In this work, the mechanism of the reaction between desflurane (CF3CHFOCHF2) and Cl was investigated at the CCSD(T)/CBS level of theory. The reaction between an anaesthetic and Cl is described by a three-step mechanism. The reaction channel where the hydrogen atom from the CHF group is abstracted is the most favorable. The CCSD(T)/CBS electronic energy calculated for this channel is 0.47 kcal mol(-1). The CCSD(T)/CBS enthalpies of three channels range between 1.17 and 5.25 kcal mol(-1), which indicates the endothermic processes. All the steps of the reaction studied are discussed in details. (C) 2012 Elsevier B.V. All rights reserved.