Theoretical studies of Phenylmercury carboxylates - Complexation Constants and Gas Phase Photo-Oxidation of Phenylmercurycarboxylates

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Engelsk
TA-nummer: TA-2750
Tittel: Theoretical studies of Phenylmercury carboxylates - Complexation Constants and Gas Phase Photo-Oxidation of Phenylmercurycarboxylates

Phenylmercury(II)-carboxylates used as catalysts in PU-systems will eventually be released into the environment. The phenylmercury(II) cation, C6H5Hg+, forms various complexes with ligands present in natural and biological systems and knowledge about the stability of the carboxylates complexation constants are important in this respect. The phenylmercury(II)-carboxylates may also be emitted into the atmosphere where they will undergo photo-oxidation reactions. The chemical bonding in a series of phenylmercury(II)-carboxylates, including estimates of the UV-absorption spectra and the carboxylate complexation constants have been obtained from quantum chemistry calculations.
The results indicate that the phenylmercury(II)-carboxylates (acetate, propionate, 2-ethylhexanoate, octanoate and neodecanoate) have nearly the same dissociation constants and UV-spectra. The aqueous phase fate of these compounds and their rate of photolysis in the aqueous phase will therefore essentially be the same. An evaluation of atmospheric radical reactions and direct photolysis of gaseous phenylmercury(II)-carboxylates suggests that direct photolysis b solar radiation is the dominant daytime sink, and that reactions with NO3
radicals are equally important during night-time. The atmospheric lifetime of phenylmercury(II)-carboxylates is estimated to be around 1 day.