Talk:Alkene

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Confused introduction

The article says: "The term is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.[2] However, the IUPAC recommends using the name "alkene" only for acyclic hydrocarbons with just one double bond; alkadiene, alkatriene, etc., or polyene for acyclic hydrocarbons with two or more double bonds; cycloalkene, cycloakadiene, etc. for cyclic ones; and "olefin" for the general class — cyclic or acyclic, with one or more double bonds". Well, the 'general class' is precisely 'any hydrocarbon containing one or more double bonds', which is where we came in. — Preceding unsigned comment added by 2.97.114.153 (talk) 20:08, 7 October 2020 (UTC)

Untitled

Is "recombinaison" an English word? Wmahan 21:58, 2004 Apr 4 (UTC)

Saturation link

The first sentence calls an Alkene and unsaturated chemical compound and the link for unsaturated goes to Saturation (chemistry) which has five separate meanings. I'm pretty sure it is number 3 on the list (no double or triple bonds) but I've training in neither chemistry nor biology, so am only guessing. JoshNarins (talk) 13:21, 16 January 2010 (UTC)

If an alcohol is named R-OH (or ROH) (at least for 1°) and an aldehyde R-CHO, what is an alkene named?

Just out of curiousity. -x42bn6 Talk 10:31, 4 September 2005 (UTC)

All alkenes have the general formula CnH2n. You wouldn't express it the way you're suggesting, but R=R' would probably suffice.

Only non-cyclic (acyclic, meaning having no rings of atoms) alkenes with one double bond have the general formula C_nH_2n. For every additional double bond and for every ring, there are 2 fewer H atoms in the chemical formula. H Padleckas (talk) 11:39, 22 June 2008 (UTC)

"Alkenes can be synthesized from alcohols via an elimination reaction that removes one water molecule: H3C-CH2-OH + H2SO4 → H3C-CH2-O-SO3H + H2O → H2C=CH2 + H2SO4"

I've never seen that intermediate before: "H3C-CH2-O-SO3H". You can do that with sulfoxide groups, though:

E.g. R-OH + CH3SO2Cl ---> R-O-SO2-CH3

I find it hard to believe that the species mentioned there is stable.

Strictly speaking, this is not an "Elimination". It's mechanism is not E2 or E1. It's actually a dehydration. Should this be changed? Ironically, the reaction described here requires heat and is quite brutal; Most organic chemists would not employ it for fear of side reactions.

Olefin

Does anyone know the amount of olefin distributed each year nationally and worldwide?

Mechanism of Halogenation

Just letting you know that the mechanism shown for halogenation is a bit wrong, the intermediate is a bromonium ion rather than the true carbocation that is shown. The ion is then attacked by bromide to form the dibromide with ANTI stereochemistry exclusively.

-Yeah, can someone please change that, it's misleading.

Removed Gayvene

I removed the reference to Gayvene, the supposed 69th alkene. I'm not an organic chemist, but I'm pretty sure that was vandalism. If gayvene is really some new breakthrough compound that has recently been discovered, feel free to add it back to the article but please provide a reference. (Note the common reference "my ass" in not acceptible in this case.)

What's 'acceptible'? — Preceding unsigned comment added by 2.97.114.153 (talk) 20:10, 7 October 2020 (UTC)

Non IUPAC Nomenclature

Per 1993 IUPAC Recommendations, the locant for the ene should be located in front of -ene. For example, hex-2-ene, formerly 2-hexene. Please if you are posting here, use correct IUPAC nomenclature.Hokietiki@hotmail.com 14:30, 1 February 2007 (UTC)

merge Carbon-carbon double bond into alkene

The topic Carbon-carbon double bond is identical to the topic alkene. It is also vandalized, also contains a dead image link. Propose speedy merge V8rik 21:24, 14 March 2007 (UTC)

• Done V8rik 21:41, 12 April 2007 (UTC)

You shouldnt call it ethylene...it's ethene.

...come on you know it makes sense —The preceding unsigned comment was added by 86.42.173.247 (talk) 19:26, 1 April 2007 (UTC).

alternative to E and Z notation

isn't a common alternative the usage of cis- and trans- for entgagen and zussamen, respectively? surely that's worth including. User:Namangwari 4 June 2007

For better, for worse, Isomers of butylene uses that notation under the "IUPAC" column. Is it a deprecated usage or still used? -- atropos235 ✄ (blah blah, my past) 05:07, 7 August 2007 (UTC)

I've added a quickie Cis-Trans section, and provided links to the main articles JeramieHicks (talk) 18:57, 20 November 2007 (UTC)

why does alkyne have no cis_trans geometry? — Preceding unsigned comment added by 213.55.95.17 (talk) 14:44, 24 November 2011 (UTC)

The geometry of the atoms and bonds in an alkyne does not give any situation of "two different direction possibilities". There is only a single way they can be (and it is neither cis nor trans), so there is no additional detail needed. DMacks (talk) 15:05, 24 November 2011 (UTC)

prefix / infix numbers

Perhaps it's worth being consistent by using either infix numbering ("but-1-ene") or prefix numbering ("1-butene") throughout? -- 119.11.7.177 (talk) 02:11, 3 January 2008 (UTC)

Good point. I'm revising this article at the moment (in case you couldn't tell!) so I'll specifically check that. Thanks, Walkerma (talk) 07:02, 4 January 2008 (UTC)

Same style of first paragraph as "alkane" page?

I was wondering...to compare to alkanes, should the first paragraph be similar in style to that of the alkane page? Possibly me being pedantic, but I think that they should be similar - they relate to each other as hydrocarbons. Although the content is there later on in the article, I think that the first paragraphs from both articles should be succinct in giving a general idea of them! I know I should be bold and do it straight away, but I just want at least another person in agreement! --Itsalive4 (talk) 19:57, 1 June 2008 (UTC)

I agree. I just did a search to find the alkene article from the alkyne page, as there was no cross link between them. Whatever other connection there may be between them (such their transmutations) they are linked by taxonomy and in peoples personal term hierarchies and anyone who's looking up one may need to look up and compare with another. The core definition of the terms is also the same with only a very small variation of specifics. That the encyclopedic articles would reflect that in the intro statements would be good practice IMHO. But of course enforcing complete consistency between articles over a long time period is almost impossible on a wiki. Wiki-BT (talk) 22:24, 9 June 2009 (UTC)

Table needed

I have noticed that while the Alkane article sports a table showing the first dozen or so alkanes, the Alkene article provides no such list. Can someone more gifted at Chemistry (and coding) please provide other users with such a table? I wish that someone would style it in the same way as seen on the Alkane page. Here is the header to provide a starting point:

NAME, Formula, B.P./oC, M.P./oC, Density/g cm -3(20 degrees Centigrate) Thanks much, A Prodigy ~In Pursuit of Perfection~ 18:55, 3 September 2008 (UTC)

What is it?

the category has a bunch of stuff is it 'hydrocarbon' or 'anything containing a double bond'

Try reading the very first sentence of the article. DMacks (talk) 01:14, 10 March 2009 (UTC)

You made [1] an excellent point, and it's a shame it was ignored.

According to IUPAC, it's a hydrocarbon; http://goldbook.iupac.org/A00224.html reads alkenes: Acyclic branched or unbranched hydrocarbons having one carbon–carbon double bond and the general formula CnH2n . Acyclic branched or unbranched hydrocarbons having more than one double bond are alkadienes, alkatrienes, etc. This is contrasted to http://goldbook.iupac.org/O04281.html olefins: Acyclic and cyclic hydrocarbons having one or more carbon–carbon double bonds, apart from the formal ones in aromatic compounds. The class olefins subsumes alkenes and cycloalkenes and the corresponding polyenes. However our article at the time of your writing [2] read In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond (my emphasis, and it still says something similar currently).

The reference given is Wade, L.G. (Sixth Ed., 2006). Organic Chemistry. Pearson Prentice Hall. p. 279., which does not appear to be available online. I think we should prefer the IUPAC definitions and references, but we should at least acknowledge them prominently if we are going with Wade instead. Watch this space and/or see #Definition and #Gold book definitions below. Andrewa (talk) 14:06, 30 December 2013 (UTC)

New Picture?

Congrats to whomever donated the picture; however in practice in the 3D structure of the molecule, H atoms repel each other; this means that instead of the 4 H atoms being in the same plane, the 2 H atoms linked to one of the carbon atoms form a perpendicular line to the H atoms linked to the other C atom; does someone have the 3D model to correct this? —Preceding unsigned comment added by 207.45.249.142 (talk) 10:04, 2 June 2009 (UTC)

All 4 attachments to an alkene are indeed coplanar. Look at the "Bonding" section, where you can see that there is actually a whole other electron cloud perpendicular to it all. That electron cloud actually is the "second" bond of the alkene, and it keeps the attachments planar and even prevents rotation, leading to distinct cis and trans molecules. DMacks (talk) 16:04, 2 June 2009 (UTC)

I can see complete symmetry. Where is the cis and trans? — Preceding unsigned comment added by 2.97.114.153 (talk) 20:16, 7 October 2020 (UTC)

alkenes

Alkene form another homologous series of hydrocarbon of the general formula:

                            CnH2n

where n is the number of carbon atoms. the Alkene are more reactive than the alkenes because they each contain a double covalent bond between the carbons atoms.molecules that possess a double covalent bond of this are said to be unsaturated.

all alkenes have name ending in -ene. alkenes, especially ethenes, are used extensively in the plastics industry and in the production of the alcohols such as ethanol and propanol. —Preceding unsigned comment added by 112.110.192.2 (talk) 02:58, 19 June 2010 (UTC)

Definition

Is our definition correct? I suspect not.

Article currently [3] starts In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon–carbon double bond and gives a ref which is unfortunately not available online. However http://chemistry.about.com/od/chemistryglossary/a/alkenedef.htm reads Definition: An alkene is a hydrocarbon containing a double carbon-carbon bond (my emphasis), which is a much narrower definition, and closer to the one I have always understood (but the one I learned decades ago in high school is narrower still, and would also disallow hydrocarbons containing rings for example).

Under our current definition, dichlorodifluoroethylene would be an alkene, despite not being a hydrocarbon. That's actually how I come to ask the question, as that page is currently flagged as an alkene-stub, which I think is confusing. If my understamding is correct and if this stub notice is to stay, then Template:alkene-stub needs to read This article about an alkene or related compound... rather than just This article about an alkene... as at present.

The main problem I suspect is that dichlorodifluoroethylene is a halogenated alkene but not an alkene. Language is complicated! Andrewa (talk) 01:00, 27 December 2013 (UTC)

Gold Book agrees with the hydrocarbon wrording. But by that strict reading of it, even chloroethylene or allyl alcohol would not qualify! These, as with the extreme case of a Tetrahaloethylene, are Substituted by other elements/groups on the parent alkene structure. DMacks (talk) 04:30, 28 December 2013 (UTC)

So you (and the Gold Book) are saying that dichlorodifluoroethylene, chloroethylene and allyl alcohol are all alkenes, is that correct?

In the same way then, acetic acid and glycerol would both be alkanes, would they not? And yet our article on alkanes currently [4] says in part Alkanes consist only of hydrogen and carbon atoms, all bonds are single bonds, and the carbon atoms are not joined in cyclic structures but instead form an open chain (my emphasis). That's what I understood too.

That alkenes differ in such a radical way from alkanes is news to me. I was taught that alkanes, alkenes and alkynes were all hydrocarbons, ie consisted only of carbon and hydrogen (so no oxygen, chlorine or flourine), and our definition of an alkane was exactly the one currently in the alkane article. But that was a long time ago.

Have things changed? Or perhaps they are in a state of flux? We must make sure that our articles are consistent with current terminology, but perhaps also the previous definitions should receive a mention? Andrewa (talk) 11:26, 28 December 2013 (UTC)

Is a bicycle with a sidecar or training wheels still s bicycle, given that there are not two wheels? I think you are trying to distinguish the basic definition of the parent or core from that of a compound that contains several identifiable parts (were you taught "functional group analysis" or "substituents" in the context of "systematic nomenclature"?). Acetic acid does exactly contain a "methyl group" (alkyl part) but the whole molecule is not an alkane. 1-Octene is an alkene molecule because that's its distinguishing feature, but it contains both alkene and alkane areas. DMacks (talk) 18:01, 28 December 2013 (UTC)

Exactly.

To the layman, it's confusing, whether I am right or wrong. We need to be clear and consistent either way, and at present we are neither.

I think that here we are using alkane etc in its technical sense, and that it has a precise definition.

But I may be wrong in this, or my definition may be wrong. It may even be that there is no agreed technical definition, but I would be surprised.

Just because it contains... alkane areas (or area) doesn't necessarily make acetic acid (or anything else) an alkane. Or to pursue your analogy, a unicycle could accurately be called a truncated bicycle, but strictly speaking it's not a bicycle.

There are certainly classes of chemical compound, including of organic compounds, that are characterised by only parts of the molecule. I think that the organosulfates may be a case in point. But there are also classes, such as the hydrocarbons, where the whole of the molecule must conform to the pattern. Acetic acid is not a hydrocarbon, despite containing a hydrocarbon area.

I think that alkane, alkene, alkyne, and alkanone are all cases of this latter type of classification. But I'm not sure where cycloalkanes, for example, fit in.

I admit that my organic chemistry ended at high school more than forty years ago (I was fairly keen then, however). But as a general encyclopedia, our primary audience is people with no more chemistry than I have, if that. Currently our coverage does not seem terribly consistent, and there are important gaps. The goal is to consistently use terminology that a specialist finds accurate, but to introduce and define it in a way that a non-specialist finds helpful. It is a challenge!

Thank you for your input so far. Andrewa (talk) 20:58, 29 December 2013 (UTC)

Well, I looked up this thing in Britannica... It says alkenes are (simply) organic compounds with a C=C bond, whereas olefins are hydrocarbons (not just any organic compound) with a C=C bond (i.e. an alkene functional group). So, this might be a difference which gets unnoticed? —ШαмıQ✍ @ 21:22, 29 December 2013 (UTC)

Very interesting indeed... and there may be a similar difference between a ketone and an alkanone. We currently seem to treat these as synonyms. I would have expected the difference to be the other way around, with the more recent term being more carefully defined. And dare I say it, a more specialised source than EB would be good too.

And I'm wondering... many of these chemicals are important in the petrochemical industry, whose chemical engineers are possibly not the most scholarly when it comes to their terminology (hence the BBU [5]). I would think Wikipedia would prefer the scholarly definitions if there is a conflict, while also citing any others that we can source. Andrewa (talk) 22:16, 29 December 2013 (UTC)

Gold book definitions

I didn't realise that the Gold Book was online (although our article does link to it and somehow my Google searches didn't find it either). Very interesting.

• http://goldbook.iupac.org/A00222.html alkanes: Acyclic branched or unbranched hydrocarbons having the general formula CnH2n+2 , and therefore consisting entirely of hydrogen atoms and saturated carbon atoms. (my emphasis)
• http://goldbook.iupac.org/A00224.html alkenes: Acyclic branched or unbranched hydrocarbons having one carbon–carbon double bond and the general formula CnH2n. (my emphasis)
• http://goldbook.iupac.org/H02889.html hydrocarbons: Compounds consisting of carbon and hydrogen only. (my emphasis)

I think we'd need a very good reason for departing from the IUPAC definitions, in fact I think we should have a policy or guideline somewhere that says whenever such terms are used, the IUPAC definition is assumed unless otherwise stated. Or perhaps we already do? Andrewa (talk) 23:28, 29 December 2013 (UTC)

Actually, the Gold Bbook states the difference exactly the opposite of what is given in EB. Compare alkene and olefin. —ШαмıQ✍ @ 12:47, 30 December 2013 (UTC)

Yes... and IMO we should follow the IUPAC terminology, consistently. I think that's what the MOS says too (Wikipedia:Manual of Style/Chemistry#Compound classes and Wikipedia:Manual of Style/Chemistry/Compound classes), but perhaps not as clearly as it might.

Perhaps and at most we should note that some authorities differ from this terminology. I did say perhaps and I did say at most. I'd question whether EB is an authority even to mention in the same breath as IUPAC. They've simply got it wrong, and that's their problem not ours. But perhaps it explains some of the discussion, and dare I say, some of the misinformation currently in our articles.

On the other hand, any time we prefer another authority (EB or otherwise) to IUPAC, we should definitely call attention to this. I did say any time and I did say definitely. Andrewa (talk) 13:11, 30 December 2013 (UTC)

So this means our articles should say that olefins are organic compounds with a C=C bond and alkenes are in turn, those hydrocarbons which are olefins (having the olefinic functional group inside them). BTW the free dictionary says that olefins are mono-alkenes. —ШαмıQ✍ @ 13:22, 30 December 2013 (UTC)

Again, I think I'd simply defer to IUPAC rather than the free dictionary.

Wade might be more of a problem. The cited work was the 6th edition, and there is now an 8th (amazon) which appears to be a major work and an authority. We probably should have an article on its author, Leroy G. Wade, but don't seem to have at present. Again, see amazon [6] for a very impressive list of titles. Andrewa (talk) 13:58, 30 December 2013 (UTC)

I support deviating from IUPAC on the definition of alkene. The last thing Wikipedia-chem needs at this stage is yet another nomenclature purist enforcing some rules. These nomenclature purification campaigns disrupt a lot of articles and make topics opaque just to satisfy a few students who have little experience in the chemistry world.--Smokefoot (talk) 14:42, 30 December 2013 (UTC)

I think yet another nomenclature purist is a bit harsh. But I'm very interested in the yet another. I take it that these nomenclature purification campaigns have happened before.

And I'm therefore suspecting that you are quite right that a lot of articles are involved.

But I am certainly not suggesting that we make topics opaque. Just the opposite.

I am very concerned that there is no concern for a few students who have little experience in the chemistry world. I think they (we) are an important part of Wikipedia's readership.

Where forward? On this talk page, we should focus on the alkene article of course, and it's a good start.

If we are to continue deviating from IUPAC on the definition of alkene, I propose that we also need, in the lede to the article, to explain that there is an alternative meaning of the term, sanctioned by IUPAC, and that we also need to cite a reliable source for the meaning that we are using, and that this source needs to be comparable to IUPAC in its authority. Wade (see above) may be a possibility.

But I would still prefer for the article title to be interpreted according to the IUPAC definition. This doesn't mean that related compounds or classes of compound get no mention, there can be sections on them, and links to main articles for those that warrant them.

And it doesn't mean that other definitions and/or meanings of the word are ignored. Do you have a copy of Wade (or a comparable source)? What does it say an alkene is? Andrewa (talk) 20:19, 30 December 2013 (UTC)

• The IUPAC definition strikes me as idiotic, the cyclic or acyclic nature is irrelevant and degree of branching is also irrelevant. IUPAC does also not have an entry for double bond, so it is not much of a help. The current Wikipedia definition exists as of 2001 ,hydrocarbon switched to chemical compound in 2003 and in 2006 olefins got equated to alkenes for the wrong reasons but everybody seems to be happy about it. Internet sources are not more relevant than non-internet sources. IUPAC is distracting. Good resources are the university textbooks like Wade. According to my McMurry "alkenes are hydrocarbons that contain a carbon-carbon double bond functional group". V8rik (talk) 21:01, 30 December 2013 (UTC)

• McMurry seems to agree with the IUPAC definition exactly. Or have I missed something? Andrewa (talk) 23:30, 30 December 2013 (UTC)

Almost, except that McMurry does not mention acyclic, branched or CnH2n and all for a good reason. V8rik (talk) 18:20, 2 January 2014 (UTC)

Yes, good observation. But on other occasions as we've seen elsewhere, McMurry uses the term alkene to mean things that aren't hydrocarbons at all. Or are they? As McMurry uses the term, can a hydrocarbon contain chlorine and oxygen? Andrewa (talk) 03:38, 5 January 2014 (UTC)

Sources

With fear and trembling, I think it might be helpful to point out that we've now had at least four very similar comments disparaging adherence to the IUPAC Gold Book, by three different contributors.

• diff To me, dichlorodifluoroethylene is an alkene with edit summary its an alkene in my book.
• diff Frankly though, this would be the first time I'd have encountered an ethylene that wasn't an alkene (I would certainly expect it to react like an alkene) with edit summary An alternative description is possible - but I think we're splitting hairs here.
• diff I support deviating from IUPAC on the definition of alkene... with edit summary These nomenclature purification campaigns disrupt a lot of articles and make topics opaque.
• diff The IUPAC definition strikes me as idiotic... with edit summary IUPAC is not an authority.

Now I do not wish to disparage any of these contributors. IMO these are all valuable contributions to the discussion, and things that needed to be said. But nor do I think this should be the last word, even if we are to some extent revisiting old discussions.

Only one of them cites a source at all, and that one not very specifically. So these are the opinions of contributors, and I'm sure they all know more chemistry than I do, but they still need to cite their sources. That is, opinions are useful on talk pages, but everything that goes into an article... including its name and the interpretation of that name... needs to be based on citations of reliable sources. We do not cite ourselves!

I'm very interested that the online Gold Book is not agreed to be an authority. I had not expected that. It seems to be exactly what we would normally consider to be a very reliable online source. Again, have we sources that justify ignoring it? Andrewa (talk) 05:38, 31 December 2013 (UTC)

MOS

I note that Wikipedia:Manual of Style/Chemistry reads in part Being affiliated with or bound by no scientific organizations, the content in Wikipedia-Chemistry is not constrained by recommendations or rules, but seeks to objectively describe knowledge. For example, the International Union of Pure and Applied Chemistry (IUPAC) provides recommendations and definitions for nomenclature and terminology. Wikipedia editors strive to be mindful of IUPAC's advice but do not follow this advice rigidly, especially when the advice deviates from mainstream usage (see comments below on nomenclature).

However that's not a blank cheque, and it would run badly foul of WP:OR if it were to be. Wikipedia:Manual of Style/Chemistry#Nomenclature reads in part IUPAC recommends the use of non-systematic names for some organic compounds, and these recommendations should be followed in article titles. There's a link from this to http://www.acdlabs.com/iupac/nomenclature/ which has a subpage http://www.acdlabs.com/iupac/nomenclature/79/r79_53.htm which reads in part The generic names of these hydrocarbons (branched or unbranched) are "alkene", "alkadiene", "alkatriene", etc. (my emphasis).

So there it is, in the MOS. An alkene is a type of hydrocarbon according to IUPAC recommendations, and these recommendations should be followed in article titles.

But the MOS goes further, that section links to a main article at Wikipedia:Naming conventions (chemistry) which links to http://media.iupac.org/publications/pac/1995/pdf/6708x1307.pdf which reads in part alkenes: Acyclic branched or unbranched hydrocarbons having one carbon-carbon double bond and the general formula C_nH_2n (my emphasis). Even if there's doubt as to whether dichlorodifluoroethylene is a hydrocarbon (I'm still skeptical that there is any reasonable doubt, it's not, but even if there is doubt) surely nobody is going to try to tell me that C₂Cl₂F₂ is of the form C_nH_2n. Surely?

OK so far? Andrewa (talk) 05:30, 31 December 2013 (UTC)

I think following this IUPAC definition as recommended by the MOS is not bad at all... Let's see what others have to say. —ШαмıQ✍ @ 22:59, 1 January 2014 (UTC)

Someone else has also raised the question of whether dichlorodifluoroethylene (which I think I'll call DDE in future unless anyone objects, I don't think in this context anyone will think I mean dichlorodiphenyldichloroethylene) is even organic, as it contains no C-H bonds at all, compare to carbon tetrachloride or even carbon dioxide for that matter. The lede of our article at organic compound deals very well with this issue, with citations. It's not all bad news! Andrewa (talk) 01:14, 2 January 2014 (UTC)

Food for thought

This discussion is straying completely in the wrong direction. We do not call an alkene and alkene because IUPAC recommends it, and, per WP:V, not everything needs a reference (and this is one of those typical things). This compound is an alkene, an olefin, and no, we do not need a reference to evidence that. --Dirk Beetstra ^{T C} 09:07, 2 January 2014 (UTC)

WP:V: any material challenged or likely to be challenged must be attributed to a reliable, published source using an inline citation. The claim that DDE is an alkene has been challenged, several times now. As it does not conform to the IUPAC definition, it was always likely to be challenged. It therefore requires a citation, on several grounds. That is Wikipedia policy. Andrewa (talk) 11:47, 2 January 2014 (UTC)

The problem is, are those challenges real challenges, or questions. What would you say if someone 'challenges' the remark 'water is a liquid at room temperature'? Would you request a reference for the remark 'grass is green' and 'the sky is blue'. --Dirk Beetstra ^{T C} 11:59, 2 January 2014 (UTC)

I'd say that the person lived in an igloo (;->. No, I wouldn't ask for references for grass being green or the sky being blue. But these appear to be straw men.

I have requested a reference for DDE being an alkene, and it's a reasonable request. But providing that reference (and I would still like it, and it's been stated and implied several times that it's easily found) is not the main issue. The main issue is, do you see why one is required? Andrewa (talk) 12:40, 2 January 2014 (UTC)

I still think that it is not reasonably required. Basic textbook chemistry (high-school level) will show you that compounds with a carbon-to-carbon double bond are called alkenes, I think that it is similar to calling a spade a spade. I would find it very hard to defend, and even more likely to be challenged, if one would suggest that dichlorodifluoroethylene is not an alkene. --Dirk Beetstra ^{T C} 12:44, 2 January 2014 (UTC)

OK. We seem to have reached an impasse. How would you like to proceed from here? Andrewa (talk) 12:57, 2 January 2014 (UTC)

Can you show me sources (besides an IUPAC recommendation), saying that DDE or TFE are not alkenes? I'm throwing in all high school chemistry books and encyclopedia to say that compounds with an isolated carbon-to-carbon double bonds, including dichlorodifluoroethylene and tetrafluoroethylene, are alkenes. --Dirk Beetstra ^{T C} 13:49, 2 January 2014 (UTC)

I'm not sure what it would prove... the source would probably just be quoting the IUPAC recommendation whether it cited it or not.

But in IUPAC we do at least have one source that does say DDE is not an alkene, while we don't have any sources that say it is. We do have you and others saying that they have sources, and/or that it's common knowledge (among the initiated at least). But none of you have provided any citeable sources at all, so far.

Tetrafluoroethylene is an interesting article, it currently [7] reads in part It is the simplest alkene fluorocarbon. An alkene fluorocarbon is not necessarily an alkene, any more than a toy poodle is necessarily a toy (although it is a fluorocarbon, just as a toy poodle is a poodle). But the wording, while it may be fine for a chemistry textbook, is unfortunate in a general encyclopedia, assuming that there's doubt as to whether the substance concerned is an alkene. I think it's a side issue, and not of first importance. Andrewa (talk) 14:17, 2 January 2014 (UTC)

Agree with Beestra. Andrew, please look at the titles in the top (or not so top) chem journals and see the extent that IUPAC nomenclature is ignored. Just go to ChemAbs. We want our Wikipedia readers to be able to read such content without pondering hair-splitting nomenclature questions, which the pro's ignore.

People really want to contribute to Wikipedia-Chem but when the content is over their heads, they resort to debating nomenclature rules, which one can quickly fathom and perhaps gain sense of righteousness. This collision between righteousness and knowledge is awkward because then editors cannot walk away and say, "maybe I dont really know that much chemistry after all." Walking away from a debate is the most difficult thing to do in Wikipedia.

Per WP:RIGHTGREATWRONGS. "Wikipedia is a popular site and appears high in the search engine rankings. You might think that it is a great place to set the record straight and Right Great Wrongs, but that’s not the case." --Smokefoot (talk) 14:21, 2 January 2014 (UTC)

(edit conflict)I'll withdraw the 'it does not need a citation', it should (I thought that Wikipedia had a wider definition of 'common knowledge' than it has (hence my 'grass is green' - analogy), my apologies). I do however think that there are many, many tertiary sources (most printed encyclopedia, most general chemistry textbooks, etc.) that will tell you that a compound with a carbon-to-carbon double bond is an alkene/olefin .. alkene functionality .. eh .....

.... I am starting to think in semantics here now. Do we mean that DDE has an 'alkene functionality', though it is not strictly an alkene .. it is not there where the confusion is, is it? --Dirk Beetstra ^{T C} 14:23, 2 January 2014 (UTC)

(The stringing is getting messed up so I'll start again.)

I hope WP:RIGHTGREATWRONGS is not applicable here. I note it's a section of an essay titled tendentious editing.

I'm not yet ready to walk away from this one. Almost, perhaps. If I decide that the case is hopeless that's exactly what I will do. (And you may like to consider it a compliment that I have not already done so.)

I appreciate that you've had to deal with people who resort to debating nomenclature rules, which one can quickly fathom and perhaps gain sense of righteousness and that it becomes a collision between righteousness and knowledge... with you on the side of knowledge of course.

But I'm not trying to do any of that. Are you really sure you have the moral high ground on this one?

All I'm saying is, cite your sources. You're running around in circles saying at one time you don't need to, at another that you already do. Wrong on both counts I'm afraid. You don't do it, and you do need to. And that is Wikipedia policy.

I'm not quibbling that you should stick to IUPAC definitions or any others. I am saying, cite your sources, whatever they may be. Your knowledge of chemistry is invaluable in writing and editing articles of course. But it's not enough. You can't cite yourself (with a few exceptions).

I do suspect that you may find these sources harder to find than you think. But none of us will know until you try, and if you do find them I won't be at all miffed. Mission accomplished. And if you can't, then yes, I'm going to suggest that in that case the IUPAC recommendation should be used.

I'm not going to dredge through Chemical Abstracts trying to guess which papers you think support your case or cases. That's your job. You will do it better than I will. Please, just one or two paywall-free URLs would make such a big difference to the discussion. Any chemistry book says is not even remotely verifiable. Is it now?

Thank you for withdrawing the it does not need a citation comment. I'm not quite sure which one you mean, it's been said several times, but probably in each case it does. There are a few similar comments I think should also be withdrawn, but let's move on instead.

Progress. I think. Andrewa (talk) 15:59, 2 January 2014 (UTC)

I don't think that IUPAC is a good substitute - it is a recommendation of rules, almost any generation from those rules is WP:OR - and that is where part of the problem lies with naming of esoteric compounds. The only thing verifiable is often a tradename or a synonym (the rigorousness of the systematic namechecking in even peer-reviewed articles is not of a level that I would trust, and likely if they did, they followed the same algorithm-software as the writers, and have seen that the two are the same). Some .. most names are simply not verifiable and OR by definition (please, show me a reference that verifies '1-[4-ethoxy-3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)phenylsulfonyl]-4-methylpiperazine' .. you find it on Wikipedia, in databases, and probably behind paywalls in literature .. but how did those places get the name - the structure of the compound is verifiable, and the tradenames linking to it often as well (that is part of the registration of a medicine), but I doubt the systematic name (there is no {{cn}} on that on Wikipedia ..)).

Anyways. I am sure that someone has a book on a shelf next to them (I don't .. sorry, may have online access here) who can that the carbon-to-carbon double bond is named the alkene functionality .. free source .. not sure about that being available. --Dirk Beetstra ^{T C} 16:26, 2 January 2014 (UTC)

Responding to Beetstra's suggestion, here are a few of many quotes from March's Advanced Organic Chemistry, which many chemists view as the bible in the area. I searched for "alkene" and got about 10% through the book. To support its authority, one can check the extent that this book is cited in Wikipedia (or easier, ask some of the heavy editors in the project):

• "Weak hydrogen bonds can be formed between an appropriate hydrogen and a pi-bond, both with alkenes and with aromatic compounds. For example, IR data in dilute dichloromethane suggests that the predominant conformation for bis(amide) contains an N–H…p hydrogen bond involving the C=C unit" point being: alkenes can have amide substituents
• "The generally accepted picture of the bonding in these complexes, first proposed by Dewar, can be illustrated by the ethylene complex with silver, 9, in which the alkene unit forms an eta2-complex with the silver ion (the alkene functions as a 2-electron donating ligand to the metal)." point being: ethylene= alkene
• "In a number of cases, alkenes that are too unstable for isolation have been isolated in the form of metal complexes. As example is norbornadienone," point being: norbornadienone is viewed as an alkene
• "Alkenes that contain electron-withdrawing substituents also act as acceptor molecules," point being: alkenes can bear EWG functionality
• "A particularly strong alkene acceptor is tetracyanoethylene." point being: TCNQ = C₂(CN)₄ = alkene
• "It is also important to note that trans-alkenes are often more stable than cis alkenes due to diminished steric hindrance (p. 232), but this is not always the case. It is known, for example, that cis-1,2-difluoroethene is thermodynamically more stable than trans-1,2-difluoroethene." point being: C₂H₂F₂ isomers = alkenes.

The source is downloadable (probably illegal copy) for verification. I think that these address some of the questions being raised above. Cheers, --Smokefoot (talk) 16:55, 2 January 2014 (UTC)

• March unfortunately does not bother to present a clear definition of an alkene. I already mentioned McMurry. Morrison&Boyd have this to offer: "the carbon-carbon double bond is the distinguishing feature of the alkene structure". The chapter entirely devoted to alkenes also describes pheromones, alkenes with alcohol or ester groups V8rik (talk) 18:42, 2 January 2014 (UTC)

More progress. And some of my suspicions I'm afraid are confirmed - at least some of those quotes above use alkene in an adjectival sense or as a sort of professional shorthand or jargon, or both. Now this jargon sense is important, but we need to distinguish it from the strict usage, and provide our readers with the information they need to distinguish these two senses and correctly interpret both - at the level of their understanding of course. And yes, it's a challenge. And that's why it's important for those steeped in chemistry to work together with those who aren't, as a team. Thank you for allowing me to be part of that team.

Overall this material is very good. Thank you for that as well.

Morrison&Boyd is exactly the sort of citation I was seeking all along. Let's look at it carefully. They speak of alkene structure, using the word alkene as an adjective. That could mean the structure of a (particular) alkene, but it could also mean a structure that is significantly similar to that of an alkene in general... the toy poodle construction again. So this occurrence doesn't support the broadening of the sense of alkene when used as a noun. Do you see why I'm wondering whether a great many of the other occurrences which at first seem to substantiate common usage might be of this nature?

Yes, McMurry has been mentioned, but not cited, just name-dropped. If they do say something relevant, we need to know exactly what and where. If not, or if you're just relying on a personal memory, then I suggest we drop it as irrelevant. So could I either have a useable citation, or can we agree to drop that particular attempt at verification? (It's not as bad a name-drop as any Chemistry text, but not a lot more helpful - do you see the point?)

By all indications, March is an excellent citeable source, and the hint that it was online was invaluable. Again, a link to https://archive.org/details/AdvancedOrganicChemistry6thEd or a similar site would have been helpful. The guess that it wasn't legally available on the other hand seems completely unhelpful. There seem to be many downloadable versions and formats - or am I missing something?

I have now downloaded two different PDFs of the 6th edition, 2007, ISBN 13: 978-0-471-72091-1 (ISBN 10: 0-471-72091-7), from two different sites. They seem identical, and legal. Do you see any pitfalls in my citing them?

Do you see why I feel I'm doing your work for you? It would have been so easy for you to find these legal PDFs, and link to one of them, and settle those two last (fairly obvious) questions without my even having to ask them. You are the experts on chemistry. Give me the benefit of that expertise. Perhaps I can find McMurry online, but even if you've tried and failed, at least say that and give me its ISBN or the URL of its Amazon entry or whatever you do have. It's so easy for you to provide this but takes me a great deal of time and trouble. The URLs of your Google web and books searches that failed to find it are other examples of helpful links.

It will take me a little while to respond to this all of this, but it's excellent. Meantime, please notice I have asked a number of questions. These are not rhetoric, I'm trying very hard not to employ that at all here (without wanting the prose to be too boring either). They're serious questions, which may have simple answers, and if not need I think to be explored further. Andrewa (talk) 21:44, 2 January 2014 (UTC)

• Yes, there is the alkene as the compound class and there is the alkene the functional group. May cause confusion. When I say McMurry I am just lazy, I am referring to John McMurry Organic Chemistry, 2nd Edition. I do not bother with ISBN numbers V8rik (talk) 22:25, 2 January 2014 (UTC)

• OK... by John E. McMurry and the 8th edition is on Google Books at http://books.google.com.au/books?id=oVv4Az7VJRYC&printsec=frontcover&dq=john+mcmurry+organic+chemistry+pdf&hl=en&sa=X&ei=u_bFUoGzIYfwkgWTpIGACQ&ved=0CEcQ6AEwAQ#v=onepage&q=alkene&f=false and on p252 says An alkene is a hydrocarbon that contains a carbon-carbon double bond (my emphasis) and says something similar on p222. It appears to me that when McMurry uses alkene as an unqualified noun, he's consistently following the IUPAC recommendation exactly. Not to you? Andrewa (talk) 00:12, 3 January 2014 (UTC)

McMurry's end-of-chapter summary is clearly just talking about a parent compound (that could have other functional group substituents) or a small area of a more complex molecule. The stricter reading you advocate of his wording is contradicted by his usage in that and other chapters' actual text. Exercise 7.22, on the very next page, says to "name the following alkenes", one of which is cyclic and therefore does not meet the C/H IUPAC formula rule (though it is still a hydrocarbon). Exercise 7.23 asks about "the double bonds in each of the following alkenes" (therefore the "alkene" is not just the double-bond part), both of which contain oxygen(s) and one also a chlorine. In-chapter problem 7.13 asks about E/Z of "the following alkenes", all of which contain heteroatoms--he's clearly talking about the double-bond part of the molecule. Note that even his hydrocarbon examples, which he simply calls "alkenes" are sometimes cyclic and sometimes multiple double-bond units, which would contradict the C/H ratio formula of the strict definition. DMacks (talk) 02:43, 3 January 2014 (UTC)

(We really must do better with the stringing here) I'm at a bit of a disadvantage here because I think we may be working from different editions (V8rik has 2nd, I have 8th, you haven't said) and the page numbers and even exercise numbers may differ. My preview is missing pp249-250 which I think may contain exercises 7.23 and 7.22, and other pages, and I think that 7.13 to you may be 7.15 to me.

See the 8th edition problem 7.15 here. Is it the right one?

As you say, (c) is a cycloalkene, and that is not consistent with the current IUPAC recommendation. [8] Under IUPAC it would be an olefin [9] but not an alkene.

(I looked back at my initial comment... I said and would also disallow hydrocarbons containing rings for example.[10] Perhaps it should have read ...disallow some hydrocarbons.... It is more than forty years...)

I must focus. These examples raise the standard of discussion a great deal, in my opinion. Let me digest them a little. Andrewa (talk) 06:05, 3 January 2014 (UTC)

I was using 8th because that's what you were using. I have the actual printed text (and also of several previous ones, but I don't think 2nd), and its p252 end-of-chapter summary matches what's in your google-books link, so I'm confident we are looking at the same thing. As I said, 7.22 is on "the very next page", that's p253. My ex 7.15 matches what you have also. DMacks (talk) 06:11, 3 January 2014 (UTC)

OK... got 7.22, thank you.[11] Yes, Assign E or Z stereochemistry to the double bonds in each of the following alkenes, and convert each into a skeletal structure (red - O, green - Cl... And (a) and (b) both have oxygen, (a) has chlorine as well. Point made. Thank you!

You actually said 7.13 I think, which I didn't find, but 7.15 seems to make exactly the same point. Andrewa (talk) 07:15, 3 January 2014 (UTC)

What does Wade have to say on the subject of alkenes? I can't find an online version as yet, and wasn't planning a trip to a library anytime soon. Surely someone has it on hand and can quote the relevant passage? Andrewa (talk) 00:48, 3 January 2014 (UTC)

I have at least one edition of Wade in my office, not sure which one though...will check on Monday if nobody else finds it before then. DMacks (talk) 06:11, 3 January 2014 (UTC)

Awesome! Andrewa (talk) 06:50, 3 January 2014 (UTC)

IUPAC nomenclature

Andrewa (sorry, tl;dr post, I am splitting this off), of course you do not have to take our word on 'this is an alkene, trust me, I am a chemist' - and you are right in that it should be referenced properly.

One thing though - regarding reliable sources, I as a chemist, and quite some with me I think, do not see the IUPAC publications as an ultimate source (I am afraid it is a primary source, and a recommendation of rules). There are some 'direct' rules in there:

• ethanoic acid is the systematic name, but we allow acetic acid as well, for which it hence is a good (primary?) source that we call that compound actually acetic acid; note that something like the Encyclopedia Brittanica likely has an article on Acetic acid, which is hence a tertiary source for the information, way better; and with acetic acid gets close to the primary-school-level common knowledge of chemistry

But most of the information is of a type:

• find the longest chain, how long is it, what is the most important functional group on that chain/skeleton, there is the base-name of your compound, if there is another chain on the n-th atom from the functional group, it gets a prefix 'n-' and the name based on the length of that other chain' .. it is hence not a source for the information that 4-methyl-octanoic acid is the name for a compound with that skeleton.

And since thát information is ALL based on the IUPAC recommendation, and there is no authoritative source that vets that name (IUPAC is not contacted to check whether the writers of a publication, even in the highest level of sources, have actually applied the rules correctly), it is practically all WP:OR.

Now some of those names are used throughout, are widespread, and could be referenced to the conglomerate of information out there (pff, how to use that for a reference - really, every chemistry book with a chapter on basic organic chemistry, encyclopedia, and everything beyond that, will base their names of compounds with a double bond on the alkene nomenclature (1-hexene -> 'cyclohexene', propene-> 'propenoic acid', 1-butene -> butadiene, ethylene -> 1,1-dichloro-2,2-difluoroethylene, even ethylene oxide ('the oxide of ethylene?')), and group 'C2H4', 'C2H3Cl', 'C2H2Cl2', 'C2H1Cl3', 'C2Cl4' as 'these alkenes'. Other names are, though following the rules, so esoteric that no-one ever uses them and are of no 'real meaning', even to chemists (we don't even bother to redirect (5R,9R,13S,14S)-4,5α-epoxy-14-hydroxy-3-methoxy-17-methylmorphinan-6-one <- unreferenced in the article I pulled it from, I wonder if it is correct (maybe that is why the redirect did not work?) or even if a reliable source for that exists?).

So, though I agree that the IUPAC is a respectable organisation, and that the publications from them are a reliable source - as a chemist I recommend that one considers what is being used from that source, and how that information is being used. They obviously base the name of DDE on the alkene skeleton (dichlorodifluoroethylene .. that recognises a chain lenght of 2 with as most important functional group the double bond), whereas they say that that if a compound does not follow the CnH2n-rule, it is not an alkene ..). I think that is where the problem is - if you tell a chemist that something is not an alkene because it does not follow the IUPAC rules, then they say 'it is written everywhere, take an encyclopedia, high-school level general chemistry text-book, review article, or even direct publications in respectable journals and you will see' (I agree, we should have referenced that general chemistry textbook directly). IUPAC sourcing is a subject that has to be done carefully (and I think I am quite safe to say that chemists generally ignore IUPAC, at worst it is 'the last thing to do before finishing a publication'). The naming of compounds is a grey area, some systematic names being verifiable, but most not.

Agreeing that it should have been referenced, but I think that the statement 'DDE is described as an alkene, but IUPAC says it is not an alkene' is giving way too much weight to the IUPAC, it was an alkene way before the IUPAC was founded. --Dirk Beetstra ^{T C} 07:05, 4 January 2014 (UTC)

How about we reserve IUPAC nomenclature for chembox fields specifically designed for it, and use customized ontologies for categorization, classification and maintenance, and reserve popular nomenclature for everything else? Plasmic Physics (talk) 07:18, 4 January 2014 (UTC)

Most of it would still be WP:OR. And the categorization/classification etc. is another situation with closely related, though different problems. --Dirk Beetstra ^{T C} 07:25, 4 January 2014 (UTC)

I was of the persuasion that the OR point has already been settled as an unavoidable issue. Plasmic Physics (talk) 08:33, 4 January 2014 (UTC)

Unavoidable issue? More an issue that should be avoided. --Dirk Beetstra ^{T C} 12:48, 4 January 2014 (UTC)

In my opinion, the only solution, now that we have sources that indicate unequivocally both that DDE is and isn't an alkene, is to report both of these views. It's as simple as that. This may be a little alarming to those who view science through the lens of the How and Why Wonder Books, and we should try to minimise this alarm, but we can't completely avoid it, in fact we must not.

It's an inevitable part of our mission to inform and even sometimes to educate people (including ourselves).

My father was a director of scientific research from the time I was in primary school until his retirement, and before that a research scientist since before I was born. He still has an active interest in his field (not chemistry, but nuclear materials, so closely related), and we just had dinner together. One of his mantras is the result that surprises you was the whole reason for the experiment. That's science as I grew up with it.

Back to DDE. Yes, OR is a sin, but sometimes the line is hard to draw. Falsehood is an even worse sin. The first step (only) towards encyclopedic content is accurate content, and content that presents DDE as either an alkene or a non-alkene without qualification as to the sense intended is inaccurate. We've now established that.

References are one form of what I've called qualification. Often they are enough. But in this case, I think the lede to the alkene article needs to explicitly say that there are several possible senses of the term, and to explicitly describe both the strict IUPAC one, and the one adopted by McMurry (as an example). And to cite the best sources we have for both. We can do no more.

This may seem cumbersome, but anything else is misleading and not encyclopedic (whatever that means). OK so far? Andrewa (talk) 11:04, 4 January 2014 (UTC)

Such as, a regular alkene is ... Furthermore, there are various schools of thought, which disagree over whether substituted, and or structural analogues are also be defined as alkenes? Plasmic Physics (talk) 11:23, 4 January 2014 (UTC)

Frankly I don't much like that wording... but it's the general idea.

Let me try... In chemistry, an alkene is an organic compound containing at least one carbon–carbon double bond, and with other restrictions that vary from authority to authority. Similar terms are olefin and olefine. New paragraph: IUPAC recommends that the term "alkene" should be restricted to hydrocarbons with straight or branched structures, as opposed to cycloalkenes, aromatic compounds, and compounds with other elements or groups substituted for some or all of the hydrogen atoms. Most other authorities however commonly use the term "alkene" to include other compounds with similar structures and properties.

That's more to give the idea than a final version, and I'm very interested in how it reads to a real chemist! And I'd put in a couple of references, they're troublesome on talk pages so I didn't, and the double quotes would be italics instead. And I'd have a section on Olefins and olefines later in the article, again saying how they are defined by several different authorities, their historic usage, and probably point the relevant redirects to that section.

This would I hope satisfy questions such as #What is it? above and also be useful to those who want to read chemistry textbooks and papers with some hope of comprehension, and would be encyclopedic if properly sourced. Very interested in other views, however. This isn't a proposed new lede... yet... Andrewa (talk) 12:04, 4 January 2014 (UTC)

Some thoughts EdChem (talk) 05:14, 5 January 2014 (UTC)

A quibble

I didn't want to interrupt the discussion above with this, and the formatting is such that I couldn't insert it as an inline reply. So I'm starting yet another subsection... which lets me waffle a bit, too.

I as a chemist, and quite some with me I think, do not see the IUPAC publications as an ultimate source... Agree... and disagree. I don't think any ultimate source as such is part of science, or of writing an encyclopedia. Rather, I described the Gold Book as a source of the highest possible quality, and I still think it is that, for our purposes. But that doesn't mean that we need to swallow it whole. I think I said that before too, in fact.

The Bible is also a source of the highest possible quality in my opinion, but we do not report all of its contents as unqualified truths. One result if we did, one which I claim to have invented, would be creation mathematics, which is based on the clear inference from the Books of Kings that π=3 (;->. And on a similar vein, I have yet another favourite T shirt (from Sydney University Mathematics Society) that reads 22/7 - say π and die. Now that is math with attitude, and dare I say it, even purity. Andrewa (talk) 11:04, 4 January 2014 (UTC)

I still think this gives too much weight to the IUPAC, and comparing it to the bible is hence, IMHO, a huge stretch (I've heard that for the above mentioned book by Jerry March, and for the CRC-handbook .. but not for IUPAC). --Dirk Beetstra ^{T C} 12:48, 4 January 2014 (UTC)

The comparison was intended itself to be biblical... Jesus often says if this is the case, how much more is it the case that....

So just to re-repeat, I'm not saying we should swallow the IUPAC recommendations whole. I do say, we need reason to depart from them, and we need to cite those reasons.

And those other texts you mentioned may be reason in themselves. The CRC Handbook of Chemistry and Physics is one I assume, and we have an article on Jerry March and it mentions his book March's Advanced Organic Chemistry but is assessed as a low-importance stub. Do these have authority superior to the Gold Book? Are they available online? Andrewa (talk) 14:29, 4 January 2014 (UTC)

Let me try to put it this way - ever since, probably, high school, books have told me that compounds with a carbon-to-carbon double bond are alkenes. That has been so probably since, what, the beginning of the 20th century (I don't know when the word alkene was coined, though I think we first had olefins and alkanes, and then by analogy we got alkenes and alkynes). You have ethylene, that is an alkene, propylene, that is also an alkene, vinyl chloride, yet another alkene, cyclohexene, also one. Well, practically everything with a double bond. Those are simply alkenes. School books tell you that, encyclopedia tell you that, authorative books like March will commonly group them as alkenes, peer reviewed literature will do it. So why do we single out the IUPAC recommendation here? Why do we need reason to depart from IUPAC, and not need reason to depart from all those other sources (some older than IUPAC). Actually, does IUPAC themselves adhere to it when they suggest that 1,1-dichloro- 2,2-difluoroethylene needs a name based on the alkene skeleton.

Nobody is suggesting that DDE is not based on an alkene skeleton. The issue is, in what sense does this make it an alkene? It's also based on carbon, but it's not carbon.— Preceding unsigned comment added by Andrewa (talk • contribs) Actually I did sign this edit, but apparently the stringing was not clear - apologies Andrewa (talk) 07:55, 6 January 2014 (UTC)

It is an alkene because the compound is based on an alkene skeleton... it is also an organochloride, an organofluoride .. --Dirk Beetstra ^{T C} 04:19, 5 January 2014 (UTC)

Important point, taken up below. Andrewa (talk) 05:49, 5 January 2014 (UTC)

Sources do not have to be online - they are available from (maybe specialised) libraries, from (maybe specialised) book stores, or maybe can be bought online from online book sellers. That they are not (freely) available online does not mean that they could not be an authorative source (and that reasoning also goes the other way around). --Dirk Beetstra ^{T C} 15:39, 4 January 2014 (UTC)

Agree. I'm very sorry if I gave the impression that I thought they did need to be online at all.

The freely available online sources have their advantages, but for some reason that escapes me most Wikipedians actually prefer dead-tree citations. There is nothing whatsoever wrong with them. I have a copy of Groves dated 1883, possibly the last remaining copy in the world of this particular edition (for reasons I won't go into) and certainly only available in closed reserve in major libraries, and perhaps in private collections and museums. But I have no qualms whatsoever about citing it, and so far nobody has questioned my right to do so. And I do not expect any challenge to happen. But when they see the citation as 1883, people are able to assess the reliability or otherwise, depending on the exact subject. That is part of verifiability too. Andrewa (talk) 18:11, 4 January 2014 (UTC)

It is not that they are only dead-tree citations - most of this stuff is copyrighted and behind paywalls. I am not even sure if the journals from the ACS are still printed, it is all pdf format but only accessible through subscriptions or a pay-per-view download. The books that dmacks, Smokefoot and others are mentioning are all not freely accessible online (only parts of it through Google), though surely behind the walls (the university that I have access to here has most of its subscriptions as eBooks, the library is pretty empty (bookwise). I must however agree, sometimes it is nice to have a dead tree in your hands, it has its advantages. --Dirk Beetstra ^{T C} 19:48, 4 January 2014 (UTC)

Someone just added the article Nitroalkene to Alkene - our article on nitroalkene cites (at least) two authorative, peer reviewed sources that use the word 'nitroalkene' in the title of the publication. A nitroalkene - that can never have the formula CnH2n, it should be CnH(2n-1)NO2. Does IUPAC even have authority over all the rest, or is it a mere suggestion? Or does IUPAC actually mean that any compound which is based on the alkene-skeleton is in itself also an alkene? --Dirk Beetstra ^{T C} 15:48, 4 January 2014 (UTC)

This is an excellent question... but again, one that we should not be attempting to answer. Surely, it is a question that citeable authorities have sought to answer? As an encyclopedia, it is their answer that we should (re)-publish, not our own contributions to the discussion.

However expert we may be, our own understanding is published elsewhere, not here. I think I could claim to be an expert on some aspects of percussion instruments, and on the tuning of fretted instruments. I have even published some tunings on the web. But alas, I am not a citeable authority on either of these subjects. I have also published some papers on computer security in professional journals, and read others at international conferences, the proceedings of which are available in those few major libraries with sufficiently specialised sections. I've even once (only) had a conference paper republished in a refereed journal. Those dead-tree sources are citeable. My opinions on the topics, except where literally expressed in those citeable papers, would still be borderline at best.

On a talk page, these discussions are fine. To re-repeat, the first step towards encyclopedic information is accurate information. Inaccuracy is a sin too, and I'll add another sin... incompleteness. But in the article namespace, we need references.

To attempt to answer your question about nitroalkenes, it would seem to me that if a cycloalkene is not an alkene, then a nitroalkene certainly wouldn't be on structural grounds. On reactivity grounds, I have no idea.

I'm more interested right now in the attempts above to rewrite the lede. Any comments? Andrewa (talk) 18:25, 4 January 2014 (UTC)

Citeable authorities .. that is now just the question. You could try and get it from the IUPAC recommendation by following the rules and extract the name. However, the reliable source has no problem to call something that is not CnH2n an alkene - a nitroalkene, according to IUPAC that does not even exist, alkenes are CnH2n ... And that is where I wanted to go ... Does IUPAC even have authority over all the rest, or is it a mere suggestion? Or does IUPAC actually mean that any compound which is based on the alkene-skeleton is in itself also an alkene? If the answer is no/yes the the former, or a yes to the latter, then the lede does not even need rewriting. --Dirk Beetstra ^{T C} 19:37, 4 January 2014 (UTC)

Note, I am talking pure symantics here, about the rules for naming - not chemistry/reactivity. IUPAC does not care about reactivity either here (they don't have rules like 'if it quacks like a duck, its most likely a duck, even if it looks like a horse'). --Dirk Beetstra ^{T C} 19:42, 4 January 2014 (UTC)

a nitroalkene, according to IUPAC that does not even exist, alkenes are CnH2n... not so. And as you say, this is a problem of semantics. You could similarly say a cycloalkene, according to IUPAC that does not even exist, alkenes are CnH2n.... but IUPAC does have a definition (recommendation) for cycloalkene, and it's not CnH2n either.

The logical fallacy here seems to be to assume that cycloalkenes and nitroalkenes are necessarily alkenes simply by virtue of their names. This works for some names, but not generally. And I'm now guessing that attempts to make it work for all chemical substance names may be part of the reason for the variety in nomenclature. But there's no linguistic reason that a cycloalkene needs to be a type of alkene, any more than a ballboy is necessarily a boy (I'm sure there are better examples, but you get my drift). Andrewa (talk) 03:54, 5 January 2014 (UTC)

No, I did not make the logical fallacy that cycloalkenes and nitroalkenes are alkenes because of their names. I say that they are alkenes because that is what the chemical world is calling compounds with a carbon-to-carbon-double bond in themthat are based on an alkene skeleton. --Dirk Beetstra ^{T C} 04:19, 5 January 2014 (UTC)

OK, good, I withdraw the allegation and I'm glad we seem to have (two person at least) consensus that it is a fallacy.

...cycloalkenes and nitroalkenes are alkenes ... because that is what the chemical world is calling compounds ... that are based on an alkene skeleton. That's a really important point that belongs in the alkene article.

So again I'm going to ask, what's the best source you have to support that statement? Behind a paywall is fine, if you have access through it. If you just provide the citation and the quotation, that is absolutely perfect.

(Such assumption of good faith of course sometimes comes unstuck when dealing with the more subtle vandals. [12] [ T ] But I am completely confident that neither of us is one of those, and I hope you are too.)

Again I say, progress. And I apologise unreservedly for any offence taken at my falsely accusing you of a logical fallacy. Andrewa (talk) 04:40, 5 January 2014 (UTC)

And again we go back to the sources mentioned above - chemistry books, encyclopedia, literature references - you've already seen the examples that that is how that class of compounds is called. Again, we don't call an alkene an alkene because IUPAC tells us that way, it is earlier the other way around. IUPAC is not the authority there. --Dirk Beetstra ^{T C} 07:04, 5 January 2014 (UTC)

At the risk of again accusing you of poor logic, is there an assumption here that for IUPAC to be an authority, it must be the authority here? It is one of several noteworthy authorities, and ideally we cover all of them. Andrewa (talk) 09:26, 5 January 2014 (UTC)

Poor logic - I don't know, but I think that you are avoiding the base of the remark: "we don't call an alkene an alkene because IUPAC tells us that way, it is earlier the other way around". --Dirk Beetstra ^{T C} 10:36, 5 January 2014 (UTC)

I find your edit summary you avoided the base of the argument, quibble whether it is 'the' or 'an' authority [13] more easily understood than the post, so I hope I've interpreted it correctly. What I've been trying to say, and trying to say consistently, is that it's an authority. Does that address the base of the remark? Andrewa (talk) 04:58, 6 January 2014 (UTC)

Not exactly - I think we are calling an alkene an alkene because that is what tertiary sources tell us, and all IUPAC is doing is to formalize that same thing, putting it into 'rules', 'algorithms' if you wish, that can be used systematically to, in the end, do the same. But an alkene is not an alkene because IUPAC tells us. --Dirk Beetstra ^{T C} 05:06, 6 January 2014 (UTC)

Your point escapes me. Are you saying that IUPAC is not an authority at all, or that's it's not a reliable source? They're subtly different things, but it seems a stretch either way. Or, that it is greatly inferior to other sources we have? That seems a more promising line, but I'd like to be sure it's what you mean before pursuing it. Andrewa (talk) 05:20, 6 January 2014 (UTC)

That is the point that we try to get through all the time. The real question. Why do we call a compound with a carbon-to-carbon double bond an alkene? The answer to that is pretty much the same as why IUPAC calls it an alkene. In a way it is the last answer, though 'inferior' is not the right word, much weaker than that. Again, we call a compound with a carbon-to-carbon double bond an alkene because encyclopedia, general chemistry school books (down to high-school level), organic chemistry books, peer reviewed literature .. naming of olefins/alkenes goes way back before the existence of the IUPAC, the 1911 Encyclopaedia Brittannica uses the term 'olefin series'. IUPAC is trying to put the naming of chemical compounds into rules that can be used by the (chemical) community, but an alkene is not an alkene because the IUPAC calls it an alkene. --Dirk Beetstra ^{T C} 05:50, 6 January 2014 (UTC)

Wikipedia calls something an alkene because reliable sources call it an alkene. Where reliable sources differ, we do not take sides, but describe the various views, citing each. That is true of alkenes, of other terms used in chemistry, of terms used in computing, terms used in astrology, and everything else.

Answering the question of why IUPAC makes any particular recommendation may even be beyond the scope of Wikipedia entirely. Again, are there any reliable secondary sources that attempt to answer this question? What do they say? Andrewa (talk) 07:50, 6 January 2014 (UTC)

Note that the definition of an alcohol in 1911 Encyclopaedia Brittannica "ALCOHOLS, in organic chemistry, a class of compounds which may be considered as derived from hydrocarbons by the replacement of one or more hydrogen atoms by hydroxyl groups. It is convenient to restrict the term to compounds in which the hydroxyl group is attached to an aliphatic residue .." is not that dissimilar from the Gold book IUPAC recommendation "Compounds in which a hydroxy group, –OH, is attached to a saturated carbon atom R3COH." (note, again, in 1911, IUPAC did not exist). So, are we calling an alcohol an alcohol because the world calls those compounds alcohol, or because IUPAC tells us that it is an alcohol? --Dirk Beetstra ^{T C} 07:16, 6 January 2014 (UTC)

Again, we should call something an alcohol if reliable secondary sources do, and not otherwise. Andrewa (talk) 07:50, 6 January 2014 (UTC)

Dichlorodifluoroethylene is an olefin

... according to this book, and this journal abstract refers to the 1,1-isomer as an alkene. Here is a reference to a 1300 page book title The Chemistry of Alkenes, and I will bet a vast amount that this is not a 1300 page discussion of acyclic C_nH_2n hydrocarbons. So, we now have reliable sources describing DDE as an alkene or olefin. Can we now just accept that the unanimous view of WP:CHEM contributors matches the rest of the chemical world (except for the very restricted IUPAC definition)? EdChem (talk) 14:36, 5 January 2014 (UTC)

Yes, with some relief. Hopefully, this information will also make its way into the article namespace in a suitably prominent position. Andrewa (talk) 04:52, 6 January 2014 (UTC)

H2 appearance

Can someone help me understand? In the reaction under Oxidation H2 just appears out of thin air...

R1-CH=CH-R2 + O3 → R1-CHO + R2-CHO + H2O

Where does it come from? Thnx

That's a pretty confusing equation! The ozonolysis article details the two-stage process of this type of reaction, noting that there is a second step in which one of the three oxygen atoms is extracted from the "R1-CH=CH-R2 + O3" result. But even the ozonolysis article is pretty weak in discussing the second reaction--I left a note on its talkpage:( Depending on the chemical used for the second step, the byproduct containing that third oxygen can vary. If one uses zinc dust, that reduces two H+ (from water or other solvent) to supply those H. I think the generic reaction should probably just have a single neutral oxygen atom in quotes (making the equation balanced and not ascribing any particular identity to the byproduct because the second reactant is not stated). DMacks (talk) 12:40, 29 May 2014 (UTC)

Thnx Levi Gillis (talk) 08:29, 8 June 2014 (UTC)

Suitable?

For a general intro to alkenes, this bit seemed narrow and difficult to understand: "Twisting to a 90° dihedral angle between two of the groups on the carbons requires less energy than the strength of a pi bond, and the bond still holds. The carbons of the double bond become pyramidal, which allows preserving some p orbital alignment—and hence pi bonding. The other two attached groups remain at a larger dihedral angle. This contradicts a common textbook assertion that the two carbons retain their planar nature when twisting, in which case the p orbitals would rotate enough away from each other to be unable to sustain a pi bond. In a 90°-twisted alkene, the p orbitals are only misaligned by 42° and the strain energy is only around 40 kcal/mol. In contrast, a fully broken pi bond has an energetic cost of around 65 kcal/mol.<ref name=":0">{{cite journal|last1=Barrows|first1=Susan E.|last2=Eberlein|first2=Thomas H.|year=2005|title=Understanding Rotation about a C=C Double Bond|journal=J. Chem. Educ.|volume=82|issue=9|pages=1329|bibcode=2005JChEd..82.1329B|doi=10.1021/ed082p1329}}</ref>

Some pyramidal alkenes are stable. For example, trans-cyclooctene is a stable strained alkene and the orbital misalignment is only 19°, despite having a significant dihedral angle of 137° (a planar system has a dihedral angle of 180°) and a degree of pyramidalization of 18°. Even trans-cycloheptene is stable at low temperatures.<ref name=":0" />"

So I took it out and put it in pyramidal alkene.--Smokefoot (talk) 13:33, 8 May 2021 (UTC)

Olefin underserved

Just for the record, it strikes me as messy that the strict sense of alkene is incrementally conflated throughout the lead with the broad group of olefins (possibly cyclic, possibly more than one double bond).

I don't think this usefully serves any explanatory purpose. However, the criteria at Wikipedia does not foreground explanatory virtue, and policy often dictates that we must run along the groove of the established muddle.

Nevertheless, as I see this, from a pure clarity perspective and speaking from way outside the Wikipedia policy fold, this current mishmash sucks. — MaxEnt 23:01, 29 November 2022 (UTC)

I completely agree with you: "olefins" is well defined term according to IUPAC (https://goldbook.iupac.org/terms/view/O04281). It is broader than alkenes. So redirection of the page Olefin to the page Alkene is very strange for me. Canceling this redirection and giving for olefins a definition which is common worldwide among the chemists would be the first step to diminish "this current mishmash sucks" such "Alkene is often used as synonym of olefin..." - why it is important to know that somebody is using the terms incorrectly? Wikipedia should be the place where people may find correct information but not the place where they share their misconceptions with each other. ChemEdit (talk) 22:58, 24 March 2023 (UTC)