Anthrols (sometimes called anthranols) are the hydroxylated derivatives of anthracene. For the monohydroxo derivatives, three isomers are possible: 1-anthrol, 2-anthrol, and 9-anthrol. The latter exists as a minor tautomer of 9-anthrone.
^Ośmiałowski, Borys; Raczyńska, Ewa D.; Krygowski, Tadeusz M. (2006). "Tautomeric Equilibria and Pi Electron Delocalization for Some Monohydroxyarenes Quantum Chemical Studies". The Journal of Organic Chemistry. 71 (10): 3727–3736. doi:10.1021/jo052615q. PMID16674042.