Comments on: Molecular Orbitals of The Allyl Cation, Allyl Radical, and Allyl Anion

By: Sean C

Sean C — Sat, 10 Feb 2024 13:58:51 +0000

Extending the logic from note 2: when looking at pentadienyl cation. The electrons in pi-1 have no nodes so they delocalized along the entire chain. In pi-2, we have a pair with one node. Would we say that the electrons are delocalized at c1-c2 OR c4-c5? I guess I am asking if the nodes tell us where the electrons are delocalized?

By: James Ashenhurst

James Ashenhurst — Fri, 25 Aug 2023 14:33:08 +0000

In reply to Vernika Gupta. The first shows you the three energy levels and the phases of the p-orbitals within them. The second fills it with electrons. It's this second factor that ultimately determines which of the three pi molecular orbitals is the highest-occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO).

By: Vernika Gupta

Vernika Gupta — Fri, 25 Aug 2023 10:05:34 +0000

I am confused between the MO diagram of allyl system using atomic p orbitals given first and the full MO diagram given in the last.

By: James Ashenhurst

James Ashenhurst — Sun, 23 Oct 2022 11:44:12 +0000

In reply to Moe. It is difficult to compare the relative stabilities of anions, cations, and radicals. It really is like comparing apples, oranges, and bananas. It's much easier to compare anions relative to other anions, cations to other cations, etc.

By: James Ashenhurst

James Ashenhurst — Sun, 23 Oct 2022 11:44:03 +0000

In reply to Rahul Krishnakumar. It is difficult to compare the relative stabilities of anions, cations, and radicals. It really is like comparing apples, oranges, and bananas. It's much easier to compare anions relative to other anions, cations to other cations, etc.

By: James Ashenhurst

James Ashenhurst — Sun, 23 Oct 2022 11:41:32 +0000

In reply to George. Right. The lone pair would be in an sp3 orbital, and the overlap of the sp3 orbtial with the adjacent p-orbitals isn't as good. Re-hybridization of the sp3 orbital to p gives a lower energy structure.

By: George

George — Fri, 01 Jan 2021 08:09:41 +0000

This website is quickly becoming one of my favourites. I love seeing complex subjects like this explained so effectively!

I’m assuming I’m missing something obvious as I wasn’t able to find this question posed anywhere else, so I’m hoping a kind reader might be able to help me here.

I was under the impression that to find the hybridisation of an atom, you could use the steric number (# of sigma bonds + # of lone pairs). If we do this for the allyl anion though, we’d get a SN of 4 (1 LP and 3 sigma bonds), corresponding to sp3 hybridisation. But if this were the case, we wouldn’t have the available p orbital to give us the resonance structure…

By: Moe

Moe — Sat, 05 Dec 2020 21:57:26 +0000

Out of the cation, radical, and anion allylic carbons, which is the most stable in terms of energy? I’ve been looking around, but I can’t quite seem to find the answer ton this.

By: Bipin Sunar

Bipin Sunar — Sun, 12 Jul 2020 18:59:24 +0000

I meant C1 and C3 by end carbon atoms sir,sorry for mistyping

By: Bipin Sunar

Bipin Sunar — Sun, 12 Jul 2020 18:55:29 +0000

sir,i have a question for you(may seem silly though)..In the allyl anion or radical system,it is said that two electrons in anion and one electron in radical respectively(in reference to non-bonding orbitals) is shared by end carbon atoms (C2 and C3)..How is it possible if there is node in the middle carbon between them?please clear my doubt sir