A DFT Study of the Cheletropic Reaction between Diacetyl and Trimethylphosphite

The mechanism of the cheletropic reaction between diacetyl and trimethylphosphite has beenstudied by density functional-based hybrid functional M062x with 6-31+G(d,p) basis set [1,2]. The ground and transition states were confirmed by the frequency calculations. The rateconstants and activation energies of this reaction is 12.71×10-11 M-1s-1 and 22.26 kcalmol-1.The global reactivity index analysis was performed for the related reactants. The frontier molecularorbital (FMO) analysis allowed us to understand the nature of these [4 + 2] cycloaddition.An analysis of the FMO for diacetyl and trimethylphosphite indicated that the most favorableinteraction along the cycloaddition process takes place between HOMO trimethylphosphiteand LUMO diacetyl, the energy gap was 7.22 eV. A good electrophile wascharacterized by a low value of chemical potential (μ) and hardness (η) and high value of ω.The μ, η and ω for diacetyl (-4.86, 8.77, 1.56) and trimethylphosphite (-3.90, 7.59, 0.87) isshown that diactyl is electrophile. The trimethylphosphite and diactylewas classified as marginaland moderate electrophile within the electrophilicity scale [3]. The Δω for the reactionhad a low value (0.68 eV), thus indicating that the corresponding cycloaddition will have alow polar character.