Styrene trimers cyclic

During the manufacturing process of styrene-butadiene rubber the polymerisation is stopped at a conversion rate of less than 90%. The residual monomers styrene and butadiene are removed by distillation. The odour-in-tensive compounds 4-phenylcyclohexene (from styrene and cis-butadiene) and 4-vinyl cyclohexene (from cis-butadiene and trans-butadiene) can be formed from the remaining monomers under the conditions of a thermally permitted Ti2s-t- 4s Diels-Alder cyclic addition. During indoor air measurements, carried out in six different office rooms in each case 3 days after new carpets had been laid, concentrations of 4-phenylcyclohexene of 29-45 pg m could be ascertained. It is suspected that the emission of the trimer of 2-methyl-l-propene from a glued carpet is also caused by chemical reaction. 

Most unsaturated substances such as alkenes, alkynes, aldehydes, acrylonitrile, epoxides, isocyanates, etc., can be converted into polymeric materials of some sort—either very high polymers, or low-molecular-weight polymers, or oligomers such as linear or cyclic dimers, trimers, etc. In addition, copolymerization of several components, e.g., styrene-butadiene-dicyclo-pentadiene, is very important in the synthesis of rubbers. Not all such polymerizations, of course, require transition-metal catalysts and we consider here only a few examples that do. The most important is Ziegler-Natta polymerization of ethylene and propene. 

In the cationic polymerization of styrene, the attack on the j8-C atom has been established by copolymerizing with trioxane, the cyclic trimer of formaldehyde. Trioxane eliminates formaldehyde during polymerization (see Section 26.1.2) See equation (16-66) on p. 570. 

With vinyl monomers other than isobutene, attempts to prepare selectively trimers or tetramers from linear dimers have been unsuccessful thus far. The linear dimer of styrene (7) was expected to give an unsaturated tetramer 27, when dimerized by an 0x0 acid (Eq. (23)). However, the oligomerization of 1 with CF3SO3H or AcClO in benzene at 50 °C resulted in a mixture of oligomers with cyclic terminals, consisting... 

At 26.7 mbar pressure 40% weight toss main product is 2,4-diphenyl thiophene at least 11 unidentified minor products CO2, H2O, butene, isobutene, dimethyl ketene, styrene, methacrylic acid, succinic-type 5-membered cyclic anhydrides Chlorotrifluoroethylene, styrene, HQ, chloropentafluoropropene, ethene, chloroethene, totuene, a-melhylstyiene, dimer and trimer structures with some unsaturation S1F4 (fiom reaction of HF with glass). Distribution of products varies with polymer composition CO, CO2, propene, isobutene, dimethyl ketene, acrolein, allyl alcohol, toluene, styrene, cl-methylstyrene, ethylbenzene, glycidol, glycidylmethacrylate product distribution depends on copolymer composition... 

---