Repeat unit

Constitutional recurring or repeating unit is a term used in organic chemistry or from the polymer material science. The constitutional repeating unit ( KRE ) is the smallest repeating unit in a polymer.

During the polymerization, the monomers from which the polymer is produced, a variation will be subjected. In the simplest case, for example, Ethylene to polyethylene is dissolved their double bonds and will see to the chain-forming bonds as in the example image. Formally, the chain of methylene groups, although, as these but can never occur in an odd number, is the sum of the repeating formula C2H4 and the molar mass of the repeat unit to 28.05 g · mol -1.

Other polymers such as polyethylene terephthalate (PET) molecules are cleaved during the polymerization, so that the composition of the repeating unit differs from the sum of the monomers.

Terephthalic acid - Molecular Formula: C8H6O4; Molar mass: 166.13 g · mol -1

Repeat unit of PET - Molecular Formula: C10H8O4; Molar mass: 192.17 g · mol of 1