Arsenic organic arsenicals

Generally, inorganic arsenic can occur in the environment in several forms but in natural waters and thus in drinking water, it is mostly found as trivalent arsenite or pentavalent arsenate. Organic arsenic species, abundant in seafood, are very much less harmful to health and are readily eliminated by the body5. 

Table 4.1 Examples of arsenic compounds of environmental and biological interest. Inorganic arsenicals Organic arsenicals...

CHjSH CHSH-CHjOH. Usually obtained as an oil, m.p. 77 C. Developed as an antidote to poisoning by organic arsenicals by external application, it is of use in poisoning by Hg, Cu, Zn, Cd but not Pb. It acts by forming a chelate with the metal and so removing it from the system. 

Both chloramine-T and dichloramine-T have marked antiseptic properties, chloramine-T being most frequently used because of its solubility in water. Aqueous solutions of chloramine-T can be used either for external application, or for internal application to the mouth, throat, etc, as chloramine-T in moderate quantities is non-toxic its aqueous solution can also be effectively used when the skin has come in contact with many of the vesicant liquid poison-gases, as the latter are frequently organic sulphur or arsenic derivatives which combine with or are oxidised by chloramine-T and are thus rendered harmless. 

Lead oxide is used in producing fine "crystal glass" and "flint glass" of a high index of refraction for achromatic lenses. The nitrate and the acetate are soluble salts. Lead salts such as lead arsenate have been used as insecticides, but their use in recent years has been practically eliminated in favor of less harmful organic compounds. 

A major concern when remediating wood-treatment sites is that pentachlorophenol was often used in combination with metal salts, and these compounds, such as chromated copper—arsenate, are potent inhibitors of at least some pentachlorophenol degrading organisms (49). Sites with significant levels of such inorganics may not be suitable candidates for bioremediation. 

Metal Organics and Inorganics. The metal organic herbicides are arsenicals used for the selective, post-emergence control of grass and broadleaved weeds in cropland and noncroplands. These herbicides are particularly usehil for weed control in cotton and turf crops (2,296,294). CacodyUc acid is a contact herbicide used for nonselective weed control in cropland and noncropland (299). Ammonium sulfamate [7773-06-0] (AMS) is an inorganic herbicide used for control of woody plants and herbaceous perennials (2). 

The standard electrode potential for zinc reduction (—0.763 V) is much more cathodic than the potential for hydrogen evolution, and the two reactions proceed simultaneously, thereby reducing the electrochemical yield of zinc. Current efficiencies slightly above 90% are achieved in modem plants by careful purification of the electrolyte to bring the concentration of the most harmful impurities, eg, germanium, arsenic, and antimony, down to ca 0.01 mg/L. Addition of organic surfactants (qv) like glue, improves the quaUty of the deposit and the current efficiency. 

Many organic peroxides of metals have been hydrolyzed to alkyl hydroperoxides. The alkylperoxy derivatives of aluminum, antimony, arsenic, boron, cadmium, germanium, lead, magnesium, phosphoms, silicon, tin, and zinc yield alkyl hydroperoxides upon hydrolysis (10,33,60,61). 

Solvent extraction—purification of wet-process phosphoric acid is based on preferential extraction of H PO by an organic solvent vs the cationic impurities present in the acid. Because selectivity of acid over anionic impurities is usually not sufficient, precipitation or evaporation steps are included in the purification process for removal. Cmde wet-process acid is typically concentrated and clarified prior to extraction to remove post-precipitated sludge and improve partition of the acid into the solvent. Concentration also partially eliminates fluoride by evaporation of HF and/or SiF. Chemical precipitation of sulfate (as Ba or Ca salts), fluorosiUcates (as Na salt), and arsenic (as sulfides) may also be used as a prepurification step preceding solvent extraction. 

A novel interface to connect a ce system with an inductively coupled plasma mass spectrometric (icpms) detector has been developed (88). The interface was built using a direct injection nebulizer (din) system. The ce/din/icpms system was evaluated using samples containing selected alkah, alkaline earths, and heavy-metal ions, as well as selenium (Se(IV) and Se(VI)), and various inorganic and organic arsenic species. The preliminary results show that the system can be used to determine metal species at ppt to ppb level. 

Stibonium Ylids and Related Compounds. In contrast to phosphoms and arsenic, only a few antimony yhds have been prepared. Until quite recendy triphenyl stibonium tetraphenylcyclopentadienyUde [15081 -36-4] C H Sb, was the only antimony yUd that had been isolated and adequately characteri2ed (192). A new method, uti1i2ing an organic copper compound as a catalyst, has resulted ia the synthesis of a number of new antimony yhds (193) ... 

The toxicity of arsenic ranges from very low to extremely high depending on the chemical state. Metallic arsenic and arsenious sulfide [1303-33-9] AS2S2, have low toxicity. Arsine is extremely toxic. The toxicity of other organic and inorganic arsenic compounds varies (28). 

Arsenic compounds have numerous practical appHcations. Although a variety of inorganic and organic arsenicals are used in commerce, arsenic trioxide [1327-53-3] AS2O2, accounted for 98% of the arsenic consumed in 1988 (2). 

Also formed by the direct combination of the elements is a red soHd compound, arsenic diiodide [13453-17-3] AS2I4 or ASI2, which melts at 130°C and dissolves in organic solvents. Treatment of this compound with water causes disproportionation. 

Diarsines and Diarsenes. Under certain conditions, the reduction of compounds with two organic groups attached to arsenic may give rise to tetraalkyl-or tetraaryldiarsines. Thus a number of diarsines have been obtained by the reduction of arsinic acids with phosphorous or hypophosphorous acid (100). Diarsines can also be prepared by the treatment of a metal dialkyl- or diarylarsenide with iodine (101) or a 1,2-dihaloethane (102). 

Arsonic and Arsinic Acids. The arsonic acids, compounds of the type RAsO(OH)2, are among the most important organic arsenicals. The ahphatic arsonic acids are generally prepared by the Meyer reaction ie, heating an alkyl haUde with As O in alkaline solution ... 

The Bart reaction is successful with a wide variety of aromatic and heterocycHc amines. A variation in which an aromatic amine, in the presence of arsenic trichloride, is dia2oti2ed in an organic solvent (the ScheUer reaction) has also found wide appHcation. Both arsonic and arsinic acids can be prepared by the ScheUer reaction which often gives better yields than the Bart reaction with electron-attracting substituents on the aromatic ring. For the commercial preparation of 4-aminophenylarsonic acid [98-50-0] (arsaniUc acid), C HgAsNO, and 4-hydroxyphenylarsonic acid [98-14-6] C H AsO, the Bnchamp reaction is used ... 

G. T. Morgan, Organic Compounds of Arsenic and Antimony, Longmans, Green and Co., London, UK, 1918. 

G. W. Raiziss and J. L. Gavron, Organic Arsenical Compounds, The Chemical Catalog Co., New York, 1923. 

---