Isolation of bright blue fluorescent substances from sonochemical hydroxylation of methyl p-cyanobenzoate

Sonochemical hydroxylation of methyl p-cyanobenzoate (la) in water gave a b right blue fluorescence, which are mainly ascribed to three new fluorescent compounds, 3-hydroxy, 2,3- and 2,5-dihydroxy derivatives of la. Other benz enes substituted with electron-withdrawing groups also gave similar fluores cence from their hydroxylated derivatives. Among the fluorescence substance s, methyl 2,5-dihydroxybenzoate was supposed to be applicable for a fluores cent chemosensor.