1 -butene polymerisation

For example, the rates of propylene and 1-butene polymerisation by the rac.-(IndCH2)2ZrCl2—[Al(Me)0]x catalyst increase in the presence of hydrogen roughly by a factor of 10-60 respectively [260]. These polymers were found to be free of misinserted units hydrogenolysis apparently eliminates the slowly inserted 2,1-enchained monomer units and allows the start of a new, fastgrowing polymer chain [scheme (44)] [30],... 

Syndiotactic polymers of higher a-olefins such as 1-butene and 4-methyl-1-pentene are produced by homogeneous metallocene-based catalysts [117, 429, 430], In contrast to polymerisation with metallocene-based catalysts, higher a-olefins are much less reactive in polymerisation with soluble vanadium-based catalysts, and already in the case of 1-butene polymerisation only yield trace amounts of low molecular weight syndiotactic polymer [394]. 

The molar heat of formation of this endothermic compound (+230-250 kJ, 4.5 kJ/g) is comparable with that of buten-3-yne (vinylacety lene). While no explosive decomposition of the isocyanide has been reported, the possibility should be borne in mind [1], It is stable at — 15°C, but isomerises to acrylonitrile and polymerises at ambient temperature [2],... 

The extreme hazards involved in handling this highly reactive material are stressed. Freshly distilled material rapidly polymerises at ambient temperature to produce a gel and then a hard resin. These products can neither be distilled nor manipulated without explosions ranging from rapid decomposition to violent detonation. The hydrocarbon should be stored in the mixture with catalyst used to prepare it, and distilled out as required [1], The dangerously explosive gel is a peroxidic species not formed in absence of air, when some l,2-di(3-buten-l-ynyl)cyclobutane is produced by polymerisation [2], The dienyne reacts readily with atmospheric oxygen, forming an explosively unstable polymeric peroxide. Equipment used with it should be rinsed with a dilute solution of a polymerisation inhibitor to prevent formation of unstable residual films. Adequate shielding of operations is essential [3],... 

This discussion is certainly an over-simplification. Unfortunately there are no detailed experimental results for this reaction under strictly homogeneous conditions, but even with heterogeneous catalysts (e.g., AlCl3 and Ni [13]) only mixtures of branched paraffins, naphthenes and polyenes of low molecular weight are obtained. If isomerisation is slower than propagation, as indicated, e.g., by the experiments of Meier [5] on the polymerisation of 3,3-dimethyl butene-1, this would modify in detail but would not invalidate the above general conclusions. 

With respect to the co-catalytic activity of alkyl halides, BF3 occupies a special position, since these (other than fluorides) cannot form complexes with BF3 for steric reasons. It has indeed been found [31a] that in MeCl solution the n-butenes are not polymerised by BF3. MeCl cannot act as co-catalyst in this system and some other (e.g., S02) was required. The mode of action of S02 is still obscure, but it is possible that H2S03 was the real co-catalyst. 

Some exploratory experiments with ethyl vinyl ether showed that it polymerised too rapidly for our method to be useful. The polymerisation of 2-methyl butene-2 had a manageable rate but the results showed inconsistencies which we did not have time to resolve, as this was the last monomer to be studied. 

Catalytic forms of copper, mercury and silver acetylides, supported on alumina, carbon or silica and used for polymerisation of alkanes, are relatively stable [3], In contact with acetylene, silver and mercury salts will also give explosive acetylides, the mercury derivatives being complex [4], Many of the metal acetylides react violently with oxidants. Impact sensitivities of the dry copper derivatives of acetylene, buten-3-yne and l,3-hexadien-5-yne were determined as 2.4, 2.4 and 4.0 kg m, respectively. The copper derivative of a polyacetylene mixture generated by low-temperature polymerisation of acetylene detonated under 1.2 kg m impact. Sensitivities were much lower for the moist compounds [5], Explosive copper and silver derivatives give non-explosive complexes with trimethyl-, tributyl- or triphenyl-phosphine [6], Formation of silver acetylide on silver-containing solders needs higher acetylene and ammonia concentrations than for formation of copper acetylide. Acetylides are always formed on brass and copper or on silver-containing solders in an atmosphere of acetylene derived from calcium carbide (and which contains traces of phosphine). Silver acetylide is a more efficient explosion initiator than copper acetylide [7],... 

Bci dcr Copolymerisation von Athylcn und cis-Buten-2 liefem Katalysa-toren, die bei der Polymerisation von Propylen (76) keine taktischen Polymcren synthctisicren, wic Vanadiumacctylacctonat und Diathyl-aluminiumchlorid, ebenfalls keine kiistallinen Copol5Tnercn. Copol3unere von Athylen und trans-Buten-2 sind mit alien verwendeten Katalysato-ren nicht kristallin crhaltcn worden. 

Abb. 20. Zusammenhang der Konfiguration von Monomerem und Poly-merem bei der Polymerisation von cis- und trans-Buten-2-oxid die Polymerisation erfolgt unter Konfigurationsumkehr... 

Non-activated double bonds, e.g. in the allylic disulfide 1 (Fig. 10.2) in which there are no substituents in conjugation with the double bond, require high initiator concentrations in order to achieve reasonable polymerisation rates. This indicates that competition between addition of initiator radicals (R = 2-cyanoisopropyl from AIBN) to the double bond of 1 and bimolecular side reactions (e.g. bimolecular initiator radical-initiator radical reactions outside the solvent cage with rate = 2A t[R ]2 where k, is the second-order rate constant) cannot be neglected. To quantify this effect, [R ] was evaluated using the quadratic Equation 10.5 describing the steady-state approximation for R (i.e. the balance between the radical production and reaction). In Equation 10.5, [M]0 is the initial monomer concentration, k is as in Equation 10.4 (and approximately equal to the value for the addition of the cyanoisopropyl radical to 1-butene) [3] and k, = 109 dm3 mol 1 s l / is assumed to be 0.5, which is typical for azo-initiators (Section 10.2). The value of 11, for the cyanoisopropyl radicals and 1 was estimated to be less than Rpr (Equation 10.3) by factors of 0.59, 0.79 and 0.96 at 50, 60 and 70°C, respectively, at the monomer and initiator concentrations used in benzene [5] ... 

Of the lower members of this reactive group of compounds, the more lightly substituted are of high flammability and many are classed as peroxidisable and as polymerisable compounds. Individually indexed compounds are f Acrylonitrile, 1104 f 4-Bromo-l-butene, 1544 f 3-Bromo-l-propene, 1149 f l-Bromo-2-butene, 1543 4-Bromocyclopentene, 1878 f Bromoethylene, 0723 f Bromotrifluoroethylene, 0576 f 2-Chloro-1,3-butadiene, 1447 f 3-Chloro-l-butene, 1547... 

Some radical reactions are used industrially on a large scale including radical-induced polymerisations but these are beyond the scope of this book. A few simple molecules are also made this way including the diene 29 needed for the manufacture of pyrethroid insecticides. As the molecule is symmetrical, disconnection in the middle gives two identical halves providing we make them radicals and not cations or anions. The reaction is carried out at ICI by mixing butene 31 and the allylic chloride 32 at very high temperature.7... 

Extensive efforts have also been made to develop olefin polymerisation catalysts based on metallocenes with only one ligand of the cyclopentadienyl type. Ethylene-,dimethylsilylene- or tetramethyldisilylene-bridged mono(l-tetra -methylcyclopentadienyl), mono(l-indenyl) or mono(9-fluorenyl)-amidotita-nium complexes, such as dimethylsilylene(l-tetramethylcyclopentadienyl)(t-butyl)amidotitanium dichloride [Me2Si(Me4Cp)N(/-Bu)TiCl2] (Figure 3.10), have recently attracted both industrial and scientific interest as precursors for methylaluminoxane-activated catalysts, which polymerise ethylene and copolymerise ethylene with 1-butene, 1-hexene and 1-octene [30,105,148-152]. 

Cationic [ZrBz3]+ species are capable of polymerising oc-olefins such as propylene, 1-butene and 1-pentene at elevated temperature. It is worth emphasising that the non-metallocene [Zr(CH2Ph)3] + [PhCH2B(C6F5)3] catalyst, which is a cationic arene zirconium complex [189], is capable, at least partially, of isospecific a-olefin polymerisation at relatively high temperature [162,189,190],... 

Curves presented in Figure 3.13 testify to the large specificity of supported Ziegler-Natta catalysts regarding the kind of monomer some centres that polymerise ethylene do not polymerise propylene (or higher a-olefins, which may also be differentiated by particular catalyst centres, depending on the structure of the oc-olefin, e.g. branched as in 3-methyl-1-butene or not branched). Therefore, no hints about the monomer reactivity can be obtained by simple comparison of polymerisation rates without simultaneous estimation of the concentration of active sites [241]. 

As regards the polymerisation of higher linear oc-olefins, e.g. 1-butene, with homogeneous vanadium-based syndiospecific catalysts, it rarely occurs and affords only trace amounts of a low molecular weight syndiotactic polymer [394]. 

If 1-butene or 1-hexene is chosen instead of propylene as the monomer polymerising with the Me2C(MeCp)(Flu)ZrCl2-based catalyst, the polymers obtained become enriched in m diads. This has been suggested to testify to the preference of site isomerisation prior to the coordination of the next monomer molecule with increasing size of the polymerising a-olefin [121]. 

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