Functionality (chemistry)
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In chemistry, functionality is the presence of functional groups in a molecule. In organic chemistry (and other fields of chemistry) functionality of a molecule has a decisive influence on its reactivity. In polymer chemistry the functionality of a monomer means its number of polymerizable groups, it affects the formation and the degree of crosslinking of polymers.
A monofunctional molecule possesses one function, a difunctional two, a trifunctional three, etc.
Functionality in organic chemistry and material science
In organic chemistry, functionality is often used as a synonym for functional group. For example a hydroxyl group can also be called a HO-function.[1][2]
Functionalisation means the introduction of functional groups, for example
- the functionalisation of a surface[3] (e. g. silanization for the specific modification of the adhesion of a surface)
- the functionalization of nanoparticles of a metal or metal oxide to stabilize such nanoparticles[4] or
- the so-called C-H functionalization,[5] which means the substituion of a C-H bond by a functional group, bonded at the same carbon atom
Functionality in polymer chemistry
According to IUPAC, the functionality of a monomer is defined as the number of bonds that an monomer respectively its repeating unit forms in a polymer with other monomers. Thus in the case of a functionality of f = 2 a linear polymer is formed by polymerizing (a thermoplastic). Monomers with a functionality f ≥ 3 lead to a branching point, which can lead to cross-linked polymers (thermosets). Monofunctional monomers do not exist therefore as such molecules lead to a chain termination.[6]
From the average functionality of the used monomers the reaching of the gel point can be calculated as a function of reaction progress.[7] Side reactions may increase or decrease the functionality.[8]
However, IUPAC definition and the use of the term in organic chemistry differ with respect to the functionality of a double bond.[6][9] A double bond possesses in polymer chemistry a functionality of two (because two points of contact for further polymer chain are present, on each of two adjacent carbon atom a), while the double bond is in organic chemistry a functional group and thus has a functionality of one.
References
- ↑ Kurt Peter C. Vollhardt, Neil Eric Schore: Organische Chemie, S. 73 (, p. 74, at Google Books).
- ↑ Riedel: Moderne Anorganische Chemie von Christoph Janiak, S. 401 (, p. 401, at Google Books).
- ↑ Alexander Langner, Anthony Panarello, Sandrine Rivillon, Oleksiy Vassylyev, Johannes G. Khinast, Yves J. Chabal: Controlled Silicon Surface Functionalization by Alkene Hydrosilylation, J. Am. Chem.
- ↑ Marie-Alexandra Neouze, Ulrich Schubert: Surface Modification and Functionalization of Metal and Metal Oxide Nanoparticles by Organic Ligands, Monatsh.
- ↑ Dirk Steinborn: Grundlagen der metallorganischen Komplexkatalyse, S. 305 (, p. 239, at Google Books
- 1 2 Eintrag zu functionality, f of a monomer.
- ↑ Koltzenburg: Polymere: Synthese, Eigenschaften und Anwendungen, S. 187 (, p. 188, at Google Books).
- ↑ Hans-Georg Elias: Makromoleküle: Chemische Struktur und Synthesen, S. 468 und 477 (, p. 468, at Google Books).
- ↑ http://goldbook.iupac.org/CT07503.html