Benzene, with formula C₆H₆ is a cyclic planar molecule in which six methyne (C-H) groups are linked by sp² bonds. The hydrogen atoms (black spheres in the figure) point outwards the six-membered ring defined by the carbon atoms. The C-C distance is 0.140 nm and the C-H distance is 0.108 nm.

Aniline is a derivative of bezene where a NH₂ group is substituted for a H atom. It is a simple aromatic amine with chemical formula C₆H₅NH₂. Among many other applications, anniline is involved in the production process of dyes and artificial pigments. In the context of electrochromism, anniline is widely used in the form of polyaniline polymers.