(2Z)-1-(4-chlorophenyl)-2-[(3E)-3-[2-(4-chlorophenyl)-2-oxoethylidene]-3,4dihydro quinoxalin- 2 (1H)-ylidene]ethanone (Q4) was tested as inhibitor for the corrosion of copper in 2M HNO3 using gravimetric method at 303 – 343 K. The inhibitor (Q4) showed about 90% inhibition efficiency (E (%)) at an optimum concentration of 10-3M. The inhibition efficiency increases with increase in inhibitor concentration but decrease with rise in temperature. Various parameters (Ea, DG° ads, Kads) for adsorption reveal a strong interaction between inhibitor and copper surface. The negative values of DG° ads indicate the spontaneous adsorption of the inhibitor on copper surface. Kinetic parameters activation such as Ea , DHa° , a DS° and pre-exponential factor have been calculated and discussed. Further, theoretical calculations were carried out and relations between computed parameters and experimental inhibition efficiency were discussed.