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Is it me, or are the labels for singlet and triplet reversed in the carbene addition to the alkene reaction? The singlet should be the top, concerted, stereospecific reaction, correct? That's what the text implies... Ed Sanville 07:12, 14 January 2006 (UTC)
I think the top one should be the singlet, at least according to the text. (unsigned comment)
Please provide Morrison & Boyd edition on reference. Mine does not have Carbenes on that page! —Preceding unsigned comment added by 69.248.104.103 ( talk) 21:57, 2 December 2007 (UTC)
I think 'further research' remarks like:
should not be in the original text. Probably more groups are studying these systems. -- Dirk Beetstra 08:33, 10 May 2006 (UTC)
I was informed that 'persistent carbenes' (a section in the main article) was a candidate for a seperate article later on (that is, when it was big enough).
Somehow I feel that it might be a good plan to split of a part, but I would then like to suggest to make a seperate article about the N-Heterocyclic Carbenes (and the like). To me the subject/term 'persistent carbene' belongs in this article (because, persistent is a relative measure, for someone studying a compound by NMR, persistent is several minutes, for a laser-spectroscopist, femtoseconds are already long enough). The NHC's, on the other hand, grow into a seperate group of organic molecules (and there are even organometallic analogues, the silylenes and germylenes), with their own chemistry, and they get extensively used nowadays in organometallic chemistry as ligands. I'd like to hear some pro's and con's before starting to move things around.
By the way, I noticed that there is already an article Transition metal carbene complex (I don't know if I would search it there ..). This one might also be taken into consideration in this discussion (I'll make a link from the talk-page of that page). Dirk Beetstra 21:35, 11 May 2006 (UTC)
Please use the Edit summary field to document what changes you are making. A stream of blank-summary changes from an anon-IP is a common sign of vandalism...help your worthwhile changes get the respect they deserve:) Which leads me to my other suggestion: if you're going to be doing a log of Wiki editing, consider creating an account and log in so that edits are associated with a specific editor instead of an IP. Multiple editors could have the same IP and any given editor might use several different IPs. DMacks 16:26, 11 August 2006 (UTC)
Improve the difference between singlet and triplet carbene and their hybradization concept also Uzmansaab ( talk) 18:04, 11 March 2017 (UTC)
In the section on bonding it is stated this is the ground state for carbenes. And than a series of exceptions is mentioned. To what part of the statement are they exceptions? Are they
The text suggests at least singlet, but what about the spacial aspect? T.vanschaik ( talk) 06:47, 23 March 2012 (UTC)
141.201.165.33 commented out a sentence saying that it didn't make sense and wasn't in the source see diff, to avoid any further reverts, etc. I'm leaving these quotes from the paper:
"in accord with Si's electronegativity, these carbenes exhibit the largest Te values [...] the dependence of Te on the choice of β-substituents is the least pronounced in the series of silyl carbenes"
"In searching for electronically stabilized triplet ground state carbenes, one should thus focus on silyl carbenes. Furthermore, SiF, SiO, and SiCl substitution provides exceptional kinetic stability toward homolysis and rearrangement. While 3C(SiF3)2 should be the global minimum on the PES of respective stoichiometry, sterically demanding siloxy-substituents appear to be the most promising to facilitate kinetic stability toward inter- and intramolecular reactions." Tomásdearg92 ( talk) 05:08, 30 October 2013 (UTC)
Hi Tomásdearg92, the group electronegativity of -SiF3 is around 3.5, so its almost as eletronegative as fluorine (EN = 4, both on th Pauling scale). Si itself is of course more electropositive then C, true. But that is not a matter of debate here. If you read the text carefully, you will realize that it was stated nowhere there that -SiF3 substitution leads to stable triplett carbened because of its high electropositivity! -SiF3 supports stable triplett carbenes (for kinetic reasons) and Si functions in general are more electropositive than homolgous C functions and electropositive substituents may stabilize triplett carbenes. That might be all true. But its is certainly not true that -SiF3 is a strongly electropositive substituent and it is also not true that SiF3 stabilizes triplett carbenes due to its electropositivity. And if you read careful enough you find that this is stated nowhere in your reference. The passge in the article is wrong and very confusing, and the lonely primary literature reference might not be the best choice for referenceing an encyclopedian article, I would suggest. Secondary literature would be strongly preferred. Cheers --
141.201.165.33 (
talk)
12:52, 4 November 2013 (UTC)
Isn't a carbene a radical since it has two unpaired valence electrons? Worth pointing out in lede section. 89.217.27.113 ( talk) 23:27, 28 January 2015 (UTC)