# Drawing bonds and delocalised electrons in condensed formulae

The $$\LaTeX$$ mhchem package provides commands for drawing bonds within condensed chemical formulae. Some of them have a clear allocation to covalent bonds while others have not. Single, double, and triple bonds can be drawn in a very easy and convenient way and, of course, delocalised $$\pi$$-electrons in condensed formulae like $$\text{H}_2\text{C}=\text{CH}-\text{CH}=\text{CH}_2\;\;$$of 1,3-butadiene can easily be drawn by dashed lines, too (see image below). However, the following four general formulae remain incomprehensible with respect to their application.

Does anyone know semi-structural (condensed) formulae of chemical compounds in which such chemical bonds (dashed lines/arrows) are drawn? Or are they just a "nice to have feature" provided by the package?