Effects of Water Molecules on Rearrangements of Formamide on the Kaolinite Basal (001) Surface

Revealing the mechanisms of mercury adsorption on metal-doped kaolinite(001) surfaces by first principles

Natural kaolinite exhibit high affinity for heavy metals while the interaction mechanisms in the presence of heteroatoms remain largely elusive, which are tackled by first principles. In this paper, three common dopants (Mg, Ca, Fe) were employed to construct metal-doped kaolinite(001) (K(001)) surfaces. We found that Mg-doped K(001) was the most stable surface in terms of thermal stability and structural analysis, consistent with the pervasive isomorphic substitution in kaolinite minerals. The interaction of mercury with Mg-doped K(001) surface was investigated in the form of predominant top-site and bridge-site models. The effects of chloride on the interaction were also studied. The results demonstrated that the strongest adsorption occured in the present of dopants and the absence of chloride. The electronic properties revealed a significant charge transfer (up to 1.28 electrons) and chemisorption character at the interfaces when dopants were introduced, which could be ascribed to the overlapping of Hg-5d and O_s-2p (surface O) orbitals in the range of -7.5 eV to +0.5 eV. Additionally, the chloride had a profoundly adverse influence on mercury adsorption due to the upward shift of Hg-6s and Hg-6p orbitals. The studies are beneficial to understand the interaction mechanisms of natural minerals toward environmental pollutants in actual applications.

Aminohydroxymethylene (H2N-C̈-OH), the Simplest Aminooxycarbene

We generated and isolated hitherto unreported aminohydroxymethylene (1, aminohydroxycarbene) in solid Ar via pyrolysis of oxalic acid monoamide (2). Astrochemically relevant carbene 1 is persistent under cryogenic conditions and only decomposes to HNCO + H₂ and NH₃ + CO upon irradiation of the matrix at 254 nm. This photoreactivity is contrary to other hydroxycarbenes and aminomethylene, which undergo [1,2]H shifts to the corresponding carbonyls or imine. The experimental data are well supported by the results of CCSD(T)/cc-pVTZ and B3LYP/6-311++G(3df,3pd) computations.

Unimolecular decomposition of formamide via direct chemical dynamics simulations

Classical chemical dynamics simulations show that formamide (NH₂CHO) can dissociate via multiple pathways, either by direct dissociations or via intramolecular rearrangements to different isomers followed by dissociation.

Decomposition pathways of formamide in the presence of vanadium and titanium monoxides

Thermally feasible decomposition pathways of formamide (FM) in the presence of vanadium VO(X⁴Σ⁻) and titanium TiO(X³Δ) monoxides are determined using density functional theory (the BP86 functional) and coupled-cluster theory (CCSD(T)) computations with large basis sets.