My teacher had once told me that graphite was just an insanely huge polymer of benzene (Those weren't his exact words but the gist). Today While we were studying aromaticity in organic compounds we steadily advanced from benzene to napthalene the annulenes and so on. What really stuck me was how as the number of benzene rings increased the stuff tended towards graphite (atleast thats what the structure seemed to indicate). So the main question is why isn't graphite aromatic if its just a big collection of benzene molecules
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Graphite/graphene is aromatic. The first image below is a common crystallographic representation of graphite and does not account for covalent bonding. The second one shows the molecular structure of graphite as a kekule representation. Graphite is made of planar sheets of carbon atoms in 6-atoms rings with conjugated double bonds. This also satisfies the 4n+2 π electrons criteria needed within the aromatic ring for graphite to be aromatic. This aromaticity is why graphite is not only stable to high temperatures but also a more thermodynamically favorable allotrope than diamond under typical conditions.
Crystallogrphic Representation of Graphite.
Kekule Representation of Graphite.
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+1(possibly helpful ion.chem.usu.edu/~boldyrev/graphene.php) and so I've just asked How is the aromaticity in graphene different from the aromaticity in benzene? $\endgroup$– uhohMay 13, 2019 at 0:57 -
$\begingroup$ +1. To OP: I copy a comment from the thread mentioned by uhoh. Indeed related arguments. Benzene is one cycle, no other cores have the same aromaticity. "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." Replace graphene with graphite. $\endgroup$ Mar 14, 2021 at 10:20
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$\begingroup$ @Alchimista "... the delocalisation over the neighbours results in just two pi electrons delocalised but pinned onto a single ring." 1- Does neighbours mean upper & below rings for that ring of graphene? 2- What do you mean by ... pinned onto a single ring? $\endgroup$– ApurviumDec 27, 2022 at 6:04
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$\begingroup$ @apurvium a) read on plane neighbors. Planes do interact, but yet they can "slide" on each other. The interaction, or bond, is less strong between plane (think also of the anisotropic conductivity). b) pinned in the sense that while as benzene has a delocalised sextet, only two remain for each ring of graphite. The third being the one spreading along the sheet as per a) $\endgroup$ Dec 28, 2022 at 8:47