Halogenated Ketones

One of the earliest lachrymators used was bromoacetone. Because of the difficulty of obtaining pure material, the commercial product, containing considerable dibromoacetone and probably higher halogenated bodies, was used. The presence of these higher bromine derivatives considerably decreased its efficiency as a lachrymator. The preparation of bromoacetone involved the loss of considerable bromine in the form of hydrobromic acid. This led the French to study various methods of preparation, and they finally obtained a product containing 80 per cent bromoacetone and 20 per cent chloroacetone, which they called “martonite.” As the war progressed, acetone became scarce, and the Germans substituted methylethylketone, for which there was little use in other war activities. This led to the French “homomartonite.”

Various other halogen derivatives of ketones have been studied in the laboratory, but none have proven of as great value as bromoacetone, either from the standpoint of toxicity or lachrymatory power.

Bromoacetone may be prepared by the action of bromine (liquid or vapor) upon acetone (with or without a solvent). Aqueous solutions of acetone, or potassium bromide solutions of bromine, have also been used.

Pure bromoacetone is a water clear liquid. There are great differences in the properties ascribed to this body by different investigators. This probably is due to the fact that the monobromo derivative is mixed with those containing two or more atoms of bromine. A sample boiling at 126-127° and melting at -54°, had a specific gravity of 1.631 at 0°. It has a vapor pressure of 9 mm. of mercury at 20°.

While bromoacetone is a good lachrymator, it possesses the disadvantage that it is not very stable. Special shell linings are necessary, and even then the material may be decomposed before the shell is fired. The Germans used a lead-lined shell, while considerable work has been carried out in this country with enamel lined shell. Glass lined shell may also be used. It is interesting to note that, while bromoacetone decomposes upon standing in the shell, it is stable upon detonation. No decomposition products are found after the explosion, and even unchanged liquid is found in the shell. It may be considered as having a low persistency, since the odor entirely disappears from the surface of the ground in twenty-four hours.

Bromoacetone was also used by the Germans in glass hand grenades (Hand-a-Stink Kugel) and later in metal grenades. The metal grenades weighed about two pounds and contained about a pound and a half of the liquid.

Martonite was prepared by the French in an attempt more completely to utilize the bromine in the preparation of bromoacetone. They regenerated the bromine by the use of sodium chlorate:

NaClO₃ + 6HBr = NaCl + 3Br₂ + 3H₂O

In practice sulfuric acid is used with the sodium chlorate, so that the final products are sodium acid sulfate and a mixture of 20 per cent chloroacetone and 80 per cent bromoacetone, according to the reaction:

5(CH₃)₂CO + 4Br + H₂SO₄ + NaClO₃ =
4CH₂BrCOCH₃ + CH₂ClCO CH₃ + NaHSO₄ + 3H₂O.

This product is equally as effective as bromoacetone alone and is very much cheaper to manufacture. In general its properties resemble very closely those of bromoacetone.

German Manufacture of Bromoacetone
and Bromomethylethyl ketone[17]

These two products were prepared by identical methods. About two-thirds of the product produced by the factory was prepared from methylethyl ketone which was obtained from the product resulting from the distillation of wood. The method employed was to treat an aqueous solution of potassium or sodium chlorate with acetone or methylethyl ketone, and then add slowly the required amount of bromine. The equation for the reaction in the case of acetone is as follows:

CH₃COCH₃ + Br₂ = CH₂BrCOCH₃ + HBr

Ten kg.-mols of acetone or methylethyl ketone were used in a single operation. About 10 per cent excess of chlorate over that required to oxidize the hydrobromic acid formed in the reaction was used. The relation between the water and the ketone was in the proportion of 2 parts by weight of the former to 1 part by weight of the latter. For 1 kg.-mol. wt. of the ketone, 10 per cent excess over 1 kg. atomic-weight of bromine was used.

The reaction was carried out either in earthenware vessels or in iron kettles lined with earthenware. The kettles were furnished with a stirrer made of wood, and varied in capacity from 4,000 to 5,000 liters. They were set in wooden tanks and cooled by circulating water. The chlorate was first dissolved in the water and then the ketone added. Into this mixture the bromine was allowed to run slowly while the solution was stirred and kept at a temperature of from 30° to 40° C. The time required for the addition of the bromine was about 48 hrs. When the reaction was complete, the oil was drawn off into an iron vessel and stirred with magnesium oxide in the presence of a small amount of water in order to neutralize the free acid. It was then separated and dried with calcium chloride. At this point a sample of the material was taken and tested. The product was distilled to tell how much of it boiled over below 130° when methylethyl ketone had been used. If less than 10 per cent distilled over, the bromination was considered to be satisfactory. If, however, a larger percentage of low boiling material was obtained, the product was submitted to further bromination. The material obtained in this way was found on analysis to contain slightly less than the theoretical amount of monobromoketone.

It was finally transferred by suction or by pressure into tank-wagons. At first lead-lined tanks were used, but later it was found that tanks made of iron could be substituted. In order to take care of the small amount of hydrobromic acid, which is slowly formed, a small amount of magnesium oxide was added to the material. The amount of the oxide used was approximately in the proportion of 1 part to 1000 parts of ketone. When the magnesium oxide was used, it was found that the bromoketone kept without appreciable decomposition for about 2 months. The yield of the product from 580 kg. of acetone (10 kg.-mol. wts.) was 1,100 kg. The yield from 720 kg. of methylethyl ketone (10 kg.-mol. wts.) was 1,250 kg.