- Chemical structure
- Nomenclature
- Properties
- Physical state
- Molecular weight
- Melting point
- Boiling point
- Flashpoint
- Density
- Solubility
- Chemical properties
- TNT explosion process
- TNT oxidation reaction
- Obtaining TNT
- Uses of TNT
- In military activities
- In industrial applications
- Risks of TNT
- Contamination of the environment with TNT
- Solution to TNT contamination
- Remediation with bacteria and fungi
- Remediation with algae
- References
The trinitrotoluene is an organic compound consisting of carbon, oxygen, hydrogen and nitrogen three nitro groups -NO 2. Its chemical formula is C 6 H 2 (CH 3) (NO 2) 3 or also the condensed formula C 7 H 5 N 3 O 6.
Its full name is 2,4,6-trinitrotoluene, but it is commonly known as TNT. It is a white crystalline solid that can explode when heated above a certain temperature.
2,4,6-trinitrotoluene crystals, TNT. Wremmerswaal. Source: Wikimedia Commons.
The presence in trinitrotoluene of the three nitro -NO 2 groups favors the fact that it explodes with some ease. For this reason, it has been widely used in explosive devices, projectiles, bombs and grenades.
It has also been used for blasting underwater, in deep wells and for industrial or non-war explosions.
TNT is a delicate product that can also explode from very strong blows. It is also toxic to humans, animals and plants. The places where their explosions have occurred have been contaminated and investigations are being carried out to eliminate the remains of this compound.
One way that can be effective and inexpensive to reduce the concentration of TNT in the contaminated environment is by using some types of bacteria and fungi.
Chemical structure
2,4,6-trinitrotoluene is formed by a C 6 H 5 -CH 3 toluene molecule, to which three nitro -NO 2 groups have been added.
The three nitro -NO 2 groups are located symmetrically on the benzene ring of toluene. They are found in positions 2, 4 and 6, where position 1 corresponds to methyl -CH 3.
Chemical structure of 2,4,6-trinitrotoluene. Edgar181. Source: Wikimedia Commons.
Nomenclature
- Trinitrotoluene
- 2,4,6-Trinitrotoluene
- TNT
- Trilita
- 2-Methyl-1,3,5-trinitrobenzene
Properties
Physical state
Colorless to pale yellow crystalline solid. Needle-shaped crystals.
Molecular weight
227.13 g / mol.
Melting point
80.5 ° C.
Boiling point
It does not boil. It decomposes with an explosion at 240 ºC.
Flashpoint
It is not possible to measure it because it explodes.
Density
1.65 g / cm 3
Solubility
Almost insoluble in water: 115 mg / L at 23 ° C. Very slightly soluble in ethanol. Very soluble in acetone, pyridine, benzene and toluene.
Chemical properties
May decompose explosively when heated. Upon reaching 240 ° C it explodes. It can also explode when it is hit very hard.
When heated to decomposition it produces toxic gases of nitrogen oxides NO x.
TNT explosion process
The explosion of TNT leads to a chemical reaction. Basically it is a combustion process in which energy is released very quickly. In addition, gases are emitted which are agents to transfer energy.
TNT easily explodes when heated above 240 ° C. Author: OpenClipart-Vectors. Source: Pixabay.
For a combustion reaction (oxidation) to occur, fuel and oxidant must be present.
In the case of TNT, both are in the same molecule, since the carbon (C) and hydrogen (H) atoms are the fuels and the oxidant is the oxygen (O) of the nitro -NO 2 groups. This allows the reaction to be faster.
TNT oxidation reaction
During the combustion reaction of TNT the atoms rearrange and oxygen (O) stays closer to carbon (C). In addition, the nitrogen in –NO 2 is reduced to form nitrogen gas N 2, which is a much more stable compound.
The explosion chemical reaction of TNT can be summarized as follows:
2 C 7 H 5 N 3 O 6 → 7 CO ↑ + 7 C + 5 H 2 O ↑ + 3 N 2 ↑
Carbon (C) is produced during the explosion, in the form of a black cloud, and also carbon monoxide (CO) is formed, which is because there is not enough oxygen in the molecule to completely oxidize all the carbon atoms (C) and hydrogen (H) present.
Obtaining TNT
TNT is a compound made only artificially by man.
It is not found naturally in the environment. It is produced only in some military installations.
It is prepared by nitration of toluene (C 6 H 5 –CH 3) with a mixture of nitric acid HNO 3 and sulfuric acid H 2 SO 4. First, a mixture of ortho- and para-nitrotoluenes is obtained which, by subsequent vigorous nitration, form the symmetric trinitrotoluene.
Uses of TNT
In military activities
TNT is an explosive that has been used in military devices and explosions.
Hand grenades can contain TNT. Authors: Materialscientist, Nemo5576, and Tronno. Source: Wikimedia Commons.
It is used to fill projectiles, grenades and airborne bombs, since it is insensitive enough to the impact received to leave the barrel of a weapon, but it can explode when hit by a detonating mechanism.
Aerial bombs can contain TNT. Author: Christian Wittmann. Source: Pixabay.
It is not designed to produce significant fragmentation or launch projectiles.
In industrial applications
It has been used for explosions of industrial interest, in underwater blasting (due to its insolubility in water) and deep well explosions. In the past it was most often used for demolitions. It is currently used in conjunction with other compounds.
Photo of the result of an explosion to demolish rocks in 1912. At that time TNT was used in blasting required, for example, to open roads for railways. Internet Archive Book Images. Source: Wikimedia Commons.
It has also been an intermediary for colorants and photographic chemicals.
Risks of TNT
May explode if exposed to intense heat, fire, or severe shock.
It is irritating to the eyes, skin and respiratory tract. It is a very toxic compound both for humans and for animals, plants and many microorganisms.
Symptoms of exposure to TNT include headache, weakness, anemia, toxic hepatitis, cyanosis, dermatitis, liver damage, conjunctivitis, poor appetite, nausea, vomiting, diarrhea, among others.
It is a mutagen, that is, it can change the genetic information (DNA) of an organism causing changes that can be related to the appearance of hereditary diseases.
It has also been classified as a carcinogen or cancer generator.
Contamination of the environment with TNT
TNT has been detected in soils and waters in areas of military operations, in munitions manufacturing sites and where military training operations are carried out.
The soils and waters of war zones or military operations have been contaminated with TNT. Author: Michael Gaida. Source: Pixabay.
Contamination with TNT is dangerous for the life of animals, humans and plants. Although TNT is currently used in smaller quantities, it is one of the nitroaromatic compounds that have been used the most in the explosives industry.
For this reason it is one of those that contributes the most to environmental pollution.
Solution to TNT contamination
The need to "clean" regions contaminated with TNT has motivated the development of several remediation processes. Remediation is the removal of pollutants from the environment.
Remediation with bacteria and fungi
Many microorganisms are capable of bioremediating TNT, such as bacteria of the genus Pseudomonas, Enterobacter, Mycobacterium and Clostridium.
It has also been found that there are certain bacteria that have evolved in places contaminated with TNT and that can survive and also degrade or metabolize it as a nutrient source.
Escherichia coli, for example, has shown an outstanding ability to biotransformation of TNT, as it has multiple enzymes to attack it, while demonstrating a high tolerance towards its toxicity.
In addition, some species of fungi can biotransform TNT, turning it into non-harmful minerals.
Remediation with algae
On the other hand, some researchers have found that the Spirulina platensis alga has the ability to adsorb on the surface of its cells and assimilate up to 87% of the TNT present in waters contaminated with this compound.
The tolerance of this algae towards TNT and its ability to clean water contaminated with it indicate the high potential of this algae as a phytoremediator.
References
- US National Library of Medicine. (2019). 2,4,6-Trinitrotoluene. Recovered from pubchem.ncbi.nlm.nih.gov.
- Murray, SG (2000). Explosives. Mechanism of Explosion. In Encyclopedia of Forensic Sciences 2000, Pages 758-764. Recovered from sciencedirect.com.
- Adamia, G. et al. (2018). About possibility of alga Spirulina application for phytoremediation of water polluted with 2,4,6-trinitrotoluene. Annals of Agrarian Science 16 (2018) 348-351. Recovered from reader.elsevier.com.
- Serrano-González, MY et al. (2018). Biotransformation and degradation of 2,4,6-trinitrotoluene by microbial metabolism and their interaction. Defense Technology 14 (2018) 151-164. Recovered from pdf.sciencedirectassets.com.
- Iman, M. et al. (2017). Systems Biology Approach to Bioremediation of Nitroaromatics: Constraint-Based Analysis of 2,4,6-Trinitrotoluene Biotransformation by Escherichia coli. Molecules 2017, 22, 1242. Recovered from mdpi.com.
- Windholz, M. et al. (editors) (1983). The Merck Index. An Encyclopedia of Chemicals, Drugs, and Biologicals. Tenth Edition. Merck & CO., Inc.
- Morrison, RT and Boyd, RN (2002). Organic Chemistry. 6th Edition. Prentice-Hall.