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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.
lapo_dk
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)
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)
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)
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)
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)
The text in the diagram currently in the article is not in English. -- Beland ( talk) 19:09, 2 June 2008 (UTC)
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)
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)
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)
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)
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)
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 (3Σg) 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 1Δg 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)
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)
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)
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] better source needed [2]
References
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:
An excited or higher-energy form of oxygen characterized by the spin of a pair of electrons in opposite directions, whereas electron spin is unidirectional in normal molecular oxygen.Boghog ( talk) 20:16, 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 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.
Singlet oxygen is the lowest excited state of the dioxygen molecule.Boghog ( talk) 20:30, 18 August 2015 (UTC)
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)
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.)
Le Prof Leprof 7272 ( talk) 02:12, 19 August 2015 (UTC)
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.
Le Prof Leprof 7272 ( talk) 02:12, 19 August 2015 (UTC)
@ Leprof 7272 and Padillah:
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:
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 [1] [2]: 205–6 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. [3]: 355–68 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. | ” |
References
Singlet oxygen is the lowest excited state of the dioxygen molecule.
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)
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)
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)
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)
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)
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)
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)
"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)
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:
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:
and
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 {16O, 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?":
— PaulTanenbaum ( talk) 20:19, 9 April 2018 (UTC)
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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.
lapo_dk
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)
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)
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)
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)
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)
The text in the diagram currently in the article is not in English. -- Beland ( talk) 19:09, 2 June 2008 (UTC)
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)
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)
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)
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)
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)
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 (3Σg) 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 1Δg 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)
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)
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)
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] better source needed [2]
References
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:
An excited or higher-energy form of oxygen characterized by the spin of a pair of electrons in opposite directions, whereas electron spin is unidirectional in normal molecular oxygen.Boghog ( talk) 20:16, 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 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.
Singlet oxygen is the lowest excited state of the dioxygen molecule.Boghog ( talk) 20:30, 18 August 2015 (UTC)
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)
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.)
Le Prof Leprof 7272 ( talk) 02:12, 19 August 2015 (UTC)
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.
Le Prof Leprof 7272 ( talk) 02:12, 19 August 2015 (UTC)
@ Leprof 7272 and Padillah:
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:
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 [1] [2]: 205–6 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. [3]: 355–68 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. | ” |
References
Singlet oxygen is the lowest excited state of the dioxygen molecule.
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)
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)
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)
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)
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)
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)
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)
"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)
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:
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:
and
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 {16O, 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?":
— PaulTanenbaum ( talk) 20:19, 9 April 2018 (UTC)