Organoarsenic compounds preparation

Primary and Secondary Arsines. Compared to the vast number of known organoarsenic compounds, relatively few primary (RASH2) and secondary (R2ASH) arsines have been described. Primary arsines are commonly prepared by the 2inc—hydrochloric acid reduction of substances containing... 

Cyclic and Polymeric Substances Containing Arsenic—Arsenic Bonds. A number of organoarsenic compounds containing rings of four, five, or six arsenic atoms have been prepared (cycHc polyarsines). The first such four-membered ring compound to be adequately characterized, tetrakis (trifluoromethyl) tetrarsetane [7547-15-17, was obtained by the interaction of a diiodoarsine and mercury (107,108) ... 

Many organoarsenic compounds are prepared by reactions of AsC13 with alkyl group transfer agents such as Grignard reagents, lithium alkyls, or aluminum alkyls. Typical reactions include... 

The most common structures of arsenic compounds are tetrahedral and pyramidal, which are similar when the sterically active lone pair is counted. Tetrahedral symmetry holds the potential for chirality and indeed many chiral organoarsenic compounds have been prepared. Arsenic may also use d orbitals for (d-d)n bonding and for hybridization with s2 and p3 orbitals, resulting in trigonal bipyramidal or octahedral structures. In the former the more electronegative substituents occupy the apical position. 

Is tetramethyldiarsine an organometallic compound By definition, arsenic is a so-called metalloid or semi-metal , not a metal, and thus organoarsenic compounds like the organic compounds of boron or silicon are not per se organometallics. There is no doubt that the preparation of tetramethyldiarsine and the elucidation of its structure may in retrospect be linked to the development of organometallic chemistry, but it would be far beyond the scope of this book, if the chemistry of the organic compounds of the metalloids in its entirety was discussed. 

Krynitsky has studied the preparation of biological tissue for the determination of arsenic by graphite furnace atomic absorption spectrometry. Zeeman graphite furnace atomic absorption spectrometry has been used to determine organoarsenic compounds in horse urine . 

The pyrolysis of organoarsenic compounds containing the arsenyl moiety has some limited preparative applications [arsenyl (As=0) by analogy with phosphoryl (P=0)]. The compounds are based on the arsonic acid RAs(0)(0H)2, the arsinic acid R2As(0)0H and the arsine oxide R3As=0 structures. The acids are in interesting contrast with the phosphorus series. The phosphonic and phosphinic esters are prepared from the phosphorus(III) precursors via the Arbuzov synthesis. This synthetic route fails with the arsenic analogues, and further, if an alkyl halide or a salt is added in the pyrolysis of arsonic or arsinic acid esters a retro-Arbuzov reaction takes place . ... 

Organoarsenic compounds can be prepared from arsenic trihalides and organic derivatives of other metals. For example, trialkylarsines are obtained in good, yield from dialkylzincs and arsenic trichloride,484 and dichloro-(ethyl)arsine can be prepared from diethylmercury and arsenic trichloride 485... 

Based on the Draft Final Standard Operating Procedure for the EDS (U.S. Army, 2001e), the mixture of sulfur mustard and phenylarsenic chlorides contained in Winterlost is likely to be treated according to the same protocol as HD alone, i.e., 90 percent MEA, 10 percent water, at 60 C for 4 hours. While MEA will break the As-Cl bonds associated with the vesicant activity of DA and PD, it is unclear whether the treatment will break the phenyl-As bonds. Further posttreatment may be needed to prepare the neutralent for disposal. Much the same situation arises with the proposed neutralization of DA and PD in the absence of HD. The Army plans to treat the agent and mnnition residues in the EDS with denatured 95 percent ethanol (or possibly acetone for DA) at ambient temperature for 1 hour. While this treatment will dissolve the organoarsenic compounds and partially hydrolyze the As-Cl bonds, it will produce a neutralent requiring signiflcant further treatment. 

Reactions of organoarsenic compounds are summarized in Fig. 4.10. Alkyl-arsonic and dialkylarsinic acids can be prepared by the Meyer reaction. An alkyl halide or sulphate is treated with an alkali metal arsenite in aqueous solution. 

Catenation. Metal-metal bonds are a feature of many organoarsenic compounds. For example, the first to be prepared (by Cadet de Gassi-court in 1760) was the spontaneously air-inflammable liquid cacodyl which was later shown to be tetramethyldiarsine, Me2As-AsMe2, and several of the compounds found by Ehrlich to be useful chemotherapeutic agents were derivatives of arsenobenzene, (PhAs). The structure of the parent compound has recently been shown to be based on a chair-shaped Asg ring (4.18). Arsenomethane (MeAs)5 is a pentamer with a puckered Asj ring (4.19). 

Relatively few applications of optically active tertiary arsines to asymmetric synthesis have been reported by comparison with the extensive work with phosphines . Authoritative accounts of the synthesis and stereochemistry of compounds of Group V elements are available other reviews cover the subject up until 1979 . For general treatments of organoarsenic chemistry up until 1976, including optically active compounds, two important works are available . Of related interest is an article on stereochemical aspects of phosphorus chemistry and another published in this series on optically active phosphines preparation, uses and chiroptical properties . On matters concerning the intricacies of resolutions work, the reader should consult Reference 21, especially Chapter 7, which is entitled Experimental Aspects and Art of Resolutions. 

---