Chemicals and Solvents

What’s The Difference Between Pentane and n-Pentane?

Pentane Versus n-Pentane: The Five-Carbon Conundrum

Pentane is an alkane with the chemical formula C₅H₁₂. The three structural isomers of pentane are n-pentane, isopentane, and neopentane. Although these three similar compounds are often sold as a mixture of the three, the isomers have different boiling and melting points. It is important to note that the IUPAC name for pentane is n-pentane. To avoid confusion when purchasing pentane, check the SDS or technical data sheet to ensure that you are ordering the correct isomer or mixture.

Pentanes are often used for liquid chromatography, as blowing agents, and as solvents. Due to the non-polar nature of pentane and its low boiling point, it is well-suited as a solvent for cleaning in the aerospace, automobile, electronic, and defense manufacturing industries. Other sectors that utilize pentane as a solvent are petrochemical, pharmaceutical, and coatings. Lab Pro offers pentane, n-pentane, and the octane 2,2,4-treimethylpentane in convenient quantities for your research or production endeavors.

Pentanes: Structure and Function

The three isomers of pentane are shown below (n-pentane, isopentane, and neopentane). Pentanes are cost-effective solvents that are the most volatile liquid alkanes at room temperature. These quick-to evaporate chemicals are non-polar and will only dissolve in solvents with similar properties such as aromatics, chloroalkanes, and ethers.

Some of the properties of pentane isomers are listed in Table 1. The more branched isomers of pentane have higher stability, higher vapor pressures, and higher flash points, than n-pentane.  Neopentane has the lowest boiling points of the three and is a gas at room temperature. N-pentane is the preferred blowing agent for expanded polystyrene and polyethylene manufacturing and used as a solvent in column chromatography. Chinese patent CN102558480A an isopentane and n-pentane co-foaming system for rigid polyurethane foam.

Cyclopentane has a ring structure and has two fewer hydrogen atoms than pentane (C₅H₁₀), so it is not an isomer of pentane. Cyclopentane is gaining popularity as a replacement for traditional refrigerants such as CFCs. Cyclopentane is a major component of gasoline, diesel, and jet fuel. The National Renewable Energy Laboratory recently announced that it will be scaling up a process of converting corn stover into a cyclohexane-rich sustainable aviation fuel.¹

 2,2,4-trimethylpentane, or isooctane, is an octane with a pentane backbone with the chemical formula C₈H₁₈. It is frequently used as a solvent in organic synthesis and an entrainer for azeotropic distillation, for example to dehydrate ethanol. In 2020, Łukasz Dąbrowski found that isooctane is an effective keeper for the determination of organic pollutants.²

 

Table 1: Properties of Pentanes, Cyclopentane, and Isooctane

	Isomer of Pentane			5-Carbon that is not an Isomer of Pentane	Octane with Pentane Backbone
Preferred IUPAC name	Pentane	2-Methylbutane	2,2-Dimethylpropane	Cyclopentane	2,2,4 Trimethylpentane
Other names	n-Pentane	Methylbutane	Neopentane	Pentamethylene	Isooctane
	Quintane	Isopentane	Tetramethylmethane
	Refrigerant -4-13-0
CAS	109-66-0	78-78-4	462-82-1	287-92-3	540-84-1
Chemical formula	C5H12	C5H12	C5H12	C5H10	C8H18
Description	Alkane	Branched-chain saturated alkane	Double-branched chain alkane	Alicyclic hydrocarbon	Isomer of octane
Vapor pressure	57.9 kPa at 20°C	76.992 kPa at 20°C	146 kPa at 20°C	45 kPa at 20°C	5.5 kPa at 21°C
Flash point	-49°C	-51°C	<-7°C	-37.2°C	-12°C
Melting point	-130.5 to -129.1°C	-159.9°C	-16.6°C	-93.9°C	-107.38°C
Boiling point	35.9 to 36.3°C	27.8 to 28.2°C	9.5°C	49.2°C	99.30°C
Density (O°C, kg/m3)	621	616	586	751	692
Uses	Solvent, raw material, fuel component, aerosol propellant, reaction media for polymerization, HPLC solvent	Drive turbines in geothermal power production, cryosectioning in histology, component of natural gasoline	Raw material for butyl rubber, chemical intermediate in research, present in natural gas and petrol fuel mixture	Raw material for resins and rubber adhesives, blowing agent for polyurethane foam, refrigerant alternative	Increase knock resistance of gasoline
	Uses for mixture of pentanes
	Blowing agent for foams
	Working medium geothermal power stations and refrigerants
	Solvents for pesticides
	Solvent for liquid chromatography

Safety

Pentanes and related solvents highly flammable. Heating will cause rise in pressure with risk of bursting. Vapor/air mixtures are explosive. Store in tightly closed containers in a cool, well-ventilated area. Pentanes are incompatible with strong oxidizers. Air-supplied respirators are recommended when handling, as pentanes will irritate eyes, skin, nose, and lungs. Isooctane is a nephrotoxin.

Pentanes

Pentanes are often sold as mixtures of the three isomers, or as single components. Compounds like cyclopentane and trimethylpentane are not true pentanes per definition. These compounds are similar in that they are highly flammable and have similar uses, but they are not always interchangeable. Lab Pro stocks technical grade pentane and n-pentane for your ground-breaking manufacturing or research needs.

Note: These products and chemicals are meant to be used for research, industrial work, cleaning or disinfecting and should always be stored out of the reach of young children or infants. 

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References

1. Hermens, G.H; Freese, Thomas; J. an den Berg, Keimpe; Van Germer, Rogier; Feringa, Ben. Coating from Nature. Science Advances. 2020 Dec 16; Vol. 6, no. 51, eabe0026. DOI: 10.1126/sciadv.abe0026
2. Dąbrowski Ł. Evaluation of Solvents Used as Keepers in the Determination of Organic Pollutants by GC/MS. Molecules. 2020 Sep 25;25(19):4419. doi: 10.3390/molecules25194419. PMID: 32992997; PMCID: PMC7582485.