DFT Theoretical Study on the Reaction Mechanism of the Nitrate Radical with Alkenes:  2-Butene, Isobutene, 2-Methyl-2-butene, and 2,3-Dimethyl-2-butene

Abstract

A general mechanism for the reactions of the NO3 radical with 2-butene, isobutene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene is proposed on the basis of density functional theory (DFT) calculations. This mechanism is compared with previously reported model experimental kinetic studies at low pressures and temperatures in anaerobic conditions. In our theoretical proposal of mechanism, the initial step is the addition of the NO3 radical to the double bond. For the systems showing different substitution on both sides of the double bond, two adducts have been obtained, one following the Markovnikov rule and the other with the anti-Markovnikov orientation. Starting from the adduct we have found that three main reaction pathways follow. The first one leads to epoxide and NO2 formation, the second to carbonyl compounds, and the third, through the cleavage of the C−C bond, to carbonyl compounds with a lower number of carbon atoms than the original substrate and NO. The theoretical proposal of mechanism leads to the following products: (a) for 2-butene, 2,3-dimethyloxirane, butanone, and ethanal; (b) for isobutene, 2-methylepoxypropane, 2-methylpropanal, butanone, propanone, and formaldehyde; (c) for 2-methyl-2-butene, 2-methylepoxybutane, 3-methylbutanone, propanone, 2-dimethylpropanal, and ethanal; (d) for 2,3-dimethyl-2-butene, 2,3-dimethylepoxybutane, 3-dimethylbutanone, and propanone. In all cases, NO2 and NO are also obtained as products. The geometry of all the involved stationary points in the potential energy hypersurface has been optimized at the DFT level with the B3LYP functional and a 6-31G* basis set. All these conformations were characterized at the same calculation level.

Theoretical Investigation of the NO3 Radical Addition to Double Bonds of Limonene

“…The activation energies of the NO 3 -limonene reaction are positive activation energies and significantly overestimate with MP2 method. B3LYP/6–311 + G(d,p), B3LYP/6–311 + G(3df,2pd) (except for ΔE 2-exo ), CCSD(T)/6–31G(d) and CCSD(T)/6–31G(d) + CF (except for ΔE 2-exo ) levels are negative activation energies, which corresponds to the NO 3 + propene reaction, ozonolysis of isoprene and the OH + ethane reaction reported in the previous theoretical studies [ 15 , 22 , 29 , 30 ]. The negative activation energies given by B3LYP/6–311 + G(3df,2pd) and CCSD(T)/6–31G(d) are comparable, with a largest difference of 4.04 kcal mol −1 for ΔE 2-exo .…”

In-silico prediction of novel drug-target complex of nsp3 of CHIKV through molecular dynamic simulation

“…Further, IM2 loose a molecule of water and cyclization occurs to give P, the product of interest. The adduct formation is justified based on energy diagram using B3LYP/6-311G∗method [ 29 , 30 ]. The following parameters of global reacting indices were calculated from reactant to product such as total energy (E), E HOMO , E LUMO & LUMO-HOMO energy gap (ΔE) are calculated [ 31 , 32 ].…”

The quadrapolar character of the Markovnikov reaction transition state

“…The conclusion of the study is that the ground state properties are most important for defining reactivity. [6,7,12,54] The hypothesis of ground state properties as the foundation of reactivity is consistent with the quadrupolar transition state, since the addition of the H atom will occur in such a way as to create the most stable C-H bond. That bond is also dipolar and we can see the trend in the calculation that the bond is more stable for C1 than C2 in the molecules studied.…”