Sartori The War Gases Chemistry and analysis

Potassium Cyanide. When an alcoholic solution of ]8j8' dichlorovinyl arsine is treated with potassium cyanide, it is converted into ftp' dichlorovinyl cyanoarsine,1 (ClCH=CH)2AsCN, which is a colourless oil with a high toxicity (Libermann).

Hydrogen Sulphide. When hydrogen sulphide is passed into a solution of dichlorovinyl chloroarsine in absolute alcohol an exothermic reaction takes place and dichlorovinyl arsenious sulphide is formed :

(C1CH = CH)2As—S—As(CH = CHC1)2.

This is a viscous, yellowish-brown substance, soluble in alcohol, insoluble in water, having vigorous irritant properties on the mucous membranes and a nauseating odour (Lewis).

Chloramine-T. Treatment of dichlorovinyl chloroarsine with an equivalent amount of chloramine-T (CH3=C6H4— SO2Na=NCl) produces no additive-compound, unlike trichlorovinyl arsine.

The biological action of dichlorovinyl chloroarsine is similar to that of chlorovinyl dichloroarsine, but less violent.

m.p. 21-5° C.2 It has a specific gravity at 1-572 at 20° C. and has a vapour density of 9.

The vapour tension at temperature t may be calculated from the following formula (see p. 5).

in this respect from the other two chlorovinyl arsines which are both soluble in all proportions in alcohol. This, and its melting point, may be used for its detection.

296 ARSENIC COMPOUNDS

CHEMICAL PROPERTIES

Water. Trichlorovinyl arsine does not react with water and may be distilled in steam without any decomposition.

They consist of trichlorovinyl dibromo arsine (Mann and Pope) :

/Br

(Cl-CH=CH)3As(

NBr

On treating this dibromo compound with hydrogen sulphide, it decomposes to form hydrobromic acid and trichlorovinyl arsine and deposit sulphur :

Nitric Acid. Concentrated nitric acid reacts vigorously with trichlorovinyl arsine, and in order to moderate the violence of the reaction, it is advisable to treat a small quantity of trichlorovinyl arsine (not more than 2 gm.) with an equal volume of nitric acid and warm cautiously. On allowingto cool, a colourless crystalline mass is deposited and when this is crystallised from chloroform, small needles, melting at 103° C. are obtained. This substance is trichlorovinyl hydroxyarsonium nitrate.

/OH

(Cl-CH=CH)sAs(

XN03

When this nitrate is treated with an aqueous solution of sodium hydroxide in equivalent quantity, the product extracted with chloroform and the solvent evaporated, a crystalline residue remains. This consists of trichlorovinyl arsenic oxide (C1CH = CH)3AsO. On crystallising this from benzene containing a little chloroform, long colourless needles are obtained melting at 154° C. with decomposition (Mann and Pope).

Chloramine-T. This tertiary arsine condenses with chloramine-T (CH3—C6H4—S02Na: NCI) to give an additive compound of the formula (C1CH = CH)3As = N—SO2—C6H4—CH3. This contains the grouping

: As = N—

which according to Mann and Pope may be termed the " arsilimine " group, by analogy with the sulphilimine group

298 ARSENIC COMPOUNDS

biological action of these substances is similar to that of the aromatic arsines described in this chapter.1

Recently several arsenical derivatives of naphthalene have been prepared:

Naphthyl methyl chloroarsine:

C10H,\)AsCl CH3'

and Naphthyl methyl fluoroarsine :

C10H,v ^ >AsF

CH/

The biological properties of these have not been reported in the literature.2

XI

C6H6—As<

\C1

Phenyl dichloroarsine was prepared in 1878 by La Coste and Michaelis8 by passing the vapours of benzene and arsenic trichloride through a heated tube. The product obtained was impure with the diphenyl compound and could be purified by distillation or crystallisation only with some difficulty. The same workers later studied another method for its preparation.4 This is more convenient and consists in heating mercury diphenyl to 250° C. with an excess of arsenic trichloride.

Phenyl dichloroarsine may also be obtained by heating triphenylarsine with arsenic trichloride in a closed tube to 250°C. for 30 hours 8 :

As(C6H6)3 + 2AsCl3 = 3C6H6AsCl2,

or by heating phenyl mercuri-chloride with arsenic trichloride to 100° C. for 4-5 hours (Roeder and Blasi's method).6

LABORATORY PREPARATION

Roeder and Blasi's method, mentioned above, is usually employed for the preparation. 50 gm. mercuric acetate are dissolved in 50 ml. acetic acid in a thick-walled flask. 100 ml. benzene, free from thiophene, are added and the mixture heated

300 ARSENIC COMPOUNDS

Alkali Hydroxides. Phenyl dichloroarsine is also hydrolysed by the action of alkali hydroxide solutions. The phenyl arsenious oxide in presence of excess alkali is converted to the salt of the corresponding phenyl arsenious acid :

/ONa

C6H5AsO + 2 NaOH = C6H6As( + H2O NONa

Halogens, With chlorine and phenyl dichloroarsine, an additive compound is formed, tetrachloro phenylarsine. This decomposes into phenyl arsenic acid in the presence of moisture.

Bromine, however, forms no additive compound. By treatment of phenyl dichloroarsine with excess of bromine, the molecule is decomposed with formation of dibromobenzene, arsenic chlorobromide and hydrobromic acid,1 as follows :

C6H8AsCl2 + 2Br2 = C6H4Br2 + AsBrCl2 + HBr.

Ammonia. By the action of gaseous bromine on phenyl dichloroarsine in benzene solution, phenyl arsenimide2 is obtained:

C6HBAsCl2 + 3NH3 = C6H5AsNH + 2NH4C1.

This forms crystals melting at 26-5° C. and decomposes rapidly with formation of phenyl arsenious oxide by the action of water or even on exposure to moist air :

C6H6AsNH + H20 = C6H8AsO + NH3.

Phenyl arsenimide both dispersed in the air and in solution has a very irritant action on the skin.3

Amines. Primary and secondary amines, both of the aliphatic and aromatic series, react vigorously with phenyl dichloroarsine, giving compounds of the following types :

and liberating hydrochloric acid. With aniline, for example, a compound of the following structure is formed :

/NHC6H5 C6H6As(

NC1

This is readily hydrolysed by the action of moisture forming phenyl arsenious oxide and aniline hydrochloride.

PHENYL DICHLOROARSINE : PROPERTIES 301

With diphenylamine, 10 chloro 5-10 dihydro phenarsazine is formed 1 :

C* TT

C6H5AsCl2 + NH(C6H5)2 = NH( 6 4)AsCl + C6H6 +HC1

With tertiary aliphatic amines, additive products are formed ; triethylamine, for instance, forms :

/Cl C6H5-AsfCl

Hydrogen Sulphide. By the action of hydrogen sulphide on phenyl dichloroarsine in alcoholic solution, phenyl arsenious

sulphide obtained is insoluble in water, its formation may be employed to detect small quantities of the arsine (0-05 mgm. in i ml. water).

Silver Cyanide. By prolonged boiling (5 hours) of silver cyanide with phenyl dichloroarsine in benzene solution, phenyl dicyanoarsine,4 C6H5As(CN)2, is formed as crystals with an odour which is both aromatic and also resembles hydrocyanic acid. It melts at 78-5° to 79-5° C., and is readily decomposed by water or even by damp air, with formation of phenyl arsenious oxide and hydrocyanic acid.

Acid Chlorides. Phenyl dichloroarsine, when treated with the aliphatic acid chlorides, e.g., acetyl chloride, in carbon disulphide solution and in presence of aluminium chloride, forms acetophenone and arsenic trichloride 5 :

C6H5AsCl2 + CHjCOCl = C8H5COCH3 + AsCls.

With chloroacetyl chloride, chloroacetophenone is obtained 6 :

C6H5AsCl2 + C1CH3COC1 = C6H5COCH2C1 + AsCl3.

Dimethyl Arsine. With dimethyl arsine a white crystalline product, C6H5AsCl2.(CH3)2AsH, is formed, which is readily decomposed by the action of moisture.7

1 BURTON and GIBSON, /. Chem. Soc., 1926, 464; GIBSON, /. Am. Chem. Soc., 1931, 53, 376.

302 ARSENIC COMPOUNDS

Diphenyl Arsine. By the action of diphenyl arsine on phenyl dichloroarsine, arsenobenzene and diphenyl chloroarsine are formed 1 :

4 C8H5AsClz + 4 (C6H5)2AsH =

= 2 C6H5-As=As-C6H5 + 4 (C6H5)2AsCl + 4 HC1

Pure phenyl dichloroarsine does not attack iron.

Phenyl dichloroarsine was employed during the war of 1914-18 first by the Germans as a solvent for diphenyl cyanoarsine and later by the French in admixture with 40% of diphenyl chloroarsine under the name of " Sternite."

Phenyl dichloroarsine is a lung irritant, a vesicant 2 and a lachrymatory. The maximum concentration which a normal man can support for not more than a minute is 16 mgm. per cu. m.

C6H/

Diphenyl chloroarsine was prepared in 1880 by La Coste and Michaelis3byheating mercurydiphenyl withphenyl dichloroarsine :

v~\|

2 C6H5-As( + (C«H5)2 Hg = 2 (C6H5)2As-Cl + HgCl2

NC1

Its employment in September 1917 was a great surprise to the Allies because of its peculiar physical properties which enabled it, when properly dispersed in the atmosphere, to pass through the respirator-filters then inuse.

PREPARATION

Diphenyl chloroarsine may be prepared in various ways :

• MICHAELIS and LACOSTE, Ann., 1880, 201,219.

DIPHENYL CHLOROARSINE: PREPARATION 303

(3)By the action of phenyl magnesium bromide on arsenious oxide. Triphenyl arsine is obtained at the same time.1

(4)By the reaction between phenyl dichloroarsine and diphenyl arsine 2 :

4 C6H5AsCl2 + 4 (C6H5)2AsH -v 4 (C6H5)2AsCl +

2 C6H5As=AsC6HB + 4 HC1

(5) By the action of arsenic trichloride on lead tetraphenyl in toluene solution3 :

AsCl3 + (C6H6)4Pb = (C6H5)2AsCl + (C6H5)2PbCl2.

During the war the Allies, in order to obtain rapid production of diphenyl chloroarsine, followed the method of Michaelis,4 modified by Morgan and Vining.5 This method consists in preparing triphenyl arsine from chlorobenzene and arsenic trichloride, in the presence of metallic sodium :

3C6H5C1 + AsCl3 + 6Na= (C6H8)3As + 6NaCl,

and then heating this substance with more arsenic trichloride :

2(C6H6)3As + AsCl3 = 3(C.HB)1AsCl.

The Germans, however, used an entirely different process (see p. 306), based on the reaction between the diazom'um salts and sodium arsenite which Bart had studied for the first time in 1912.'

LABORATORY PREPARATION

The preparation of diphenyl chloroarsine in the laboratory 7 is most conveniently carried out by Pope and Turner's 8 modification of the method of Michaelis.

57 gm. sodium cut into slices are placed in a round-bottomed flask fitted with a reflux condenser and covered with 300 ml. benzene containing r-2% ethyl acetate (which catalyses the reaction). After allowing this mixture to stand for £ hour (in order to activate the metal) 136 gm. chlorobenzene and 85% arsenic chloride are slowly added. After a few minutes the reaction is considerably accelerated, and if necessary the flask should be cooled externally with a. freezing mixture. It is then

7NENITZESCU, Antigaz, 1929, No. 2.

8POPE and TURNER, /. Chem. Soc., 1920, 117, 1447.