We have studied theoretically the rate determining steps of reactions of benzene with permanganate, perchlorate, ozone and dioxygen in the gas phase and aqueous solution as well as phenol and dichlorophenol in protonated and unprotonated forms in aqueous solution. Kinetic isotope effects were then calculated for all carbon atoms and based on their values isotopic fractionation factors corresponding to compound specific isotopic analysis have been evaluated. The influence of the oxidant, substituents, environment and protonation on the isotopic fractionation factors has been analyzed.