Definition of Octadecane (C₁₈H₃₈) in chemistry
Octadecane is a type of hydrocarbon that belongs to the alkane group. It is composed of 18 carbon atoms and 38 hydrogen atoms, with a chemical formula of C₁₈H₃₈. It is a straight-chain hydrocarbon, meaning that the carbon atoms are arranged in a continuous chain. Octadecane is a colorless and odorless liquid at room temperature and is insoluble in water. It is often used as a reference compound in analytical chemistry or in various industrial applications, such as being a component of fuels or lubricants.
Chemical formula and structure of Octadecane
The chemical formula for octadecane is C18H38. It is an alkane compound and belongs to the family of hydrocarbons. Octadecane has 18 carbon atoms and 38 hydrogen atoms, making it a saturated hydrocarbon with a straight-chain structure.
The structure of octadecane can be represented by a series of carbon atoms bonded together in a straight line, with the remaining valences of each carbon atom occupied by hydrogen atoms. The structure can be written as:
CH3-(CH2)16-CH3
This indicates that there are 16 methylene (CH2) groups between the two methyl (CH3) groups at either end of the carbon chain.
The condensed structural formula for octadecane is:
CH3(CH2)16CH3
In this representation, the carbon atoms are shown in a row with the attached hydrogen atoms understood.
It is worth mentioning that there can be different isomers or arrangements of carbon atoms in a compound with the same molecular formula. However, for octadecane, the most common and simplest structure is the straight-chain arrangement as described above.
Physical properties of Octadecane
Octadecane is a linear hydrocarbon with the chemical formula C18H38. It is a waxy solid at room temperature and exhibits the following physical properties:
1. Melting point: Octadecane has a high melting point of around 28-30°C (82-86°F). Due to its highly ordered arrangement of molecules, it requires a significant amount of energy to break the intermolecular forces and change to a liquid state.
2. Boiling point: Octadecane has a relatively high boiling point of approximately 316-320°C (601-608°F). This indicates that it requires a significant amount of heat energy to completely convert into a gaseous state.
3. Density: The density of octadecane is around 0.771 g/cm³ at 20°C (68°F). This value indicates that it is less dense than water, which has a density of 1 g/cm³. Therefore, octadecane will float on water.
4. Solubility: Octadecane is classified as a nonpolar molecule and is insoluble in polar solvents such as water. However, it is highly soluble in nonpolar solvents, including other hydrocarbons (e.g., hexane, heptane, etc.).
5. Odor: Octadecane is odorless.
6. Appearance: It appears as a white crystalline solid or as a waxy substance.
7. State of matter: Octadecane is typically found in the solid state at room temperature but can easily transition to a liquid or gaseous state under appropriate conditions.
8. Viscosity: It has a relatively high viscosity, meaning it flows slowly. Its viscosity decreases as the temperature increases.
These physical properties are essential for understanding the behavior and the potential applications of octadecane in various industries, such as lubricants, cosmetics, and pharmaceuticals.
Common uses and applications of Octadecane
Octadecane, also known as n-octadecane, is a complex hydrocarbon compound with the molecular formula C18H38. It is derived from the alkane group of hydrocarbons and consists of 18 carbon atoms, with a long hydrocarbon chain. Octadecane has several applications in chemistry, including:
1. Solvent: Octadecane is often used as a non-polar solvent in various chemical reactions and processes. Its non-polar nature makes it useful for dissolving non-polar compounds, such as waxes, oils, and grease.
2. Solid-state phase change material: Octadecane exhibits a solid-liquid phase change behavior at around 28-29°C. This characteristic is utilized in the development of phase change materials (PCMs) used for thermal energy storage applications. Octadecane can absorb and release large amounts of heat during its phase transition, making it useful for applications like energy storage systems, heating, and air conditioning.
3. Surfactant and emulsifier: Octadecane can act as a surfactant or emulsifier due to its amphiphilic nature. It can form micelles or emulsions, aiding in the dispersion of immiscible substances such as oil and water. This property is especially valuable in the formulation of various cosmetic, pharmaceutical, and agricultural products.
4. Lubricant and corrosion inhibitor: Octadecane can be used as a lubricant due to its long hydrocarbon chain, which provides a high viscosity and low volatility. It can reduce friction between moving parts in machinery and serve as a protective barrier against corrosion and rust.
5. Chemical intermediate: Octadecane can serve as a starting material or intermediate in the synthesis of various organic compounds. It can undergo reactions such as hydrogenation, oxidation, and functional group transformations to produce valuable chemicals, including fatty alcohols, fatty acids, and esters.
6. Reference compound: Octadecane is often used as a reference compound in analytical chemistry techniques, such as gas chromatography. Its well-defined physical and chemical properties make it useful as a standard to calibrate and evaluate the performance of analytical instruments.
Overall, octadecane has diverse applications in various fields of chemistry, including solvents, phase change materials, surfactants, lubricants, and chemical intermediates. Its unique properties make it a versatile compound for numerous industrial processes and applications.
Safety considerations and handling of Octadecane
Handling octadecane, like any chemical, requires adherence to proper safety protocols to ensure the safety of the user and those in the surrounding environment. Here are some safety considerations and guidelines for handling octadecane in a chemistry setting:
1. Personal Protective Equipment (PPE): Always wear appropriate PPE, including lab coat, goggles, gloves, and closed-toe shoes when working with octadecane. The gloves should be resistant to organic solvents and provide sufficient chemical barrier.
2. Ventilation: Conduct all procedures involving octadecane in a well-ventilated fume hood to prevent inhalation of vapors.
3. Storage: Store octadecane in a tightly sealed container in a cool, dry place away from incompatible materials. Ensure the storage area is adequately ventilated.
4. Fire Safety: Octadecane is combustible and can ignite under certain conditions. Keep it away from open flames, sparks, and heat sources. In case of a fire, use a suitable extinguisher, such as carbon dioxide or dry chemical powder, to put out the fire.
5. Spill and Leak Response: In the event of a spill, contain and absorb the octadecane with appropriate absorbent material (e.g., vermiculite or sand). Place the contaminated material in a labeled, tightly sealed container for disposal. Clean the spill area thoroughly, following proper waste disposal procedures.
6. Handling: When handling octadecane, avoid contact with eyes, skin, and clothing. In case of contact, rinse the affected area immediately with plenty of water for at least 15 minutes. Seek medical attention if irritation persists.
7. Disposal: Dispose of octadecane according to local regulations. Do not pour it down the drain or discard it in regular trash. Consult with waste management experts or your institution’s waste disposal guidelines to ensure proper disposal methods.
8. Manual Handling: Octadecane is a liquid at room temperature, so exercise caution when carrying or transporting containers to avoid spills and leaks. Use secondary containment measures like trays or spill pallets to minimize the risk of spreading the chemical in case of accidental release.
9. Emergency Response: Familiarize yourself with emergency procedures and equipment in case of accidental ingestion, inhalation, or exposure to octadecane. Keep emergency eyewash stations, safety showers, and spill response kits readily accessible in the lab.
Remember, these guidelines are general recommendations, and it is crucial to consult the Safety Data Sheet (SDS) and any specific handling instructions provided by the manufacturer or your institution’s safety department for comprehensive information on safety considerations related to octadecane.
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.