In the present study we were interested in determined tensioning of screen σ and the chemical shifts δ of carbon (13C) relative to the epoxy-himachlene in the presence of a Lewis acid using GIAO (Gauge Independent Atomic Orbital), GTSB (Continuous Set of Gauge Transformations) and Individual Gauges for Atoms in Molecules IGAIM a slight variation on the GTSB method) methods. Theoretical calculations were performed using the method of the density functional theory DFT/B3LYP which is implanted in the program Gaussian 09 with a 6-31G (d,p) basis set.
Firstly, we obtained the following results for the reagent R1: [2α.3α-epoxy-cis- himachal-7.13-ene] showed that the GIAO method is the most reliable in the first place. Secondly, we calculated the chemical shifts of the reaction products: P1[(1S.3R.7S)-(3.11.11)- trimethyltricyclo [5.4 (3.7)] dodecan-2-one] and compound: P2[(1S.2S.3R.6R)-(3.10.10)-trimethyltricyclo [5.4.4] dodec-4-en-2- ol] formed from the epoxy-himachalene (R1) in the presence of the Lewis acid.
This theoretical study was also conducted using the method GIAO and different bases of atomic orbitals: 6-31G, 6-311G, 6-31G (d.p), 6-31G (2d.p), 6-31G(d), 6-311G(d.2p). The obtained theoretical calculations results show a perfect correlation between the experimental and theoretical results with the basis 6-31G (d.p).