Naphthalene and Anthracene

Difference Between Naphthalene and Anthracene

A Brief overview of Naphthalene and Anthracene

Naphthalene and Anthracene are the fact that the structure of naphthalene has two similar rings. The anthracene structure is composed of three identical rings. Both anthracene and naphthalene are essential organic compounds that can be classified by their classification as polycyclic aromatic hydrocarbons. 

What is Naphthalene?

Naphthalene is an organic chemical with a chemical formula of C 108. It is simple to recognize it as the most basic organic aromatic polycyclic hydrocarbon compound. Naphthalene is an odorless white solid.

It possesses a distinctive odor comparable with coal tar however, it is present even at small concentrations. In analyzing the chemical structure of Naphthalene it is composed of a fused pair of the benzene rings. 

Figure 01: Naphthalene

Naphthalene molecules tend to be a result of a combination of two rings of benzene. This leads to the classification of the compound as a Polycyclic Aromatic Hydrocarbon Benzenoid known as PAH. The atoms of carbon are 8 which don’t share two different rings. Each of the eight carbon atoms has one hydrogen atom for each carbon atom.

As for the name of this naphthalene-based molecule, eight carbon atoms have a number between 1 and 8 within a sequence that runs around the entire perimeter of the molecule. Beginning by the carbon atom that is next to another common one. In general, carbon atoms that share a number are by 4a or 8a.

Naphthalene molecules have an arrangement that is planar. But, in contrast to the benzene ring C-C bonds of this molecule differ in length. This difference can be observed using X-ray diffraction. it’s consistent with the model for valence bonds for naphthalene.

Naphthalene can be used as a precursor for various chemical compounds used in the manufacture of phthalic Anhydride and a variety of attractive azo dyes as well as insecticides and various other agrochemicals that are useful.

Naphthalene’s behavior at its melting point?

At its melting point of approximately 80.2degC (176.4degF), naphthalene goes through an exothermic reaction which changes it from solid into liquid form.

Here’s what happens at naphthalene’s melting point:

  • Phase Transition: Naphthalene typically exists as a solid white crystal at room temperature; upon reaching its melting point and heating further, however, its structure begins to fracture as the solid becomes liquid and eventually melts completely.
  • Solid to Liquid Transition: At its melting point, heat energy causes the crystal lattice of naphthalene molecules to vibrate more violently, breaking apart intermolecular bonds that hold it together, thus freeing their fixed positions within it. This disruption allows free flow between individual molecules.
  • Liquid Formation: As intermolecular forces weaken, naphthalene molecules transition to an orderly arrangement and form liquid form. Once in liquid state, molecules can freely move past each other without binding to rigid crystal structure forming rigid molecular bonds as the rigid crystal form disintegrates into solution form.
  • Temperature Stability: When maintained at its melting point, naphthalene remains liquid state and does not continue heating until all samples have become solidified; rather, its temperature will gradually plateau until all samples have completely melted away.

What is Anthracene?

Anthracene could be defined as solid compounds that have three benzene rings that are fused in straight chains. The chemical formula for the chemical compound can be described as C 1410. and it is a colorless solid. Also, it has a mild aroma. Its chemical structure anthracene is more unstable because it is less effective in pi bonding.

The main ingredient in anthracene can be found in coal tar. The coal tar contains about 1.5 percent anthracene. The most frequent impurities that we find in anthracene are carbazole and phenanthrene.

Figure 02: Anthracene

It is possible to make this substance through the process of cyclodehydration using O-methyl substituted diaryl ketones. Additionally, the compound is able to undergo photodimerization in the presence of ultraviolet sunlight. This dimer is known as anthracene.

The primary use of anthracene is for the manufacture of alizarin, a red-colored dye. There are also other dyes we can create by using this chemical. Additionally, it can be used for scintillation in detectors that detect high-energy protons. Alongside, similar to many aromatic polycyclic hydrocarbons anthracene can also be found in smoke from cigarettes.

Anthracene’s behavior at its melting point?

At its melting point of approximately 216degC (421degF), anthracene undergoes a phase transition from solid to liquid form, making its melting point the key factor.

Here’s what happens at that temperature point for anthracene:

  • Phase Change: At room temperature, Anthracene typically presents itself as a white to light yellow solid structure; upon being heated up past its melting point and reaching the melting point however, its solid state begins to shift as its solid structure begins to disassemble and change into liquid state.
  • Solid to Liquid Transition: At its melting point, heat energy increases kinetic energy of anthracene molecules enough that their increased speed overcomes intermolecular forces such as van der Waals forces that hold solid lattice together.
  • Liquid Formation: As intermolecular forces weaken and the kinetic energy of molecules increases, anthracene molecules move toward more disordered arrangements forming liquid state. Once there, molecules have less tightly packed arrangements compared to solid form and can move more freely around within it.
  • Temperature Stability: By keeping anthracene near its melting point temperature, its liquid state should remain uninterrupted by further heating up; instead, temperatures should stabilize until all samples have melted completely.

Chemical Structures of Naphthalene and Anthracene

Naphthalene and anthracene both possess similar chemical structures which can be described as follows:

Naphthalene (C10H8), with the molecular formula C10H8, consists of two fused benzene rings connected by hydrogen bonds. It forms a flat, planar structure where each carbon atom in one ring bonds to two hydrogen atoms and one carbon atom from another adjacent ring resulting in hexagonal-arranged carbons with alternate double bonds.

Anthracene, on the other hand, is a larger aromatic hydrocarbon with the molecular formula C14H10. It consists of three fused benzene rings connected by bonding between them; each carbon in one ring bonds to two carbon atoms in adjacent rings, giving this compound its unique properties and enhanced aromaticity compared to naphthalene’s two fused rings.

Physical Properties

Naphthalene’s relatively low melting point of approximately 80.2degC allows it to sublimate directly from a solid to vapor at room temperature, giving its characteristic scent.

  • Boiling Point of Naphthalene: Naphthalene has an approximate boiling point of 218degC.
  • Solubility: Naphthalene is insoluble in water but soluble in various organic solvents such as benzene, toluene and ethanol – making its solubility in these organic solvents key for multiple applications.
  • Appearance: At room temperature, a mothball-like smell emanates from its white crystalline solid form.
  • Anthracene: it has a much higher melting point, approximately 216degC, making it solid at room temperatures.
  • Boiling Point: Anthracene boasts a significantly higher boiling point of approximately 340degC than its counterpart naphthalene.
  • Solubility: Like its relative, naphthalene, anthracene is insoluble in water and sparingly soluble in organic solvents like benzene and toluene; its solubility in such solvents tends to be relatively lower compared with that of naphthalene.
  • Appearance: At room temperature, white to light yellow crystals can often be seen.

What are the Medicinal uses of Naphthalene and Anthracene?

Naphthalene and anthracene are no longer commonly used in modern medicine due to their toxic potential and adverse health effects, yet historically these chemicals were employed for various medicinal applications – these have since been replaced by safer options.

Here are some historical medicinal uses of naphthalene and anthracene:


  • Topical Antiseptic: Naphthalene was once widely used topically as an antiseptic and disinfectant to treat skin ailments and wounds, thought to have antibacterial properties Naphthalene’s strong odor and insect-repelling properties made it a vital ingredient of older insect repellent products, used to deter moths and other insects from infesting clothing or stored items often in the form of mothballs.
  • Anthracene as Laxative: Historically, Anthracene derivatives such as anthraquinones found in certain plants such as Senna and Cascara were employed as natural laxatives for relieving constipation. These stimulating agents would stimulate the colon and aid with relieving constipation symptoms.

The natural sources and occurrence

Naphthalene’s Natural Sources: In nature, Naphthalene does not usually occur naturally in significant quantities; rather it is often produced as an end-product from carbonization of coal or refinement of petroleum refining processes, particularly coal tar formation. Some plants in the Cercocarpus genera also produce small amounts as natural defense mechanisms against herbivorous animals that seek shelter within them.

Naphthalene can often be found in coal tar, an opaque substance formed through the carbonization of coal. In small amounts, it may also exist in crude oil and natural gas reserves but should typically be extracted during refining processes.

Anthracene can be found both naturally and synthetically in its native environment. Small quantities exist within coal tar – similar to naphthalene – obtained through carbonization of coal; while certain species of mushrooms produce it naturally.

Occurrence: Anthracene can often be found in coal tar, an unstable mixture of different hydrocarbons produced during destructive distillation of coal, as well as some plant species and released to the environment through combustion of organic matter like wood and fossil fuels.

How does Naphthalene and Anthracene Affect the Environment

Naphthalene and anthracene release into the environment can have many damaging impacts due to their persistence and potential toxicity, with effects including:

  • Naphthalene Water contamination: Naphthalene can enter water bodies through runoff from industrial facilities or spills from consumers who ingest products that contain it; its poor solubility in water means it tends to build up over time in sediments accumulating as sediment-formers; this accumulation in turn threatens aquatic organisms as well as alter aquatic ecosystems over time.
  • Air Pollution: Naphthalene can enter the atmosphere through products like mothballs and deodorizers or by burning fossil fuels, where it then reacts with other pollutants to form photochemical smog; prolonged exposure can harm human health as well as lead to lower air quality standards.
  • Soil Contamination: Naphthalene can contaminate soil when released from industrial sites or improperly disposed. This contamination may persist for extended periods, potentially harming organisms living within it and even having negative impacts on plant growth and health.
  • Anthracene Contamination in Water Bodies and Soils: Like naphthalene, anthracene has the potential to pollute both bodies of water and soil through various means such as runoff from industrial sites or the release of coal tar from coal mines. While relatively insoluble in water bodies it can accumulate sediments over time while persisting for extended periods in soil environments with adverse consequences to organisms and plants alike.
  • Bioaccumulation: Naphthalene and anthracene compounds have the capacity to accumulate in aquatic and terrestrial organisms’ tissues, potentially increasing up the food chain to affect higher trophic levels.
  • Toxicity to Organisms: Both compounds have long been recognized for being toxic to various forms of life, from aquatic creatures and soil-dwellers to certain plants and even humans. Their toxic effects have the ability to undermine ecosystems while diminishing species’ health and causing irreparable harm.
  • Persistence: Naphthalene and anthracene remain persistent pollutants for an extended period in the environment, meaning they do not easily break down into smaller compounds that decompose over time. This leads to long-term environmental contamination.

It’s essential to keep in mind, that the environmental impacts of these compounds vary based on factors like concentration, exposure duration and environmental conditions, measures are taken to regulate and minimize their release into the environment, particularly where industrial settings exist where these agents commonly come into contact.

Key Difference Between Naphthalene and Anthracene

One of the main differences between the two naphthalene structures anthracene is the fact that naphthalene features two rings similar to each other while anthracene structure is composed of three identical rings.

Naphthalene is found as clear solid crystals or as flakes and is characterized by a strong smell of coal tar in contrast, anthracene is a colorless crystal and is mildly fragrant. The chemical formula for Naphthalene can be described as C 108. and the chemical formula for anthracene’s chemical formula is C 1410.

Here’s a simplified comparison chart highlighting the key differences between naphthalene and anthracene:

Property Naphthalene Anthracene
Molecular Formula C10H8 C14H10
Chemical Structure Fused benzene rings Fused benzene rings
Aromaticity Aromatic Aromatic
Melting Point 80.2°C 216°C
Boiling Point 218°C 340°C
Solubility Insoluble in water Insoluble in water
Appearance White crystalline solid White to light yellow
Reactivity Less reactive More reactive
Electrophilic Substitution Slower reactions Faster reactions
Natural Sources Occurs in coal tar Found in coal tar and some plants
Industrial Production From coal tar or petroleum Synthesized from coal tar
Common Uses Mothballs, deodorizers Used in dyes, photoluminescent materials
Toxicity Toxic when ingested or inhaled Moderately toxic
Environmental Impact Persistent, potentially harmful Less persistent


Naphthalene and anthracene are aromatic hydrocarbons with distinct properties. Naphthalene’s molecular formula of C10H8 comprises two fused benzene rings and has low melting and boiling points making it popularly used in mothballs and deodorizers.

Anthracene’s molecular formula C14H10 features three fused benzene rings with its molecular formula of C9H11 that have low melting and boiling points, making a white crystalline solid used widely in mothballs and deodorizers.

Anthracene has more complex structures with three fused benzene rings (C14H10) and significantly higher melting and boiling points, while it remains water soluble. Anthracene’s electrophilic aromatic substitution reactions tend to be slower.

Anthracene is widely used as a dye and photoluminescent material, and its more reactive nature makes it more prone to chemical reactions than naphthalene – knowing these differences is vital in order to understand their respective applications and environmental implications.