Monomer
Definition and meaning of Monomer in chemistry.
Monomers are relatively small, reactive molecules that can chemically bond with other identical or similar molecules to form a large, chain-like macromolecule known as a polymer. The chemical process of linking these discrete monomer units together is known as polymerization.
In more detail
The chemical structure and functional groups of a monomer directly dictate the final physical and chemical properties of the resulting polymer, including its tensile strength, flexibility, thermal stability, and melting point. Monomers must possess at least two reactive sites, typically consisting of carbon-carbon double bonds or specific functional groups like hydroxyl, amine, or carboxyl groups, allowing them to link sequentially into a chain. Addition polymerization involves unsaturated monomers breaking their pi bonds to form new single sigma bonds with adjacent monomers without yielding any byproducts. Condensation polymerization occurs when polyfunctional monomers react, joining together and simultaneously eliminating a small byproduct molecule like water, hydrogen chloride, or methanol. Natural biological monomers include amino acids, nucleotides, and simple monosaccharides, while synthetic industrial monomers include molecules like ethylene, styrene, and vinyl chloride.
Key facts
| Field | Organic Chemistry |
|---|---|
| Reaction process | Addition or condensation polymerization |
| Valency requirement | Must be bifunctional or polyfunctional to form chains |
| Natural examples | Amino acids (forming proteins), nucleotides (forming nucleic acids) |
| Synthetic examples | Ethylene, styrene, vinyl chloride, tetrafluoroethylene |
Ethylene (C2H4) is a simple hydrocarbon monomer that undergoes rapid addition polymerization to form polyethylene, which is the most widely produced synthetic plastic used in packaging and pipes.
Frequently asked questions
What is the fundamental difference between a monomer and an oligomer?
A monomer is a single basic building block molecule capable of polymerization. An oligomer consists of a small, finite number of monomers (typically between two and ten) linked together, whereas a true polymer contains a virtually unlimited and very large number of repeating units.
Can different types of monomers combine to form a single chain?
Yes, two or more chemically distinct monomers can polymerize together to form a copolymer. This process yields advanced materials with highly specific, hybrid physical properties that are distinct from those of pure homopolymers made from a single monomer type.