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Arsenic (III) binding sites usually use thiol groups of cysteine residues. The catalysis involves thiolates of Cys72, Cys174, and Cys224. In an SN2 reaction, the positive charge on the SAM sulfur atom pulls the bonding electron from the carbon of the methyl group, which interacts with the arsenic lone pair to form an As−C bond, leaving SAH. [32]
Arsenic forms colorless, odorless, crystalline oxides As 2 O 3 ("white arsenic") and As 2 O 5 which are hygroscopic and readily soluble in water to form acidic solutions. Arsenic(V) acid is a weak acid and the salts are called arsenates , [ 5 ] the most common arsenic contamination of groundwater , and a problem that affects many people.
Arsenic-arsenic bonds are very weak, and oligomeric arsenic compounds are even more liable to oxidize than their hydrogenated precursors. [6]: 318–320 The following reaction can, however, be prepared through electrochemical reduction in a zinc-sulfate cell. [6]: 473 Oxidation first forms polymeric arsinoxides, e.g.: MeAs + O → MeAsO
Bioremediation of ground water contaminated with arsenic aims to convert arsenite, the toxic form of arsenic to humans, to arsenate. Arsenate (+5 oxidation state) is the dominant form of arsenic in surface water, while arsenite (+3 oxidation state) is the dominant form in hypoxic to anoxic environments.
The Marsh test treats the sample with sulfuric acid and arsenic-free zinc. Even if there are minute amounts of arsenic present, the zinc reduces the trivalent arsenic (As 3+). Here are the two half-reactions: Oxidation: Zn → Zn 2+ + 2 e − Reduction: As 2 O 3 + 12 e − + 6 H + → 2 As 3− + 3 H 2 O. Overall, we have this reaction:
A 2007 study found that over 137 million people in more than 70 countries are probably affected by arsenic poisoning of drinking water. The problem became a serious health concern after mass poisoning of water in Bangladesh. [1] Arsenic contamination of ground water is found in many countries throughout the world, including the US. [2]
Arsenic trichloride can be prepared by the reaction of arsenic oxide and sulfur monochloride. This method requires simple apparatus and proceeds efficiently: [8] 2 As 2 O 3 + 6 S 2 Cl 2 → 4 AsCl 3 + 3 SO 2 + 9 S. A convenient laboratory method is refluxing arsenic(III) oxide with thionyl chloride: [9] 2 As 2 O 3 + 3 SOCl 2 → 2 AsCl 3 + 3 SO 2
Cummins' Mo(N(tBu)Ar) 3 catalyst, also known to split the N-N triple bond in dinitrogen, reacts with yellow arsenic to form a terminal arsenic moiety triple-bonded to the metal center - one of only several compounds known to contain a terminal arsenic atom. [15] Complexes with metal-metal multiple bonds also enable mild As 4 activation ...