Synthesis, crystal structure and determination of the pK a value of 2,6-dimethoxycyclohexa-2,5-diene-1,4-dione 1-[2-(quinolin-8-yl)hydrazone].

The azo-coupling reaction between 8-aminoquinoline and 3,5-dimethoxyphenol produces 2,6-dimethoxycyclohexa-2,5-diene-1,4-dione 1-[2-(quinolin-8-yl)hydrazone], C 17 H 15 N 3 O 3 . Crystallization from methanol and strong alkaline solutions produced nonsolvated and solvated crystals, respectively. The crystal structure analysis and 1 H NMR spectroscopy studies revealed that the compound exists only as the hydrazone form. A UV-Vis spectroscopic titration study revealed that the hydrazone compound has a relatively high pK a value of 10.0.