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Sartori The War Gases Chemistry and analysis

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144

ALDEHYDES

Water reacts with acrolein only at 100°, forming the corresponding hydroxy-aldehyde :

CH2 = CH—CHO + H2O = CH2OH—CH2—CHO.

Alkalies rapidly polymerise acrolein.1 An ethereal solution of potassium cyanide in presence of acetic acid forms the nitrile of a hydroxy vinylacetic acid 2 :

CH2 = CH—CHO + HCN = CH2 = CH—CHOHCN

This is a colourless liquid, boiling at 93° to 94° C. at 16 mm. of mercury. Its density at 15° C. is 1-009, and it is rniscible in all proportions with alcohol, ether and water, but sparingly soluble in petroleum ether.

Pure acrolein does not attack metals.

The minimum concentration of acrolein which causes lachrymation is 7 mgm. per cu. m. of air. The limit of insupportability is 50 mgm. per cu. m. The mortality-product is 2,000 according to Miiller, and 7,000 according to Meyer.

DETECTION

Lewin's Reactions,3 On treatment of acrolein with a solution of sodium nitroprusside in piperidine, an intense blue coloration is produced which passes to violet with ammonia and to brown with mineral acids. The same colour changes are produced by bubbling air containing acrolein vapour through the reagent. Sensitivity : 25 mgm. acrolein per cu. m. of air.4 Instead of piperidine, dimethylamine may be employed, but the sensitivity of the reaction is then less.

Nierensteiri's Reaction.5 This reaction is based on the change of colour of a solution of phloroglucinol in presence of acrolein. On treatment of the solution to be tested with 2-3 ml. 5% phloroglucinol and addition of 5-10 drops of alkali, and then boiling rapidly, the presence of acrolein is detected by a bluishgreen colour.

p-Nitro Phenylhydrazine Reaction.6 An aqueous solution of ^>-nitro phenylhydrazine hydrochloride, which should remain colourless on addition of a few drops of acetic acid, produces an orange-yellow precipitate with acrolein. This precipitate consists of small stellar crystals, easily visible under the microscope.

1 NEF, Ann., 1904, 335, 220.

1 LOBRY DE BRUYN, Rec. trav. chim., 1885, 4, 223 ; V. DERSLEEN, Rec. trav. chim., 1902, 21, 211.

3LEWIN, Ber., 1899, 32, 3388.

4GRODSOVSKY, Analis Voxduxa, Moscow, 1931, 206.

6

NIERENSTEIN, Collegium, 1905, 158 ; Cfiem. Zentr., 1905 (II), 169.

6

H. BEHRENS, Chem. Zlg., 1905, 27, 1105.

ACROLEIN : DETERMINATION

145

QUANTITATIVE DETERMINATION

Ivanov's Method.1 This is founded on the reaction of acrolein with sodium bisulphite already mentioned. The excess bisulphite is titrated with iodine according to the following equations :

CH2=CH-CHO + z NaHSO3 = CH2(SO8Na)-CHa-CH(OH)SO3Na

NaHS03 + I2 + H20 = NaHSO4 + 2 HI

0-1-0-15 gm. of the substance to be analysed is placed in a small glass bulb which is then sealed in the blowpipe and weighed. The bulb is placed in a bottle together with 100 ml. water. The bulb is then broken and a standardised solution of sodium bisulphite added, sufficient being employed to react with 50% more acrolein than is actually present in the sample. The mixture is allowed to stand for about 6 hours and then the excess of bisulphite is titrated with iodine solution in presence of starch, to a blue coloration stable for 15 minutes.

The bisulphite and iodine solutions are standardised so that i ml. of each is equivalent to i mgm. acrolein.

This method has also been suggested by Zappi.2

1N. IVANOV, Arch. Hyg., 1911, 74, 307.

2E. ZAPPI and LABRIOLA, Anales Asoc. Quim. Argentina, 1930, 18, 243.

CHAPTER XI

HALOGENATED KETONES

(A) ALIPHATIC

IN the ketone group, the halogenated derivatives are of great interest as war gases.

They are usually prepared by the direct action of the halogens on the corresponding ketones. The introduction of a halogen atom into the molecule of a ketone usually takes place according to a definite rule : The first halogen atom entering substitutes a hydrogen of the least hydrogenated alkyl group, whether secondary or tertiary, and it is only the second halogen atom which can enter a different group.

For example, in chlorinating methyl ethyl ketone, CH3—CO—CH2—CH3, methyl-a-chloroethyl ketone is first obtained:

CH3-CO-CH-CH3

and then on further, chlorination, methyl-a-/?-dichloroethyl ketone:

CH3-CO-CH-CH2C1

Cl

The introduction of-ar second halogen atom into the molecule of these substances affects their properties differently according to the position it occupies. It is found that the symmetric dihalogenated ketones have higher specific gravities, higher boiling points and, in particular, more powerful toxic properties than the asymmetric dihalogenated ketones. Thus in chlorinating acetone, chloroacetone is first obtained, CH2C1—CO—CH3, and then by further chlorination a mixture of the symmetric and asymmetric dichloro-derivatives is obtained :

CH2C1—CO—CH2C1 and CHC12—CO—CH3.

On examining these two compounds,1 it is found that the symmetric compound (S.G. 1-383 and b.p. 171° C.) is more toxic

1 T. POSNBR and K. ROHDE, Ber., 1909, 42, 3233.

146

ALIPHATIC HALOGENATED KETONES

147

than the asymmetric derivative (S.G. 1-236 and b.p. 120° C.).1 Symmetric dichloroacetone, besides its normal irritant action on the eyes and the respiratory organs, has, even in low concentrations, an irritant action on the skin which is more precisely termed " orticant " action.2

In the preparation of the halogenated ketones by direct halogenation only half the halogen reacting enters the ketone molecule, the other half forming the halogen hydracid :

CH3—CO—CH3 + Br2 = CH3—CO—CH2Br + HBr.

In order to prevent this loss of halogen, especially in the industrial manufacture of the bromoand iododerivatives, the halogen of the hydracid is regenerated by adding to the reaction mixture an oxidising agent, usually sodium chlorate. By reaction with the hydracid this liberates the halogen which can re-enter the reaction :

NaClO3 + 6HBr = 3Br2 + 3H2O + NaCl.

The halogenated aliphatic ketones are, in general, somewhat unstable compounds. In time, decomposition or resinification takes place. These processes are partly prevented by the addition of stabilising substances which impede the changes for some time.

Because of the presence of the carbonyl group in the molecule, they react with sodium bisulphite to form well-crystallised additive products. This behaviour is employed in practice to separate the halogenated ketones from the secondary products of the reaction.

The halogenated ketones have powerful lachrymatory properties. The iodine compounds are the most irritant, then following the bromine and lastly the chlorine.

During the war of 1914-18, bromoacetone and bromomethyl ethyl ketone were especially used. Chloroacetone was employed only for a short time, being soon superseded by other substances having a more powerful aggressive action.

Since the war several other halogenated ketones have been prepared and examined, such as

«''-fi-dichloromethyl ethyl ketone, C1CH2—CO—CH2—CH2C1,

obtained by the action of ethylene on chloroacetyl chloride in presence of aluminium chloride, or, in better yield, by the action of diazomethane on /3-chloropropionyl chloride and then treat-

1

LINDEMANN, Toksykologya chem. srodkow bojowch, Warsaw, 1925, 381.

1

HACKMANN, Chem. Weekblad., 1934, 31, 366.

148 HALOGENATED KETONES

ment with hydrochloric acid. It is a liquid boiling at 65° C. at a pressure of 3 mm. and has strong lachrymatory properties.1

Fluoroacetone, obtained by the action of thallium fluoride on bromoacetone,2 is a yellow liquid boiling at 72-5° C. It has a density of 0-967 at 20° C. It is described as having a pungent odour, but nothing has been reported concerning its aggressive action.

1. Chloroacetone. C1CH2—CO—CH3

(M.Wt. 92-5)

Chloroacetone was obtained by Riche in 1859 3 in electrolysing

a mixture of hydrochloric acid and acetone.

It was used in the

last war, especially by the French, to replace bromoacetone during the period of bromine shortage (1914-15).

LABORATORY PREPARATION 4

It is prepared bythe action of chlorine on acetone.

80 gm. acetone and 20 gm. calcium carbonate in lumps are placed in a wide-necked flask fitted with a three-holed stopper. Through one of the holes in the stopper a reflux condenser passes, through the second a tap-funnel and through the third a delivery tube for the chlorine. The calcium carbonate is added in order to neutralise the hydrochloric acid liberated in the reaction. A current of chlorine is passed in from a cylinder, and 30-40 ml. water are gradually added from the tap-funnel. The temperature is raised to 60° C. on a water-bath. When the calcium carbonate in the flask is almost exhausted, the current of gas is stopped and the mixture allowed to stand overnight. The liquid then settles into two layers; the top layer is separated and fractionally distilled.

PHYSICAL AND CHEMICAL PROPERTIES

Chloroacetone is a clear liquid boiling at 119° C. It is sparingly soluble in water, but easily in alcohol, ether, chloroform and other organic solvents. Its specific gravity is 1-162 at 16° C., and its vapour density is 3-2. It is relatively slightly volatile : its volatility at 20° C. is about 61,000 mgm. per cu. m. (Libermann).

On exposure to light in sealed glass containers it is converted in about i year into a solid carbonaceous substance which fumes in air giving off hydrochloric acid, and does not react with phenylhydrazine, hydroxylamine or oleum, but dissolves in fuming nitric acid.5

1

R. CARROLLand SMITH, /. Am. Chem. Soc., 1933, 55, 370.

2

P. RAYand coll., /. Indian Chem. Soc., 1935, 12, 93.

3RICHE, Ann., 1859, 112, 321.

4P. FKITSCH, Ber., 1893, 26, 597.

8 GIUA and Rocciu, Atti accad. sci. Torino, 1932, 67, 409.

CHLOROACETONE : PROPERTIES

149

When the vapour of chloroacetone is passed through a tube heated to 450° C., acetone, acetaldehyde and crotonaldehyde are formed.1

Chloroacetone does not react with water.2 Chlorine even in the cold converts it into more highly chlorinated compounds ; treatment at 100° C. in sunlight converts it into pentachloroacetone of the formula 3 CHC12—CO—CC13. Bromine is almost without action in the cold, but on heating to about 100° C. it reacts vigorously forming chlorotribromoacetone.4 Potash decomposes chloroacetone, forming potassium chloride and red or brown products whose composition has not yet been determined.5

The manner in which chloroacetone reacts with other compounds is also interesting. With gaseous ammonia, for example, aminoacetone is formed,6 and with nascent hydrogen (from zinc and acetic acid) it is converted into acetone.7 Damp silver oxide oxidises it to glycollic, formic and acetic acids. On combination with sodium bisulphite, acicular crystals are formed, probably of an additive compound of the formula 8 :

CH2C1

OH

CH3

An additive compound is also formed with hexamethylene tetramine ; this consists of crystals melting at 122° C. (Nef).

By the action of sulphuretted hydrogen or sodium sulphide on chloroacetone, diacetonyl sulphide is formed :

2CH2C1—CO—CH3 + Na2S = (CH3—COCHa)2S + aNaCl.

This forms crystals melting at 47° C. and boiling at 136° to 137° C. at 15 mm. mercury pressure.

Chloroacetone reacts with hydrocyanic acid, forming chloroacetone chlorohydrin 9 :

CH3—CO—CH2C1 + HCN = CH3C(OH)(CN)—CH2C1.

With potassium cyanide, cyanoacetone is not formed, but various polymerisation products are produced.

1NEF,Ann., 1904, 335, 278. LINNEMANN, Ann., 1865, 134, 171.

FRITSCH, Ber., 1893, 26, 597.-

CLOEZ, Ann. chim. phys., 1886, [6] 9, 207.

MULDER, Ber., 1872, 5, 1009.

G. PINKUS, Ber., 1893, 26, 2197.

LINNEMANN, loc. cit.

NEKRASSOV, op. cit.

BISCHOF, Ber., 1872, 5, 864.

HALOGENATED KETONES

Chloroacetone decomposes in contact with iron and cannot be loaded directly into projectiles.

The lowest concentration producing irritation of the eyes is 18 mgm. per cu. m. of air. The limit of insupportability is 100 mgm. per cu. m. and the mortality-product is 3,000 (Muller).

2. Bromoacetone. BrCH2—CO—CH3

(M.Wt. 136-5)

Bromoacetone was prepared by Linnemann1 in 1863, and because of its powerful lachrymatory properties was used by the Germans in 1915 in shells and hand-bombs.

LABORATORY PREPARATION

This compound is obtained in a similar manner tochloroacetone, by the action of bromine on

 

 

acetone.

 

 

 

 

 

30

gm.

acetone,

30

gm.

 

 

acetic acid and 120 ml. water

 

 

are placed in a flask of 250-

 

 

300

ml. capacity

which is

 

 

fitted with a reflux condenser

 

 

and

a tap-funnel (Fig.

10).

 

 

The

whole is heated on a

 

 

water-bath

to 70° C. and then

 

 

91 gm. bromine are added

 

 

from

the tap-funnel, the flask

 

 

being exposed to the direct

 

 

light from a 750-watt lamp.

 

 

When the liquid is decolour-

 

 

ised 60 ml. of water are added,

 

 

the flaskcooled anda saturated

 

 

solution of soda added. An oil

 

 

separates and this is dried and

 

 

distilled in vacua.

 

 

FIG.

10.

Bromoacetone may be also

 

 

 

 

 

obtained in the laboratory by the action of brominedissolved in acetone on an aqueous solution of sodium bromate and sulphuric acid at 30° to 35°C.a The following reaction then takes place :

10 CH3-CO-CH3 + 4 Bra +

+ 2 NaBr03 + 2 H2SO4 =

= 10 CH3-CO-CH2Br +

2 NaHSO4 6 H8O

1LINNEMANN, Ann., 1863, 125, 307.

A. CHRZASZCZEVSKA and W. SOBIERANSKY, Roczniki Chem., 1927, 7, 79.

BROMOACETONE: MANUFACTURE 151

INDUSTRIAL MANUFACTURE

French Method. Because of the limited availability of bromine the manufacture of bromoacetone was carried out in France during the war by treating acetone with sodium bromate and sodium chlorate in presence of sulphuric acid instead of by the direct action of bromine on acetone. The following reaction takes place:

NaC103 + 3 NaBr + 3 CH3-CO-CH3 + 3 H2SO4 =

= 3 CH2Br-CO-CH3 + 3 NaHSO4 + NaCl -h 3 H2O

In this method, if the solution remains acid, hydrochloric acid is formed and this reacts with the sodium chlorate, liberating chlorine:

HC103 + 5HC1 = 3C12 + 3H20.

Hence there is simultaneous chlorination and bromination of the acetone, with the formation of a mixture of bromoacetone and chloroacetone.

German Method. The manufacture of bromoacetone in Germany1 was carried out by treating an aqueous solution of sodium or potassium chlorate with acetone and then adding in

small quantities the proper quantity

of bromine.

The

reaction

is

carried out in

iron vessels A (Fig. n) of

4-5

cu. m. capacity

(900-

 

1,100 gallons)

coated in-

 

ternally with resistant tiles

 

and fitted with an agitator

 

D.

These are

set

in a

 

wooden framework E.

 

The aqueous solution of

 

sodium

chlorate

is

first

 

prepared, the

acetone is

 

added,

and

then

the

FIG. ii.

 

 

 

 

 

 

bromine introducedslowly,

stirring and maintaining the internal temperature at 30° to 40°C. At the end of the reaction the oily layer is separated and transferred to a vessel where it is treated with magnesium oxide to neutralise the excess of free acid.

In order to determine the quantity of bromoacetone formed, a part of the product is dried with calcium chloride and distilled. If more than 10% of the product distils below 136° C. the product is brominated further, if less than 10% then the operation is considered satisfactory. The product is stored with the addition

1 NORRIS, /. Ind. Eng. Chem., 1919, 11, 828.

152 HALOGENATED KETONES

of about i part of magnesium oxide to 1,000 parts of bromoacetone in order to neutralise the hydrobromic acid slowly formed on storage.

PHYSICAL AND CHEMICAL PROPERTIES

Pure bromoacetone is a colourless liquid with a pungent odour and a boiling point of 23-5° C. to 24-5° C. at 3-5 mm. mercury and

31-4° C. at 8 mm. mercury pressure.

At ordinary

pressure it

boils at

136° C. with partial

decomposition, hydrobromic acid

and a resinous residue slightly

soluble in water and alcohol being

formed.

On cooling strongly

it solidifies to a mass which melts

at —54° C. Its specific gravity

at

o° C. is 1-631, its vapour

tension

at 10° C. is i mm. and at

20°C., 9 mm.

The vapour

density is 475 and its volatility at 20°C. is 75,000 mgm. per cu. m. (Muller).

The commercial product is yellow or brown.

Bromoacetone is only slightly soluble in water, but very soluble in alcohol, ether, acetone and other organic solvents. It is not very stable, even in the pure state.1 It polymerises in time, especially under the influence of light and heat,2 though this process may be impeded by the addition of stabilising substances. During the war a small quantity of magnesium oxide was added to bromoacetone and this checked the polymerisation for several months (Meyer).

Bromoacetone when distilled with steam partly passes over unaltered and partly decomposes to give an oily product containing little bromine, while the water is coloured brown.

It combines readily with a variety of substances. With sodium bisulphite it forms a crystalline substance of the formula :

CH2Br

/OH

SS03Na

On passing well-dried ammonia into bromoacetone in ethereal solution, acicular crystals separate, probably due to the formation

of an additive compound.3

 

By the

action of hydrocyanic acid on bromoacetone 4

in the

cold (i.e.,

at about o° C.) bromoacetone cyanohydrin is

formed.

1EMMERLING and WAGNER, Ann., 1880, 204, 29.

2GIUA and Rocciu, Atti accad. set. Torino, 1932, 67, 409.

8SOKOLOVSKY, Ber., 1876, 9, 1687.

*A. CHRZASZCZBVSKA and W. SOBIERANSKY, loc. cit.

 

BROMOMETHYL

ETHYL KETONE

153

This is

a colourless liquid with a boiling point

of 94-5° C. at a

pressure

of 5 mm. of mercury. Its specific

gravity is

1-584

at 13° C., and it is soluble in water, alcohol and ether.

 

The bromine atom of bromoacetone is easily separated

from

the molecule and substituted

by other atoms or radicles.

Thus

on treating bromoacetone with alcoholic potash, hydroxyacetone and potassium bromide are obtained; with sodium iodide iodoacetone is formed, this being a substance with strongly lachrymatory properties, but of little importance as a war gas because of its high cost.

Bromoacetone reacts with iron, but does not attack lead, so it is essential to store it in lead-lined containers.

The animal fibres absorb more bromoacetone than do the vegetable fibres. The absorption capacity is fairly high and textiles are discoloured. It is found that textiles which are merely air-dried absorb more bromoacetone than those which have been completely freed from all water.1

For the purificationof places contaminated with bromoacetone, spraying with a solution of 240 gm. " liver of sulphur " in 140 ml. of a soap solution diluted with 10 litres of water is recommended.

The lower limit of irritation is i mgm. per cu. m. of air. The maximum concentration which a normal man can support for not more than i minute is 10 mgm. per cu. m. The mortalityproduct is 4,000 (Miiller) or 32,000 (Prentiss).

During the war of 1914-18 the French used a mixture of bromoacetone and chloroacetone (80 : 20) known as " Martonite." The reasons for the employment of this mixture are of a technical nature (see p. 151).

3. Bromomethyl Ethyl Ketone. BrCH2—CO—C2H5

(M.Wt. 151)

This substance was employed in place of bromoacetone, whose production during the war period was impeded by the necessity of reserving acetone for the needs of the explosives industry.

On the other hand, methyl ethyl ketone, the primary material in the preparation of this war gas, is easily obtainable even in wartime, for it is a by-product in the manufacture of acetone from pyroligneous acid. The monobromoderivative of methyl ethyl ketone has similar aggressive properties to bromoacetone and was used by both the French and the Germans in the war of 1914-18.

PREPARATION

This compound is prepared both in the laboratory and on the plant scale by a method similar to that already described for

1 ALEXEJEVSKY, /. Prikl. Khimii., 1929, 1, 184.

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