Comments on: 7 Factors that stabilize negative charge in organic chemistry

By: Franny

Franny — Sun, 01 Jun 2025 07:21:45 +0000

this was really helpful thank you!

By: James Ashenhurst

James Ashenhurst — Thu, 12 Sep 2019 21:12:16 +0000

According to the Evans Pka Table, http://evans.rc.fas.harvard.edu/pdf/evans_pKa_table.pdf , the pKa of triphenylmethane is 31 and the pKa of diphenylmethane is 33. So there’s about a 100 fold increase in stability for the triphenylmethane conjugate base. Why do you think that is?

By: James Ashenhurst

James Ashenhurst — Tue, 21 May 2019 16:46:22 +0000

In reply to Kiara. The pKa of toluene is about 42. The pKa of ethyne is about 25. So the anion on the conjugate base of ethyne is much more stable than the anion in the conjugate base of toluene.

By: Kiara

Kiara — Mon, 24 Sep 2018 03:16:38 +0000

Thanks for the classification,but will anion on ethyne be more stable than a benzylic anion?
(I mean where cases cross each other electronegativity vs resonance.
Resonance is taking place in carbons with sp2 configuration(in case of benzylic anion),
so which would me more stable?

By: James

James — Fri, 20 Apr 2018 19:43:07 +0000

In reply to Ana. It means it's less concentrated; it's spread out over a greater volume.

By: Ana

Ana — Thu, 19 Apr 2018 09:33:49 +0000

More dispersal of charge means what?

By: Narsimhareddy.k

Narsimhareddy.k — Sat, 26 Nov 2016 05:51:21 +0000

Triphenyl methyl carbanion and diphenyl methyl carbanion which is stable why

By: Idan

Idan — Sat, 28 May 2016 09:32:13 +0000

In reply to James. Edit: Noticed that the lone pair on the carbon is localized so it can't be stabilized through delocalization so never mind that last question :). Thanks again.

By: Idan

Idan — Sat, 28 May 2016 09:18:27 +0000

In reply to James. Thank you, I think I am starting to get it. This is analogous to electronegativity since in both cases (higher sp character / electronegativity) the bond is pulled closer towards the nucleus. Would it be right to say that the delocalization of the p orbitals between both atoms in CN(-) also plays a part in stabilizing the negative charge?

By: James

James — Fri, 27 May 2016 17:23:34 +0000

In reply to Idan. The charge is localized in the sp(n) orbitals so the p orbitals in CN(-) are irrelevant to the stability. One way of looking at it is that an sp orbital has a higher effective electronegativity than an sp2, which has high effective electronegativity than an sp3 orbital. The negative charge is held more tightly to the nucleus.