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Diphenylchlorarsine
Names
	Preferred IUPAC name Diphenylarsinous chloride
	Other names diphenylchlorarsine, diphenylchloroarsenic, chlorodiphenylarsane, sneezing gas
Identifiers
CAS Number	712-48-1 ;
3D model (JSmol)	Interactive image; Interactive image;
Abbreviations	Ph2AsCl
ChemSpider	12306 ;
ECHA InfoCard	100.010.839
PubChem CID	12836;
UNII	1H39V3559B ;
CompTox Dashboard (EPA)	DTXSID30858733 ;
	InChI InChI=1S/C12H10AsCl/c14-13(11-7-3-1-4-8-11)12-9-5-2-6-10-12/h1-10H Key: YHHKGKCOLGRKKB-UHFFFAOYSA-N ; InChI=1/C12H10AsCl/c14-13(11-7-3-1-4-8-11)12-9-5-2-6-10-12/h1-10H Key: YHHKGKCOLGRKKB-UHFFFAOYAA;
	SMILES Cl[As](C1=CC=CC=C1)C2=CC=CC=C2; Cl[As](c1ccccc1)c2ccccc2;
Properties
Chemical formula	C12H10AsCl
Molar mass	264.59 g mol−1
Appearance	colorless crystalline solid
Density	1.55 g/cm3
Melting point	42 °C (108 °F; 315 K)
Boiling point	307.2 °C (585.0 °F; 580.3 K)
Magnetic susceptibility (χ)	-145.5·10−6 cm3/mol
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Diphenylchloroarsine (DA) is the organoarsenic compound with the formula (C₆H₅)₂AsCl. It is highly toxic and was once used in chemical warfare. It is also an intermediate in the preparation of other organoarsenic compounds. The molecule consists of a pyramidal As(III) center attached to two phenyl rings and one chloride. It was also known as sneezing oil during World War I by the Allies.

Preparation and structure

It was first produced in 1878 by the German chemists August Michaelis (1847–1916) and Wilhelm La Coste (1854–1885).^[1]^[2] It is prepared by the reduction of diphenylarsinic acid with sulfur dioxide. An idealized equation is shown:^[3]

Ph₂AsO₂H + SO₂ + HCl → Ph₂AsCl + H₂SO₄

The process adopted by Edgewood Arsenal, the "sodium process", for the production of DA for chemical warfare purposes, employed a reaction between chlorobenzene and arsenic trichloride in the presence of sodium.^[4]^[5]

The German process, used in the first war, applied at Hochstam-Main, used the Sandmeyer reaction between phenyldiazonium chloride and sodium arsenite. The acidified product was reduced and then neutralized. The salt was condensed again by the Sandmeyer reaction and reduced again, the final product was then acidified, resulting in DA.^[5]

The structure consists of pyramidal As centre. The As-Cl distance is 2.26 A and the Cl-As-C and C-As-C angles are 96 and 105°, respectively.^[6]

Uses

It is a useful reagent for the preparation of other diphenylarsenic compounds, e.g. by reactions with Grignard reagents:

RMgBr + (C₆H₅)₂AsCl → (C₆H₅)₂AsR + MgBrCl

(R = alkyl, aryl)

Chemical warfare

Diphenylchlorarsine was used as a chemical weapon on the Western front during the trench warfare of World War I.^[7] It belongs to the class of chemicals classified as vomiting agents. Other such agents are diphenylcyanoarsine (DC) and diphenylaminechlorarsine (DM, Adamsite).^[8] Diphenylchlorarsine was sometimes believed to penetrate the gas masks of the time and to cause violent sneezing, forcing removal of the protecting device. The Germans called it Maskenbrecher (mask breaker), together with other substances with similar effects, such as Adamsite, diphenylarsincyanide, and diphenylaminarsincyanide.^{[citation needed]} This gas did not actually penetrate masks any better than other gases.^[9]

DA (military code and acronym for diphenylchloroarsine) is a precursor to DC (diphenylcyanoarsine), generated by the reaction of an aqueous solution of sodium cyanide and DA (DC process, NaCN method), with cyanide being used in excess of 5%, for military purposes.^[5]

Toxicity

Diphenylchlorarsine is known to cause sneezing, coughing, headache, salivation, and vomiting. China and Japan are negotiating remediation of stocks of a variety of organoarsenic weapons, including diphenylchlorarsine, dumped in northeastern China after Japan's numerous invasions of China.^[10]

References

^ As early as 1875, Michaelis found diphenylchlorarsine as a side-product in a reaction to produce monophenylarsenic chloride: Michaelis, A. (1875). "Ueber aromatische Arsenverbindungen" [On aromatic arsenic compounds]. Berichte der Deutschen Chemischen Gesellschaft (in German). 8 (2): 1316–1317. doi:10.1002/cber.187500802125. From p. 1317: "Der zweite neben Phenylarsenchlorid gebildete weisse Körper ist noch nicht untersucht, er ist wahrscheinlich Diphenylarsenchlorid, … " (The second white substance that formed beside phenylarsenic chloride has still not been investigated, it's probably diphenylarsenic chloride, … ) In 1878, Michaelis confirmed that it was indeed diphenylarsenic chloride.(La Coste & Michaelis, 1878), p. 1885
^ La Coste, W.; Michaelis, A. (1878). "Ueber Mono- und Diphenylarsenverbindungen" [On mono- and di-phenyl arsenic compounds]. Berichte der Deutschen Chemischen Gesellschaft (in German). 11 (2): 1883–1887. doi:10.1002/cber.187801102177. See Diphenylarsenchlorür on p. 1885.
^ Blicke, F. F.; Smith, F. D. (1929). "Action of Aromatic Grignard Reagents on Arsenic Trioxide". Journal of the American Chemical Society. 51 (5): 1558–1565. doi:10.1021/ja01380a038.
^ An Historical Sketch of Edgewood Arsenal. p 66
^ ^a ^b ^c CHEMICAL CORPS CHEMICAL AND RADIOLOGICAL LABORATORIES. Army Chemical Center Maryland. Project: 4-72-05-005. 25 October, 1954
^ Trotter, J. (1962). "Stereochemistry of Arsenic. IV. Chlorodiphenylarsine". Canadian Journal of Chemistry. 40 (8): 1590–1593. doi:10.1139/v62-241.
^ Gilbert, M. (1995). The First World War—A Complete History. HarperCollins. ISBN 0805047344.
^ Holstege, C. P.; Boyle, J. S. (2008-11-26). "CBRNE - Vomiting Agents - Dm, Da, Dc". Medscape.
^ Gas and Flame in Modern Warfare, 1918, Chapter IX.
^ "Abandoned Chemical Weapons (ACW) in China". February 6, 2004. Archived from the original on July 4, 2008.