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Nitroglycerin ( NG) (alternative spelling of nitroglycerine), also known as trinitroglycerin ( TNG), nitro, glyceryl trinitrate ( GTN), or 1,2,3-trinitroxypropane, is a dense, colorless, oily, liquid most commonly produced by with white fuming nitric acid under conditions appropriate to the formation of the nitric acid . Chemically, the substance is an compound rather than a , but the traditional name is retained. Discovered in 1847 by , nitroglycerin has been used as an active ingredient in the manufacture of , namely , and as such it is employed in the , , and industries. It is combined with to form double-based , which has been used as a in artillery and firearms since the 1880s.

Nitroglycerin has been used for over 130 years in medicine as a potent (causing dilation of the vascular system) to treat conditions, such as and chronic heart failure. Though it was previously known that these beneficial effects are due to nitroglycerin being converted to , a potent venodilator, the enzyme for this conversion was only discovered to be mitochondrial aldehyde dehydrogenase (ALDH2) in 2002. Nitroglycerin is available in sublingual tablets, sprays, ointments, and patches.

Nitroglycerin was the first practical explosive produced that was stronger than . It was synthesized by the Italian in 1847, working under Théophile-Jules Pelouze at the University of Turin. Sobrero initially called his discovery pyroglycerine and warned vigorously against its use as an explosive. On p. 197, Sobrero names nitroglycerin "pyroglycerine":
"Quelle gocciole costituiscono il corpo nuovo di cui descriverò ora le proprietà, e che chiamerò Piroglicerina." (Those drops constitute the new substance whose properties I will now describe, and which I will call "pyroglycerine".)

Nitroglycerin was adopted as a commercially useful explosive by , who experimented with safer ways to handle the dangerous compound after his younger brother, Emil Oskar Nobel, and several factory workers were killed in an explosion at the Nobels' armaments factory in 1864 in , Sweden.

One year later, Nobel founded Alfred Nobel and Company in Germany and built an isolated factory in the Krümmel hills of near . This business exported a liquid combination of nitroglycerin and called "Blasting Oil", but this was extremely unstable and difficult to handle, as evidenced in numerous catastrophes. The buildings of the Krümmel factory were destroyed twice..

In April 1866, several crates of nitroglycerin were shipped to , three of which were destined for the Central Pacific Railroad, which planned to experiment with it as a blasting explosive to expedite the construction of the Summit Tunnel through the Sierra Nevada Mountains. One of the remaining crates exploded, destroying a company office in and killing 15 people. This led to a complete ban on the transportation of liquid nitroglycerin in California. The on-site manufacture of nitroglycerin was thus required for the remaining hard-rock drilling and blasting required for the completion of the First transcontinental railroad in North America.

On Christmas Day 1867, an attempt to dispose of nine canisters of Blasting Oil that had been illegally stored at the White Swan Inn in the centre of Newcastle upon Tyne resulted in an explosion on the Town Moor that killed eight people. In June 1869, two one-ton wagons loaded with nitroglycerin, then known locally as Powder-Oil, exploded in the road at the North Wales village of . The explosion led to the loss of six lives, many injuries and much damage to the village. Little trace was found of the two horses. The UK Government was so alarmed at the damage caused and what could have happened in a city location (these two tons were part of a larger load coming from Germany via Liverpool) that they soon passed the Nitro-Glycerine Act of 1869.North Wales Daily Post newspaper of October 14th 2018. Liquid nitroglycerin was widely banned elsewhere, as well, and these legal restrictions led to Alfred Nobel and his company's developing in 1867. This was made by mixing nitroglycerin with diatomaceous earth (" Kieselguhr in German) found in the Krümmel hills. Similar mixtures, such as "dualine" (1867), "lithofracteur" (1869), and "" (1875), were formed by mixing nitroglycerin with other inert absorbents, and many combinations were tried by other companies in attempts to get around Nobel's tightly held patents for dynamite.

Dynamite mixtures containing , which increases the viscosity of the mix, are commonly known as "gelatins".

Following the discovery that helped alleviate chest pain, the physician William Murrell experimented with the use of nitroglycerin to alleviate angina pectoris and to reduce the . He began treating his patients with small diluted doses of nitroglycerin in 1878, and this treatment was soon adopted into widespread use after Murrell published his results in the journal in 1879.

(2024). 9780471899808, John Wiley and Sons.
A few months before his death in 1896, Alfred Nobel was prescribed nitroglycerin for this heart condition, writing to a friend: "Isn't it the irony of fate that I have been prescribed nitro-glycerin, to be taken internally! They call it Trinitrin, so as not to scare the chemist and the public." The medical establishment also used the name "glyceryl trinitrate" for the same reason.

Wartime production rates
Large quantities of nitroglycerin were manufactured during World War I and World War II for use as military propellants and in military engineering work. During World War I, HM Factory, Gretna, the largest propellant factory in the , produced about 800 of cordite RDB per week. This amount required at least 336 tonnes of nitroglycerin per week (assuming no losses in production). The had its own factory at the Royal Navy Cordite Factory, Holton Heath, in , England. A large cordite factory was also built in Canada during World War I. The Canadian Explosives Limited cordite factory at Nobel, Ontario, was designed to produce of cordite per month, requiring about 286 tonnes of nitroglycerin per month.

Instability and desensitization
In its undiluted form, nitroglycerin is a contact explosive, with physical shock causing it to explode. If it has not been adequately purified during manufacture it can degrade over time to even more unstable forms. This makes nitroglycerin highly dangerous to transport or use. In its undiluted form, it is one of the world's most powerful explosives, comparable to the more recently developed and .

Early in its history, liquid nitroglycerin was found to be "" by freezing it at a temperature below depending on its purity. Its sensitivity to shock while frozen is somewhat unpredictable: "It is more insensitive to the shock from a or a rifle ball when in that condition but on the other hand it appears to be more liable to explode on breaking, crushing, tamping, etc." Frozen nitroglycerine is much less energetic than liquid, and so must be thawed before use. Thawing it out can be extremely sensitizing, especially if impurities are present or the warming is too rapid. Ethylene glycol dinitrate or another polynitrate may be added to lower the melting point and thereby avoid the necessity of thawing frozen explosive.

Chemically "desensitizing" nitroglycerin is possible to a point where it can be considered about as "safe" as modern , such as by the addition of , , or . The nitroglycerin may have to be extracted from the desensitizer chemical to restore its effectiveness before use, for example by adding water to draw off ethanol used as a desensitizer.

When nitroglycerin explodes the products after cooling are given by:
→ 3 + 2.5 + 1.5 + 0.5

The heat released can be calculated from the heats of formation. Using −371 kJ/mol for the heat of formation of condensed phase nitroglycerin gives 1414 kJ/mol released if forming water vapor, and 1524 if forming liquid water.

The detonation velocity of nitroglycerin is 7820 meters per second, which is about 113% the speed of . Accordingly, nitroglycerin is considered to be a high- explosive, which is to say, it has excellent shattering ability. The heat liberated during detonation raises the temperature of the gaseous byproducts to about . With a standard enthalpy of explosive decomposition of −1414 kJ/mol and a molecular weight of 227.0865 g/mol, nitroglycerin has a specific explosive energy density of 1.488  per gram, or 6.23 kJ/g, making nitroglycerin 49% more energetic on a mass basis than the standard definitional value assigned to TNT (precisely 1 kcal/g).

Nitroglycerin can be produced by acid-catalyzed nitration of (glycerin).

The industrial manufacturing process often reacts with a nearly 1:1 mixture of concentrated and concentrated . This can be produced by mixing white fuming nitric acid—a quite expensive pure in which the oxides of nitrogen have been removed, as opposed to red fuming nitric acid, which contains —and concentrated . More often, this mixture is attained by the cheaper method of mixing fuming , also known as containing excess —and nitric acid (consisting of about 70% , with the rest being water).

(2014). 9780123864543, Academic Press.

The produces species, which are attacked by 's atoms. The is thus added as an ester C−O−NO2 and water is produced. This is different from an electrophilic aromatic substitution reaction in which are the .

The addition of results in an exothermic reaction (i.e., heat is produced), as usual for mixed-acid nitrations. If the mixture becomes too hot, it results in a runaway reaction, a state of accelerated nitration accompanied by the destructive of organic materials by the hot and the release of poisonous gas at high risk of an explosion. Thus, the mixture is added slowly to the reaction vessel containing the mixed acid (not acid to glycerin). The nitrator is cooled with cold water or some other coolant mixture and maintained throughout the addition at about , hot enough for esterification to occur at a fast rate but cold enough to avoid runaway reaction. The nitrator vessel, often constructed of or and generally stirred with , has an emergency trap door at its base, which hangs over a large pool of very cold water and into which the whole reaction mixture (called the charge) can be dumped to prevent an explosion, a process referred to as drowning. If the temperature of the charge exceeds about (actual value varying by country) or brown fumes are seen in the nitrator's vent, then it is immediately drowned.

Use as an explosive and a propellant
The main use of nitroglycerin, by , is in explosives such as dynamite and in propellants.

Nitroglycerin is an oily liquid that may explode when subjected to heat, shock, or flame.

developed the use of nitroglycerin as a blasting explosive by mixing nitroglycerin with inert absorbents, particularly " Kieselgur", or diatomaceous earth. He named this explosive and it in 1867. It was supplied ready for use in the form of sticks, individually wrapped in greased waterproof paper. Dynamite and similar explosives were widely adopted for civil engineering tasks, such as in drilling and , for , for clearing farmland of stumps, in , and in . Likewise, military engineers have used dynamite for construction and demolition work.

Nitroglycerin was also used as an ingredient in military propellants for use in .

Nitroglycerin has been used in conjunction with hydraulic fracturing, a process used to recover and from formations. The technique involves displacing and detonating nitroglycerin in natural or hydraulically induced fracture systems, or displacing and detonating nitroglycerin in hydraulically induced fractures followed by wellbore shots using pelletized .

Nitroglycerin has an advantage over some other high explosives that on detonation it produces practically no visible smoke. Therefore, it is useful as an ingredient in the formulation of various kinds of .

Its sensitivity has limited the usefulness of nitroglycerin as a military explosive, and less sensitive explosives such as , , and have largely replaced it in munitions. It remains important in military engineering, and still use dynamite.

Alfred Nobel then developed , by combining nitroglycerin and . He patented it in 1887. Ballistite was adopted by a number of European governments, as a military propellant. Italy was the first to adopt it. The British government and the Commonwealth governments adopted instead, which had been developed by Sir and Sir of the United Kingdom in 1889. The original Cordite Mk I consisted of 58% nitroglycerin, 37% guncotton, and 5.0% . Ballistite and cordite were both manufactured in the form of "cords".

Smokeless powders were originally developed using nitrocellulose as the sole explosive ingredient. Therefore, they were known as single-base propellants. A range of smokeless powders that contains both nitrocellulose and nitroglycerin, known as double-base propellants, were also developed. Smokeless powders were originally supplied only for military use, but they were also soon developed for civilian use and were quickly adopted for sports. Some are known as sporting powders. Triple-base propellants contain nitrocellulose, nitroglycerin, and , but are reserved mainly for extremely high-caliber ammunition rounds such as those used in tank cannons and . Blasting gelatin, also known as , was invented by Nobel in 1875, using nitroglycerin, , and or potassium nitrate. This was an early, low-cost, flexible explosive.

Medical use
Nitroglycerin belongs to a group of drugs called nitrates, which includes many other nitrates like isosorbide dinitrate (Isordil) and isosorbide mononitrate (Imdur, Ismo, Monoket). These agents all exert their effect by being converted to in the body by mitochondrial aldehyde dehydrogenase (ALDH2), and nitric oxide is a potent natural vasodilator.

In , nitroglycerin is probably most commonly prescribed for , a painful symptom of ischemic heart disease caused by inadequate flow of blood and oxygen to the heart and as a potent antihypertensive agent. Nitroglycerin corrects the imbalance between the flow of oxygen and blood to the heart and the heart's energy demand. There are many formulations on the market at different doses. At low doses, nitroglycerin dilates veins more than arteries, thereby reducing preload (volume of blood in the heart after filling); this is thought to be its primary mechanism of action. By decreasing preload, the heart has less blood to pump, which decreases oxygen requirement since the heart does not have to work as hard. Additionally, having a smaller preload reduces the ventricular transmural pressure (pressure exerted on the walls of the heart), which decreases the compression of heart arteries to allow more blood to flow through the heart. At higher doses, it also dilates arteries, thereby reducing (decreasing the pressure against which the heart must pump). An improved ratio of myocardial oxygen demand to supply leads to the following therapeutic effects during episodes of angina pectoris: subsiding of chest pain, decrease of , increase of heart rate, and orthostatic hypotension. Patients experiencing angina when doing certain physical activities can often prevent symptoms by taking nitroglycerin 5 to 10 minutes before the activity. Overdoses may generate methemoglobinemia.

Nitroglycerin is available in tablets, ointment, solution for use, transdermal patches, or sprays administered . Some forms of nitroglycerin last much longer in the body than others. Nitroglycerin as well as the onset and duration of action of each form is different. The sublingual or tablet spray of nitroglycerin has a two minute onset and twenty five minute duration of action. The oral formulation of nitroglycerin has a thirty five minute onset and a duration of action of 4–8 hours. The transdermal patch has an onset of thirty minutes and a duration of action of ten to twelve hours. Continuous exposure to nitrates has been shown to cause the body to stop responding normally to this medicine. Experts recommend that the patches be removed at night, allowing the body a few hours to restore its responsiveness to nitrates. Shorter-acting preparations of nitroglycerin can be used several times a day with less risk of developing tolerance. Nitroglycerin was first used by William Murrell to treat angina attacks in 1878, with the discovery published that same year.

Industrial exposure
Infrequent exposure to high doses of nitroglycerin can cause severe known as "NG head" or "bang head". These headaches can be severe enough to incapacitate some people; however, humans develop a to and dependence on nitroglycerin after long-term exposure. Although rare, withdrawal can be fatal.
(1991). 9780071052399, Elsevier.
Withdrawal symptoms include chest pain and other heart problems. These symptoms may be relieved with re-exposure to nitroglycerin or other suitable organic nitrates.
(2024). 9780683080278, Lippincott Williams & Wilkins. .

For workers in nitroglycerin (NTG) manufacturing facilities, the effects of withdrawal sometimes include "Sunday heart attacks" in those experiencing regular nitroglycerin exposure in the workplace, leading to the development of tolerance for the venodilating effects. Over the weekend, the workers lose the tolerance, and when they are re-exposed on Monday, the drastic produces a , dizziness, and a headache. This is referred to as "Monday disease."

People can be exposed to nitroglycerin in the workplace by breathing it in, skin absorption, swallowing it, or eye contact. The Occupational Safety and Health Administration has set the legal limit (permissible exposure limit) for nitroglycerin exposure in the workplace as 0.2 ppm (2 mg/m3) skin exposure over an 8-hour workday. The National Institute for Occupational Safety and Health has set a recommended exposure limit of 0.1 mg/m3 skin exposure over an 8-hour workday. At levels of 75 mg/m3, nitroglycerin is .

See also
  • Erythritol tetranitrate
  • Ethylene glycol dinitrate
  • Mannitol hexanitrate
  • Tetranitratoxycarbon
  • Xylitol pentanitrate

External links

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