Trimerization

As trimerization , also cyclotrimerization (sometimes trimerization or cyclotrimerization ), is defined as the union of three molecules, the monomers to a trimer . The resulting substances usually contain a six-membered ring .

chemistry

In chemistry, it is generally about the union of three identical molecules into a new molecule through addition reactions . The trimer thus has three times the molecular weight of the starting material. The trimerization often also produces tetramers and higher by-products, i.e. higher oligomers .

Formation of alicyclics

The cyclotrimerization of acetylene was discovered in 1866 by Marcelin Berthelot (1827–1907). Benzene is formed at a reaction temperature of 500 ° C. and a low yield .

Trimerization of buta-1,3-diene to ( Z , E , E ,) -cyclododeca-1,5,9-triene.

Better yields are obtained if the reaction is carried out at 60–70 ° C. in the presence of catalysts such as tricarbonyl (triphenylphosphine) nickel (0). In addition to 88% benzene, 12% styrene is also formed. This chemistry is based on the work of Walter Reppe (1892–1969).

The cyclotrimerization of buta-1,3-diene in the presence of Ziegler catalysts from titanium (IV) chloride and diethylaluminum chloride yields ( Z , E , E ,) -cyclododecane-1,5,9-triene in a remarkably smooth reaction . This process goes back to the work of Günther Wilke .

Formation of heterocycles

Reaction scheme for the trimerization of cyanogen chloride to cyanuric chloride.

1,3,5- Triazines ( s- Triazines) are accessible by trimerizing compounds with a triple bond between a carbon and a nitrogen atom. Cyanuric chloride is produced by trimerizing cyanogen chloride. Cyanuric bromide is produced analogously by the trimerization of cyanogen bromide . Similarly , cyanuric acid is produced by the cyclotrimerization of isocyanic acid .

The formation of 1,3,5-trioxane (see trioxane ) from formaldehyde is another example of the formation of a six-membered heterocycle .
A Lewis acid such as boron trifluoride (BF ₃ ) can be added to a non- bonding electron pair on the O atom of the oxetane . Cyclooligomerization then takes place in dichloromethane as solvent. The main product is the cyclic ether 1 :

biology

In biology, trimerization is usually the term used to describe the accumulation of three proteins , the monomers, to form a protein complex .

A distinction is made between trimers composed of three identical monomers, the homotrimers (e.g. hemagglutinin ), and trimers composed of different monomers, the heterotrimers (e.g. collagen ).

Individual evidence

1. ^ Siegfried Hauptmann : Organic Chemistry , 2nd revised edition, VEB Deutscher Verlag für Grundstoffindindustrie, Leipzig, 1985, p. 262, ISBN 3-342-00280-8 .
2. ^ Klaus Weissermel , Hans-Jürgen Arpe : Industrial Organic Chemistry . 4th edition. Wiley-VCH, Weinheim 2003, ISBN 3-527-30578-5 ( limited preview in Google book search).
3. ^ Siegfried Hauptmann: Organic Chemistry , 2nd reviewed edition, VEB Deutscher Verlag für Grundstoffindindustrie, Leipzig, 1985, pp. 244–245, ISBN 3-342-00280-8 .
4. ↑ Günther Wilke : Organo Transition Metal Compounds as Intermediates in Homogenous Catalytic Reactions ] ( PDF ; 390 kB).
5. ↑ F. Oberhauser: The behavior of cyanogen bromide towards metal salts in Chem. Ber. 60 (1927) 1434-1439 doi : 10.1002 / cber.19270600628 .
6. ^ Siegfried Hauptmann: Organic Chemistry , 2nd revised edition, VEB Deutscher Verlag für Grundstoffindustrie, Leipzig, 1985, p. 613, ISBN 3-342-00280-8 .
7. ↑ METHOD FOR THE PRODUCTION OF CRUDE TRIOXANE .
8. ↑ Theophil Eicher , Siegfried Hauptmann, Andreas Speicher: The Chemistry of Heterocycles, Wiley-VCH, 2012, ISBN 978-3-527-32747-8 , pp. 45-48.
9. ↑ Example: Studies on the enrichment of influenza hemagglutinin with a hexahistidine sequence by affinity chromatography , 1998; urn : nbn: de: kobv: 188-1998000401