Pentane

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Pentane
Pentane sample.jpg
Distilled lab-grade pentane.
Names
IUPAC name
Pentane
Systematic IUPAC name
n-Pentane
Identifiers
Jmol-3D images Image
Properties
C5H12
Molar mass 72.15 g/mol
Appearance Colorless volatile liquid
Odor Lighter-fluid like
Density 0.626 g/cm3
Melting point −129.8 °C (−201.6 °F; 143.3 K) (decomposes)
Boiling point 36 °C (97 °F; 309 K)
40 mg/L (at 20 °C)
Solubility Miscible with ethanol
Vapor pressure 57.90 kPa (at 20.0 °C)
Acidity (pKa) ~45
Viscosity 0.240 cP (at 20 °C)
Thermochemistry
263.47 J K−1 mol−1
−174.1–−172.9 kJ mol−1
Hazards
Safety data sheet BOC
Flash point −49 °C
Lethal dose or concentration (LD, LC):
3,000 mg/kg (dermal, rabbit)
5,000 mg/kg (oral, mouse)
130,000 mg/m3 (mouse, 30 min)
128,200 ppm (mouse, 37 min)
325,000 mg/m3 (mouse, 2 hr)
Related compounds
Related compounds
Butane
Hexane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Pentane is an organic compound, an alkane with 5 carbon atoms, with the chemical formula C5H12. It is composed of three isomers, n-pentane, isopentane (or methylbutane) and neopentane. While the term "pentane" may refer to any of the isomers, the IUPAC nomenclature specifies that the term must only be used for the n isomer.

Properties

Chemical

Pentane, like other hydrocarbons, will burn in air when ignited by an open flame to release carbon dioxide and water vapor.

Physical

Pentane is a colorless liquid hydrocarbon, with a characteristic smell. It is insoluble in water, but miscible with other organic solvents. It has a density of 0.621 g/cm3, meaning it's lighter than water. It boils at 36°C and melts at -130°C.

Its isomer neopentane, though, is a gas that boils at 9.5°C, is the heaviest and the most high-boiling of all hydrocarbon gases.

Availability

Pentane can be purchased form chemical suppliers. Certain pesticides contain pentane.

Some car starter fluids contain pentane to increase the volatility of the fluid. You will need a long fractional distillation column or repeated distillations, as the boiling point of diethyl ether (34.6 °C), the other useful compound from starter fluid, is very close to that of pentane (36.3 °C).

Some type of charcoal lighter fluids can contain up to 25% n-pentane. Fractional distillation is required to extract it from the mixture.

Preparation

Pentane can be prepared by decarboxylating the salts of caproic acid, found in various oily plants, with a strong base.

Projects

  • Extraction (solvent)
  • Phthalic and maleic anhydride synthesis

Handling

Safety

Pentane evaporates very fast and the vapors are hazardous if inhaled, work should be performed in a fumehood or outside. If pentane is inhaled in large amounts, further exposure should be limited and one should seek fresh air.

Storage

Due to its low boiling point, pentane should be stored in closed glass bottles, at constant temperature, away from any source of heat, even small ones. If it's stored at low temperatures, and then brought at room temperatures or slightly higher, pressure will build up in the bottle from the vapors and the bottle can explode. It is mandatory to open the bottle from time to time, to release the pressure.

Commercial pentane contains small amounts of inhibitors, that prevent its degradation, over long periods of time. They can be removed by distillation, as their boiling point is much higher than that of pentane.

Disposal

Pentane can be safely burned, as it theoretically should not generate any toxic byproducts. However, like other hydrocarbons, carbon monoxide can be formed so this should not be performed indoors.

References

Relevant Sciencemadness threads

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