Anthracene: Meaning, Reactions and Uses

Dhristi JEE 2022-24

What is Anthracene?

Anthracene is a colourless crystalline aromatic hydrocarbon utilised in the chemical industry that is created by distilling natural crude oils. Anthracene is a three-fused benzene ring solid polycyclic aromatic hydrocarbon (PAH) with the formula C14H10. It's a substance found in coal tar. Anthracene is used to make the red dye alizarin as well as other dyes. It is colourless but fluoresces blue (400–500 nm peak) when exposed to ultraviolet light. This article will study the use of anthracene in detail.


Anthracene Sigma Aldrich

Three benzene rings are fused together to form anthracene, a polycyclic aromatic hydrocarbon. A polycyclic refers to a molecule with more than one ring, aromatic refers to a molecule with alternating double-single bonds all over the ring structure, and hydrocarbon refers to a molecule composed entirely of carbon and hydrogen atoms.


Anthracene Sigma

It is the three rings that were bound together, as well as the network of alternating double and single bonds that ran all the way around them.


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Reactions of Anthracene

  1. Anthracene to Anthraquinone

Anthracene is converted to anthraquinone when it is reacted with an oxidising agent like hydrogen peroxide. Anthracene with two carbon-oxygen double bonds at the two middle carbons of the molecule is easily recognised as anthraquinone. Anthraquinone may be formed from direct combustion processes in motor-operated vehicles and engines. They are the extensive category of naturally occurring quinones, together with some of the most crucial native colourants like alizarin, purpurin, munjistin, emodin, chrysophanol, aloe-emodin, physcion, rhein, etc. With over 700 chemicals identified, anthraquinone is the biggest group of natural pigments.


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  1. Methyl Anthracene

The Elbs reaction is an organic reaction in which an ortho methyl-substituted benzophenone is pyrolyzed to produce a condensed polyaromatic. The reaction is named after Karl Elbs, a German chemist, who also invented the Elbs oxidation. In 1884, the reaction was written. Elbs, on the other hand, misinterpreted the reaction product due to a lack of understanding of naphthalene structure.


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  1. Dibenzo Anthracene

The action of UV light causes anthracene to photo dimerize. The 4+4 cycloaddition results in a pair of new carbon-carbon bonds connecting the dimer, which is known as Dianthracene (or sometimes paranthracene). Thermally or with UV irradiation below 300 nm, it reverts to anthracene. The behaviour of substituted anthracene derivatives is similar. The presence of oxygen has an effect on the reaction.

  1. Magnesium Anthracene

Magnesium anthracene is an organomagnesium compound that is almost always isolated as tetrahydrofuran (THF) adduct with three ligands. The air and water sensitive orange solid Mg(C14H10)(thf)3 is made by heating a suspension of magnesium in a thf solution of anthracene.


Use of Anthracene

  1. Anthracene is primarily converted to anthraquinone, a dye precursor.

  2. Anthracene, an organic semiconductor with a large bandgap, is used as a scintillator for high-energy photon, electron, and alpha particle detectors. Plastics, such as polyvinyl toluene, can be doped with anthracene to create a water-equivalent plastic scintillator for use in radiation therapy dosimetry. The emission spectrum of anthracene peaks between 400 and 440 nm.

  3. It is present in wood preservatives, insecticides, and coating materials.

  4. Anthracene is widely used as a UV tracer in printed wiring board conformal coatings. The anthracene tracer allows for UV inspection of the conformal coating. Anthracene is also used in anthraquinone use.

  5. Anthracene derivatives are used in a number of applications. 1-hydroxyanthracene and 2-hydroxyanthracene are hydroxylated derivatives of phenol and naphthols, and hydroxyanthracene (also known as anthrol and anthracenol) is pharmacologically active. 9,10-dihydroxy anthracene is an example of anthracene with several hydroxyl groups.

  6. During combustion processes, anthracene, like many other polycyclic aromatic hydrocarbons, is produced. Tobacco smoke and consumption of food tainted with combustion materials are the primary sources of human exposure.

  7. Anthracene is non-carcinogenic, as according to several studies it "consistently gives negative results in numerous in vitro and in vivo genotoxicity experiments." Since crude samples were tainted with other polycyclic aromatic compounds, early studies suggested otherwise. It is also easily biodegradable in soil. In the presence of light, it is particularly vulnerable to deterioration.

  8. It is also used as a smokescreen, scintillation counter crystals, and inorganic semiconductor research.

 

Did You Know?

A polycyclic aromatic hydrocarbon (PAH) is a hydrocarbon with many aromatic rings and is a chemical compound containing only carbon and hydrogen. The aromatic hydrocarbons are a significant subset of this category. Naphthalene, which has two aromatic rings, and the three-ring compounds anthracene and phenanthrene are the most basic of these chemicals. This principle is also known as polyaromatic hydrocarbon or polynuclear aromatic hydrocarbon. PAHs are non-polar, uncharged molecules with unique properties owing to delocalized electrons in their aromatic rings. Many are contained in coal and oil fields, as well as the thermal decomposition of organic matter in engines and incinerators, or when biomass burns in forest fires.


Polycyclic aromatic hydrocarbons are addressed as potential starting materials for the abiotic synthesis of materials needed by life's earliest forms. When inhaled, Anthracene can irritate the throat, nose and lungs leading to wheezing and coughing. Contact to the skin may cause irritation, burns, itching which is provoked by sunlight. Regular contact may cause thickening of the skin and changes in pigment. Studies show, Anthracene may turn into an allergy and once the allergy is developed completely in an individual even very low future exposure can cause a skin rash.


How to Identify Anthracene?

Anthracene is between colourless to pale yellow, which feels like sand when touched with a bluish glow. Exposure to such harmful substances should be regularly checked thoroughly. It may include collecting personal samples and surrounding samples. Remember you have a legal right to this information under OSHA 1910.1020. You can obtain copies of samples from your respective employer. If you feel you are experiencing any health problems due to the nature of your work, see a doctor who has expertise in recognizing occupational diseases. 


How to Reduce Exposure to Anthracene?

Use local exhaust ventilation where the chemical is released. If local exhaust ventilation is not suitable for the job make sure to use respirators which can be worn easily. Protective work clothing will help to reduce exposure. After exposure to anthracene, immediately wash at the end of the shift. Wear a face shield along with safety glasses when working with toxic substances to protect your eyes. Never use contact lenses while working with such substances.


Dimerization of Anthracene

When we expose anthracene to ultraviolet light, it undergoes a dimerization reaction. This occurs when two anthracene molecules join together to produce a bigger hydrocarbon structure. Also, the prefix “di” in dimerization signifies 'two' (e.g. two molecules of anthracene)


Compounds like anthracene dimers and other polycyclic aromatic hydrocarbons play a key part in organic semiconductors in terms of utility. They've also gotten a lot of interest from scientists for their potential use as organic materials in solar panels to harness the sun's energy.


Oxidation of Anthracene

When anthracene is exposed to an oxidising agent such as hydrogen peroxide, it is converted to anthraquinone. Anthracene with two carbon-oxygen double bonds at the two middle carbons of the molecule is easily identified as anthraquinone.


Interesting facts 

The melting point of Anthracene is 218 degrees Celsius and the boiling point is 354 degrees Celsius. When Anthracene is at its purest form it is colourless. When anthracene is exposed to daylight it darkens. It is quite soluble in carbon disulfide but insoluble in water. However, Anthracene is relatively soluble in methanol, ethanol, chloroform, benzene, etc.


FAQs on Anthracene: Meaning, Reactions and Uses

1. Where do you find Anthracene?

Vehicle exhaust gases, coal, coal tar, and hazardous waste sites have been found to contain anthracene. These are all potential sources of contamination. Since anthracene has been discovered in cigarettes, you may be exposed by inhaling tobacco and cigarette smoke. Anthracene enters the human body through breathing this contaminated air, which can get inside your lungs when you breathe the air in. Anthracene can cause skin and blood problems as well in humans. 

2. How do you prepare Anthracene?

Anthracene, with the formula C₁₄H₁₀, is a three-fused benzene ring solid polycyclic aromatic hydrocarbon (PAH). It's a substance found in coal tar. Anthracene is used to make the red colour alizarin as well as other dyes. Anthracene is colourless, but when exposed to ultraviolet light, it fluoresces blue (400-500 nm peak). The cyclodehydration of O-methyl or o-methyl-substituted diaryl ketones in the so-called Elbs reaction is a classic process for preparing anthracene in the laboratory. 

3. How do you get Anthracene out of coal tar?

A high-boiling coal-tar fraction crystallises crude Anthracene. Recrystallization and sublimation are used to purify it. Anthraquinone is produced by oxidation and is used as an intermediate in the manufacture of dyes and pigments. Sublimation is used to purify anthracene as well. The process of sublimation involves purifying my means of transferring anthracene directly from solid-state to gas state without transferring into the liquid state. These two processes can help extract anthracene out of coal tar. 

4. How is Anthracene purified?

Physical change in state refers to sublimation. Sublimation is used to purify anthracene. It is the process of converting a solid into a gaseous state without passing through the liquid phase, and the process in which substances are passed directly from gas to solid-state is called deposition or desublimation.

In simple words, Anthracene can be purified using the process of sublimation or desublimation. Converting the state without passing through the liquid phase depends upon the nature of the work.

5. Is Anthracene poisonous?

The simple answer to the question is yes. Anthracene is also referred to as “Green Oil.” Anthracene is soluble in many solvents. Studies show that Anthracene is absorbed on dermal and oral exposure. Major target areas for Anthracene are skin, eyes and lungs. Itching and irritation are common symptoms. Unpleasant dermatologic effects have been observed in both humans and animals. Anthracene exposure has also been linked to headaches, nausea, lack of appetite, gastrointestinal irritation, sluggish reactions, and weakness in humans.

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