Talk:Singlet oxygen

Comments
Comment to Mathchem271828: In the first paragraph, I think it be more appropriate to use S.I. energy units for a energy difference between the two states instead of giving it as a temperature.


 * A the moment, it reads "The energy difference...is about 11,400 Kelvins... = 7918.1 cm-1" In dimensional terms, of course, neither K nor cm-1 is an energy. Joules everywhere, please -- no Hartrees, kcal, kcal/mole, kJ/mole, BTU, quads, foot-pounds, etc., etc., unless SI is there first.
 * Wavenumbers is the basic currency that chemists of all types, organic, physical, inorganic.. have an intuitive feel for because we are all familiar with IR spectroscopy. They are a fully accepted currency of energy as are kelvins for questions of thermodynamics.  SI units are fine for other areas but not for chemistry, in general. Mathchem271828 00:21, 6 February 2007 (UTC)

lapo_dk
 * lapo_dk; I'll just throw this out there that the temperature is good for people to put the data into a thermodynamics perspective.  The temperature might give you an idea of relative populations of the species. Mathchem271828 19:29, 15 December 2006 (UTC)

That temperature was totally wrong. It didn't take into account the O2's degrees of freedom and lookd like it took two atoms as one free atom. -lysdexia 11:01, 24 March 2007 (UTC)

"72 minutes" is a half-life, right? — Omegatron 00:16, 5 April 2007 (UTC)


 * I had that question, too, 4 years later. Given the sorry state of this article, it might be some sort of average! The best I could find on the Web was "lifetime", which is ambiguous. I don't think it can be half-life, because the decay is probably not exponential. Someone who knows should correct this poor information. David Spector (talk) 17:42, 30 December 2011 (UTC)

Lots of useful information, but the article is barely readable to someone outside the field (a link to nomenclature is not sufficient). 198.202.66.219 23:54, 3 May 2007 (UTC)

Energy difference
The article is self-contradictory: In the introductory paragraph the difference to the ground state is given as 7918.1 cm-1, corresponding to an energy of 94.7 kJ/mol or a wavelength of 1263 nm, while later the energy is given as 94.2 kJ/mol. And what does the "3625 kelvin" in the introductory paragraph refer to? It's not E/kB and not the temperature for maximum radiation in Wien's law, neither in the wavelength nor in the frequency view ... and even if it were, we should use a more common notation here. Icek 12:48, 27 August 2007 (UTC)
 * cf. Talk:Singlet oxygen. (Sorry for splitting this discussion up...I didn't notice this thread until after I posted.)--GregRM (talk) 03:16, 1 February 2009 (UTC)

Orbital occupancy of the singlet state
Cotton and Wilkinson 6th edition shows 2 singlet states, the 1Δg where both electrons occupy the same orbital and the 1Σg+ where the electrons are of opposite spin but in different orbitals. The latter is higher energy. Axiosaurus 11:50, 9 November 2007 (UTC)

what image to use
Lets hold on to the original image in the lead. The replacement image is in German! so why not have both images V8rik (talk) 21:15, 11 March 2008 (UTC)

Image text
The text in the diagram currently in the article is not in English. -- Beland (talk) 19:09, 2 June 2008 (UTC)

Singlet-triplet energy gap
I have made the energy gap in the article consistent using the value from the "ChemRev" reference of 7882cm^(-1). The value previously in the article (7918.1 cm^-1) appears in the Webbook link in External links, but Webbook doesn't seem to provide a reference for the singlet state energy. The value from the ChemRev reference appears to agree better with the wavelength used elsewhere in the article of ~1270 nm. (Perhaps the discrepancy between the two references can be explained by the difference between the speed of light in air vs. vacuum?; I have used speed of light in vacuum in my conversions). Thus, I have limited justification for choosing the 7882 value over the 7918.1 value so if someone is familiar with this, feel free to change it to a more accurate value.

Also, I should note that I fixed the temperature. It looks like the correct temperature was originally in the article but was changed to 3625 K(cf. discussion at the top of this page). I believe the correct value is around 11340 K (rather than 3625 K) based on E/k or E/R. (Maybe 3625 K was meant to correspond to something else, like the vibrational temperature?)--GregRM (talk) 03:09, 1 February 2009 (UTC)

Singlet oxygen contains oxygen-oxygen double bond? --83.100.0.5 (talk) 17:23, 13 July 2009 (UTC)

Update 2016


I have found the reason for the two values of the singlet-triplet energy gap: 7918 and 7882 cm-1. Both values appear in Figure 1 of the Chem. Revs. source article by Schweitzer and Schmidt. 7918 cm-1 is in the column labelled Te, meaning term value for the equilibrium position at the bottom of the potential curve, so that electronic energy is included but not vibrational. 7882 cm-1 is in the column labelled ν00, referring to the difference between v = 0 vibrational levels of the singlet and triplet states. This corresponds to the total singlet-triplet energy difference including vibrational energy, and is therefore the more appropriate value to use, as assumed by GregRM above.

Similarly for the 1Σ state, the same source gives Te = 13195.2 cm-1 and ν00 = 13120.9 cm-1, and again we should use the second value. Dirac66 (talk) 19:04, 27 November 2016 (UTC)

Reactivty
The below was in the article on Triple Oxygen, shouldn't the same statement be made in this article. Singlet oxygen, .. is many times more reactive than triplet oxygen,... Dave 2346 (talk) 22:10, 19 July 2009 (UTC)

The essence is that triplet and singlet oxygen participate in different reactions, so whether or not singlet oxygen is "more reactive" than triplet oxygen depends on the kind on reaction we are talking about.

It can be confusing because singlet oxygen is often called a "reactive oxygen species" together with a bunch of highly reactive oxygen radical species. I would suggest that we stick with "The chemistry of singlet oxygen is different from that of ground state oxygen." Lapo dk (talk) 09:31, 28 July 2009 (UTC)

"Ene" Reaction
You might want to note that the apparent ene reaction for singlet oxygen is actually only a net ene reaction. It actually is a non-concerted but non-radical process involving a zwitterionic intermediate. For more info, or possibly a good sitation for this page see:

"Mechanism of the ene reaction between singlet oxygen and olefins"

L. M. Stephenson, Mary Jo Grdina, Michael Orfanopoulos

Acc. Chem. Res., 1980, 13 (11), pp 419–425

DOI: 10.1021/ar50155a006

Publication Date: November 1980

Here is the link to the article serving page on the ACS website: http://pubs.acs.org/doi/abs/10.1021/ar50155a006

I only bring this up because I have been seeing a number of young people incorrectly declare this to be a true ene reaction (even in presentations) and many of them seem to be getting their info from here.149.155.3.152 (talk) 18:13, 24 January 2012 (UTC)


 * Yeah, this is a previously known fact, but full treatment of this would require some more work on this, this is why it was weaselled as "ene reaction-like". --vuo (talk) 00:15, 25 January 2012 (UTC)


 * this source says otherwise: http://evans.harvard.edu/pdf/smnr_2005_nagorny_pavel.pdf V8rik (talk) 21:38, 25 January 2012 (UTC)

Delta Singlet oxygen is not diamagnetic but paramagnetic
The first sentence "Singlet oxygen (or 1O2) is the common name used for the diamagnetic form of molecular oxygen (O2)" is wrong. While spins are paired, there is still a considerable magnetic moment due to the non-vanishing orbital angular momentum which makes at least the more stable Delta singlet oxygen nearly as paramagnetic as triplett oxygen. See e.g. references 20 and 21 from the German page on oxygen. http://de.wikipedia.org/wiki/Sauerstoff 195.126.85.201 (talk) 08:33, 12 April 2012 (UTC)
 * Ref 20 and 21 in the German article are to Gastrennung" (separation of O2 from air) and Greenwood and Earnshaw (G&E). The latter is the bible of main group chemistry, does not indicate that singlet oxygen is not (essentially) diamagnetic and doesnt discuss "orbital angular momentum".  So we need to verify the high paramagnetism for singlet O2. G&E also states several times that triplet is blue BTW.  --Smokefoot (talk) 13:14, 12 August 2015 (UTC)
 * Re references 20 and 21, note that the comment by 195.126.85.201 is dated 12 April 2012, so s/he means the comments which were then numbered 20 and 21. On comparing the April 2012 version in the edit history with the current version, I see that these 2 references are now 25 and 26. However on looking at the titles I think it should be 26 and 27, as 25 is just a photo of a spectrum. Perhaps 26 by Hasegawa and 27 by Shinkorenko and Aleskovskiji will be more relevant.
 * I also found a paper saying that singlet delta oxygen has an EPR (electron paramagnetic resonance) spectrum, which can only be true if it is in fact paramagnetic. See J. Am. Chem. Soc., 1969, 91 (4), pp 1039–1040 here: Dirac66 (talk) 02:14, 13 August 2015 (UTC)
 * Look also to Greer (2006) Accounts, which I am adding to the Further reading. Truro also had a JACS paper I recall, on gas phase EPR of both singlet and triplet dioxygen — just before he passed away (in collaboration with an Italian group?). Le Prof Leprof 7272 (talk) 15:01, 18 August 2015 (UTC)
 * The EPR spectrum of singlet oxygen in the gas phase was first measured by Falick et al in 1965, see, Falick, A. M., Mahan, B. H., & Myers, R. J. (1965). Paramagnetic resonance spectrum of the 1Δg oxygen molecule. The Journal of Chemical Physics, 42(5), 1837-1838.


 * I have now added a brief subsection on paramagnetism, mentioning the EPR observation and the orbital explanation. I have cited 3 of the 6 abovementioned papers: Hasegawa et al, Ruzzi et al (including Turro, not Truro) and Falick et al. As for the previous incorrect claim that the delta state is diamagnetic which started this discussion, it was deleted on 8 May 2012. Dirac66 (talk) 02:43, 18 March 2016 (UTC)

Call for experts to take this rest of way
The issues I began to address in the first three paragraphs of the lede—which may, in the long run, be shortened, and migrate into the main text—require review by an expert, as does the new combined section on structure and bonding. Need is for a physical or inorganic chemistry professional.

As well, despite relevant, rich secondary and tertiary literature on the subject, the article still fails to present an accessible, self-consistent, readable encyclopedic article (apart from the organic chemistry section stub, and, I hope, the newly revised lede opening.

Note, in today's edit, I found the "blue color" sentence unverifiable (citing an Inorg book with no page nos., and otherwise unsearchable). I corrected that sentence based on an alternative source, not the best, but it was what I could locate. (Because it was badly written — confusing — I was not leaving anything like it in without some source.) In addition, I made article opening parallel triplet ( 3 Σg) oxygen article, thereby building on that related article. I then tried to explain, based on sources, the relationship between triplet oxygen and this article's title "singlet oxygen" concept. including that the 1 Δg is but one of the accessible singlet oxygen states.

Have at it, but please do not let it slide back into being unsourced, unscholarly material. Cheers. Le Prof Leprof 7272 (talk) 03:01, 12 August 2015 (UTC)

First three paragraphs of lede, [AGAIN UN]satisfactory now
Please comment. I am a chemist and educator, but not a physical or inorganic chemist, and recalling how to explain MO theory of homonuclear diatomics to a lay audience is outside my normal activities. Note, only the first three paragraphs of the lede have been brought up to standard. The rest of the lede, and the rest of the article, must be for someone who works in this area. Le Prof Leprof 7272 (talk) 14:48, 18 August 2015 (UTC)


 * With Boghog's edit, that he describes in following, I retract my statement that the lede is satisfactory for the interim. The edits gutted its content, including its attempt to reflect the whole of the article, and its attempt to define terms that secondary students and above could understand. (The redacted third paragraph leaves terms next appearing undefined, etc.) In short, the lead is now, [AGAIN, UN]satisfactory. Le Prof Leprof 7272 (talk) 20:02, 18 August 2015 (UTC)


 * Per WP:LEAD, the lead (or at lead the first paragraph of the lead), should be written in a way that it can be understood by a wide audience. According to this criteria, the lead is not satisfactory and needs further work to simplify the language. Boghog (talk) 16:01, 18 August 2015 (UTC) I have made a attempt to simplify the language in this edit. Boghog (talk) 16:27, 18 August 2015 (UTC)


 * You also are not a physical or inorganic chemist, nor an expert at what works with students coming to Wikipedia articles, and based on my experience, your fly-by visits and reversions of my work harm that large body of general readers, rather than helping them. See below for the parallel construction that you destroyed. Leprof 7272 (talk) 18:25, 18 August 2015 (UTC)


 * It is clear that you still do not understand how Wikipedia works. I am a chemist and educator – is relevant at Citizendium but not relevant in Wikipedia. Any intelligent editor that bases their edits on reliable sources and makes their edits in good faith has just as much right to contribute an article as experts. You also are not a physical or inorganic chemist – also not relevant and also untrue. I am a physical organic chemist by training and I am very familiar with singlet oxygen.  You are making assumptions about other editors which are often erroneous. If you remember to comment on the edits and not the editors, you will avoid making this mistake. Boghog (talk) 19:55, 18 August 2015 (UTC)


 * I understand very well how WP works, and how you work. Your motives are personal, and these, your latest stalking edits are deeply flawed. Moreover, you are still not a "physical... chemist" (but rather a physical organic chemist, as you admit) which is not the same.


 * The call I made was for an expert who knows MO theory applied to inorganics, especially homonuclear diatomics, to attend to the article. You are clearly, as a trained physical organic chemist—and working not as a teacher, but as a corporate chemist, I believe?—not a true expert at the presentation of the material in question. Congrats for, like me, knowing what 1O2 is, and perhaps having done some 1O2 reactions in the past. Neither of these, nor your training, make you an expert in student presentations on the subject matter at hand (how to explain the existence, in modern terms, of a particular inorganic excited state).


 * Nor am I, which is why I called for a true expert to attend. A true expert, not a WP:LEAD-excuse using stalking editor that you are. And you are correct, WP stops no one, however marginally qualified in exact expertise or appropriate demeanor—what is WP policy on editors who follow, and pick fights?—from intervening in an article unnecessarily. Personal character and discernment should do that, within the person.  Le Prof Leprof 7272 (talk) 20:16, 18 August 2015 (UTC)


 * I have also removed the second paragraph which is really out of place. We do not need an extended explanation of the differences between singlet and  triplet states. We already have separate articles on these two topics and wiki links to those articles should be sufficient. Boghog (talk) 16:06, 18 August 2015 (UTC)


 * Your opinion, that in an oxygen-specific discussion, about how oxygen's structure specifically gives rise to two low-lying singlet states, does not belong in the singlet oxygen article lede, when it appears in the article's later Structure section, is [a] contrary to policy, which states ledes should summarize articles (and the Structure section was rich and long, years before I got here), and is [b] specious, for how oxygen's MOs give rise to that particular molecule's excited states belongs more in this article than in the generic, and [c] is imposed without discussion, despite knowing that an interested, professional chemist was editing the article in the hour before.


 * Moreover, had you compared what is in place before your edit, to what was in place before my editing began some days ago, and looked to the Edit histories and Talk for reasons, and even looked to the parallel triplet oxygen article, you might have slowed down (unless this is intended as a form of personal attack, that is).


 * Had you done any of these, you would see that the article was moving, and in better directions—and that what I conveyed was not that the lead was ultimately sufficient but that the lede was satisfactory — meaning that it was sufficient with material that an expert in PChem or IOChem could edit toward a better, final article. The point was to hand this off.


 * You wrecked the parallel structure between the triplet oxygen and singlet oxygen articles that was respectfully based on content already there when I arrived at each (wrecked, because the parallels were much of what you removed in your opening paragraph edit). With the paragraph deletion, you removed useful sources and extra material that others—who take more time than you, and do more than just deleting—could have turned into a better final article.


 * Finally, in deleting the student friendly intermediate paragraph, you removed the definitions of the term symbol abbreviations making the third paragraph begin with jargon, removed the entire summary of the substantial Structure description Section in the article, and so made it impossible to understand where the two singlet states discussed in the third lede paragraph come from—and so violated a variety of WP principles.


 * In short, by interrupting this, in a knee jerk—and personal, as you clearly follow me about—and reductive way, you have both violated the WP:LEAD that you use to justify your following, and have interrupted the movement of these articles—the very definition of destructive editing. Most importantly, you are wasting precious time, and poisoning the editing experience by doing so. Leprof 7272 (talk) 18:01, 18 August 2015 (UTC)

Redacted paragraph
Excited states of oxygen can be seen as arising from the ground state of the same molecule. According to one type of modern bonding theory, the electronic configuration of the ground state of oxygen molecule has the last two electrons to fill its molecular orbitals (MOs) occupy two orbitals of equal energy (that is, degenerate MOs), therefore remaining unpaired. These two orbitals are classified as antibonding and are of higher energy, and the electrons occupying them are represented as having electrons of like (same) spin. Two excited states are readily accessible from this ground state; the first moves one of the high energy unpaired ground state electrons from one degenerate orbital to the other, where it pairs the other and creates a new state, a singlet state referred to as the 1Σg+ state (a term symbol. where the preceding superscripted "1" indicates it as a singlet state). Alternatively, both electrons can remain in their degenerate ground state orbitals, but the spin of one can "flip" so that it is now opposite to the second (i.e., it is still in a separate degenerate orbital, but no longer of like spin); this also creates a new state, a singlet state referred to as the 1Δg state.

Continuing discussion

 * To summarize: I created this Talk entry, and the earlier expert needed tag, not so that this lede would remain in place, as is, but so that a sufficient quantity of temporary accurate material remained in the lede that a better qualified individual, which Boghog is not, could come along and use as a starting point, which Boghog clearly did not do, constructively. The further point was, in the mean time, to have ledes in the triplet and singlet articles that were parallel in structure, so that lower form university students (and secondary school) could begin to understand, until the article as a whole was edited. The redaction of the paragraph leaving jargon/undefined terms and a disconnect about where singlet species come from is clearly counterproductive.


 * Otherwise, I note again, Boghog is why people leave this place -- immediate edits, without discussion, when an editor is actually working on an article, with edits that are knee jerk reversions or deletions most frequent. Boghog is incorrigible, stalking, and the only recourse remaining is to take this forward to administrative action. Le Prof Leprof 7272 (talk) 16:48, 18 August 2015 (UTC)


 * how oxygen's structure specifically gives rise to two low-lying singlet states does not belong in the ... lede. This is part of the definition of singlet oxygen and clearly belongs in the first paragraph of the lead. Others define it in a similar way. For example:
 * Boghog (talk) 20:16, 18 August 2015 (UTC)
 * All obfuscation. "My statement was "Your opinion, that in an oxygen-specific discussion, about how oxygen's structure specifically gives rise to two low-lying singlet states, does not belong in the lede…" were words attributed to your action, and they stand. You gutted the explanation of singlet state structure, which—even if overly long—were derived from the article's Structure section, and explained precisely how, in this more specialized, oxygen-specific article, the title state and related states arise from the ground state and each other. Hence, you gut the how and other critical defining content, and interrupt the lede's flow, leaving the new third paragraph to open with term symbols and ideas that are not identified… and now return to self-justify via limited quoting and reply. All smoke, mate.


 * Forget the justifications, just hurry on and edit out your clearly klutzy initial mis-edits, so anyone coming on a bit later can't see the problems you created or what the fuss is about. Go on. But try to find a good modern, advance IOChem, and not a medical text, to use as as a source for your material. Done with you, again, on this article, Poisonous you are. Leprof 7272 (talk) 20:19, 18 August 2015 (UTC)


 * We need a simple short definition to start the article. How about the following: Boghog (talk) 20:30, 18 August 2015 (UTC)
 * You are arguing out of both sides of mouth. This sentence is chemist's jargon, and not understandable to a layperson. Moreover, the lead at the triplet oxygen page started at a point of nominal knowledge, and progressed to the technical definition, which I cut, pasted, and edited in here with an aim to make it the layperson friendly opening you purport to want. (No, what you clearly want is your opening, at this article, since it was one I was working on.)


 * Otherwise, this source you propose is a self-published professor page, and so a poor and unnecessary turn in a field with hundreds of IOChem and PChem books that present and discuss the O2 structure.


 * Moreover, your turning attention to the definition is just more self-justifying, quick-I-have-to-fix-the-mess-I-made rapid work. Did you ask yourself, what deinfintion is already used in the article? Is it sourced, and is it a good source? No, your aim is to come quickly to an article I have been at for many days, and plant your flag.


 * Finally, quick edits to the definition ignore the big picture that is at issue—your stalking (which should lead you to revert and retreat), and the disastrous effect of your unnecessary paragraph redaction and destroying the parallel structure with the triplet oxygen article (which would be solved if you did a corrective revert, to start). Unless you are on vacation (as I am), if not reverting, leave improving your mess. It requries focused, hard work, not fly-by efforts between emails. Leprof 7272 (talk) 20:41, 18 August 2015 (UTC)

Making it one of nature's most forbidden transitions
I am again removing this prose, even though I do not personally disagree with it, because it is a scholarly and professional judgment, and needs to appear with a secondary source. Or at least in quotes, from the only primary source that appears. Le Prof Leprof 7272 (talk) 16:48, 18 August 2015 (UTC)

Recent lede edits, part 1
Today, a number of major deletions and edits occurred in the lede, under the Edit summary, "it is important to keep the lead dead simple so that it can be understood by a wide audience."

For reference, this was the opening of the related triplet oxygen article:"Triplet oxygen, systematically but less commonly, 1,2-dioxidanediyl, is a term that refers to normal, gaseous oxygen (O2, dioxygen) in its ground state. It is therefore classified as an inorganic chemical, and more specifically as a particular electronic state of one allotrope of the inorganic chemical element, oxygen. In this particular state, according to one type of modern bonding theory, the electron configuration of the oxygen molecule has two electrons occupying two molecular orbitals (MOs) of equal energy (that is, degenerate MOs), therefore remaining unpaired. These orbitals are classified as antibonding and are of higher energy, so the resulting bonding structure between the oxygen atoms is weakened (i.e., is higher in energy)—for instance, it is higher in energy than the bonding in dinitrogen, where bonding MOs are filled instead. The spectroscopic molecular term symbol for triplet (ground state) oxygen is 3Σg−."

For reference, this was the opening of the original singlet oxygen article:"Singlet oxygen, systematically but less commonly dioxidene, is a term that refers to oxygen (dioxygen, O2), including its gaseous physical state, except only the subset of molecules in a particular excited state. It is therefore classified as an inorganic chemical, more specifically, a particular electronic state of one allotrope of the inorganic chemical element, oxygen. The specific excited stated referred to as the title singlet oxygen is the accessible, lowest energy state, termed the 1Δg, or more simply 1O2, and it is chemically reactive, which underlies its utility as a reagent in preparative organic chemistry, as well as its damaging effects to materials in sunlight and air and its utility in such therapeutic areas as photodynamic therapy."

Here is the new lede opening"Singlet oxygen (systematically named dioxidene and abbreviated as 1O2 or 1Δg) is a high energy form of molecular oxygen in which the spin of all pairs electrons are opposite to each other. Hence the quantum state of this form of oxygen is singlet. This differs from the lowest energy form (ground state) of molecular oxygen in which spin of one pair of electrons is in the same direction resulting in triplet oxygen (abbreviated as 3O2). Singlet oxygen is chemically reactive and as a consequence has utility in such therapeutic areas as photodynamic therapy as well as reagent in preparative organic chemistry. In marked contrast to triplet oxygen which generally participates in free-radical mediated reactions, singlet oxygen engages in cycloaddition reactions."

In the case of this, and all remaining edits, they were performed without prior discussion, though the incoming new editor knew an editor was active in creating the new lede structure. (The editor in question has no substantial history of editing at this site, before arriving today.)


 * I invite opinion as to whether sacrificing the parallel structure between the triplet oxygen and singlet oxygen ledes, and substituting in reference to electron spin pairs, quantum states, ground state, and referring to "spin of one pair of electrons [being] in the same direction" and removing the narrowing prose that it is an "inorganic chemical, and more specifically as a particular electronic state of one allotrope of the inorganic chemical element, oxygen" actually accomplishes the stated aim, relative to the original lede, of  "keep[ing] the lead dead simple so that it can be understood by a wide audience."

Le Prof Leprof 7272 (talk) 02:12, 19 August 2015 (UTC)
 * The first thing I'd like to mention is the WP:DR page. It has a few resources for handling disputes between two or more editors. If an editor is being obtuse these are the agreed upon methods for handling it. But, since I'm here, I may as well weigh in.
 * I agree that the edits mentioned do not make the entry easier to understand. It's a difficult subject in the first place and even with a little knowledge (which I do have... a little) I can clearly see the edits made do not clarify for a layperson. In the spirit of WP:BRD I have no problem reverting them and directing discussion to this talk page. I would recommend we restrict discussion of other editors. Let's keep this about the article. Padillah (talk) 12:34, 19 August 2015 (UTC)

Recent lede edits, part 2
Today, a number of major deletions and edits occurred in the lede, under the Edit summary, "it is important to keep the lead dead simple so that it can be understood by a wide audience."

For reference, this is the original third paragraph of this singlet oxygen article, ''which remains in the current version. unchanged, as the new second paragraph'':"The 1Σg+ and 1Δg singlet states are 158 and 95 kilojoules per mole higher in energy than the triplet ground state of oxygen (referred to as the 3Σg−).[1][2] [3][better source needed] Under most common laboratory conditions, the higher energy 1Σg+ singlet state rapidly converts to the more stable, lower energy 1Δg singlet state;[1] it is this, the more stable of the the two excited states, the one with its electrons remaining in separate degenerate orbital but no longer with like spin, that is referred to by the title term, singlet oxygen, commonly abbreviated 1O2, to distinguish it from the triplet ground state molecule, 3O2.[1]."

Following today's drive-by edit, here is the current transition from paragraph 1 (last Talk section), to the technical "difference in energy of states" paragraph just quoted: [That is correct, there is no seque or introduction to the discussion of the difference in the energies of the 1Σg+ and 1Δg singlet states, and in fact these two terms and "degenerate orbital," etc., are not currently explained in the lede.]

Here was transition made, in the earlier lede version, via a paragraph 2, where the structure and origin of these two states were defined:"Excited states of oxygen can be seen as arising from the ground state of the same molecule. According to one type of modern bonding theory, the electronic configuration of the ground state of oxygen molecule has the last two electrons to fill its molecular orbitals (MOs) occupy two orbitals of equal energy (that is, degenerate MOs), therefore remaining unpaired. These two orbitals are classified as antibonding and are of higher energy, and the electrons occupying them are represented as having electrons of like (same) spin. Two excited states are readily accessible from this ground state; the first moves one of the high energy unpaired ground state electrons from one degenerate orbital to the other, where it pairs the other and creates a new state, a singlet state referred to as the 1Σg+ state (a term symbol. where the preceding superscripted "1" indicates it as a singlet state).[1][better source needed] [2] Alternatively, both electrons can remain in their degenerate ground state orbitals, but the spin of one can "flip" so that it is now opposite to the second (i.e., it is still in a separate degenerate orbital, but no longer of like spin); this also creates a new state, a singlet state referred to as the 1Δg state.[1]"

Note, eight wikilinks of key terms are present but not visible, which were also removed with this paragraph deleting edit.

As in the case of the foregoing edits, this whole paragraph deletion was performed without prior discussion, though the incoming editor doing the deletion knew an editor was active in creating the new lede structure.


 * I invite opinion as to whether sacrificing this paragraph, so that the technical third paragraph begins without definitions and explanation, actually accomplishes the stated aim, relative to the original lede, of "keep[ing] the lead dead simple so that it can be understood by a wide audience." 

Le Prof Leprof 7272 (talk) 02:12, 19 August 2015 (UTC)


 * You clearly do not know how to write a Wikipedia article nor do you understand the intended audience. There are three reason why this paragraph does not belong the in lead:
 * Wikipedia articles do not need to be self-contained. We already have separate articles on  singlet and  triplet states.  Wikilinks to those articles should be sufficient.
 * The lead should be a summary of the entire article. Apart from short definitions, there should be nothing in the lead that is not already contained in the body of the article. A paragraph in the lead should be a summary of one or more sections in the article which this paragraph is not.
 * This paragraph is highly technical and thus fails MOS:INTRO. Boghog (talk) 11:21, 19 August 2015 (UTC)
 * I will caution you as I have cautioned LeProf, please do not make comments about the other authors. They are irrelevant to the task at hand. We are here to improve the article. If the contribution helps, fine. If it doesn't I don't care if Hawking wrote it - it's gone. The author is irrelevant. We don't need this straying into personal attacks. Padillah (talk) 12:37, 19 August 2015 (UTC)
 * Sorry, but I am really getting frustrated with LeProf and irritated by his arrogant, condescending tone which has no place on a Wikipedia talk page. I also suggested that he "comment about the edits and not the editors" above, yet his personal attacks continue. I completely agree with you that the author is irrelevant.  Boghog (talk) 13:06, 19 August 2015 (UTC)

Current lead
The lead currently reads:

Singlet oxygen, systematically but less commonly dioxidene, is a term that refers to oxygen (dioxygen, O2), including its gaseous physical state, except only the subset of molecules in a particular excited state. It is therefore classified as an inorganic chemical, more specifically, a particular electronic state of one allotrope of the inorganic chemical element, oxygen. The specific excited stated referred to as the title singlet oxygen is the accessible, lowest energy state, termed the 1Δg, or more simply 1O2, and it is chemically reactive, which underlies its utility as a reagent in preparative organic chemistry, as well as its damaging effects to materials in sunlight and air and its utility in such therapeutic areas as photodynamic therapy.

Questions:
 * 1) Why mention "gaseous physical state" in the definition?  This besides the point and distracting.
 * 2) Why isn't the subject of the article defined in the first sentence? (see WP:BEGIN)
 * 3) "It is therefore classified as inorganic chemical, ..."? There is nothing proceeding this phrase that would lead the reader to that conclusion.  It would be better to write "Singlet oxygen is an inorganic chemical that ...".
 * 4) Why is it even necessary to mention allotrope?  Stating that singlet oxygen is a particular electronic state of dioxygen is sufficient.

It is essential that the lead be write in a way that can be understood by a wide audience. Even for an expert, the current lead is ponderous and hard to follow. This lead is clearly deficient and needs to be rewritten.

The following paragraph starts with a simple declarative sentence that concisely defines what singlet oxygen is. The second, third, and fourth sentences state why it is important:

Singlet oxygen (abbreviated as 1O2 or 1Δg) is the lowest excited state of the oxygen (O2) molecule whereas the most stable ground state of oxygen is known as triplet oxygen (3O2). Trace amounts of singlet oxygen are found in the upper atmosphere and also in polluted urban atmosphere where it contributes to the formation of lung damaging nitrogen dioxide. Singlet oxygen is chemically reactive and as a consequence has utility in such therapeutic areas as photodynamic therapy as well as a reagent in preparative organic chemistry. In contrast to triplet oxygen which generally participates in free-radical mediated chemical reactions, singlet oxygen engages in cycloaddition reactions.

I reject the proposition that definition can only come from an inorganic text book or be written by an expert. This is not how Wikipedia works. Per WP:UGC, Self-published material may sometimes be acceptable when its author is an established expert. Boghog (talk) 09:23, 19 August 2015 (UTC)
 * As noted earlier, this is an area where there are tens to hundred of reviews providing the definitions and other material that we need. There is no need to use a self-published web page of a faculty member (except perhaps, if we are unwilling to do the scholarly work, or are looking to pick a citation which definition we in particular agree). I accuse people who temporarily place or retain such citations of neither of these, but there is no longterm justification for reliance on any self-published work in such a rich field. There every good reason here for going with a small set of peer reviewed definitions from the best sources, to set the definition of an important article such as this—to establish that the definition belongs to no one of us (through its selection from an obscure or self-published source), but instead reflects the preponderance of expert, scholarly opinion on the matter. Le Prof 71.201.62.200 (talk) 23:59, 21 August 2015 (UTC)
 * I came by this article today to comment. Despite my technical biomed background (with plenty of pharmacology and biochemistry) I found this much too complicated for me to understand and certainly for a general audience.  The lead should be simplified to something like the paragraph immediately above.  I think much of what is in the lead can go later -- for a specialized chemical encyclopedia.  It makes sense to have parallel structure and statements in triplet oxygen (? and others).  I cannot contribute specialist editing here.  Sorry!  Jrfw51 (talk) 10:22, 19 August 2015 (UTC)
 * I hope that I am not screwing things up, but having written a lot of inorganicky articles, I have a sense for what it should look like by conventional Wiki standards. Readers dont want to be hit by a bunch of chemical physics off the bat. --Smokefoot (talk) 11:10, 19 August 2015 (UTC)
 * First off, I don't know if the first version is more understandable or not. I only know that it SEEMED more understandable to me. I reverted simply because that's the first step in WP:BRD, there is no other driving force behind my participation here.
 * I agree that the lead needs to be written so that a non-specialist can read it. As a non-specialist I'm telling you: "Singlet oxygen (abbreviated as 1O2 or 1Δg) is the lowest excited state of the oxygen (O2) molecule..." does not flow trippingly off the tongue. And we need to be careful with links, there's a fine line between linking and WP:EGG. First things first, the average layperson doesn't need the symbols or the scientific abbreviations. That stuff can wait until the body. Simply put, If you had to tell a 7 year-old what this stuff was, how would you do it? Don't worry about getting all the nuance and technique right, just a simple "Electric current is the flow of electricity ..." kind of thing. Even if the broad strokes are not quite right, we can work on that in the body. Padillah (talk) 12:34, 19 August 2015 (UTC)
 * I don't know if it's right or not but I like the suggestions. That is something a layperson can understand. And you moved the symbols to the end so as to cause little confusion when introducing them. I like it, thanks. I hope it holds up to technical scrutiny. Padillah (talk) 12:47, 19 August 2015 (UTC)
 * My guess is that more readers check photodegradation than singlet oxygen. Photodegradation is in sorry shape.  It does not need to be elevated to an academic journal, but it merits a look.  --Smokefoot (talk) 13:03, 19 August 2015 (UTC)
 * I agree that the current lead is a big improvement. I added "high energy" to the lead sentence since I think it is a defining characteristic. I hope that is OK. Boghog (talk) 13:16, 19 August 2015 (UTC)

readers are going to choke on 1Δg and 3Σg−. Should link to a relevant page that explains this notation. V8rik (talk) 17:43, 19 August 2015 (UTC)
 * Concur. Further definitions, or at least wikilinks, could be added back, Le Prof 71.201.62.200 (talk) 07:15, 20 August 2015 (UTC)
 * Thanks to all for looking at the article, and making corrections toward fulfilling Boghog's stated aim. I am especially thankful for both the lay perspective, and for the specific inorganic expertise. I leave it, in longer term, in these capable hands.


 * I would ask once dust settles on the lede revisions, that the rest of the article be checked to make sure it is consistent. I had derived the lede paragraph on the origin of the two singlet states from the Structure section of the existing article, after checking the MO diagram image against published sources to make sure that the MO states were correctly represented. Otherwise, the language of the Structure section is an amalgam of what appeared earlier, and my "watering down" paragraph or so, installed so that a lower form university student could understand, descriptively/textually, the relationships and origin of the singlets from the triplet state shown in the image. In short, making sure the Structure section is summarized in the lede, and that it and the lede are copacetic is important. Otherwise, the closing language of the earlier lede, as I found it, was based either on no sourcing, or on sourcing I had not yet had time to check. So, the text statements at the close of the earlier lede — wherever they ultimately end up — I would view with suspicion until they are verified in the main body text (and that text verified at its sources).


 * Other specific matters that might lead to small additions or clarifications, I will leave for later, after a group of student readers can come to the article and make suggestions. Words like "gas" and "inorganic" — which were present in the article when I arrived — were retained in trying to take readers from what the might know and have experienced (oxygen as a gas, oxygen as a simple inorganic compound) on into the technicalities of what the singlet state meant, and how it arose. Whether this much watering down is needed is up to the consensus; the earlier consensus, before I started editing, seemed to believe it was. My personal experience is limited to having generated 1O2 at near STP, as a gas/dissolved gas; I haven't knowledge whether it has been generated as a liquid, and if it has, that could find its way into the article. Regardless of the esoterica, it is clear that the way that most people experience the parent material, the triplet state, is as a gas, the way that most can understand O2 is the same, and the way that most who go on to generate and use 1O2 will again do so as a gaseous material. This is not to argue for including this term, only that it made sense to me why the original editors did so.


 * One last matter: I came to the page because a non-chemist editor asked me a question asked of him by students, "Is singlet oxygen an allotrope of oxygen?" He then proceeded to give me several appearances of phrases that made it possible to arrive at this conclusion of from Wikipedia. This query directed me to the lede of this article, so I left the lede with the clarification prompted by this layperson-channeled, student question, when I posted the Expert needed tag. Hence, even that term, now apparently dubious in its inclusion, has origins in student perceptions (and misperceptions) about the relationship between oxygen allotropes and states. I will look for that original at-WP query, and post it below, if I can find it again.


 * Here was the on-WP discussion that began my look at this article,, which reflects why the word allotrope appeared in the earlier version of the lede opening. I invite those deleting allotrope from this lede to settle the discrepancy that is said to exist between the two articles. Cheers, Le Prof 71.201.62.200 (talk) 23:59, 21 August 2015 (UTC)


 * Finally, I would note in general terms that there is little hope for peace between editors when one follows another about, intruding in real time in his or her attempts to edit. That following—failure to wait until a period of editing had ended, and others not personally interested had a chance to see and appreciate or reject the edits—shows a failure to show even a modicum of the collegial respect that WP asks. When the routine arrival of a following editor are accompanied by large deletions (as happened here), creating clear disconnections in understanding, yes—I am going to be frustrated at the wasted effort, and at the provocation. Notably, all that was accomplished today could likewise have been accomplished over the next week or two, as the same editors and experts, responding to the expert needed tag, or to private pings to have a look, arrived and made changes. I would have responded to gradual, weeklong, respectfully addressed changes—including if by some editors finding me personally distasteful, as some of you do—just as acceptable, as I do the work that everyone did today.


 * In closing, I thank you for the attention and effort, both lay and scholarly, and for providing an example of how collegially edits might be taken when there is disagreement about approach. If peace is wanted, then encourage me—as some of you have done, to not be so "snotty"—but also encourage others to stop from following and provoking, however personally distasteful I am found to be as a person (indeed especially because I am found that way). Count to ten three [days]? Cheers, Le Prof 71.201.62.200 (talk) 05:18, 20 August 2015 (UTC)

Things that might yet be done with the article
The opening paragraph of the lede is indeed much better in its communicating to a general audience than anything that appeared before. There are some things that I think might still need to be done, for the lede of this article to be finished: That is all I can think of right now. Thanks very much, again, for the clearly helpful lay perspective, and for the IOChem expertise that helped—and in the case of the remaining Electronic structure issues, can only continue helping—make this article accurate, and accessible to a middle range of readers. When I feel welcome again—after the dust settles, and if there is a commitment not to hound—I will return and help out. For now, I will add some lost citations to a Further reading section, and stand by. Cheers. Le Prof. 71.201.62.200 (talk) 06:05, 20 August 2015 (UTC)
 * Make clear that the citations provided in the lede actually support the text; for instance, neither the Atkins or Hill citations, as they were originally used, were to explain anything more than oxygen's term symbols, if that, rather they appeared to explain term symbol appearance and interpretation in general. Hence, their relevance to 1O2 needs to be verified (and page numbers provided);
 * Check to see, section by section, if the lede captures the most significant content of the sections that appear below; that is, make sure the lede fully reflects the article per WP lede policies and guidelines;
 * specifically, make clear that there are more than one singlet oxygens, but it is to one form in particular that the title term routinely refers;
 * make clear that the forms interconvert, and, given the long Electronic structure section, here,, consider summarizing how singlet oxygen derives from triplet, ground state oxygen;
 * add back some of the key links, such as to the term symbol and other deleted links to basic information (see paragraph deletion, here,, that precipitated this editing flurry),
 * For sake of overall WP encyclopedic content, consider migrating the approach used here, and making comparable changes at the triplet oxygen article, because both interrelate and cross-reference, in their ledes;
 * Make sure that the lede content is actually covered by good sources that appear in the main body;
 * For comments on other "disappeared" terms appearing in the lede prior to the Leprof edits, see the Talk section immediately above.
 * Eventually, choose slightly different language, e.g., than "In terms of," if term symbols is reintroduced to explain the closing term symbol jargon.

Current citations to books without page numbers (early article editing legacy)
The following citations are to books, and currently lack page numbers. Rather than tag them inline, and set off a possible firestorm, I am listing them here, so they receive people's attention:

1. Klán P, Wirz J (2009). Photochemistry of organic compounds: from concepts to practice [7 occurrences]

2. Atkins P, de Paula J, Friedman R (2009). Quanta, Matter, and Change: A Molecular Approach to Physical Chemistry. [2 occurrences]

15. Carey FA, Sundberg RJ (1985). Structure and mechanisms (2 ed.)

In addition, the range of this reference is a little wide, per WP standards:

12. Ho RY, Liebman JF, Valentine JS (1995). "Overview of the Energetics and Reactivity of Oxygen"

These are important, esp. the first two, as they appear in the lede, and throughout the text, and in the first case, Klán & Wirz, constitute about 20% of all inline citations. Will try to help with this later, after things settle down. But in the meantime, wanted everyone to know that ~2 of 4 current citations in the lede can't be traced to material indicated, for lack of page numbers at least (see also first bullet preceding section). Cheers. Le Prof 71.201.62.200 (talk) 06:58, 20 August 2015 (UTC)

Reactive oxygen species
Realizing I knew little about singlet (or triplet) oxygen I went to the term I did recognise -- reactive oxygen species. There is no reference I could find there to these chemical entities. Would someone like to review this page too? Jrfw51 (talk) 15:57, 20 August 2015 (UTC)


 * There is not much chemistry at all in reactive oxygen species. The article is almost entirely about the importance of ROS to biology and medicine. We should add what they are(including triplet and singlet oxygen) and how they are formed, similar to the type of content contained in reactive nitrogen species. Boghog (talk) 17:10, 20 August 2015 (UTC)
 * ✅ Singlet oxygen appears to have a more significant role in photosynthetic plants than in animals. I have added a section on this role to the ROS article. Boghog (talk) 11:15, 22 August 2015 (UTC)

What source defines dioxidene?
The article introduces the term dioxidene in the lede, but dioxidene is not defined in the "Oxford Dictionary of Chemistry" (6th ed.) nor does a Google Books search find the term. The term was added in this edit without explanation or citation. --50.53.46.18 (talk) 05:19, 29 September 2015 (UTC)
 * I removed it. Chemicals have lot of exotic names, some of which are invented by committees with the intention of systematizing our nomenclature. Often these terms are not followed by anyone.  --Smokefoot (talk) 12:40, 29 September 2015 (UTC)
 * Thanks. --50.53.44.211 (talk) 17:32, 29 September 2015 (UTC)

Conversion of units
The paragraph on singlet-triplet energy difference has a note saying “Original research” for some values, with the following note embedded in the source code (caps not mine):

THE VARYING PRECISIONS OF THESE REPORTED ENERGY EQUIVALENCES MAKES THEM APPEAR TO BE EDITOR CALCULATED, RATHER THAN JOURNAL REPORTED—TO MY EXPERIENCE, A PROFESSIONAL PHYS SCIENTIST WOULD NOT PRESENT 7882 cm-1 = 0.98 eV. AND WHY THE APPROX. FOR THE K VALUE? HENCE THE TAGS. ALTERNATIVELY, THE INDICATED VALUES REFLECT SEPARATE MEASUREMENTS, TO SEPARATE PRECISIONS, AND/OR ARE FROM MORE THAN ONE SOURCE, AND ALL THIS NEEDS TO BE INDICATED IN THE TEXT.

My comments: 1. The sources by Schweitzer and Schmidt and by Atkins and de Paula both state energy differences in cm-1, presumably because they were originally measured by spectroscopy. So I believe each energy value should be given first in cm-1, with the reference given for that value alone.

2. Conversion of units is allowed by Wikipedia policy WP:CALC, which states that ''Routine calculations do not count as original research, provided there is consensus among editors that the result of the calculation is obvious, correct, and a meaningful reflection of the sources. Basic arithmetic, such as adding numbers, converting units, or calculating a person's age are some examples of routine calculations.''

I believe this applies to conversion of cm-1 values to kJ/mol and eV, since the relations between photon wavenumber, molar energy and molecular energy are now considered elementary in chemistry and physics. It should be made clear, however, when the values in kJ/mol and eV are not from the source.

3. The relation of molecular energy to temperature is not a simple unit conversion but is based on the distribution of energy (statistical thermodynamics). This is more complex and could be considered original research, so I will delete the temperature values from the article. Dirac66 (talk) 20:52, 27 November 2016 (UTC)

Basic Error
"The 1Σ+g state is very short lived and relaxes quickly to the lowest lying 1Δg excited state;[citation needed] it is this lower, O2(1Δg) state that is commonly referred to as singlet oxygen. The energy difference between ground state and singlet oxygen referred to above (e.g., 94.3 kJ/mol) corresponds to a transition in the near-infrared at ~1270 nm.[10] This transition is strictly forbidden by spin, symmetry, and parity selection rules;[[citation needed] hence, direct excitation of ground state oxygen by light to form singlet oxygen is very improbable.[citation needed] As a consequence, singlet oxygen in the gas phase is extremely long lived (72 minutes),[11] although interaction with solvents reduces the lifetime to microseconds or even nanoseconds.[12]"

The first line of this quotation implies that the 1Σ+g to 1Δg is allowed. However, according to the selection rules for electronic transitions in linear molecules it is forbidden as it is not in agreement with the rule ∆Λ = 0,±1. This is further corroborated by Atkins' Physical Chemistry 7th Edition pg 542 self test 17.1 which lists it as a forbidden transition.

192.76.8.69 (talk) 10:33, 4 February 2018 (UTC)
 * Forbiddeness does not prohibit transitions. Intersystem crossing often happens rapidly.  But that is as far as I can go.--Smokefoot (talk) 14:53, 4 February 2018 (UTC)


 * Yes, many selection rules are only approximative, and transitions "forbidden" by such rules are often observed with weak intensity. For the specific case of 1Σ+g to 1Δg in dioxygen, see this 1999 review article by Weldon et al., which discusses transitions in both gas phase and solution. See Table 1 on p.372 for the effect of a variety of solvents. Dirac66 (talk) 22:26, 4 February 2018 (UTC)


 * I have now found and added specific lifetime information for both singlet states, in both gas-phase and solution. The upper singlet (1Σ+g) is interesting because it transitions predominantly to the triplet in the gas-phase, but to the lower singlet in solution. Dirac66 (talk) 10:55, 29 March 2018 (UTC)

Lead sentence
Rather than simply reverting your revert, I thought it might be more constructive to actually discuss.

The first sentence as I found it (and as you have reverted it) is indeed "dead simple." The problem is that it's also quite vague. It strikes me as comparable to the sentence, "RMS Titanic was a large ship." That it is "a high-energy form of oxygen" is a property of singlet oxygen, but it falls far short of what Wikipedia's manual of style advises about the lead:


 * "If its subject is definable, then the first sentence should give a concise definition." [emphasis added]

I believe that my version goes at least a smidge further towards a definition. And even if one disagrees about that point, my version does (or anyway is intended to) get to another point from the manual of style:


 * "If the title is a specialised term, provide the context as early as possible."

and


 * "In an article about a technical or jargon term, the opening sentence or paragraph should normally contain a link to the field of study that the term comes from.
 * In heraldry, tinctures are the colours used to emblazon a coat of arms."

To me, the way that "mentioning that [it] is a quantum state of oxygen [makes] it more friendly for non-experts" is by situating the gist of how singlet oxygen is special as residing in the field of quantum physics. After all, by contrast to singlet oxygen, there are various other ways of categorizing "forms" of oxygen that require no mention of quantum physics in a lead, for instance by isotope {{{sup|16}}O, 17O, 18O, ...} among which one can distinguish in terms of neutron number alone.

I have no illusions that the version I created is fully successful. I do propose we cooperate, and perhaps iterate, to arrive at another version that each of us can endorse. The chemistry and biochemistry people at Cal State LA provide what may be a good starting point in the first sentence of their answer to the question "What is singlet oxygen?":


 * "Singlet oxygen is the lowest excited state of the dioxygen molecule."

—PaulTanenbaum (talk) 20:19, 9 April 2018 (UTC)


 * Thanks for your note. I move the discussion here, because there was already an extensive discussion on the lead above. After several iterations, this was the version that we ended up with. The problem with including quantum state in the lead sentence is that complex concept that also needs a definition.  As you mention above, one solution would be to include the field(s) of study:


 * Within the fields of inorganic and quantum chemistry, singlet oxygen is a high-energy form or excited state of molecular oxygen.
 * Does this look OK? Boghog (talk) 03:00, 10 April 2018 (UTC)


 * I would now prefer "In chemistry, singlet oxygen is the lowest excited state of the dioxygen molecule." This is Paul Tanenbaum's latest suggestion plus 2 words at the beginning to define the field of study. The word "form" is too vague and can suggest anything from isotope (as mentioned above) to allotrope (ozone etc.) And I would prefer to avoid the word "quantum" in the first paragraph because it scares some readers. "Excited state" only suggests energy levels as in the Bohr model, but "quantum" has a lot more baggage these days. Dirac66 (talk) 13:49, 10 April 2018 (UTC)


 * Done, I think :-) Now we'll see how long it stands...—PaulTanenbaum (talk) 17:50, 10 April 2018 (UTC)