Telogen

Telomerization. Polymerization of DAP is accelerated by telogens such as CBr, which are more effective chain-transfer agents than the monomer itself (65) gelation is delayed. The telomers are more readily cured in uv than DAP prepolymers. In telomerizations with CCl with peroxide initiator, at a DAP/CCl ratio of 20, the polymer recovered at low conversion has a DP of 12 (66). 

The essential difference in chemical behavior of chlorides and bromides used as telogens (addends) can be distinctly seen when the reactions of chloro- and bromoacetates are compared. In addition and telomerization reactions monochloroacetates react with 1-alkenes exclusively at C-H bond [under initiation... 

Dibromodichoromethane was studied as telogen in the reaction with vinyl chloride (ref. 7). The authors showed that the reaction occurred as telomerization (under usual conditions) the changes in monomer / telogen ratio (from 1.5 to 15) allowed to vary the adduct content from 80 to 30 %. 

CO2 [67]. Early work examining the free-radical telomerization of TFE in supercritical C02 took advantage of the high solubility of the low molecular weight perfluoroalkyl iodides products to prepare these materials homogeneously [77]. In these reactions, we utilized perfluorobutyl iodide as the telogen... 

Table 2. Experimental results from the telomerizations of TFE in supercritical C02. Perfluorobutyl iodide was employed as the telogen [77]...

Interestingly, the (co)telomers used behave as further potential telogens for subsequent telomerizations, and all of them can be end-capped with ethylene (E). 

We have constructed thermoresponsive systems utillizing semitelechelic PIPAAm chains with freely mobile ends, synthesized by telomerization using telogens as a following reaction [6] nM -i- HS-X H-(M)n-S-X. 

Chain-transfer agents have been called and employed as regulators (of molecular weight). When used in large proportions, they are called telogens, since they produce low-molecular weight polymers (telomers). 

Greenley, R. Z., Q and e Values for Free Radical Copolymerizations of Vinyl Monomers and Telogens, pp. 267-274 in Chap. II in Polymer Elandbook, 3rd ed., J. Brandrup and E. H. Immergut, eds., Wiley-Interscience, New York, 1989b. 

The telomerization of butadiene (1) with protected pentoses has been particularly studied using 2,3,4-tri-(9-acetyl-D-xylopyranose (5) [21] and 2,3,4-tri-O-benzyl-p-D-arabinofuranose (8) [22] as the telogens, in a 50-mL stainless steel autoclave... 

The telomerization has also been carried out using o-glucose (17) as the telogen. As expected, the increase of the amount of 1 and reaction time under conditions depicted in Fig. 11 increased the relative quantity of di-and tri-octadienylglycosides... 

It has been reported that the use of aqueous-organic biphasic systems may enhance the selectivity (Sect. 1.2) [12, 16, 47, 48]. In fact, sugar diethers are quasi insoluble in water and can be extracted in the organic phase. When the telomerization is carried out in the presence of Me2NCi2H25 and a large excess of 1 (15 equiv., Table 9), the conditions are already biphasic the diethers of 15 have thus been obtained in a 57% yield at 99% conversion of the telogen. 

Telomerization is the reaction of olefins having conjugated double bonds (conjugated dienes) in the presence of a nucleophile (telogen). The main... 

Carbon tetrachloride, chloroform, dibromomethane, tribromometh-ane, tribromochloromethane, and tetrabromomethane were examined as telogens, and bromomethanes were found2"0 to follow reaction pathways more complicated than those for chlorinated compounds. Thus, chloroform reacts exclusively by hydrogen transfer, giving rise to 423 and a small proportion of higher telomers whereas, for dibromo-... 

The growing polymer chain may also be terminated by abstraction of a hydrogen atom from any suitable donor molecule called telogen (S-H). In these instances, hydrogen transfer from the telogen to the growing radical produces a dead polymer macromolecule and a new free radical [Eq. (13.46)]. The latter can add to ethylene and start a new chain [chain termination with kinetic chain transfer Eq. (13.47)] ... 

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