E Oligomerization

Medium-size members of homologous polymeric series such as dimers, trimers, etc. are called oligomers. They can be linear or cyclic and are often found as byproducts of polymer syntheses, e.g., in cationic polymerizations of trioxane or in polycondensations of e-aminocaproic acid (see Example 4-9). For the preparation of linear oligomers with two generally reactive end groups, the so-called telechelics, special methods, i.e., oligomerizations, were developed. 

It is noted that Mo/DM is the best performing catalyst with the highest steady state activity and lowest deactivation rate. The deactivation rate is the lowest even under the influence of intense acid-catalyzed side reactions known to produce coke, i.e. oligomerization of styrene and cracking of ethylbenzene. Obviously, the high surface area and high connectivity of the support have played a determining role in the catalytic reaction. The effects they exert can be looked at in two ways ... 

Sudeep and co-workers [41] synthesised three series of well-defined cationic oligomers, i.e., oligomeric p-phenylene ethynylenes (OPE), with different chain lengths and different end groups on the main chain to study structure-reactivity relationships through photophysical and antimicrobial properties [41, 42]. 

The first of these is an example of induced decomposition of benzoyl peroxide (see Section 1.3.1). The second shows chain transfer to toluene, which is a solvent commonly used for solution polymerization. The last reaction is characteristic of allylic monomers and is prevalent to the extent that homopolymerizations of allylic monomers yield only chains with degrees of polymerization below about 20 (i.e. oligomeric chains). The high incidence of chain transfer to allylic monomers results from the high resonance stability of the allylic radical produced and the reaction is often referred to as autoinhibition. 

Among other conversions of a-olefins, we shall mention their structural isomerization affected by the metal-containing polymers, i.e., oligomerization processes. 

Huang, R.Y., Garai, K., Frieden, C., Gross, M.L. (2011) Hydrogen/deuterium exchange and electron-transfer dissociation mass spectrometry determine the interface and dynamics of apolipoprotein E oligomerization. Biochemistry, 50 (43), 9273-9282. 

In addition to the analysis of TATP, the synthetic impurities (i.e., oligomeric peroxides) are also observed by APCI. Figure 16.7 contains the APCI spectra, positive ion mode, from direct infusion of an HCl-catalyzedTATP synthetic product mixture. The sample was infused as a solution in methanol with ammonium acetate additive. The m/z 240 ion corresponds to [TATP + and the series of ions separated by 74 Da, m/z 422-866, correspond to [H(00C(CH3)2) 00H + NH4] (n = 5-11) [60]. Experimental parameters for direct infusion APCI analysis of TATP are given in Table 16.2. 

Furman, D. B., and Vasserberg, V E., Oligomerization of ethylene on Tt-allylnick-elchloride prepared via complexing in the absorption layer on alumina surface, Izv Akad. Nauk. SSSR, Ser. Khim., 1979, 2278 (Russian). 

Startseva, G. E, Oligomerization of hexene catalysed by reaction products of eth-ylaluminium chloride with chlorine-containing compounds, Neftekhimiya, 28, 53, 1988 (Russian). 

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