Arsenic trihalides

When the phosphorus halide is PI3, this reaction is a convenient way to produce HI. Arsenic trihalides hydrolyze in an analogous way but the trihalides of antimony and bismuth react to produce oxyhalides. 

The ammonia additive compounds of arsenic trihalides all react energetically on addition of cold concentrated sulphuric acid with formation of arsenic trilialides, a fact which Besson regards as evidence that the ammonia derivatives are true additive compounds. 

The arsenic trihalides have been shown by a variety of techniques (Table 9) to be pyramidal molecules in the gas phase. The X—As—X angles increase from X = F 96° to X = I 100°. The d(As—X) values increase with increase of temperature,53 and the X—As—X angle changes in proportion. 

The synthesis of the first arsabenzene, 9-arsaanthracene, 6, was simultaneously communicated by Bickelhaupt16) and Jutzi17> in 1969. The elimination of hydrogen chloride from 9,10-dihydroaarsanthracene 7 afforded 6. These precursors are available from either reduction of the corresponding arsinic acids 816,18) or by the exchange reaction of dihydrostannaanthracenes 9 with arsenic trihalides 17). 

All the arsenic trihalides are known compounds this is also tme for the rest of the group 15 cognates. Selected physical and molecular parameters for the arsenic halides are given in Table 2. ... 

The association of the amine hydrochloride with the aminoarsine complicates the purification of the aminoarsine. When aminolysis of the arsenic trihalide is followed by alkylation of the mono- or bisaminohaloarsine with a Grignard reagent to synthesize the aminoalkyl(or aryl)arsine, the stoichiometry of the reaction must be carefully controlled to avoid cleavage of the As N bond and formation of the tertiary arsine (see Section 2.1). A recent study has shown that the highest yields are obtained from the transamination... 

Trimetho.xyarsine was first reported by Crafts. It was obtained by three methods from silver arsenite and methyl iodide, from arsenic trioxide and tetramethoxysilane, and from arsenic trihalide and sodium methox ide. Better yields have been obtained by applying the method of this synthesis the procedure seems to be generally applicable to the preparation of trialkoxyarsines. 

The double salts formed by the interaction of zinc dialkyls arid arsenic trihalides yield tertiary arsines on treatment with potassium hydroxide ... 

By treating magnesium alkyl halides with arsenic trihalides ... 

There are six types of tertiary aromatic arsines known, if those containing aliphatic radicals are also included ArjAs, ArAr As, ArgAlkAs, ArAlk As, ArAr AlkAs, ArAlkAlk As. For the tyj>e ArjAs, theFittig reaction forms thebasisof a method of preparation, aryl halides and arsenic trihalides reacting in ether or benzene solution in th< ))re-senee of sodium as follows ... 

Arsenic trihalides, especially arsenic trichloride, are the most versatile starting radiolabelled arsenicals employed for the synthesis of a variety of organoarsenic com-... 

AsCl4] [AsFg]. Hydrolysis of the arsenic trihalides becomes more difficult with increasing atomic weight of the halogen. Unlike phosphorus and anti mony, arsenic forms no well-characterised oxohalide. 

Arsenic trioxide may be made by burning arsenic in air or by the hydrolysis of an arsenic trihalide. Commercially, it is obtained by roasting arsenopyrite [1303-18-0], FeAsS. It dissolves in water to a slight extent (1.7 g/100 g water at 25°C) to form a weaHy acidic solution which probably contains the species H3As03, orthoarsenous acid [36465-76-6]. The oxide is amphoteric and hence soluble in acids and bases. It is frequendy used as a primary analytical standard in oxidimetry because it is readily attainable in a high state of purity and is quantitatively oxidized by many reagents commonly used in volumetric analysis, eg, dichromate, nitric acid, hypochlorite, and iron(III). 

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... 

Condensation of arsenic trihalides with alkyl or aryl halides in the presence of metallic sodium, analogous to a Wurtz-Fittig reaction, leads to trialkyl- and triaryl-arsines. E.g., tribenzylarsine is obtained by prolonged boiling of benzyl chloride and arsenic trichloride in ether containing sodium and a little ethyl acetate 501 tripropylarsine is obtained similarly from propyl chloride, arsenic... 

The mixed arsenic trihalides AsX X3 and pentahalides AsX X 3 are essentially unstable compounds. But it has been observed that mixtures of AsCls and AsR favor the formation of AsClsI according to equation (16). A mixture of AsFs and AICI3 has been shown to form small amounts of AsFs Cl and AsFCls by NMR. In a similar fashion, the combination of AsCls and AsBrs forms AsCls Brand AsBrsCl. 

A normal amide of trivalent arsenic, As(NH2)3, can be synthesized by the reaction between gaseous ammonia and an arsenic trihalide (except the fluoride) at low temperatures... 

---