Talk:Alkene

message: 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)
thread_title: Confused introduction

message: 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)
thread_title:  Saturation link 

message: Just out of curiousity.  -x42bn6 Talk 10:31, 4 September 2005 (UTC)
replies: text: Only non-cyclic (acyclic, meaning having no rings of atoms) alkenes with one double bond have the general formula CnH2n.  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)
thread_title:  If an alcohol is named R-OH (or ROH) (at least for 1°) and an aldehyde R-CHO, what is an alkene named? 

message: 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)
thread_title:  Removed Gayvene 

message: 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)
thread_title: Non IUPAC Nomenclature

message: 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)
thread_title:  merge [[Carbon-carbon double bond]] into [[alkene]] 

message: ...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)
thread_title:  You shouldnt call it ethylene...it's ethene. 

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

text: 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)
thread_title:  alternative to E and Z notation 

message: 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)
replies: text: 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)
thread_title:  prefix / infix numbers 

message: 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)
thread_title:  Same style of first paragraph as "alkane" page? 

message: 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)
thread_title:  Table needed 

message: 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)
replies: text: 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)
replies: text:  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)
thread_title:  New Picture? 

message: 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)
thread_title: Sources

message: 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 CnH2n (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 CnH2n. Surely?
OK so far? Andrewa (talk) 05:30, 31 December 2013 (UTC)
replies: text: 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)
replies: text: 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)
thread_title: MOS

message: ... 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 CnH2n 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)
replies: text: 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)
thread_title: Dichlorodifluoroethylene is an olefin

message: 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)
replies: text: Thnx Levi Gillis (talk) 08:29, 8 June 2014 (UTC)
thread_title:  H2 appearance 

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

message: 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)
replies: text: 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)
thread_title:  Olefin underserved