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Oligomer

physical science Maturity 9-11 Next article →

An oligomer is a molecule made of a small number of repeating units. These units are called monomers. You can think of monomers as the individual building blocks. When a few of these blocks link together, they form an oligomer. The name comes from the Greek words "oligo," meaning a few, and "mer," meaning parts.

15-crown-5 and monomer 3D balls
15-crown-5 and monomer 3D balls

Scientists often compare oligomers to polymers. A polymer is a much larger molecule. It usually contains thousands or even millions of units. There is no strict line between an oligomer and a polymer. One way to tell them apart is by looking at their properties. If removing one unit changes how the molecule acts, it is likely an oligomer. This is because the small number of units makes the structure very sensitive to change.

Oligomers can take many different shapes depending on how the monomers connect. They can form a linear chain, which is a long, straight line. They can also form a closed ring, which looks like a circle.

Tetrapeptide structural formulae v.1
Tetrapeptide structural formulae v.1

Some structures are even more complex. For example, tellurium tetrabromide is a tetramer with a core shaped like a cube. The units can also be different from one another. If all the units are the same, it is a homo-oligomer. If the units are different, it is a hetero-oligomer.

Mpyv vp1 pentamer vp2 1sie 1cn3
Mpyv vp1 pentamer vp2 1sie 1cn3

We use specific Greek prefixes to name oligomers based on their unit count. A dimer has two units. A trimer has three units. A tetramer has four units. A pentamer has five units. A hexamer has six units. These precise names help chemists understand the exact size of the molecule. The units stay together through different types of chemical connections. They can use strong covalent bonds or weaker forces like hydrogen bonds. In biochemistry, scientists use the term "multimer" for protein oligomers that are not held together by covalent bonds.

Oligomers are essential to life and biology. Many important biological molecules are actually oligomers. For example, hemoglobin is a protein tetramer. Collagen is a homo-oligomer made of three identical protein chains.

Tetrapeptide structural formulae v.1
Tetrapeptide structural formulae v.1

We also see them in sugars and genetic material. An oligosaccharide is an oligomer made of monosaccharides, which are simple sugars. An oligonucleotide is a short fragment of nucleic acid, like DNA or RNA. These small pieces are vital for the way cells function.

Humans also use oligomers in many industrial products. Many oils, such as liquid paraffin, are oligomeric. Polybutene is an oligomeric oil used to create putty. We also use oligomeric esters as plasticizers. These are used to soften thermoplastics like PVC. These substances can be made by linking monomers together. They can also be separated from higher fractions of crude oil.

In the oil and gas industry, a specific substance called "green oil" is produced. This occurs in hydrogenation reactors at ethylene plants. Green oil is a mixture of reactive components. It contains about 90% aliphatic dienes and 10% alkanes and alkenes. These are formed through a process called oligomerization. This process converts monomers into larger macromolecular complexes. Another related process is telomerization. This is a type of oligomerization that uses chain transfer to limit the size of the molecules.

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File:15-crown-5 and monomer 3D balls.png
15-crown-5 and monomer 3D balls.png
File:Tetrapeptide structural formulae v.1.png
Tetrapeptide structural formulae v.1.png
File:Mpyv vp1 pentamer vp2 1sie 1cn3.png
Mpyv vp1 pentamer vp2 1sie 1cn3.png
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