Initiator (chemistry)
In chemistry, initiators are substances that are added to a reaction mixture to enable and start the desired reaction, i.e. to initiate it . Similar to catalysts , initiators are used when the reaction to be carried out does not take place on its own or does not take place to a sufficient extent.
However, unlike catalysts, initiators are consumed; that is, they take part in the reaction irreversibly and cannot be regenerated. In addition, initiators are usually necessary for the formation of reactive intermediates, which make the reaction possible in the first place, but then proceed on their own, while compounds that have reacted with the initiator remain part of the reaction mixture. Catalysts, on the other hand, usually lower the activation energies or act on the preparation of the substrate and thus accelerate reactions without participating in them.
Initiators such as free radical starters are used extensively in polymer chemistry , in vulcanization or in nuclear fission reactions. Initiators are of great importance in the plastics industry and are often misleadingly referred to as " vulcanization accelerators ". Most plastic polymer precursors have a certain potential for self-polymerization. In order to prevent the polymerization from taking place before the actual shaping, inhibitors are added and the polymerization is only started at the desired point in time by initiators. Initiators for starting polymerizations are often azo compounds or peroxides , which have different working temperatures depending on the structure.
Individual evidence
- ^ Hans Beyer , Wolfgang Walter : Organic chemistry. 22nd edition. S. Hirzel Verlag, Stuttgart 1991, ISBN 3-7776-0485-2 , pp. 78-84.
- ↑ Production overview of azo initiators from Wako , accessed on November 16, 2017.
- ↑ Product overview of peroxide initiators from Akzo Nobel , accessed on November 16, 2017.