8
$\begingroup$

The web page Aromaticity in Graphene and other 2-D Systems begins:

I. Graphene

While the σ-bonding in graphene is assumed to be a rigid honeycomb framework built out of two-center two-electron (2c-2e) C-C σ-bonds, the π-bonding is supposed to be delocalized. However, according to the adaptive natural density partitioning (AdNDP) analysis and the electron sharing indices, graphene is aromatic, but its aromaticity is different from the aromaticity in benzene, coronene, or circumcoronene. Aromaticity in graphene is local with two π-electrons located over every hexagon ring. (emphasis added)

II. BC3 Honeycomb Epitaxial Sheet

[...]

enter image description here


Update: The wording is similar to what is written in Is Graphene Aromatic? Popov, BozhenkoEmail & BoldyrevEmail (2012), Nano Research, 5, (2), pp 117–123 (open access here):

ABSTRACT

We analyze the chemical bonding in graphene using a fragmental approach, the adaptive natural density partitioning method, electron sharing indices, and nucleus-independent chemical shift indices. We prove that graphene is aromatic, but its aromaticity is different from the aromaticity in benzene, coronene, or circumcoronene. Aromaticity in graphene is local with two π-electrons delocalized over every hexagon ring. We believe that the chemical bonding picture developed for graphene will be helpful for understanding chemical bonding in defects such as point defects, single-, double-, and multiple vacancies, carbon adatoms, foreign adatoms, substitutional impurities, and new materials that are derivatives of graphene.

Question: How is the aromaticity in graphene different from the aromaticity in benzene? It is likely that those familliar with the topic will already understand the explanation in the block quote, but is it possible to find a simpler if less accurate way to explain the difference, in a similarly compassionate way to how this answer was extremely helpful to my question about double bonds and chromophores?

$\endgroup$
  • 2
    $\begingroup$ Might not be quite so simple - this "adaptive natural density partitioning (AdNDP) analysis and the electron sharing indices" stuff is very specialised. I've never even heard of them. $\endgroup$ – orthocresol May 13 at 1:00
  • $\begingroup$ @orthocresol the word "simple" never crossed my mind ;-) $\endgroup$ – uhoh May 13 at 1:07
  • 1
    $\begingroup$ I'm skeptical about their conclusions for circumcoronene. $\endgroup$ – A.K. May 13 at 4:26
  • 1
    $\begingroup$ I might be too naive but at the end it means that while in benzene there is a sextet delocalised in a ring, in graphene the delocalisation over the neighbours results in just two pi electrons delocalised but pinned onto a single ring. The other are described by extended orbitals and are those responsible for the in plane electrical conductivity. I am aware that worded this way might even sound trivial. $\endgroup$ – Alchimista May 13 at 9:43
  • 1
    $\begingroup$ You'll probably get some mileage from this wikipedia comment: " In fused aromatics, not all carbon–carbon bonds are necessarily equivalent, as the electrons are not delocalized over the entire molecule. The aromaticity of these molecules can be explained using their orbital picture. Like benzene and other monocyclic aromatic molecules, polycyclics have a cyclic conjugated pi system with p-orbital overlap above and below the plane of the ring." en.wikipedia.org/wiki/… $\endgroup$ – Buck Thorn May 13 at 11:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.