Trivalent arsenic

Arsenic tniodide (arsenic(III) iodide), Asl, can be precipitated from a hot solution of trivalent arsenic in hydrochloric acid by the addition of potassium iodide, or it can be formed by treating elemental arsenic with a solution of iodine in carbon disulfide. It is not as easily hydrolyzed as the other arsenic haUdes, but it decomposes slowly in air at 100 °C (rapidly at 200°C) to give a mixture of iodine, arsenic trioxide, and elemental arsenic. Solutions of Asl are unstable, particularly in the presence of moisture. 

Trimethylarsine gives a 98% yield of trimethylarsine difluoride when treated with xenon difluoride [102] in fluorotrichloromelhane. and tnsfpentafluorophen-yl)arsine gives a 94% yield of tris(pentafluornphenyl)arsme difluoride after reaction with dilute fluorine in fluorotnchloromethane at 0 C [106] Other trivalent arsenic compounds have also been fluorinated with xenon difluoride [103] In addition, arsines have been oxidatively fluorinated by iodine pentafluoride [107] or electrochemically in 26-34% yield [108]... 

Oxidation Trivalent arsenic citric acid or EDTA Potassium permanganate depending on chelating agent, metal chelate is either strongly sorbed to soil or is highly mobile and can be flumbed usinj water or dilute acid solutions. Oxidizes trivalent arsenic to pentavalent... 

Landrigan et al. (1982) conducted an epidemiologic survey to evaluate occupational exposure to arsine in a lead-acid battery manufacturing plant. Arsine concentrations ranged from nondetectable to 49 /breathing zone samples. A high correlation was found between urinary arsenic concentration and arsine exposure (r=0.84 p=0.0001 for an n of 47). Additionally, arsine levels above 15.6 /ig/m3 (=0.005 ppm) were associated with urinary arsenic concentrations in excess of 50 //g/L. The investigators concluded that exposure to a 200 /ig/m3 arsine exposure standard would not prevent chronic increased absorption of trivalent arsenic. 

Chronic ingestion of trivalent arsenic in medicinal preparations was also associated with an increased incidence of hyperkeratosis and... 

Inhaled arsine is oxidized to form elemental trivalent arsenic (As ) and arsenous oxide (AS2O3), two human carcinogens. Excess cancers from trivalent arsenic and arsenic trioxide have been associated with cumulative lifetime arsenic exposure. Exposure to arsine above 0.004ppm is associated with increased urinary arsenic excretion, indicating exposure to arsenic. Current exposure limits may not prevent potential chronic toxicity. ... 

Symptoms of poisoning by arsenite (trivalent arsenic) Include dermatitis and a variety of neurologic manifestations. Including painful paresthesias (tingling and numbness in the extremities). 

Chemically it is trivalent arsenical used for advanced CNS African trypanosomiasis. It is administered IV in propylene glycol and after administration it is rapidly excreted. It is highly toxic and used only in advanced trypanosomiasis when no alternative is there. 

Melarsoprol is a trivalent arsenical that has been available since 1949 and is first-line therapy for advanced central nervous system East African trypanosomiasis, and second-line therapy (after eflornithine) for advanced West African trypanosomiasis. 

Other organoarsenicals, most notably lewisite (dichloro[2-chlorovinyl]arsine), were developed in the early twentieth century as chemical warfare agents. Arsenic trioxide was reintroduced into the United States Pharmacopeia in 2000 as an orphan drug for the treatment of relapsed acute promyelocytic leukemia and is finding expanded use in experimental cancer treatment protocols (see Chapter 54). Melarsoprol, another trivalent arsenical, is used in the treatment of advanced African trypanosomiasis (see Chapter 52). 

Arsenic compounds are thought to exert their toxic effects by several modes of action. Interference with enzyme function may result from sulfhydryl group binding by trivalent arsenic or by substitution for phosphate. Inorganic arsenic or its metabolites may induce oxidative stress, alter gene expression, and interfere with cell signal transduction. Although on a... 

Table 8 Heteropolyanions Containing Trivalent Arsenic and Antimony...

Hood, R.D., Vedel, G.C., Zaworotko, MJ. et al. (1988) Uptake, distribution, and metabolism of trivalent arsenic in the pregnant mouse. Journal of Toxicology and Environmental Health, 25(4), 423-34. 

Naranmandura, H Suzuki, N. and Suzuki, K.T. (2006) Trivalent arsenicals are bound to proteins during reductive methylation. Chemical Research in Toxicology, 19(8), 1010-18. 

Mondal, P., Majumder, C.B. and Mohanty, B. (2007) Removal of trivalent arsenic (As(III)) from contaminated water by calcium chloride (CaC12)-impregnated rice husk carbon. Industrial and Engineering Chemistry Research, 46(8), 2550-57. 

Dimethylarsinous acid An organic trivalent arsenical with the composition of (CH3)2As(OH), abbreviated DMA(III), see Figure B.5 (compare with dimethylarsinic acid, monomethylarsonic acid, and monomethylarsonous acid). 

Thioarsenite An aqueous species, such as H2AS3S6-, that contains trivalent arsenic and sulfide (compare with arsenite, thioarsenic, thioarsenate, and methylthioarsenate). 

Friedheim EAH (1949) A five day peroral treatment of yaws with stb, a new trivalent arsenical. Am J Trop Med Hyg 29(suppl 1) 185... 

Trivalent arsenic forms strong bonds with sulfur, and thiols are therefore used for derivatizing both lewisite and CVAA, forming the same derivative (19). Lewisite reacts with mono and dithiols the reaction with dithiols occurring rapidly at ambient temperature. In a competitive environment, lewisite reacts almost exclusively with dithiols rather than monothiols (35). Three dithiols, 1,2-ethanedithiol, 1,3-propanedithiol and 2,3-dimercaptopropan-l-ol (British Anti-Lewisite, BAL) have been used for biomedical sample analysis of CVAA to form cyclic derivatives (14a, b) and (15). Unlike derivatiza-tion of TDG, CVAA can be derivatized direcdy in an aqueous solution. 2,3-Dimercaptotoluene, which has been used extensively for environmental analysis (19), does not appear to have been used. 

For instance in the synthesis of dimethyl arsinic acid (cacodylic acid) trivalent arsenic is isomerised to the pentavalent state... 

As seen, trivalent phosphorus is a far better reducing agent than both trivalent nitrogen or trivalent arsenic. 

Melarsoprol [me LAR soe prole] is a derivative of mersalyl oxide, a trivalent arsenical. 

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