Which is the best solvent for fluorene – water, methyl alcohol, or toluene?
A lot of people will make the mistake of choosing toluene, thinking that it is the “best” solvent because it dissolves the most fluorene. You are correct that this is the wrong choice because fluorene is too soluble in toluene to perform a good crystallization. But why? The answer is in questions about solvation always comes down to the polarity of the bonds in the solvent and solute and the intermolecular forces that each molecule experiences. Fluorene and toluene have the same types of bonding: aromatic π systems and non-aromatic C–C and C–H bonds, so fluorene molecules experience roughly equal attraction to toluene molecules as they do to other fluorene molecules and fluorene is highly soluble in toluene. Now consider the bonding in methanol and water and compare this to fluorene. Water contains only highly polar H—O bonds and the lone pairs on oxygen allow for extensive hydrogen bonding and a strong attraction between water and other polar molecules and ions. Like water, methanol i
