 12 July 2014 (UTC)
Here are the images I can find already on commons (according to filename-prefix search):
File:Allura Red AC Formula V.1.svg (isomer 1) does appear to be the odd one out, whereas the others (isomer 2) are what User:Albmont mentions. I agree that isomer 2 seems to be according to the systematic name in en:Allura Red AC (which also seems to match commons-chemistry CAS# 25956-17-6 and pubchem CID 6093299). I just checked SciFinder for "Allura Red AC" and got that same CAS#, which gave me a single hit: isomer 2. I tried searching for the skeletal connectivity of isomer 1 in SciFinder, and got no hits. DMacks (talk) 19:04, 12 July 2014 (UTC)
Also, the book reference (see the Portuguese article pt:Ácido beta-Schäffer) suggests that the diazo coupling prefers position ortho in the naphthol, which presumably means isomer 2 (and the image also supports isomer 2). Albmont (talk) 20:03, 13 July 2014 (UTC)