Tetranitromethane
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Tetranitromethane or TNM is an
organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...
oxidizer An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
with chemical formula . Its chemical structure consists of four
nitro group In organic chemistry, nitro compounds are organic compounds that contain one or more nitro functional groups (). The nitro group is one of the most common explosophores (functional group that makes a compound explosive) used globally. The nitr ...
s attached to one carbon atom. In 1857 it was first synthesised by the reaction of sodium
cyanoacetamide 2-Cyanoacetamide is an organic compound. It is an acetic amide with a nitrile functional group. Uses Cyanoacetamide is used in Fluorescence spectroscopy, spectrofluorimetric methods to determine the activity of Antihistamine#H1-antihistamines, an ...
with
nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
.


Uses

It has been investigated for use as an oxidizer in
bipropellant rocket A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid propellants. Liquids are desirable because they have a reasonably high density and high specific impulse (''I''sp). This allows the volume of the propellant ta ...
s; however, its high melting point makes it unsuitable. Highly purified tetranitromethane cannot be made to explode, but its sensitivity is increased dramatically by oxidizable contaminants, such as anti-freezing additives. This makes it effectively unusable as a propellant. In the laboratory it is used as a reagent for the detection of double bonds in organic compounds and as a nitrating reagent. It has also found use as an additive to diesel fuel to increase the
cetane number Cetane number (cetane rating) is an indicator of the combustion speed of diesel fuel and compression needed for ignition. It plays a similar role for diesel as octane rating does for gasoline. The CN is an important factor in determining the quali ...
.


Preparation

TNM is a pale yellow liquid that can be prepared in the laboratory by the
nitration In organic chemistry, nitration is a general class of chemical processes for the introduction of a nitro group into an organic compound. The term also is applied incorrectly to the different process of forming nitrate esters between alcohols and ...
of
acetic anhydride Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O. Commonly abbreviated Ac2O, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a col ...
with anhydrous
nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
(Chattaway's method). This method was attempted on an industrial scale in the 1950s by Nitroform Products Company in Newark, USA, but the entire plant was destroyed by an explosion in 1953. The first industrial scale production was started in Germany during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
in an effort to improve the cetane number of diesel fuel. This process improved the original method, which started with
acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
and nitric acid. Without regard to yield or cost, approximately 10 tons of TNM were produced in a few weeks. However, this production process has not been used again industrially after the end of the war, because of high associated costs. For commercial use a cheaper method starting from
acetylene Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
has been used. First, nitric acid containing mercuric nitrate is reduced by acetylene, resulting in trinitromethane (nitroform) and a mixture of
carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
and
nitrogen oxide Nitrogen oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds: Charge-neutral *Nitric oxide (NO), nitrogen(II) oxide, or nitrogen monoxide *Nitrogen dioxide (), nitrogen(IV) oxide * Nitrogen trioxide (), or n ...
as waste gas. The nitrogen oxides are valuable and normally recovered as nitric acid in an absorption tower. The resulting nitroform is converted to TNM by adding nitric and sulfuric acid at higher temperatures. With this method a yield of 90% (based on nitric acid) before purification can be reached.


Structure

TNM is a prime example of molecular flexibility. It brought structural methods to the limits of their applicability as is shown by the fact that the structure of TNM was attempted to be determined for a period of more than 70 years in various phases. Early investigations by gas electron diffractions were unable to describe the observed diffraction pattern in full and only the application of a four-dimensional model concerning the correlated movement of the four groups about the C–N bonds was able to describe the experimental observations fully. The problem occurs, because the two-fold local symmetry of the units versus the three-fold symmetry of the unit, as well as the close proximity of the groups hindering their free rotation, is the source for a very complicated mutually hindered movement of the groups. The crystal structure has also been attempted several times. A first decent solution of the problem required a model describing a highly disordered high‐temperature crystalline phase of a high-temperature phase (>174.4 K) as is shown in Figure 1. Reduction of symmetry and analysis of the twinning of the crystals led finally to a resolved disorder of the structure shown in Figure 2. The structure of an ordered low‐temperature phase contains three independent molecules in the asymmetric unit. Structural parameters of the gaseous and solid phases are listed in the following table for comparison.


Safety

The ability of TNM to detonate is greatly affected by the presence of impurities, even in small quantities. TNM forms extremely powerful explosive mixtures when fuels are added in stoichiometric proportions. Many of these mixtures show sensitivity to impact even higher than that of
nitroglycerine 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, explosive liquid most commonly produced by nitrating ...
. Tetranitromethane can be used as a component of highly explosive liquid explosives as an oxidizing agent. It forms highly
explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An expl ...
mixtures with all flammable substances. When experimenting with this substance, paper filters should not be used for filtration. Even small impurities make tetranitromethane an explosive that explodes on impact or friction. A tragic lecture experiment at the
University of Münster The University of Münster (german: Westfälische Wilhelms-Universität Münster, WWU) is a public university, public research university located in the city of Münster, North Rhine-Westphalia in Germany. With more than 43,000 students and over ...
in 1920 is well known, where a small steel tube containing tetranitromethane, toluene and absorbent cotton detonated shortly before burning out in such a way that more than 30 students were injured, some seriously; however, on the basis of the rector's office records, as many as 10 deaths and more than a dozen injuries are documented. Thereupon the German Chemical-technical Reichsanstalt determined a detonation speed of 9300 meters per second. Alfred Stettbacher then proved comparatively that this mixture was far more explosive than
hexogen RDX (abbreviation of "Research Department eXplosive") or hexogen, among other names, is an organic compound with the formula (O2N2CH2)3. It is a white solid without smell or taste, widely used as an explosive. Chemically, it is classified as a n ...
,
pentrite Pentaerythritol tetranitrate (PETN), also known as PENT, PENTA, (ПЕНТА, primarily in Russian) TEN, corpent, or penthrite (or, rarely and primarily in German, as nitropenta), is an explosive material. It is the nitrate ester of pentaerythri ...
, blasting gelatine or
panclastite Panclastites are a class of Sprengel explosives similar to oxyliquits. They were first suggested in 1881 by Eugène Turpin, a French chemist. They are a mixture of liquid dinitrogen tetroxide serving as oxidizer with a suitable fuel, e.g. carbon di ...
and thus represented the most destructive explosive of all. TNM reacts with moisture at elevated pH to produce trinitromethane (nitroform) which reacts easily with metals to form highly unstable and explosive salts. Tetranitromethane is highly toxic. Absorption of as little as 2.5 mg/kg can cause
methemoglobinemia Methemoglobinemia, or methaemoglobinaemia, is a condition of elevated methemoglobin in the blood. Symptoms may include headache, dizziness, shortness of breath, nausea, poor muscle coordination, and blue-colored skin (cyanosis). Complications m ...
, pulmonary edema, and damage to liver, kidney, and central nervous system. It is reasonably expected to be a human carcinogen.


References


External links


WebBook page for CN4O8
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