Definition of Naphthalene in Chemistry
Naphthalene is an aromatic hydrocarbon compound with a molecular formula C10H8. It is a white solid that is derived from coal tar and is commonly used as a household moth repellent due to its strong odor and ability to sublimate. In chemistry, naphthalene is known for its unique structure, consisting of two fused benzene rings. It is often used as a starting material for the synthesis of various aromatic compounds and is also employed as a solvent in certain chemical reactions.
Chemical Formula and Structure of Naphthalene
The chemical formula of naphthalene is C10H8.
Its structure consists of two fused benzene rings, resulting in a polycyclic aromatic hydrocarbon. Each carbon atom in the benzene rings is bonded to two hydrogen atoms. The structure can be represented as:
H H H H H
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H – C = C – C = C – C – H
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H H H H H
In this structure, the double bonds within the benzene rings and the alternating single bonds between them give naphthalene its unique properties and aromatic nature.
Physical Properties of Naphthalene
Naphthalene is a white crystalline solid compound with a distinctive odor, commonly found in mothballs. It has several notable physical properties:
Chemical Formula: The chemical formula of naphthalene is C10H8, indicating it consists of 10 carbon atoms and 8 hydrogen atoms.
Molecular Weight: The molecular weight of naphthalene is approximately 128.17 g/mol.
Appearance: Naphthalene appears as white, crystalline flakes or powder.
Odor: Naphthalene has a strong, distinctive, and somewhat unpleasant odor. This odor is often associated with mothballs.
Melting Point: Naphthalene has a melting point of approximately 80.2 degrees Celsius (176.4 degrees Fahrenheit). It sublimes (changes from a solid to a gas without passing through the liquid phase) at temperatures just below its melting point.
Boiling Point: The boiling point of naphthalene is around 218 degrees Celsius (424.4 degrees Fahrenheit). However, naphthalene tends to sublime at lower temperatures before reaching its boiling point.
Density: The density of naphthalene is about 1.14 g/cm³.
Solubility: Naphthalene is not very soluble in water. It is more soluble in organic solvents such as benzene, toluene, and ether.
Crystal Structure: Naphthalene crystallizes in a monoclinic crystal structure.
Flammability: Naphthalene is flammable and can burn when exposed to an open flame.
Vapor Pressure: Naphthalene has a significant vapor pressure at room temperature, which is why it sublimes readily. The vapor pressure increases with temperature.
Sublimation: Naphthalene readily sublimes from a solid to a vapor at temperatures below its melting point. This property is often exploited in mothballs, where the gradual release of naphthalene vapor helps repel moths and other insects.
Naphthalene is used in various applications beyond mothballs, including as a precursor in the synthesis of other chemicals and as a reagent in organic chemistry. Its physical properties make it useful for these purposes.
Uses and Applications of Naphthalene
Naphthalene, a white crystalline compound with a distinctive odor, has several important uses and applications in various industries and everyday life. Some of its primary uses and applications include:
Moth Repellent: Naphthalene is perhaps best known for its use in mothballs and moth flakes. Its strong odor and sublimation properties make it effective at repelling moths, as well as other insects and pests. When stored with clothing or other items, naphthalene gradually releases vapor that discourages insect infestations.
Chemical Synthesis: Naphthalene serves as a precursor in the synthesis of various chemicals, including phthalic anhydride and naphthalene sulfonic acids. These compounds are used in the production of dyes, resins, and pharmaceuticals.
Organic Chemistry: Naphthalene is used as a reagent in organic chemistry reactions. It can be involved in processes such as Friedel-Crafts acylation and alkylation, which are important for the synthesis of aromatic compounds.
Intermediate for Chemicals: Naphthalene is an intermediate compound for the production of other chemicals like naphthols, phthalic anhydride, and various azo dyes.
Deodorizers and Air Fresheners: Its odor-neutralizing properties are utilized in some deodorizers and air fresheners to mask or eliminate unpleasant odors in confined spaces.
Fuels and Fuel Additives: Naphthalene can be used as a component in some fuels and fuel additives to improve combustion efficiency. However, its use in this regard is relatively limited due to concerns about its environmental impact.
Biological Research: Naphthalene can be employed in biological research, particularly in toxicology studies and in investigations into its effects on living organisms.
Insecticides: Naphthalene has been used in the past as an insecticide. However, its use in this capacity has decreased due to environmental and health concerns.
Solid-State Electronics: In semiconductor research and manufacturing, naphthalene is sometimes used as a dopant to introduce certain impurities into semiconductor materials, thereby altering their electronic properties.
Preservation of Museum Specimens: Museums and institutions use naphthalene to protect certain insect specimens by repelling pests that could damage the specimens.
It’s important to note that while naphthalene has various applications, it should be used with caution due to its potential health and environmental risks. In some cases, alternatives with fewer associated risks may be preferred. Additionally, regulations on the use of naphthalene vary by region, so it’s essential to be aware of local guidelines and restrictions when using or handling this substance.
Safety Considerations with Naphthalene
Naphthalene, while useful for various applications, should be handled and used with caution due to its potential health and environmental risks. Here are some safety considerations when working with or around naphthalene:
Exposure and Inhalation Hazards:
Naphthalene can release potentially harmful vapors. Prolonged inhalation of these vapors may irritate the respiratory tract and can cause headache, nausea, and confusion.
Exposure to high concentrations of naphthalene vapor can lead to more severe health effects, including hemolytic anemia and damage to the liver.
Skin Contact:
Direct skin contact with naphthalene may lead to skin irritation, and prolonged exposure can result in dermatitis.
Eye Contact:
Naphthalene can cause eye irritation. In case of eye contact, it is essential to flush the eyes with water for at least 15 minutes and seek medical attention if irritation persists.
Ingestion:
Ingesting naphthalene is highly discouraged, as it can cause gastrointestinal irritation, nausea, vomiting, and potentially more serious health effects. It is essential to seek medical attention if ingested.
Ventilation:
When using naphthalene in closed spaces, ensure adequate ventilation to minimize the buildup of naphthalene vapors.
Protective Equipment:
When handling naphthalene, it is advisable to wear appropriate personal protective equipment, including gloves, safety goggles, and, if necessary, a lab coat or protective clothing.
Storage:
Store naphthalene in a cool, dry, well-ventilated area, away from incompatible substances (e.g., strong oxidizers).
Keep naphthalene away from sources of ignition and open flames due to its flammability.
Spills and Cleanup:
In case of a naphthalene spill, take appropriate measures to contain and clean it up. This may involve using absorbent materials and following local regulations for hazardous material cleanup.
Disposal:
Dispose of naphthalene and materials contaminated with naphthalene in accordance with local, state, and federal regulations. It is considered hazardous waste in many jurisdictions.
Environmental Impact:
Naphthalene is toxic to aquatic life and poses environmental risks if released into water bodies. Take care to prevent contamination of water sources.
Regulatory Compliance:
Ensure compliance with all applicable regulations and guidelines regarding the use, storage, and disposal of naphthalene. Regulatory requirements may vary by region.
Emergency Response:
Be prepared to respond to accidental exposure or spills by having appropriate emergency response procedures and materials in place.
Medical Attention:
Seek medical attention if there is any suspicion of overexposure or health effects due to contact with naphthalene.
It’s important to note that the use of naphthalene in certain applications, such as moth repellents, is regulated in many countries due to health and environmental concerns. Safer alternatives may be preferred in some cases.
Always refer to the Material Safety Data Sheet (MSDS) or Safety Data Sheet (SDS) provided by the manufacturer for specific safety information and guidelines when working with naphthalene or any chemical substance. Additionally, consult with local occupational health and safety authorities for guidance on safe handling and disposal practices.
Abigail Gutmann Doyle is a renowned Organic chemistry professor in Los Angeles. Her research focuses on the development of new chemical transformations in organic chemistry. She has won awards such as: Bayer Early Excellence in Science Award, Phi Lambda Upsilon National Fresenius Award, Presidential Early Career Award for Scientists and Engineers, BMS Unrestricted Grant in Synthetic Organic Chemistry.