2,2′-Dichlorodiethyl Sulfide

OVERVIEW

2,2′-dichlorodiethyl sulfide (two-two-prime-di-KLO-ro-di-ETH-el sul-fyd) is more commonly known as mustard gas. It is also known as bis-(2-chloroethyl) sulfide; sulfur mustard; yprite; and 1,1′-thiobis[2-chloroethane]. The compound occurs as a yellowish liquid that, in a pure form, has no odor. Small amounts of impurities give it the distinctive odor of mustard, from which it gets its common name. It may also smell like garlic or horseradish because of impurities.

KEY FACTS

OTHER NAMES:

Mustard gas; see Overview for more names

FORMULA:

(CH₂CH₂Cl)₂S

ELEMENTS:

Carbon, hydrogen, chlorine, sulfur

COMPOUND TYPE:

Organic sulfide

STATE:

Liquid

MOLECULAR WEIGHT:

159.09 g/mol

MELTING POINT:

13 to 14°C (55 to 57°F)

BOILING POINT:

217°C (423°F)

SOLUBILITY:

Insoluble in water; soluble in alcohol, ether, acetone, benzene, and other organic solvents; soluble in fats

Mustard gas was discovered by the English physicist Frederick Guthrie (1833–1886) in 1860. While working with the compound, Guthrie spilled mustard gas on his skin and found that it produced a painful red blister. That property has led to the primary use of mustard gas, as a chemical agent used in warfare. When sprayed on a person, the compound can blister the skin, burn the eyes, and irritate the lungs. In large doses, it can kill a person. Mustard gas was first used as a chemical weapon on July 12, 1917 by the German army in an attack on Canadian soldiers at Ypres, Belgium. An estimated 20,000 troops were killed in the attack. By the end of World War I, an estimated 120,000 British troops had died as a result of mustard gas attacks.

The damage caused by mustard gas was due at least in part because troops had no means of protecting themselves against the compound. It was able to penetrate virtually any type of protective clothing then available. The damage caused by mustard gas is so horrible that most nations have agreed not to use it in wars. One exception may have occurred during the Iraq-Iran war of 1980–1988, when the Iraqis sprayed Iranian troops with a gas very much like mustard gas in 1984. Later, in 1987 and 1988, Iraq's ruler Saddam Hussein also used mustard gas against Kurdish people living in northern Iraq.

HOW IT IS MADE

The usual method for making mustard gas in the United States is called the Levenstein process. In this process, ethylene gas (CH₂=CH₂) is bubbled through sulfur chloride (S₂Cl₂), a yellowish-red oil with a very strong odor. In Germany and other nations, the compound is made by treating the organic compound 2,2′-dihydroxyethyl sulfide with hydrochloric acid.

COMMON USES AND POTENTIAL HAZARDS

Virtually the only use for mustard gas is as a chemical agent in warfare. But, interestingly enough, the compound has been used in one other very different way: in the treatment of cancer. The husband and wife medical team of E.B. and H.D. Krumbhaar discovered in 1919 that mustard gas was effective in treating cancer in experimental animals. (They called the compound by its then-popular name, yellow cross gas.) The compound was one of the first chemicals to be used in the treatment of cancer. Researchers continued to study the cancer-fighting properties of mustard gas for more than twenty years, but the compound has never been widely used for that purpose.

Interesting Facts

• Another name for mustard gas, yprite, comes from the Belgian city Ypres (pronounced "EE-pr'"), where the compound was first use as a military weapon.
• The use of mustard gas was outlawed by the Chemical Weapons Convention, adopted in 1993. The United States starting destroying its stockpile of mustard gas even earlier, in 1985, and is now thought to have none of the chemical agent left.
• Mustard gas was not used during World War II. The compound was, nonetheless, responsible for the deaths of more than 100 U.S. men. On December 2, 1943, a German attack on the harbor of Bari, Italy, resulted in the sinking of about two dozen ships. Some of those ships were carrying mustard gas. When they sank, they released the gas into the surrounding water, where survivors inhaled and swallowed the poisonous compound.

The effects of exposure to mustard gas vary over time. At first, a person who has inhaled the gas may become nauseated, experience itchy and sore eyes, and begin vomiting. His or her skin turns red and blisters may develop. Exposure to large amounts of the gas may result in permanent damage to the eyes and respiratory system resulting, in the worst cases, in coma and death. People exposed to mustard gas who survive may later develop mouth, lung, or stomach cancer.

FOR FURTHER INFORMATION

"Molecule of the Month: Mustard Gas." Bristol University. http://www.chm.bris.ac.uk/motm/mustard/mustard.htm (accessed on September 13, 2005).

"Mustard Gas." International Progamme on Chemical Safety. http://www.inchem.org/documents/pims/chemical/mustardg.htm (accessed on September 13, 2005).

Strobel, Warren P. "Saddam's Lingering Atrocity." U.S. News &World Report (November 27, 2000): 52.

"ToxFAQs for Sulfur Mustard." Agency for Toxic Substances and Disease Registry. http://www.atsdr.cdc.gov/tfacts49.html (accessed on September 13, 2005).