Talk:Carbanion

Wording
"A compound is a carbon acid if deprotonation results in loss of a proton from a carbon atom." - with my very limited knowledge of chemistry this sentence sounds like nuclear reaction (atom losing proton), which is probably not what it's supposed to be. — Preceding unsigned comment added by 121.219.113.230 (talk) 03:44, 2 February 2018 (UTC)

the 'proton' referred to is actually the hydrogen cation which is nothing but a proton since it has lost its only proton. The alchemist reborn (talk) 13:35, 23 December 2018 (UTC)

corrigendum: in the previous sentence i meant "it has lost its only electron" The alchemist reborn (talk) 13:39, 23 December 2018 (UTC)

Diphenylmethyl
The text says diphenylmethyl; the diagram shows triphenylmethyl. Which is correct? —Preceding unsigned comment added by 68.107.60.161 (talk) 03:10, 17 July 2009 (UTC)


 * Both, the research cited involved both diphenyl- and triphenylmethane but the image shows the triphenylmethyl carbanion. The text is modified accordingly. V8rik (talk) 19:58, 17 July 2009 (UTC)

Trigonal planar?
After the recent change (kudos for all the work, by the way), it now says that the carbanion exists in a "Trigonal planar". How is that? The trigonal planar geometry is for sp2 hybridized atoms, unlike a carbanion, which is sp3, which three substituents, and the pair of electrons filling the fourth sp3 orbital. I've changed it to tetrahedron. okedem 21:26, 1 December 2006 (UTC)


 * Thanks for the correction: I checked with March and he says: Trigonal pyramid (chemistry) (like it was in the text). My confusion started with re-reading the Olmstead article where it speaks of a planar geometry, but I was not paying attention. What to do: switch back to Trigonal pyramid (chemistry) like it was or make it Tetrahedral molecular geometry ? V8rik 21:41, 1 December 2006 (UTC)


 * I think trigonal pyramid would be more appropriate, as this is closer to this case - it's just like ammonia, which is mentioned in that article. The tetrahedral article talks about four substituents, which would be confusing, since you would need to count the lone pair as a substituent.
 * You created some more work for me, you know? This article is on my watchlist because I translated it to Hebrew. Now I have to translate some more... okedem 22:06, 1 December 2006 (UTC)


 * switched to Trigonal pyramid (chemistry). Happy translating! V8rik 22:35, 1 December 2006 (UTC)

This is not what the IUPAC says. Please see my comment below on the status of CN- as a carbanion. Furthermore, what about acetylide? Unambiguously carbanionic and sp hybridized. I changed the definition to reflect the IUPAC gold book definition Ymwang42 (talk) 15:24, 30 July 2016 (UTC)

Cyanide
Cyanide's a carbanion too? Or is there more favoured resonance forms? --83.100.0.5 (talk) 14:49, 7 June 2009 (UTC)

IUPAC gold book: "Generic name for anions containing an even number of electrons and having an unshared pair of electrons on a tervalent carbon atom (e.g. Cl3C− or HC≡C−) or — if the ion is mesomeric (see mesomerism) — having at least one significant contributing structure with an unshared pair of electrons on a tervalent carbon atom"

Thus if it has a full octet and has either a full formal -'ve charge on carbon in one of its resonance structures, it's a carbanion. I think there is some room for ambiguity, though. For instance, it is unclear whether a enolate counts. Arguably, if it's highly covalent, like a boron enolate, it is not a carbanion because it is not an anion. However, what about borderline cases like lithium enolates, where there's a high degree of ionic character, but still has a covalent bond? Ymwang42 (talk) 15:21, 30 July 2016 (UTC)

Carborane acid is a carbon acid?!
The acid proton of the carborane acid is attached to chlorine (more precisely, bridging two chlorines) rather than to carbon (JACS article: 10.1021/ja058581l). The H attached to C, as far as I'm aware, is not particularly acidic and is generally deprotonated with BuLi in many cases.

Therefore, it is not a carbon acid. If someone can provide a source for the DMSO pKa value, it is probably worth keeping on the table, to show a lower extreme for pKa values (in DMSO -- I've seen aqueous pKa's that are lower).

Ymwang42 (talk) 15:10, 30 July 2016 (UTC)

pKa table
There were two major problems with the pKa table:

-- The use of H2O pKa values in place of DMSO values, despite the title of the table. I changed the numbers to reflect DMSO values in all cases.

-- Internal inconsistency in the highest pKa values. This is tricky, since pKa values at the high end are notoriously uncertain, and even Bordwell has revised his estimations numerous times. However, for this table to be of any use, the values need to be (somewhat) internally consistent and chemically reasonable. For instance, anisole (ortho C-H) is certainly more acidic than benzene (induction), while cyclopentane is certainly less acidic than methane (secondary vs. primary), contrary to earlier versions of this table. I have fixed what I can, but if others know more authoritative values, please change them!

Ymwang42 (talk) 16:53, 2 August 2016 (UTC)

Mixed up values in pKa table
Hey, i think the values for cyclopentane and methane are mixed up. They should be the other way around, cyclopentane is least acidic (highest pKa) according to the inductive effect and the source: http://www.chem.wisc.edu/areas/reich/pkatable/

Go to the hydrocarbon tab and you will see!

84.210.215.47 (talk) 12:51, 11 October 2016 (UTC)

Nevermind I was wrong, it is correct as it stands now! 84.210.215.47 (talk) 13:34, 11 October 2016 (UTC)

Carey and Sundberg
I highly recommend editors to consider consulting the two books produced by Francis A. Carey and Richard J. Sundberg about Advanced Organic Chemsitry. The two books are split into two parts "Part A: Structure and Mechanisms" and "Part B: Reactions and Synthesis". Zyvov 02:10, 28 October 2016 (UTC) — Preceding unsigned comment added by Zyvov (talk • contribs)

External links modified
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