What are Organic Solids

Molecules or their ions (molecular ions or radical ions) from the area of organic chemistry, i.e. expressed simply, compounds with carbon atoms as their essential 

Copyright 2007 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim 

The pz orbitals of neighbouring atoms overlap. This leads to an additional bond, the so called tt bond, and to a delocalised density of electrons above and below the plane of the molecule. This is the nodal plane for the jr-electron density. 

Fig- 1.3 Above the overall distribution of the jr electrons in the electronic ground state of the anthracene molecule, C14H10. The boundary was chosen so that ca. 90% of the total electron density was included. Centre the distribution of a jr electron in the highest occupied molecular orbital (HOMO). Below the distribution of a jr electron in the lowest unoccupied molecular orbital (LUMO). The figure was kindly provided by M. Mehring. 

These intermolecular forces which hold the molecules together in the solid state are in general weak in molecular crystals in comparison to the intramolecular forces. Molecular crystals derive their name from the fact that the molecules as such remain intact within the crystals and thus directly determine the physical 

---