Computational DFT Study of The 1,3-Dipolar Cycloaddition of (2,6-Difluoro-Phenyl)-Triazomethane to 1-Substituted-1,2,3-Triazole

• Main Authors: Li-Chen Yang, 楊麗蓁
• Other Authors: Shyi-Long Lee
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/03286038658225486666

碩士 === 國立中正大學 === 化學暨生物化學研究所 === 102 === The reaction and mechanism of the (2,6-difluoro-phenyl)-triazomethane to 1-substituted-1,2,3-triazole by 1,3-dipolar cycloaddition (1,3-DC) in the gas phase and the solvent phase have been investigated using DFT methods. The substituted 1,2,3-triazoles can be synthesized using arylazide and 2-chloroacrylonitrile in two steps by the 1,3-dipolar cycloaddition reaction (1,3-DC) and dehydrohalogenation reaction. The 1,3-dipolar cycloaddition reaction is the rate-determining step with the ΔG≠ of 36.1 and 22.1 kcal/mol at the B3LYP/6-31+G(d,p) and M06-2X/6-31+G (d,p) levels, respectively. For the solvent effect, solvent phase calculations were carried out using different solvent, respectively, water (ɛ=78.36), ethanol (ɛ=24.85), dimethylformamide (ɛ=37.22), toluene (ɛ=2.37), and n-heptane (ɛ=1.91) as the solvent in polarizable continuum model (PCM). And the results of PCM show that the energy barriers are proportional to solvents’ dielectric constants, which was disagreement with experimental observations. Further, the microsolvation was carried out using the water and ethanol as a solvent system at M06-2X/6-31+G (d,p) level. These computational results are in good agreement with the experimental observations. The aromatic azide (dipole) reacts with different alkenes (dipolarophile) such as nitrile, carboxylic acid, nitro, and amine groups. The results of HOMO-LUMO energy gap describes that the dipole reacts with different substituents of dipolarphile. The FMO gap between HOMO of R and LUMO of R- nitro is 3.90eV. The lowest band gap for nitro group among the different substituents shows that the reaction favors when the EWGs presents on the dipolarophile.