3-(para-Substituted phenylhydrazo)pentane-2,4-diones: Physicochemical and solvatochromic properties

► New para-Br and -C(O)CH3 substituted phenylhydrazo derivatives of pentane-2,4-dione were synthesized and fully characterized. ► 3-(4-Acetylphenylhydrazo)pentane-2,4-dione crystallizes from ethanol in the hydrazo form, as shown by X-ray analysis. ► They exhibit specific solvent-dependent absorptions at 236-537 nm that made them efficient solvatochromophores. ► They can be used for qualitative determinations of aprotic solvents in protic ones.