Quantum chemical calculations have been employed to understand the nature of interaction between xanthate and Cu-as part of an ore and Cu-as part of a slag. A semi-empirical parameterized model, (PM3) is used to study ethyl xanthate, propyl xanthate, iso-propyl xanthate, iso-butyl xanthate and amyl xanthate. The total interaction energy, E, is interpreted in terms of the highest occupied molecular orbital (HOMO) energy of the individual collectors with copper ions. The electron density map along with the change in heat of formation, binding energy and dipole-moment, indicate that amyl-xanthate binds to surface of copper ions strongly in comparison to other xanthates. The numerical results obtained with potassium amyl xanthate also support the experimental data on recovery of copper values from a copper ore by flotation. (C) 2011 Elsevier Ltd. All rights reserved.