- Transmetalation of Pentafluorophenylmercury Derivatives with Organylmagnesium Bromides
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The reactions of pentafluorophenylmercury derivatives with organomagnesium compounds have been studied. The interaction of pentafluorophenylmercury chloride with RMgBr (R = Et, Ph) has afforded diphenyl- and diethylmercury or phenylmercury chloride, besides the expected product (C6F5HgR). The results have been explained by the transmetalation of C6F5HgR with the Grignard reagent, followed by the reaction of the resulting C6F5MgX (X = Br, C6F5) with pentafluorophenylmercury chloride. Transmetalation of (C6F5)2Hg with organylmagnesium bromides has led to the formation of C6F5MgX and R2Hg.
- Bardin
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p. 1406 - 1408
(2019/08/21)
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- Practical and theoretical considerations for the determination of δ13CVPDB values of methylmercury in the environment
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Rationale: Analytical methods that can identify the source and fate of mercury and organomercury compounds are likely to be useful tools to investigate mercury in the environment. Carbon isotope ratio analysis of methylmercury (MeHg) together with mercury isotope ratios may offer a robust tool to study environmental cycling of organomercury compounds within fish tissues and other matrices. Methods: MeHg carbon isotope ratios were determined by gas chromatography/combustion-isotope ratio mass spectrometry (GC/C-IRMS) either directly or following derivatization using sodium tetraethylborate. The effects of a normalization protocol and of derivatization on the measurement uncertainty of the methylmercury δ13CVPDB values were investigated. Results: GC/C-IRMS analysis resulted in a δ13CVPDB value for an in-house MeHg reference material of δ13CVPDB = ?68.3 ± 7.7‰ (combined standard uncertainty, k = 1). This agreed very well with the value obtained by offline flow-injection analysis/chemical oxidation/isotope ratio mass spectrometry of δ13CVPDB = ?68.85 ± 0.17‰ (combined standard uncertainty, k = 1) although the uncertainty was substantially larger. The minimum amount of MeHg required for analysis was determined to be 20 μg. Conclusions: While the δ13CVPDB values of MeHg can be obtained by GC/C-IRMS methods with or without derivatization, the low abundance of MeHg precludes such analyses in fish tissues unless there is substantial MeHg contamination. Environmental samples with sufficient MeHg pollution can be studied using these methods provided that the MeHg can be quantitatively extracted. The more general findings from this study regarding derivatization protocol implementation within an autosampler vial as well as measurement uncertainty associated with derivatization, normalization to reporting scales and integration are applicable to other GC/C-IRMS-based measurements.
- Dunn, Philip J.H.,Bilsel, Mine,?im?ek, Adnan,G?ren, Ahmet Ceyhan,Tun?, Murat,Ogrinc, Nives,Horvat, Milena,Goenaga-Infante, Heidi
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p. 1122 - 1136
(2019/06/24)
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- Cleavage of Hg-C Bonds of Organomercurials Induced by ImOHSe via Two Distinct Pathways
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We show that the N-methylimidazole-based selone ImOHSe having an N-CH2CH2OH substituent has the remarkable ability to degrade methylmercury by two distinct pathways. Under basic conditions, ImOHSe converts MeHgCl into biologically inert HgSe nanoparticles and Me2Hg via the formation of an unstable intermediate (MeHg)2Se (pathway I). However, under neutral conditions, in the absence of any base, ImOHSe facilitates the cleavage of the Hg-C bond of MeHgCl at room temperature (23 °C), leading to the formation of a stable cleaved product, the tetracoordinated mononuclear mercury compound (ImOHSe)2HgCl2 and Me2Hg (pathway II). The initial rate of Hg-C bond cleavage of MeHgCl induced by ImOHSe is almost 2-fold higher than the initial rate observed by ImMeSe. Moreover, we show that ImYSe (Y = OH, Me) has an excellent ability to dealkylate Me2Hg at room temperature. Under acidic conditions, in the presence of excess ImYSe, the volatile and toxic Me2Hg further decomposes to the tetracoordinated mononuclear mercury compound [(ImYSe)4Hg]2+. In addition, the treatment of ImOHSe with MeHgCys or MeHgSG in phosphate buffer (pH 8.5) afforded water-soluble Hg(SeS) nanoparticles via unusual ligand exchange reactions, whereas its derivative ImOMeSe or ImMeSe, lacking the N-CH2CH2OH substituent, failed to produce Hg(SeS) nanoparticles under identical reaction conditions.
- Banerjee, Mainak,Roy, Gouriprasanna
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supporting information
p. 12739 - 12750
(2017/11/14)
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- Protection of Endogenous Thiols against Methylmercury with Benzimidazole-Based Thione by Unusual Ligand-Exchange Reactions
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Organomercurials, such as methylmercury (MeHg+), are among the most toxic materials to humans. Apart from inhibiting proteins, MeHg+ exerts its cytotoxicity through strong binding with endogenous thiols cysteine (CysH) and glutathione (GSH) to form MeHgCys and MeHgSG complexes. Herein, it is reported that the N,N-disubstituted benzimidazole-based thione 1 containing a N?CH2CH2OH substituent converts MeHgCys and MeHgSG complexes to less toxic water-soluble HgS nanoparticles (NPs) and releases the corresponding free thiols CysH and GSH from MeHgCys and MeHgSG, respectively, in solution by unusual ligand-exchange reactions in phosphate buffer at 37 °C. However, the corresponding N-substituted benzimidazole-based thione 7 and N,N-disubstituted imidazole-based thione 3, in spite of containing a N?CH2CH2OH substituent, failed to convert MeHgX (X=Cys, and SG) to HgS NPs under identical reaction conditions, which suggests that not only the N?CH2CH2OH moiety but the benzimidazole ring and N,N-disubstitution in 1, which leads to the generation of a partial positive charge at the C2 atom of the benzimidazole ring in 1:1 MeHg-conjugated complex of 1, are crucial to convert MeHgX to HgS NPs under physiologically relevant conditions.
- Banerjee, Mainak,Karri, Ramesh,Chalana, Ashish,Das, Ranajit,Rai, Rakesh Kumar,Rawat, Kuber Singh,Pathak, Biswarup,Roy, Gouriprasanna
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supporting information
p. 5696 - 5707
(2017/04/28)
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- Organomercury Compounds. XXXI. Preparations and 199Hg N.M.R. Spectra of Organomercury Derivatives of 2-Phenylpyridine, Benzoquinoline, 1-Phenylpyrazole and 3,4,5-Trimethyl-1-phenylpyrazole, and the X-Ray Crystal Structure of Bismercury
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2-)Pyridin-2'-yl)phenylmercuric acetate has been prepared by mercuration of 2-phenylpyridine.Symmetrization of the corresponding chloride by alkaline sodium stannite gave bismercury, which was also prepared from 2-(2'-aminophenyl)pyridine by the diazo method and treatment of the initial product with copper powder and aqueous ammonia.Mercuration of benzoquinoline and 3,4,5-trimethyl-1-phenylpyrazole with mercuric acetate followed by treatment with lithium chloride yielded benzoquinolin-10-ylmercuric chloride and 2-(3',4',5'-trimethylpyrazol-1'-yl)phenylmercuric chloride respectively.Treatment of the former product with tribromide ions gave 10-bromobenzoquinoline.The exchange Grignard reaction between 1-phenylpyrazole and ethylmagnesium bromide to give 2-(pyrazol-1'-yl)phenylmagnesium bromide has been monitored by reactions with benzonitrile and D2O to establish optimum conditions for reaction with mercuric bromide giving bismercury.The 199Hg n.m.r. chemical shifts of the majority of mercurials are shifted substantially downfield to the corresponding simple phenylmercurials consistent with weak intramolecular coordination by the heterocyclic nitrogen donor atoms, but a small upfield shift is observed for bismercury.The X-ray crystal structure of bismercury 1/n, a 12.746(2), b 11.660(2), c 5.698(1) Angstroem, β 92.81(1) deg, V 845.8 Angstroem3> shows a centrosymmetric molecule with strong linear two coordination and significant but much weaker Hg-N interactions giving overall distorted square planar stereochemistry.The phenyl rings are mutually coplanar, whilst the two pyridin-2'-yl rings are parallel and inclined at 10.8 deg to the phenyl groups.
- Black, David St. C.,Deacon, Glen B.,Edwards, Gavin L.,Gatehouse, Bryan M.
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p. 1323 - 1336
(2007/10/02)
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- Radical Cations of Dialkylmercury Derivatives, Radiation Synthesis and Electron Spin Resonance Detection
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Exposure of very dilute solutions of Hg(CD3)2 in tetrachloromethane to 60Co γ-rays at 77 K gave a species whose e.s.r. spectrum is characteristic of the parent cation.Interpretation of the g-values and 199Hg tensor component B derived from a computer synthesis of the spectrum suggests that the unpaired electron is strongly confined to the linear ? orbital having a node through the mercury atom.This has a large 6p(Hg) character.No extra features were obtained using Hg(13CH3)(CH3), confirming that the spin density on the CH3 groups is small (19F).The spectra for Hg(CH3)2 in this solvent were analysed in terms of the same solvent features together with coupling to a least five and probably seven protons.The small 1H coupling was almost isotropic at +/-4.5 G.In contrast, Hg(C2H5)2 gave no resolved coupling to 19F, but there was a large, well defined, triplet splitting (42 G) assigned to two specific CH3 protons.This suggests that rotation about the C-C bonds is restricted.We were unable to detect free rotation on annealing, although the lines broadened considerably, prior to radical loss.Attempts to detect .CH3 or .CH2CH3 radicals in these systems were unsuccessful, but clear evidence for .CD3 radicals was obtained for Hg(CD3)2 in CFCl3 on annealing.
- Hasegawa, Akinori,Rideout, Jan,Symons, Martyn C.R.
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p. 637 - 640
(2007/10/02)
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