coronene

It occurs naturally as the mineral carpathite, which is characterized by flakes of pure coronene embedded in sedimentary rock. This mineral may result from ancient hydrothermal vent activity.[2][3]

Coronene is produced in the petroleum refining process of hydrocracking, where it can dimerize to a fifteen ring PAH, trivially named "dicoronylene" (formally named benzo[10,11]phenanthro[2',3',4',5',6':4,5,6,7]chryseno[1,2,3-bc]coronene or benzo[1,2,3-bc:4,5,6-b'c']dicoronene). Coronene has been seen on the surface of Titan[citation needed] (Saturn's moon). It can cause DNA damage in mammals.[citation needed]

The compound is of theoretical interest to organic chemists because of its aromaticity. It can be described by 20 resonance structures or by a set of three mobile Clar sextets. In the Clar sextet case, the most stable structure for coronene has only the three isolated outer sextets as fully aromatic although superaromaticity would still be possible when these sextets are able to migrate into the next ring.

According to in silico calculations on the following hypothetical isodesmic reactions, coronene has a somewhat higher resonance energy per pi electron (REPE) than benzene [4]: coronene + 24 * ethylene → 18 * butadiene REPE 4.2 kcal/mol (17.6 kJ/mol) benzene + 3 * ethylene → 3 * butadiene REPE 3.6 kcal/mol (15 kJ/mol) On the other hand the perimeter C–C bond length alternations are larger than in benzene.