Methylarsine

Good yields of phenylarsine [822-65-17, C H As, have been obtained by the reaction of phenylarsenic tetrachloride [29181-03-17, C H AsCl, or phenyldichloroarsine [696-28-6], C3H3ASCI25 with lithium aluminum hydride or lithium borohydride (41). Electrolytic reduction has also been used to convert arsonic acids to primary arsines (42). Another method for preparing primary arsines involves the reaction of arsine with calcium and subsequent addition of an alkyl haUde. Thus methylarsine [593-52-2], CH As, is obtained in 80% yield (43) ... 

Methylarsine, trifluoromethylarsine, and bis(trifluoromethyl)arsine [371-74-4] C2HAsF, are gases at room temperature all other primary and secondary arsines are liquids or solids. These compounds are extremely sensitive to oxygen, and ia some cases are spontaneously inflammable ia air (45). They readily undergo addition reactions with alkenes (51), alkynes (52), aldehydes (qv) (53), ketones (qv) (54), isocyanates (55), and a2o compounds (56). They also react with diborane (43) and a variety of other Lewis acids. Alkyl haUdes react with primary and secondary arsiaes to yield quaternary arsenic compounds (57). 

A large number of polymeric substances, (RAs) or (ArAs), are also known (113). They are usually prepared by the reduction of arsonic acids with hypophosphorous acid (100,114) or sodium dithionite (115). Most of these polymers have not been well characterized. An insoluble, purple material, poly(methylarsinidene) [26403-94-1], (CH As), prepared by the interaction of methylarsine and a dihalomethylarsine, however, has been shown by an x-ray investigation to have a ladderlike polymeric stmcture in which the inter-mng distances correspond to one-electron bonds (116) ... 

Andreae [712] used four different detectors in his investigations the electron capture detector (for the methylarsines), the quartz cuvette atomic absorption detector (for arsenic and antimony species), the graphite furnace atomic... 

The electron-capture detector was originally found to be a sensitive detector for the methylarsines [716]. After improvements of the atomic absorption detectors had been made (especially concerning adsorptive losses and peak shapes of the methylarsines), it was found that this detector could be used to replace the electron-capture detector, which because of its lack of specificity and its sensitivity to contamination and changes in operating conditions was very inconvenient to work with. 

Marine algae transform arsenate into nonvolatile methylated arsenic compounds such as methanearsonic and dimethylarsinic acids (Tamaki and Frankenberger 1992). Freshwater algae and macrophytes, like marine algae, synthesize lipid-soluble arsenic compounds and do not produce volatile methylarsines. Terrestrial plants preferentially accumulate arsenate over arsenite by a factor of about 4. Phosphate inhibits arsenate uptake by plants, but not the reverse. The mode of toxicity of arsenate in plants is to partially block protein synthesis and interfere with protein phosphorylation — a process that is prevented by phosphate (Tamaki and Frankenberger 1992). 

The compounds MMA, DMA, and TMAO are reduced in acidic aqueous media by borohydride solutions to methylarsine (MeAsH2, bp 2°C), dimethylarsine (Me2AsH, bp 35°C), and trimethylarsine (Me3As, bp 55°C), respectively. These products are useful derivatives for speciation analysis of arsenic because they are readily separated from complex sample matrices and may be further separated from each other by distillation (41) or by gas chromatography (42) prior to their determination by element-specific detectors. Consequently, arsine generation techniques are the most commonly used methods for determining MMA, DMA, and TMAO in marine samples. 

On refluxing in THF, VC13 reacted with triarsines to yield red-brown complexes [VCl3(TAS)j (TAS = bis(dimethyIarsinophenyl)methylarsine or l,l,l-tris(dimethylarsinomethyl)ethane). These are non-electrolytes, and the ligand is terdentate. Both have a facial structure. 

The only known examples are the 1-methyl- and 1-phenyl-arsetanes no four-membered heterocycles of either antimony or bismuth have yet been reported. They were prepared (77MI11800) by the reductive cyclization of a 3-chloropropyliodoarsine with sodium. Long reaction periods (48-60 h) are required for reasonable yields to be obtained. 1-Methyl-arsetane (1) was also prepared from disodium methylarsine and 1,3-dichloropropane but in lower yield (Scheme 1). 

The energies of the electronic transitions are labelled according to the parent symmetry of the excited states. b Indicates the conditions under which the electronic spectra were obtained S, solution P, diffuse reflectance. Abbreviations diars = o -phenylene bidimethylarsi ne triars = bis(o-dimethylarsinophenyl)methylarsine dsp = bis(o-methylthiophenyl)methylarsine tas - bis(3-dimethylarsmopropyt)methylarsine dap = bis(3 dimethylarsinopropyl)-phenylphosphine dpp = bis(2-diphenylphosphinoethyl)phenylphosphine sp = diphenyl(o-mcthylthiophenyl)phosphine. 

Reaction of (triars)AgBr (triars = bis(o-dimethylarsinophenyl)methylarsine) with the carbonyl anions Mn(CO)i Fe(CO)4- and Co(CO)4 in THF gave complexes of the type (triars)Ag—Co(CO)4. 0 The crystal structure of the complex with an Ag—Co bond has been determined.211 The silver atom had a distorted tetrahedral arrangement with three Ag—As bonds (262-272 pm) and an Ag—O bond (266 pm). The tetrahedral starting material was prepared by reaction of the triarsine with AgBr in ethanol.210... 

Perhaps as much as 26 200 t of arsenic may annually volatilize into the atmosphere from soils (Matschullat, 2000), 300-301. Much of this volatilization is due to microbial activity (Frankenberger and Arshad, 2002), 363-364. Under reducing conditions in soils, fungi and other microorganisms may produce gaseous arsine and methylated arsines, such as methylarsine, dimethylarsine and trimethylarsine ((Mandal and Suzuki, 2002), 205 (Lrankenberger and Arshad, 2002), 363 (Oremland and Stolz, 2003), 939 Chapter 4). 

Methylarsinic acid and dimethylarsinic acid are the two organoarsenic compounds that are most likely to be encountered in the environment. 

Methyldiiodoarsine has been prepared in a variety of ways treatment of an alcoholic solution of methylarsenic oxide, CH3AsO, with an excess of hydriodic acid,1 passing methylarsine into an alcoholic solution of iodine,2 the action of sulfur dioxide on methylarsenic tetraiodide,3 the action of methyl iodide on arsenic,4 and treatment of a solution of disodium methanearsonate and potassium iodide with hydrochloric acid and sulfur dioxide.6 The following directions are essentially the last method combined with the preparation of the disodium methanearsonate in situ.6,7 The use of an alcoholic medium greatly facilitates the reaction between sodium arsenite and methyl iodide. 

Diamagnetic unless stated to contrary, l-triars = methylbis (-dimethylarsino-3-propyl) arsine ttas = bis-o(o-dimethylar-sinophenyl) methylarsine v-triars = tris-1,1,1 -(dimethylarsino) ethane. 

In this method, arsine and methylarsines produced by sodium borohydride reduction are collected in n-hcptanc (-80°C) and then determined. The limit of detection for a 50mL sample was 0.2-0.4pg L 1 of arsenic. Relative standard deviations ranged from 2% to 5% for distilled water replicates spiked at the lOpg L 1 level. Recoveries of all four arsenic species from river water ranged from 85% to 100%. 

Dimethyl arsenic acid yields predominantly dimethylarsine, while methylarsonic acid yields predominantly methylarsine and trimethylarsine oxide yields predominantly trimethylarsine. 

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