Hydrogen bonding and thus delocalization further increases ring aromaticity. In contrast, molecular orbital theory views aromaticity as delocalization of the -electrons. The favorability of delocalization is, in turn, interpreted as evidence for aromaticity. Spherical aromaticity is aromaticity that occurs in fullerenes. In cyclic molecules, conjugation can lead to aromaticity. With respect to the diamagnetic ring current criterion for aromaticity this cyclophane is still aromatic. Stacking, a chemical property of molecules with aromaticity, is seen occurring between phenolic molecules. Other reports suggest that the aromaticity (and planarity) can vary between arsole derivatives. The stability gain from aromaticity is estimated to be half that of naphthalene. Natural Bond Orbital (NBO) analysis suggests weak aromaticity in borazine. In dearomatization reactions the aromaticity of the reactant is permanently lost. Because of the aromaticity, the molecule is flat and lacks discrete double bonds. Measures of water purity often rely on measuring turbidity, not aromaticity. The aromaticity of these molecules can be explained using their orbital picture. They are of some academic interest in relation to aromaticity and isomerisation mechanisms.