In chemistry, a trimer is a molecule or an anion formed by combination or association of three molecules or ions of the same substance. In technical jargon, a trimer is a kind of oligomer derived from three identical precursors often in competition with polymerization.
- 3 H2N-CO-NH2 → [C(O)NH]3 + 3 NH3
- (NH2)2CO → HOCN + NH3
Then in the second step, cyanic acid polymerizes to form cyanuric acid, which condenses with the liberated ammonia from the first step to release melamine and water.
- '3 HOCN → [C(O)NH]3
- [C(O)NH]3 + 3 NH3 → C3H6N6 + 3 H2O
This water then reacts with cyanic acid present, which helps drive the trimerization reaction, generating carbon dioxide and ammonia.
- 3 HOCN + 3 H2O → 3 CO2 + 3NH3
In total, the second step is exothermic:
- 6 HCNO + 3 NH3 → C3H6N6 + 3 CO2 + 3NH3
but the overall process is endothermic.
The 1,5,9-trans-trans-cis isomer of cyclododecatriene, which has some industrial importance is obtained by cyclotrimerization of butadiene with titanium tetrachloride and an organoaluminium co-catalyst:
Breaking carbon-hetero double bonds forms symmetrical saturated 1,3,5-heterocyclesEdit
1,3,5-Trithiane is the cyclic trimer of the otherwise unstable species thioformaldehyde. This heterocycle consists of a six-membered ring with alternating methylene bridges and thioether groups. It is prepared by treatment of formaldehyde with hydrogen sulfide.
Dimethylsilanediol dehydrates to a trimer of Me2SiO as well as polydimethylsiloxane. The reaction illustrates the competition between trimerization and polymerization. The polymer and trimer are formally derived from the hypothetical sila-ketone Me2Si=O, although this species is not an intermediate.
- Hillis O. Folkins (2005). "Benzene". Ullmann’s Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_475.
- Klaus Huthmacher, Dieter Most "Cyanuric Acid and Cyanuric Chloride" Ullmann's Encyclopedia of Industrial Chemistry" 2005, Wiley-VCH, Weinheim. doi 10.1002/14356007.a08 191
- Industrial Organic Chemistry, Klaus Weissermel, Hans-Jurgen Arpe John Wiley & Sons; 3rd 1997 ISBN 3-527-28838-4
- Bost, R. W.; Constable, E. W. "sym-Trithiane" Organic Syntheses, Collected Volume 2, p.610 (1943). http://www.orgsyn.org/orgsyn/pdfs/CV2P0610.pdf
- Bonamico, M.; Dessy, G.; Fares, V.; Scaramuzza, L. (1975). "Structural Studies of Metal Complexes with Sulphur-Containing Bidentate Ligands. Part I. Crystal and Molecular Structures of Trimeric Bis-(dithiobenzoato)-nickel(II) and -palladium(II)". Journal of the Chemical Society, Dalton Transactions: 2250–2255. doi:10.1039/DT9750002250.
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