Hartwig Höcker

Kinetics and thermodynamic aspects of the metathesis reaction of cycloolefins considering particularly the molecular weight distribution of the products

Abstract The rate of polymerization of cycloolefins is to a very high degree dependent on the catalyst used and so is the induction period. The order of the reaction with respect to monomer and catalyst concentration as well as activation energy and entropy have been determined. Product distribution and configuration of the double bonds initially are kinetically controlled. The thermodynamics of the polymerization of cycloolefins are discussed in terms of ring size. The reaction products generally consist of cyclic oligomers and an acyclic polymer. As equilibrium is approached, above a certain minimum initial monomer concentration (cut-off point) an invariable concentration of oligomers is obtained. With increasing monomer concentration an increasing amount of polymer is formed. The concentration of cyclics is discussed in terms of a ring—chain equilibrium.

Tris(dialkylamino)-s-triazines, characterization and thermal properties

Abstract Several Tris(dialkylamino)-s-triazines were prepared by reaction of cyanuric chloride with the appropriate secondary amines. Some of their properties are reported.

The metathesis reaction of vinyl ethers

Abstract Chromium carbenes such as (CO)5Cr = C(C6H5)2 (I) and (CO)5Cr = C(OCH3)C6H5 (2) may be used to promote the metathesis reaction of vinyl ethers. Cyclic vinyl ethers, e.g. 2,3-dihydrofuran and 2,3,4,5-tetrahydro-oxepin-2-yl acetate, are polymerized in a fully head-to-tail fashion. Acyclic vinyl ethers undergo a co-metathesis reaction resulting in scrambled vinyl ethers. Carbene 2 is particularly suited to establish an equilibrium with respect to product distribution as well as influencing the cis/trans ratio of the double bonds in the resulting vinyl ethers.

Organic Cyclic Oligomers and Polymers

It is not only because of their ‘beauty’ but also because of their special properties that cyclic molecules have been attracting the special interest of chemists for a long time. The most ‘beautiful’ molecules incorporating cyclic structures might be the ‘platonic hydrocarbons’ such as the cubane 1, the tetrahedrane 2 and the dodecahedrane 3 system.1