What is the Difference Between Anthracene and Phenanthrene

The main difference between anthracene and phenanthrene is that anthracene is fused linearly and has four resonance structures, whereas phenanthrene is fused at an angle, which makes it have five resonance structures.

Anthracene and phenanthrene are tricyclic aromatic hydrocarbons that are found in high concentrations in polycyclic aromatic hydrocarbon (PAH) contaminated sediments, surface soils, and waste sites. Both of these hydrocarbons contain three benzene rings per molecule.

Key Areas Covered

1. What is Anthracene
     – Definition, Structure, Features
2. What is Phenanthrene
     – Definition, Structure, Features
3. Similarities Between Anthracene and Phenanthrene
     – Outline of Common Features
4. Difference Between Anthracene and Phenanthrene
     – Comparison of Key Differences

Key Terms

Anthracene, Phenanthrene

What is Anthracene

Anthracene is a white-yellow solid compound with the molecular formula C₁₄H₁₀. It is insoluble in water but relatively soluble in ethanol, methanol, benzene, and chloroform. It has a molar mass of 178.23 g/mol. The boiling point and melting point of the compound are 340 °C and 215 °C, respectively. The density of the anthracene is  1.25 g/cm³. This compound has a weak aromatic odor, and it sinks in water. It also exhibits a blue fluorescence under ultraviolet radiation. Also known as Paranaphthalene or green oil, this is the simplest tricyclic aromatic carbon.

Anthracene is added to the environment as a result of the incomplete combustion of fossil fuels. It is a component of coal tar. It is purified by recrystallization and sublimation. This chemical compound is present in exhaust emissions, the smoke of cigarettes, surface drinking water, ambient air, and edible aquatic organisms. The oxidation of anthracene yields anthraquinone, which is an intermediate in the production of dyes and pigments. Moreover, anthracene is easily biodegradable in soil. In the presence of light, the possibility of deterioration of the compound increases. Upon exposure to daylight, it darkens.

Use of Anthracene 

Anthracene has many different uses. The uses include the production of a red die called alizarin, other dyes, smoke screens, scintillation counter crystals, and organic semiconductor research. It is also present in wood preservatives, coating materials, and insecticides. Anthracene is also useful as an ultraviolet tracer in printed wiring board conformal coatings. Plastics such as polyvinyl toluene can be doped with anthracene to create a water-equivalent plastic scintillator. This is common in radiation therapy dosimetry.

However, persistent exposure to anthracene may cause deleterious effects. It is an irritant and an allergen to the nose, eyes, throat, and skin. It is not cancer-causing ( carcinogenic), as per recent studies. But it may cause mutations and aberrations.

There are different bacteria and numerous fungi that can degrade anthracene. These include Mycobacterium sp., Bacillus subtilis, Nocardia otitidiscaviarum, and white rot fungi. According to reports, there are different pathways to degrade anthracene.

What is Phenanthrene

Phenanthrene is a polycyclic aromatic hydrocarbon consisting of three fused benzene rings at an angle. Its molecular formula is C₁₄H_10, whereas its molecular weight is 178.23. Its name comes from the two terms “phenyl” and “anthracene.” The melting point and boiling point of phenanthrene are 101°C and 340°C, respectively. The density of the compound is 1.18 g/cm³.

Phenanthrene is present in fossil fuels and products of incomplete combustion. It is also present in coal and oil burning, vehicle emissions, coke plants, aluminium plants, wood combustions, iron and steel works, foundries, municipal incinerators, aluminium plants, oil shale plants, and tobacco smoke. Moreover, it is widely present in aquatic environments, including tap water, wastewater, and surface water.

Phenanthrene has many uses in different industries – for example, in making dyes, plastics, pesticides, explosives and drugs, bile acids, cholesterol, and steroids. But it should be handled with care as it is toxic. Additionally, inhaling phenanthrene can cause irritations in the throat and nose. It is also a potential cancer-causing agent.

Similarities Between Anthracene and Phenanthrene

• Both anthracene and phenanthrene have the same molecular formula.
• Moreover, both are hydrocarbons containing three benzene rings per molecule.

Difference Between Anthracene and Phenanthrene

Definition

Anthracene is a polycyclic aromatic hydrocarbon that has three fused benzene rings in a straight chain, while phenanthrene is a polycyclic aromatic hydrocarbon consisting of three fused benzene rings at an angle.

Structure

Anthracene is fused linearly and has four resonance structures, whereas phenanthrene is fused at an angle, which makes it have five resonance structures.

Density

The density of anthracene is 1.25g/cm³, whereas the density of 1.18g/cm³.

Melting Point and Boiling Point

The boiling point and melting point of anthracene are 340°C and 215°C respectively, whereas the melting point and boiling point of phenanthrene are 101°C and 340°C, respectively.

Uses

Anthracene is used to make alizarin and other dyes, smoke screens, scintillation counter crystals, and organic semiconductor research, while phenanthrene is used to make dyes, plastics, pesticides, explosives and drugs, bile acids, cholesterol, and steroids.

Conclusion

In brief, anthracene and phenanthrene are tricyclic aromatic hydrocarbons. The main difference between anthracene and phenanthrene is that anthracene is fused linearly, whereas phenanthrene is fused at an angle.

Reference:

1. “Anthracene – Overview.” ScienceDirect.
2. “CHEBI:28851 – phenanthrene.” CHEBI. EMBL-EBI

Image Courtesy:

1. “Anthracene-numbering” By Hbf878 – Own work (CC0) via Commons Wikimedia
2. “Phenanthrene-numbering” By Hbf878 – Own work (CC0) via Commons Wikimedia