text: Fusing angular rings around a benzene moiety leads to an increase in stability. The Clar structure of anthracene, for instance, has only one π-sextet, but moving one ring into the angular position phenanthrene is obtained, the Clar structure of which carries two circles instead of one – notice that this molecule can be thought of as a benzene moiety with two fused rings; a third ring can be fused to obtain triphenylene, with three aromatic π-sextets in its Clar structure. The chemical stability of these molecules is greatly influenced by the degree of aromaticity of their Clar structures. As a result, while anthracene reacts with maleic acid, phenanthrene does not, and triphenylene is the most stable species of these three.