The monohydrolysis of nine naphthoquinone bisketals and nine benzoquinone bisketals has been studied. In the acetamido, bromo, methyl, methoxy, and thiomethyl monosubstituted compounds, hydrolysis occurs at the ketal more distant from the substituent. The regiochemistry is nearly exclusive in the naphthoquinone series and is highly selective in the benzoquinone series. For disubstituted benzoquinone and ...