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sulphenic_samu

Member

Registered: 2024-07-30

Posts: 3

Fukui and Dual descriptor error with nitro compounds

Hi, Dr. Tian Lu

I've been working with Fukui functions and Dual Descriptor calculation using Multiwfn as described in the section 4.22.1 of the Manual. I've replicated the example with phenol from scratch and everything works fine.

However, when I try to use nitro compounds, I get strange results regarding this particular nitro group, as both oxygen atoms (in the example image, O19 and O20) have very high positive values in the Dual Descriptor, indicating that they are electrophilic---which contradicts chemical intuition as they have a delocalized negative charge---and also with the carbon atoms that integrate the aromatic ring at which nitro group is bonded.

At this point I've tried many functionals and basis sets (B3LYP/6-31++G ; wB97XDD/def2TZVP; and some others), but always with the same qualitative results. I've even seen this in some papers already published. I was wondering if there is some sort of consideration on the calculations that I'm not taking into account, as quantum chemistry is not my field of expertise, or if this is completely normal within Fukui functions, or if there is a bug in the Multiwfn program.

Any advice would be awesome

Sincerely yours,
Samuel

Last edited by sulphenic_samu (2024-07-30 10:32:47)

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 2,011

Website

Re: Fukui and Dual descriptor error with nitro compounds

Dear Samuel,

It is normal. You just need to focus on the sites that actually can undergo chemical reactions, while atoms in irrelevant regions should be simply ignored.

The two oxygens in nitro group show electrophilic, it doesn't contradict chemical intuition. The nitro group has large group electronegativity and thus has low chemical potential, so it is easy to accept additional electrons than carbon atoms, as can be seen from the difference between q(N+1) and q(N).

Best,

Tian