96 страниц. 2010 год. LAP Lambert Academic Publishing In this work, within the DFT framework, the chemical reactivity descriptors are evaluated and they are used to correlate the toxic nature of some Polychlorinated biphenyls. We have used semi- empirical AM1 procedure, to compute the orbital energies (HOMO, LUMO). The Ionization energies and electron affinities are calculated using the Koopmans theorem. The hardness and the electronegativity of the PCBs are calculated using the Parr Pearson formula. The electrophilicity index was calculated using the formula of Parr et al. We have plotted the computed hardness values with the observed pIC value and have found a good correlation.