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and third an alkane chain with hydogen removed at both terminal ends : ethylene, propylene, etc.
This third meaning, in a sense, can be thought of as a subset of the second case, since both terminal methyls would become radicals with the removal of a hydrogen. I'm a bit confused by whether or not a -ch2- in the middle of a straight or cyclic alkane is a methylene, or only a methylene after it is removed from the chain :ch2, where the : represents free electrons.—Preceding unsigned comment added by 22.214.171.124 (talk • contribs)
Yes, "methylene" is commonly used to refer to a -CH2- group within an alkane chain. --Ed (Edgar181) 14:14, 17 October 2007 (UTC)
It's not commonly used to refer the group within an alkane chain, but within some other "chain", as in MDMA (3,4-methylenedioxy-N-methylamphetamine) where it's between two oxygen atoms. If it were in an alkane chain, then there would be no reason to refer to it at all! What I would like to know is why methylene blue is called that, since it doesn't have any methylene group! Eric Kvaalen (talk) 16:45, 9 August 2012 (UTC)
I checked most of the articles that used the terms methylene or methylenes. About 70% used it for a bridging -CH2- group; about 20% used it for a bridging -CH2- in an open chain, including alkanes. The side/terminal =CH2 was intended in about 20% of the cases, the free molecule :CH2 perhaps 10%. --Jorge Stolfi (talk) 03:54, 29 January 2013 (UTC).
This article is essentially a disambiguation page in a non-standard format, and must be turned into one.
By the way, article titles should be singular, even when the term can have several meanings. To make things worse, there is an article called methylene, specific for one of the three meanings (the free radical molecule); but that article it is not linked from this article! Having both articles is very confusing to the reader. --Jorge Stolfi (talk) 23:16, 26 January 2013 (UTC)
Well, my comment above was written yesterday. Now I have already moved things around a bit and it is no longer pertinent.
As things are now, the methylene article is all about *one* meaning of the term, the free radical. (Perhaps it should be renamed to something more specific, but what? Carbene, its other established name, is already taken by the carbene family. Perhaps "methylene (free radical)"?) The other two meanings, methylene group (=CH2) and methylene bridge (-CH2-) are quite distinct from each other and from the free radical meaning. Each deserves, and now has, its own article. (The last two are rather short now but there is plenty that can be said about them, such as bond angles and strengths, spectroscopy, reactions, etc..)
Yes, the methylene (free radical) article mentions the other two meanings; but only *briefly*, to alert editors who may link to the wrong one. It does not "cover" them to any useful extent.
On the other hand, there is nothing much that can be said about the three concepts together, except disambiguate them.
In conlcusion: the current arrangement (3 separate articles, a disamb page, and some redirects) seems to be the best of the alternatives I can think of; and methylenes should redirect to the disamb page, not to methylene. Makes sense?
All the best, --Jorge Stolfi (talk) 06:51, 28 January 2013 (UTC)
Methene redirects here. I believe that Methene is now the preferred name for Methylene. See also Ethene. Biscuittin (talk) 19:56, 25 November 2014 (UTC)
I don't know about that, but I definitely agree with the proposed merges. bd2412T 21:00, 25 November 2014 (UTC)
I strongly disagree, a disambiguation page is needed as the name 'methylene' has several alternate uses. Plasmic Physics (talk) 21:27, 25 November 2014 (UTC)
Aside from the archaic/obsolete uses, are all of these variations of CH
2? bd2412T 21:55, 25 November 2014 (UTC)
As the pages lists, besides the obsolete and archaic uses (which are perfectly viable as alternate uses), it can be used to refer to the chemical moieties, or the chemical compound. Plasmic Physics (talk) 00:11, 26 November 2014 (UTC)
Wouldn't it be nice to use this page to explain the differences between the different formulations of CH
2 that are known as Methylene? bd2412T 18:01, 26 November 2014 (UTC)
MOS:DABENTRY allows for minimal explanation. The concept could be explained in much greater detail, which would give the reader a richer experience of understanding the scientific and historical relationship between the terms commonly used to identify variations on a chemical theme. bd2412T 01:00, 27 November 2014 (UTC)
The articles exist for an in depth explanation. Just trust me on this. Plasmic Physics (talk) 02:41, 27 November 2014 (UTC)
Oppose: Nobody calls it methene. Having everything on one page has been tried in the past (Methylene group and Methylene bridge were once one page) but it just didn't work; despite having the same name the chemistries of the various compound were just too different and the page became fragmented. Project Osprey (talk) 09:53, 5 December 2014 (UTC)
@Plasmic Physics:, @Project Osprey:, a lot of links seem to be made that point to this page. Please check these incoming links regularly and make sure that they are fixed to point to their intended targets. Cheers! bd2412T 14:33, 5 December 2014 (UTC)