Science Fair Project Encyclopedia
Mustard gas (HD) is a chemical compound that was first used as a chemical weapon in World War I. In pure form, it is a colourless, odourless, viscous liquid at room temperature and causes blistering of the skin. The name comes from impure mustard gas, which is usually yellow-brown in colour and has an odour resembling mustard, garlic or horseradish. It is otherwise not related to mustard in any way.
It was first synthesised by Frederick Guthrie in 1860, though it is possible that it was developed as early as 1822 by M. Depretz. V. Meyer would publish a paper in 1886 describing a synthesis which produced good yields. The abbreviation LOST comes from LOmmel and STeinkopf who developed a process for mass-producing the gas for war use at the German company Bayer AG.
Other names for mustard gas include HD, senfgas, sulfur mustard, blister gas, S-LOST, and Kampfstoff LOST or Yperite or Yperiet. "mustine" as shown in older medical dictionaries a substance used in chemotherapy to treat/cure cancer.The use of mustard gas in chemotherapy has ceased in most countries in recent years.
Chemically, it is a thioether with the formula C4H8Cl2S. Its structure can be described as 1,1-thio-bis-[2-chloroethane], (ClCH2CH2)2S, 2,2′-dichlorodiethyl sulfide or bis-(2-chloroethyl)-sulfide. Mustard gas can be synthesized by reacting sulfur dichloride (SCl2) with two moles of ethylene (C2H4).
The compound readily eliminates chloride ion by intramolecular nucleophilic substitution to form a cyclic sulfonium ion. This very reactive intermediate is particularly detrimental to cellular health as it has a strong tendency to bond to the guanine nitrogen in DNA strands. This leads to either immediate cellular death or, as recent research has found, cancer. Mustard gas is not very soluble in water but is very soluble in fat, contributing to its rapid absorption into the skin.
In the wider sense, compounds with the structural element BCH2CH2X, where X is any leaving group and B is a Lewis base are known as mustards. Such compounds can form cyclic onium ions that readily react with nucleophiles. Examples are bis-(2-chloroethyl)ether or the (2-haloethyl)amines.
Mustard gas is a strong vesicant (a compound that causes blisters). Those exposed usually suffer no immediate symptoms. The exposure develops (in 4 to 24 hours) into deep, itching or burning blisters wherever the mustard contacted the skin; the eyes (if exposed) become sore and the eyelids swollen, possibly leading to conjunctivitis and blindness. At very high concentrations, if inhaled, it causes bleeding and blistering within the respiratory system, damaging the mucous membrane and leading to pulmonary edema. Blister agent exposure over more than 50% body surface area is usually fatal.
Skin damage can be reduced if povidone iodine in a base of glycofurol is rapidly applied, but since mustard initially has no symptoms, the exposure is usually not identified until the blisters rise. The vesicant property can be neutralised by oxidation or chlorination, common bleach (NaOCl-) can be used or decontamination solution "DS2" (2% NaOH, 70% diethylenetriamine, 28% ethylene glycol monomethyl ether). Mustard gas is also carcinogenic (cancer causing) and mutagenic (causing damage to DNA of exposed cells).
It was first used by the German army against Canadian soldiers in 1917 and later also against the French – the name Yperite comes from its usage by the German army near the city of Ypres. It took the British over a year to develop their own mustard gas weapon, first using it in September 1918 during the breaking of the Hindenburg Line.
Mustard gas was dispersed as an aerosol in a mixture with other chemicals, giving it a yellow-brown colour and a distinctive odour. Mustard gas was lethal in only about 1% of cases. Its effectiveness was as an incapacitating agent: a wounded soldier slows an advancing army much more than a dead one. The countermeasures against the gas were quite ineffective, since a soldier wearing a gas mask was not protected against absorbing it through the skin.
Furthermore, mustard gas was a persistent agent which would remain in the environment for days and continue to cause sickness. If mustard gas contaminated a soldier's clothing and equipment, then other soldiers he came into contact with would also be poisoned. Towards the end of the war it was even used in high concentrations as an area-denial weapon, which often forced soldiers to abandon heavily contaminated positions.
Since then, mustard gas has also been reportedly used by:
- Spain against Morocco in 1923-1926;
- Italy against Ethiopia in 1935-1940;
- Soviet Union in a province of China in 1930;
- Japan against China in 1937-1945;
- Egypt against North Yemen in 1963-1967;
- Iraq against Iran in 1983-1988; and
- Iraq against Kurds in 1988.
Most of the mustard gas found in Germany after World War II was dumped into the Baltic Sea. It is possible to mistake a piece of polymerised mustard gas for amber, which can lead to severe health problems. Shells containing mustard gas and other toxic ammunition from World War I (as well as conventional explosives) can still occasionally be found in France; they used to be disposed of by explosion at sea, but current environmental regulations prohibit this; the French government is building an automated factory to dispose of the backlog of shells.
The largest stockpile of mustard gas in the United States was found at Edgewood Arsenal, Aberdeen Proving Ground in Maryland. Mustard gas was stored in several one-ton (900 kg) containers on the base under heavy guard. A disposal plant built on site neutralized the last of this stockpile in February, 2005. This stockpile had priority due to its proximity to several populated areas and schools in the area. The closest schools were fitted with overpressurization units to protect the students and staff in the event of a catastrophic explosion and fire at the site. Unexploded shells containing mustard gas and other chemical agents are still present in several test ranges in proximity to Edgewood area schools, but the smaller amounts (4–14 pounds; 2–6 kg) present considerably less risk. They are being systematically detected and excavated for disposal. There are several other sites in the United States where smaller stockpiles are awaiting neutralization in compliance with international chemical weapons treaties.
- This reference has several errors in it:
- The Fredrick Guthrie synthesis should be from ethylene and SCl2, not ethylene and Cl2 as stated.
- The hydrolysis reaction pathway produces two molecules of HCl and the last one produced is H2O, not three molecules of HCl as shown in the reference.
- The molecular structure given for nitrogen mustard (N-mustard) is not correct. The nitrogen atom should have a hydrogen bonded to it.
- This reference also has an error in it.
- In the sentence on synthesis of mustard gas, the phrase "sulfur monochloride, S2Cl2" should be "sulfur dichloride, SCl2"
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