Table of contents


Introduction to Pentane

Pentane c5h12 is a hydrocarbon (alkane) having five-carbon and twelve hydrogen atoms. This chemical compound is non-polar since all of its atoms possess nearly similar values of electronegativity. That's the very reason why it's not soluble in water or aqueous solutions. It's a volatile agent and is found as a naturally occurring product.

Isomers of Pentane

It contains three structural isomers including neopentane, isopentane, and n-pentane.

The formulas of these three isomers of pentane are as follows

H3C-CH2-CH2-CH2-CH3 (n-pentane)
H3C-CH(CH3)-CH2-CH3 (iso-pentane)
H3C-C(CH3)3 (neo-Pentane)

Before going into details about the properties of each isomer of pentane, let's recall the concept of isomerism.

What is Isomerism?

Isomerism refers to the phenomenon whereby two chemical compounds have the same chemical formula, with the same kind and number of atoms, but different structural formulas. Due to different structural formulas, their physical properties are also getting different from each other. The molecules that show this phenomenon are called isomers.

We can also define isomers as the chemical compounds having the same chemical formula but differ from each other concerning the arrangement of atoms and properties, which are called isomers.

Types of Isomerism

While studying the phenomenon of isomerism, we encounter two types of isomers; stereoisomers and structural isomers. Stereoisomers are identical to each other in their chemical formulas but different concerning the orientations of their atoms in three-dimensional space. Under this category of stereoisomerism, we also study three more types of isomers named geometrical isomerism, ionization isomerism, and optical isomerism.

On the other hand, the structural isomers are those compounds having the same chemical formula but differ in the arrangements of their atoms or functional groups in two-dimensional space. Under this category, we study five more types of isomers named chain isomers, functional isomers, position isomers, tautomers, and metamers.

Properties of N-Pentane

n-Pentane is a highly volatile but colorless liquid that is also water-soluble. We get n-Pentane by the fractional distillation of petroleum products. At low concentrations, it forms a flammable and explosive mixture with the surrounding air. On the other hand, at high concentrations, it is used as a narcotic.

Speaking of its uses then most of the n-Pentane of the world is utilized in the manufacturing of gasoline to ignite combustion engines. In addition to this, it is also used widely in low-temperature thermometers and extraction processes, as a solvent.

The molecular weight of n-Pentane is 721.151K whereas its critical density is 273.3 kg/m3. Likewise, the boiling point of n-Pentane is 309.2K and its melting point is 143.4 K.

Properties of Iso-Pentane

Iso-pentane is a watery, colorless, and volatile liquid that possesses a gasoline odor. It's a branched-chain alkane, having five carbon atoms in it. It's also called 2-methyl butane or methyl butane. At room temperature and standard atmospheric pressure, it acts as an extremely flammable liquid and the least dense chemical.

That's why the normal boiling point of iso-pentane is just a few degrees higher than normal room temperature. So, if you place iso-pentane openly on a warm day, it will evaporate in a fraction of seconds.

Speaking of its usage then isopentane is mostly used to attain the temperature of liquid bath (-160°C), with liquid nitrogen. Also, isopentane exists naturally since it forms 1% of natural gas. In this way, it forms a major portion (about 30%) of natural gas.

Properties of Neo-Pentane

Neo-Pentane is a double-branched chain that is also called 2,2-dimethylpropane. At room temperature and standard atmospheric pressure, it acts as a flammable gas that can be condensed on a highly cold day, or in ice baths, or when compressed at the lowest temperature and highest pressures, into an extremely volatile liquid.

The boiling point of neopentane is significantly lower than the other two isomers (only 9.5°C). That's the very reason why neopentane is always a gas at STP and room temperature whereas the other two isomers (iso and n-pentane) are liquids. On the other hand, the melting point of this isomer is higher than both isopentane and n-pentane - -16.6°C.

Just like pentane, neopentane is also a part of petroleum mixtures and is a significant component of gasoline and petroleum raw materials like crude oil. It is used as a gas blending agent.