Stability of Dimethylmercury and Related Mercury-containing Compounds with Respect to Selected Chemical Species Found in Aqueous Environment

Abstract

Abstract. Dimethylmercury (CH 3 −Hg−CH 3 ) and other Hg-containing compounds can be found in atmospheric and aqueous environments. These substances are highly toxic and pose a serious environmental and health hazard. Therefore, the understanding of chemical processes that affect the stability of these substances is of great interest. The mercury-containing compounds can be detected in atmosphere, as well as soil and aqueous environments where, in addition to water molecules, numerous ionic species are abundant. In this study we explore the stability of several small, Hg-containing compounds with respect to water molecules, hydronium (H 3 O + ) ions as well as other small molecules/ions using density functional theory and wave function quantum chemistry methods. It is found that the stability of such molecules, most notably of dimethylmercury, can be strongly affected by the presence of the hydronium H 3 O + ions. Although the present theoretical study represents gas phase results, it implies that pH level of a solution should be a major factor in determining the degree of abundance for dimethylmercury in aqueous environment. In particular, it is found that CH 3 −Hg−CH 3 reacts readily with the H 3 O + ion producing CH 3 −Hg−OH 2 + and methane indicating that low-pH levels favor the decomposition of dimethylmercury. On the other hand, our study suggests that high-pH levels in aqueous environment would favor stronglybound complexes of [CH 3 −Hg−CH 3 OH]  species. Overall, the theoretical evidence presented in this study offers an explanation for the available experimental data concerning the stability of dimethylmercury and other mercury-containing compounds having the general structure

Network of secondary‐substituted adamantane amines

“…Here, the reaction from one element to that below is purely hypothetical nuclear reactions, but still they manifest relations between chemical properties of elements consonant with this partial ordering. The same idea was used in the formation of Randić's “periodic table of alkanes”, Dias' “formula periodic table of benzenoids”, as well as a “periodic table of all acyclic hydrocarbons” . But in fact most of these are a little “weaker” than a partial order, in allowing more than one structure at each node of the Hasse diagram – this then is called a “quasi‐order” – but mathematically the ideas are very similar, as they remain posets on the “equivalence classes” implicit at each node.…”

A Note on the Substitution Reaction Network of Azines

“…Although, in the periodic table of elements, reaction from one element to that below are purely hypothetical nuclear reactions, the chemical properties of elements tends to follow a certain partial ordering. Such an idea was 32,33 The ideas and techniques developed in the context of our substitution reaction posets thence could have somewhat wider applicability.…”

Seniority based energy renormalization group (Ω-ERG) approach in quantum chemistry: Initial formulation and application to potential energy surfaces

“…2Re and 3Re since wave functions to be computed by the -ERG(m,M) procedure contain increasing amounts of static correlation with the increase of the bond length. We use molecular orbitals obtained from 2-state-avergaged MCSCF calculations using Full Valence Space FVS [8,6] in order to treat energetics of ground and excited states in a more balanced way (see the…”

“…method to calculate total energies at internuclear distances Re, 2Re and 3Re which are indicated by solid dots in Figure 8. In the -ERG(m,M) procedure (6-31G basis set) we use molecular orbitals obtained from 2-state-avergaged MCSCF calculations using Full Valence Space FVS [8,6] for A1 as well. FCI determinants (61,441 Slater determinants) have been constructed using these MOs and determinants have been ordered according to their  in ascending order (see Table 1).…”

“…Density functional theory (DFT) has demonstrated remarkable success [5] in describing equilibrium geometries (local minima on potential energy surfaces) and associated properties of many diverse molecular systems, e.g. organometalic molecules [6] as well as organic magnets [7][8][9]. One of the major challenges for ab initio methods is calculation of potential energy surfaces for ground and excited electronic states [10].…”