Functional groups
Density deformations also reflect
the concepts of pi cloud and aromaticity.
For deformation values over 0.01, contour surfaces of aromatic molecules
are much like those commented in case of double bonds. They only show
the charge concentrations associated to the skeleton of conjugated
double bonds (intermediate between single and double). If the contour
value is lowered to follow the corresponding evolution of the
charge accumulation, a growth of upward and downward protuberancies is
observed in the middle of the double bond. Additional lowering shows
that the protuberancies acquire a shape like two opposite mushrooms. In
aromatic compounds, the tops of adjacent mushrooms tend to
join, forming a sandwich cloud that encloses the deformations of
the internal skeleton. The following pictures show the evolution of
charge accumulation in case of benzene.
Two views (left and right plates)with only positive contours have been
chosen for a better understanding.
