Theoretical Chemistry Accounts最新文献

The B3LYP and wB97XD density functional methods were used to study the mechanisms and thermodynamic parameters of the activation and reactions of non-catalytic and catalyzed by phenol and p-toluenesulfonic acid reactions of urea with methylamine. The interaction proceeds stepwise with the intermediate formation of N-methylurea. The non-catalytic interaction has a large activation barrier. In the case of participation of methylamine dimer, the activation barrier decreases, but, nevertheless, remains high. During catalysis by phenol and p-toluenesulfonic acid, compounds exhibiting biphilic properties, the activation barrier decreases. The greatest decrease in the activation barrier is observed during catalysis with p-toluenesulfonic acid.

Acrylates are used in cosmetics, orthopedics, paints, coatings, adhesives, textiles, and biomedical applications such as contact lenses and bone cements. However, some acrylates are mutagenic and the aim of this article is to explain the mutagenicity in terms of the atomic population redistribution in the molecule using two new descriptors which are based on atomic populations framed in the quantum theory of atoms in molecules. They describe the electron-withdrawing effect of a group of atoms in a molecule. The descriptors consider substituents of prop-2-enoates, the number of the acrolein units and the electrophilicity. The cluster analysis using these descriptors allows to classify acrylates in terms of the number of acrolein backbones and the type of the substituent group. Five main groups can be distinguished: monoacrylates with monomethacrylates, diacrylates with dimethacrylates, triacrylates, trimethacrylate and monoacrylates with electron-rich substituents. The substituents of mutagenic acrylates are electron withdrawing. This makes the acrolein backbone β-carbon more electrophilic and the molecule more reactive.

In this study, the adsorption behavior of anions (F⁻, Cl⁻, Br⁻) on the surface of the single-walled boron nitride nanotube (SWBNNT) is explored using density functional theory (DFT). The interaction between the ions with the pristine BNNT and the Ge-doped BNNT is performed in the solution phase. According to the obtained data, the F⁻@BNNT and F⁻@Ge-BNNT systems have the highest adsorption energy with values of − 329.85 and − 344.71 kJ/mol, respectively. On the other hand, the lowest values have been shown in Cl⁻@BNNT and Cl⁻@Ge-BNNT structures with values of − 31.17 and − 57.79 kJ/mol, respectively. During the complexation, a decrease in the energy gap (E_g) is accompanied by an increase in the reactivity and electrical conductivity. The HOMO–LUMO energy gaps are found to be the lowest in F⁻@Ge-BNNT with 5.311 eV followed by Cl⁻@Ge-BNNT and Br⁻@Ge-BNNT with 5.299 eV and 5.293 eV, respectively, while these values are 8.028, 8.048, and 7.992 eV for F⁻@BNNT, Cl⁻@BNNT and Br⁻@BNNT, respectively. The intermolecular interactions between the species are also evaluated using the natural bond orbital (NBO) analysis. Finally, to confirm the obtained results, the calculated density of states is depicted.

The [3+2] cycloaddition (32CA) reaction between cyclic azomethine ylide (generated from N-phenacylquinolinium bromide) and N-arylmaleimide, leading to pyrrolo[1,2-a]quinolone, has been investigated using the Molecular Electron Density Theory at the B3LYP/6-311++G(d,p) computational level with D3 correction. This study focuses on the zwitter-ionic type 32CA reaction, highlighting its polar character with the electronic flux from the azomethine ylide to the alkene. The reaction proceeds with complete endo-stereoselectivity, and the activation parameters show minimal variations in different solvents, consistent with experimental observations. The activation energy is associated with the depopulation of the N2–C1 and C4–C5 bonding regions, formation of non-bonding electron density at N2 nitrogen and creation of pseudoradical centers at C3, C4 and C5. These findings suggest that the formation of new covalent bonds does not occur at the transition states, in line with the presence of non-covalent interactions at the interatomic bonding regions, as revealed by the topological analysis of the Quantum Theory of Atoms-in-Molecules.