nitroglycerin

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Nitroglycerin

OVERVIEW

Nitroglycerin (nye-tro-GLIH-cer-in) is a pale yellow oily flammable liquid that is highly explosive. It is used primarily as an explosive by itself and as an ingredient in dynamite. Nitroglycerin also finds application in medicine as a vasodilator, a substance that causes blood vessels to relax and open up, allowing blood to flow more freely through them.

KEY FACTS

OTHER NAMES:

Trinitroglycerol; trinitroglycerin; glyceryl trinitrate

FORMULA:

CH2NO2CHNOCH2NO2

ELEMENTS:

Carbon, hydrogen, nitrogen, oxygen

COMPOUND TYPE:

Ester (organic)

STATE:

Liquid

MOLECULAR WEIGHT:

227.09 g/mol

MELTING POINT:

13.5°C (56.3°F)

BOILING POINT:

Explodes at 218°C 424°F)

SOLUBILITY:

Slightly soluble in water; soluble in ethyl alcohol, acetone, and benzene

Nitroglycerin was first developed in 1847 by the Italian chemist Ascanio Sobrero (1812–1888). Sobrero used a method of synthesis that is still the primary means of producing nitroglycerin today. He added nitric acid to glycerol, then and now a popular skin lotion, with a small amount of concentrated sulfuric acid as catalyst. He initially called his discovery pyroglycerin. When he placed a trace amount of nitroglycerin on his tongue, Sobrero discovered that it "gives rise to a most pulsating, violent headache, accompanied by a great weakness of the limbs." He also discovered that the chemical was highly combustible and explosive. He considered the substance so dangerous that he warned against its use and did not disclose his discovery to the world for more than a year.

In the 1860s, the Swedish chemist Alfred Nobel (1833–1896) developed a process for manufacturing nitroglycerin on a large scale. His company sold a combination of nitroglycerin and gunpowder called Swedish blasting oil, but the product proved far too dangerous to use. Several accidents involving the substance occurred. One explosion in Nobel's factory killed several people, including his brother Emil. To make a safer explosive, Nobel found a way to combine nitroglycerin with clay, a chemically inactive material. He called the combination dynamite. Dynamite soon became the explosive of choice in construction, demolition, and mining projects around the world.

Nitroglycerin's medical uses were first explored in detail by Sir Thomas Lauder Brunton (1844–1916) of the Royal Infirmary in Edinburgh, Scotland. In 1938, the U.S. Food and Drug Administration first approved the use of nitroglycerin as a vasodilator for the treatment of heart problems.

Interesting Facts

  • Before Nobel began studying the explosive properties of nitroglycerin, people reportedly used the compound for everyday chores, such as polishing boots and greasing wagon wheels, and even as lamp oil. The consequences were often fatal.
  • Although he spent most of his life developing and manufacturing explosives, Nobel was a humanitarian who wanted to see technology used for the benefit of society and the advancement of world peace. His handwritten will, although fiercely contested, provided for the creation of the Nobel Foundation. The foundation's primary responsibility is to award prizes in chemistry, physics, physiology or medicine, and peace every year. The first Nobel prizes were awarded in 1901. Today, a Nobel prize is regarded as the highest honor given in science. Each prize is worth over a million dollars in cash.

HOW IT IS MADE

The preparation of nitroglycerin is a straightforward, but very delicate, chemical procedure. When nitric acid is added to glycerol, three nitrate groups (-NO2) replace each of the three hydroxyl (-OH) groups on glycerol. This reaction occurs only if the acid and glycerol are moderately warm, at least at room temperature. But combining nitric acid, glycerol, and sulfuric acid (the catalyst) for the reaction generates heat. Too much heat causes the nitroglycerin being produced to explode. The resolution for this dilemma is to begin the reaction at room temperature, but then encase the reaction vessel in ice as soon as the reaction begins. The ice absorbs heat generated during the reaction, allowing the formation of nitroglycerin without it becoming too warm.

COMMON USES AND POTENTIAL HAZARDS

Nitroglycerin's primary use is as an explosive, either by itself or as a component of dynamite. Today, it is marketed under more than 60 trade names, including Coro-Nitro®, Deponit®, GTN®, Nitroglin®, Nitrong®, Perglottal®, Reminitrol®, Sustac®, Tridil®, and Vasoglyn®. Nitroglycerin is classified as a high explosive, which means that it explodes very rapidly with a very large force. It is detonated ("set off") either by heat or by shock. Because of its very unstable character, it is usually transported at low temperatures (5°C to 10°C; 40°F to 50°F), at which it is more stable.

When used as a heart medication, nitroglycerin is administered in the form of a pill, patch, or intravenous solution. Nitroglycerin works in the body by releasing nitric oxide, a vasodilator. Vasodilators cause the smooth muscle surrounding blood vessels to relax, allowing the vessels to expand and improve the flow of blood. The drug is often taken when the pain of angina or a heart attack is first noticed.

People who come into contact with nitroglycerin in the workplace are at risk for a number of health problems. The compound is a skin, eye, and respiratory system irritant. It may cause nausea, vomiting, abdominal cramps, headache, mental confusion, delirium, sweating, a burning sensation on the tongue, paralysis, convulsions, and death.

Words to Know

CATALYST
A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure.
SYNTHESIS
A chemical reaction in which some desired chemical product is made from simple beginning chemicals, or reactants.

FOR FURTHER INFORMATION

"Nitroglycerin." Imperial College of London, Department of Chemistry. http://www.ch.ic.ac.uk/rzepa/mim/environmental/html/nitroglyc_text.htm (accessed on October 20, 2005).

"Nitroglycerin: Dynamite for the Heart." Chemistry Review (November 1999): 28.

Rawls, Rebecca. "Nitroglycerin Explained." Chemical & Engineering News (June 10, 2002): 12.

"Why Is Nitroglycerin Explosive?" General Chemistry Online http://antoine.frostburg.edu/chem/senese/101/consumer/faq/nitroglycerin.shtml (accessed on October 20, 2005).

See AlsoNitric Acid; Sulfuric Acid

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ni·tro·glyc·er·in / ˌnītrōˈglisərin/ (also nitroglycerine) • n. Chem. an explosive yellow liquid, CH2(NO3)CH(NO3)CH2(NO3), made by nitrating glycerol, used in explosives such as dynamite. It is also used in medicine as a vasodilator in the treatment of angina pectoris.

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nitroglycerin (ny-troh-glis-er-in) n. see glyceryl trinitrate.

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