The structure and complexation equilibria of copper(II) with 4-(\bar 4-nitrophenyl)azo-2-phenyloxazolin-5-one

Summary A spectrophotometric method for determining trace amounts of Cu^II using 4-( -nitro-phenyl)azo-2-phenyloxazolin-5-one has been devised. With this reagent, Cu^II forms a stable chelate, in the 6–9.5 pH range which obeys Beer's law at 555 nm with a molar absorptivity of 4.50 × 10³ mol^–1 cm². Other copper-group metals do not interfere with this process. The stoichiometry and stability constant of the copper chelate has been determined using spectrophotometric, potentiometric and conductometric methods.