Cocrystallization of two tautomers: 4‐(1‐{[4‐(dimethylamino)benzylidene]hydrazono}ethyl)benzene‐1,3‐diol and 6‐[(E)‐1‐{[4‐(dimethylamino)benzylidene]hydrazino}ethylidene]‐3‐hydroxycyclohexa‐2,4‐dien‐1‐one (1/1)

Two different tautomeric forms of a new Schiff base, C₁₇H₁₉N₃O₂·C₁₇H₁₉N₃O₂, are present in the crystal in a 1:1 ratio, namely the enol–imine form 4‐(1‐{4‐(dimethylamino)benzylidene]hydrazono}ethyl)benzene‐1,3‐diol and the keto–amine form 6‐(E)‐1‐{4‐(dimethylamino)benzylidene]hydrazino}ethylidene]‐3‐hydroxycyclohexa‐2,4‐dien‐1‐one. The tautomers are formed by proton transfer between the hydroxy O atom and the imine N atom and are hydrogen bonded to each other to form a one‐dimensional zigzag chain along the crystallographic b axis via intermolecular hydrogen bonds.