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An all-atom force field is developed using a combination of density functional theory calculations and OPLS force field parameter values for the 1,1,3,3-tetramethylguanidium lactate (TMG) lactic acid (LAC) ionic liquid (TMGL). The computed density of the TMGL is in good agreement with available experimental values. The internal energy components, cohesive energy density, and the self-diffusion constants are also discussed. Molecular dynamics simulations are then conducted to investigate the solubility of the SO2and CO2gases in the TMGL. The simulation results show strong organization of SO2about the TMG cation and the LAC anion, especially the LAC anion, but relatively weak organization of CO2about the cation and the anion of the TMGL, which explained well the selectivity of the TMGL toward the SO2and CO2. [ABSTRACT FROM AUTHOR]

Recent experimental studies revealed that cytochrome P450 2E1 (CYP2E1) could metabolize not only ethanol but also its primary product, acetaldehyde, accompanying the well-known acetaldehyde dehydrogenases (ALDH) in the metabolism of acetaldehyde. Mechanistic aspects of acetaldehyde hydroxylation by Compound I model active species of CYP2E1 were investigated by means of B3LYP DFT calculations in the present paper. Our study results demonstrate that acetaldehyde hydroxylation by CYP2E1 is in accord with the effectively concerted mechanisms both on the high quartet spin state (U.) and on the low doublet spin state (LS). The rate-limiting step is H-abstraction, and the activation energy is about 11.7∼14.0 kcal/mol on the quartet (doublet) reaction route, which is about one-half to one-third of that needed by methane hydroxylation. The phenomenon that the U. and LS reaction routes are both effectively concerted was shown for the first time to occur in trans-2-phenyl-iso-propylcyclopropane hydroxylation by Kumar et al. (see Figure 7 in the paper of Kumar, D.; de Visser, S. P.; Sharma, P. K.; Cohen, S.; Shaik, S. J. Am. Chem. Soc.2004, 126, 1907) and was confirmed in our work of acetaldehyde hydroxylation by cytochrome P450. Theoretical exploration of the U. O-rebound barrier degradation is also presented in the present paper on the basis of Shaik's valence bond (VB) model. [ABSTRACT FROM AUTHOR]

Possible reaction pathways of nitroethylene with the Si(100)-2 × 1 surface have been investigated by unrestricted density functional theory. The facile occurrence of the studied reactions was demonstrated by the low activation energies of the rate-determining steps (1.07−5.23 kcal/mol). It was found that the [6b+ 2] cycloaddition reaction of nitroethylene is most kinetically favorable. The isomerization reactions of the addition products were also investigated. The [1b+ 2] cycloaddition product may further undergo a rearrangement by overcoming a 12.37 kcal/mol activation energy barrier into an isomer, with an oxygen atom of the nitryl group inserted between two silicon atoms of the Si(100) surface. [ABSTRACT FROM AUTHOR]

Density functional theory calculations have been carried out for CO adsorption on the Feoct2- and Fetet1-terminated Fe3O4(111) surfaces, which are considered as active catalysts in water-gas shift reaction. It is found that the on-top configurations are most stable on these two surfaces. Some bridge configurations are also stable in which the new C−O bond formed between the surface O atom and the C atom of CO. The adsorption on the Feoct2-termiated surface is more stable than on the Fetet1-terminated surface. The density of state reveals the binding mechanism of CO adsorption on the two surfaces. Our calculations have also shown that the absorbed CO can migrate from the on-top site to the bridge site or 3-fold site. The oxidation of CO via surface oxygen atoms is feasible, which is in good agreement with experimental results. [ABSTRACT FROM AUTHOR]