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Ethylene chain reaction

Polyethylene (Section 6 21) A polymer of ethylene Polymer (Section 6 21) Large molecule formed by the repeti tive combination of many smaller molecules (monomers) Polymerase chain reaction (Section 28 16) A laboratory method for making multiple copies of DNA Polymerization (Section 6 21) Process by which a polymer is prepared The principal processes include free radical cationic coordination and condensation polymerization Polypeptide (Section 27 1) A polymer made up of many (more than eight to ten) amino acid residues Polypropylene (Section 6 21) A polymer of propene Polysaccharide (Sections 25 1 and 25 15) A carbohydrate that yields many monosacchande units on hydrolysis Potential energy (Section 2 18) The energy a system has ex elusive of Its kinetic energy... [Pg.1291]

Ethylene Dichloride Pyrolysis to Vinyl Chloride. Thermal pyrolysis or cracking of EDC to vinyl chloride and HCl occurs as a homogenous, first-order, free-radical chain reaction. The accepted general mechanism involves the four steps shown in equations 10—13 ... [Pg.419]

Polymerization processes are characterized by extremes. Industrial products are mixtures with molecular weights of lO" to 10. In a particular polymerization of styrene the viscosity increased by a fac tor of lO " as conversion went from 0 to 60 percent. The adiabatic reaction temperature for complete polymerization of ethylene is 1,800 K (3,240 R). Heat transfer coefficients in stirred tanks with high viscosities can be as low as 25 W/(m °C) (16.2 Btu/[h fH °F]). Reaction times for butadiene-styrene rubbers are 8 to 12 h polyethylene molecules continue to grow lor 30 min whereas ethyl acrylate in 20% emulsion reacts in less than 1 min, so monomer must be added gradually to keep the temperature within hmits. Initiators of the chain reactions have concentration of 10" g mol/L so they are highly sensitive to poisons and impurities. [Pg.2102]

The left-hand end of the activated monomer is sealed off by the OH terminator, but the right-hand end (with the star) is aggressively reactive and now attacks another ethylene molecule, as we illustrated earlier in Fig. 22.1. The process continues, forming a longer and longer molecule by a sort of chain reaction. The —OH used to start a chain will, of course, terminate one just as effectively, so excess initiator leads to short chains. As the monomer is exhausted the reaction slows down and finally stops. The DP depends not only on the amount of initiator, but on the pressure and temperature as well. [Pg.255]

One of the first methods of polymerizing vinyl monomers was to expose the monomer to sunlight. In 1845, Blyth and Hoffman [7] obtained by this means a clear glassy polymeric product from styrene. Berthelot and Gaudechon [8] were the first to polymerize ethylene to a solid form and they used ultraviolet (UV) light for this purpose. The first demonstration of the chain reaction nature of photoinitiation of vinyl polymerization was done by Ostromislenski in 1912 [9]. He showed that the amount of poly(vinyl bromide) produced was considerably in excess of that produced for an ordinary chemical reaction. [Pg.244]

Addition polymerization requires a chain reaction in which one monomer molecule adds to a second, then a third and so on to form a macromolecule. Addition polymerization monomers are mainly low molecular-weight olefinic compounds (e.g., ethylene or styrene) or conjugated diolefins (e.g., hutadiene or isoprene). [Pg.304]

When changing the kind of acids with relatively higher lipophilicity, the efficiency of transport is lowered by the leak reaction based on their ease of transfer across the liquid membrane 16). (Table 3) It is noteworthy that 12, which has trimethylene chains, shows selectivity for Li+ much better than 13, which has ethylene chains 17). (Table 4)... [Pg.41]

Cu(II) EPR signal in nitriles as solvent as well as by polarographic measurements 144>. Similarly, the EPR signal disappeared when Cu(OTf)2 was used for catalytic cyclo-propanation of olefins with diazoesters 64). In these cases, no evidence for radical-chain reactions has been reported, however. The Cu(acac)2- or Cu(hfacac)2-eatalyzed decomposition of N2CHCOOEt, N2C(COOEt)2, MeCOC(N2)COOEt and N2CHCOCOOEt in the presence of cyclopropyl-substituted ethylenes did not furnish any products derived from a cyclopropylcarbinyl - butenyl rearrangement128. These results rule out the possible participation of electron-transfer processes and radical intermediates which would arise from interaction between the olefin and a radical species derived from the diazocarbonyl compound. [Pg.245]

We may use the reaction mechanism for the formation of ethylene from ethane (CjHg - C2H4 + H2), Section 6.1.2, to illustrate various types of steps in a typical chain reaction ... [Pg.158]

Traditional polymerizations usually involve AB-type monomers based on substituted ethylenes, strained small ring compounds using chain reactions that may be initiated by free radical, anionic or cationic initiators [20]. Alternatively, AB-type monomers may be used in polycondensation reactions. [Pg.8]

Dialkoxycarbonylation has been reported using a Pd-catalyst/oxidant system on propynols or butynols furnishing respectively /3- or y-lactone derivatives with a-(alkoxycarbonyl)ethylene chains (Scheme 24) [83,137, 138]. This reaction occurs in a stereospecific way leading exclusively to cis-dicarbonylated products in fair to excellent yields (25-97%). Noteworthy, a butynol bearing an alkyl or an aryl substituent instead of a TMS one undergoes a different course of reaction under the same conditions here frans-alkoxycarbonylation takes place selectively (Scheme 25). [Pg.125]

Describe the contents of the reaction flask 10 min after the polymerization of (a) reactants in a stepwise polymerization such as dimethyl terephthalate and ethylene glycol and (b) monomer in chain reactions, such as isobutylene. [Pg.169]

Initiators such as BPO are used not only for the initiation of chain reaction polymerization, but also for the curing of polyesters and ethylene-propylene copolymers, and for the grafting of styrene on elastomeric polymer chains. [Pg.491]

In general, the catalysts may be classified as acids and metal halides. As will be explained below, both types of catalysts are acid-acting catalysts in the modern sense of the term. Some metals (e.g., sodium, copper, and iron) are catalysts for the polymerization of alkenes, especially ethylene. They are active probably because they can combine with one of the pi electrons of the alkene and form a free radical which can then initiate a chain reaction (p. 25). [Pg.22]

Any of the free radicals (26-30, designated as R ) may initiate the chain reaction [Eq. (13.42)]. The exact nature of R is unimportant since it merely initiates the polymerization chain and reacts only in the first cycle subsequent cycles are initiated by radicals called propagating radicals formed in the reaction with ethylene [Eq. (13.43)] ... [Pg.745]

If it is accepted that the activation energy of a chain reaction is largely that of the process generating chains, then the parallelism in the behavior of the energies of activation for the ethylene and formaldehyde oxidations may be interpreted on the basis of the degenerate-branching reaction the former is identical with the initiation reaction for the latter. Two possible reactions were suggested... [Pg.67]

In the 1950s, Semenov and Voevodskii [148] made an attempt to apply the concepts of the branching-chain reaction theory to the kinetics of heterogeneous catalysts. They applied the concept of free valencies migrating over the catalyst surface and of "semi-chemisorbed radicals. But their attempt was criticized (see, for example, ref. 149 where Temkin, using hydrogenation of ethylene on palladium as an example, proved experimentally the inapplicability of the chain theory concepts). [Pg.79]


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See also in sourсe #XX -- [ Pg.211 ]




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Ethylene reactions

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