In this work we used DFT B3LYP/6-31G*(d) to study the stoichiometric reaction between the β-himachalene and dichlorocarbene. We have shown that β-himachalene behaves as a nucleophile, while dichlorocarbene behaves as an electrophile; and that β-himachalene reacts with an equivalent quantity of dichlorocarbene to produce only one product (referred to here as P1). P1 is formed at the only α side of the C6=C7 double bond of β-himachalene this regioselectivity conformed by Parr and Zeroual functions. This reaction is exothermic, stereoselective, chemospecific, and is controlled by charge transfer. We are studying too the mechanism and the stereoselectivity of epoxydation of the product P1 by the meta-chloro-per-benzoic acid, the analysis of the surface of potential energy and the IRC calculation shows that this reaction follows a concerted mechanism asynchronous and that the mechanism of this epoxydation is an electrophile attack of the link low polarized Oxygene-Oxygene on the orbital π of the product P1. In this mechanism, the proton of the peracide is transferred from its oxygen that will form the epoxide, to give MCBA. The epoxide form is the result of an syn addition on the alkene P1 this addition is stereospecifique. We find from this study that the origin of this stereoselectivite is due to the difference of the transition state energy, and that the product P2 is kinetically favored by report to the product P3 is in good agreement with experiment.
