Colorimetric Determination of Biphenyl Based on the Janovsky Reaction

The quantitatively nitrated product of biphenyl with potassium nitrate and sulfuic acid shows a characteristic red-purple color on reaction with isobutyl alcohol, acetone and alkali; this is the Janovsky reaction. The color reaction was sensitive, and the absorbance at 550 nm obeyed Beer’s law at biphenyl concentrations between 2 and 40 μg 3.5 ml of the reaction mixture. A procedure suitable for routine use is proposed.

The nitro-compound derived from biphenyl was identified as 2,2′,4,4′-tetranitrobiphenyl by Rf on TLC, as well as by mixed melting point, IR and mass spectroscopy.