Dimethyl butene polymerization

The isomerized structure dominates even at - 100° C, but accounts for only 70% of the repeat units at - 130° C. Similar but more complicated structures are formed in 4-methyl-1-butene polymerizations by competing hydride and methide shifts [298]. Other monomers whose propagating carbenium ions isomerize include 5-methyl-l-hexene, 4,4-dimethyl-1-pen-tene and some terpenes [299]. 

In 1962, Kennedy reported the first isomerization polymerization using 3-methyl-1-butene to give a 1,1-dimethyl PP as below ... 

Polymerization of 2,3-dimethyl-l-butene (1-methyl-l-isopropylethyl-ene) in the presence of 80% sulfuric acid at about 0° gave a mixture of dimers indistinguishable from that obtained with tetramethylethylene (Whitmore and Meunier, 20). The yield of dimer was 43% as compared to 62% in the case of the tetramethylethylene. 

Penultimate effects have been observed for many comonomer pairs. Among these are the radical copolymerizations of styrene-fumaronitrile, styrene-diethyl fumarate, ethyl methacrylate-styrene, methyl methacrylate l-vinylpyridine, methyl acrylate-1,3-butadiene, methyl methacrylate-methyl acrylate, styrene-dimethyl itaconate, hexafluoroisobutylene-vinyl acetate, 2,4-dicyano-l-butene-isoprene, and other comonomer pairs [Barb, 1953 Brown and Fujimori, 1987 Buback et al., 2001 Burke et al., 1994a,b, 1995 Cowie et al., 1990 Davis et al., 1990 Fordyce and Ham, 1951 Fukuda et al., 2002 Guyot and Guillot, 1967 Hecht and Ojha, 1969 Hill et al., 1982, 1985 Ma et al., 2001 Motoc et al., 1978 Natansohn et al., 1978 Prementine and Tirrell, 1987 Rounsefell and Pittman, 1979 Van Der Meer et al., 1979 Wu et al., 1990 Yee et al., 2001 Zetterlund et al., 2002]. Although ionic copolymerizations have not been as extensively studied, penultimate effects have been found in some cases. Thus in the anionic polymerization of styrene t-vinylpyri-dine, 4-vinylpyridine adds faster to chains ending in 4-vinylpyridine if the penultimate unit is styrene [Lee et al., 1963]. 

A very useful three-carbon olefin is acrolein dimethyl acetal (5). Acrolein itself cannot be used because it polymerizes and/or reacts with amines under the normal reaction conditions. With piperidine or morpholine as the base, acrolein acetals react in good yield with a wide variety of vinylic bromides to give dienal acetals and/or ami-noenal acetals. These product mixtures, after being treated with excess aqueous oxalic acid and being steam distilled, yield E,E-conjugated dienals, usually in good yields. Methacrolein acetals and 3-buten-2-one ethylene ketal also react well, but the crotonaldehyde acetals do not. 

Mechanism of formation of trithiacycloheptane derivative and trans-butene by polymerization-degradation of trans(2,3-dimethyl thikane)... 

In the cationic polymerization of heterocycles, a similar phenomenon was observed by Goethals in the polymerization of propylene sulfide and trans 2,3-dimethyl-thiirane. The latter monomer polymerizes rapidly and quantitatively to a linear polymer which is then relatively slowly converted into 3,4,6,7-tetramethyl-l, 2,5-tri-thiepane (J67a). In this particular process, the macroring formation is a practically irreversible reaction and differs in this sense from the equilibrium processes discussed so far. The irreversibility is due to the formation of one molecule of cis-butene per one molecule of a cyclic trithiepane ... 

Taking into account [81,82] that photodegradation of poly(4,4-dimethyl-l-penten-3-one) [poly(BVK)] and poly(3-methyl-3-buten-2-one) [poly(MIK)] proceeds predominantly through a Norrish type I mechanism via the triplet state (Scheme 15), the above homopolymers have been studied as initiators in the photoinduced polymerization of vinyl monomers such as MMA, St, AN and VAc [83]. 

Finally, the stereospecificity of the phosphorane-promoted cyclodehydration is adequately demonstrated in the reaction of d,Z-2,3-butanediol (9) with DTPP in CD2CI2 (35 C, 10 h). The stepwise nature of the cyclodehydration process gives exclusively d5-2,3-epoxybutane (10 >99%) by NMR analysis [6 12.9 (CH3) and 52.4 (CHO)] (76). This latter result is consonant with the previous findings of Denney etal. 24) where a mixture containing 88% d,/- and 12% zne5o-4,5-dimethyl-2,2,2-triethoxy-1,3,2X5-dioxaphospholanes (11) gave a mixture of 85% cis- and 15% /rans-2,3-butene oxides (10), respectively, during tiiermolysis (117°C, 42 h) (equations 2 and 3). Polymeric Dioxaphospholanes. 

As background information, an attempt was made to copolymerize cis-2-butene-l,4-diol diacetate with MA. Heating equimolar mixtures of the two monomers with AIBN (2 wt%) for 15 hr. at 75°C produced only a very low yield (<10%) of polymeric material. Using the same conditions, equimolar mixtures of IA-di-t-butyl fumarate and IA-dimethyl maleate gave only a trace of copolymer. Yokayama and Hall (10) also repored that diethyl maleate and diethyl fumarate undergo free-radical copolymerization with IA to give very low yields of non-equimolar copolymer. 

As previously mentioned, the molecular masses of the polymers obtained from these aqueous reactions are generally higher than desired due to the small number of active species. Although the propagating species in these polymerizations do not typically react with acyclic alkenes, modest control over molecular mass is possible when certain acyclic chain-transfer agents are employed [35, 44]. For example, Feast and Harrison have used very high concentrations of as-2-butene-l,4-diol or its dimethyl ether as chain-transfer agents [35]. The chain-transfer constants in these reactions were small, and inclusion of these alkenes in the reaction... 

Explain why a random copolymer is obtained when 3,3-dimethyl-1-butene undergoes cationic polymerization. 

Next to isobutene, other 1,1-dialkyl substituted ethenes can also be polymerized cationically. Suitable monomers are 2-methyl-1-butene, 2-methyl-1-pentene, and 2,3-dimethyl-1-butene [613] Polymers with very high molecular weights of Mn>300000 are obtained by catalysis with aluminum alkyl halogenides. Also, cyclic hydrocarbons with a methylene group (methylenecyclopropane, methylene cyclobutane, methylene cyclohexane, a-pinene) are suitable monomers [614-619]. 1,1-Disubstituted ethenes with stronger steric hindrance as camphene or 2-methylene-bicyclo-[2.2.1] heptane, however, could not be polymerized cationically [574]. 

In addition, the anionic polymerization of l,l-dimethyl-2,3-benzo-l-silacyclo butene with the use of K-mirror in THF (or n-BuLi in a hydrocarbon solvent) was performed in [82]. As a result, powderlike polymers with lower molecular weight and melting point than those in the case of TROP were isolated. 

This test method provides for the determination of butadiene-1,3 purity and impurities such as propane, propylene, isobutane, n-butane, butene-1, isobutylene, propadiene, fra/i5-butene-2, cu-butene-2, butadiene-1,2, pentadiene-1,4, and, methyl, dimethyl, ethyl, and vinyl acetylene in polymerization grade buta ene by gas chromatography. Impurities including butadiene dimer, carbonyls, inhibitor, and residue are measured by appropriate ASTM procedures and the results used to normalize the component distribution obtained by chromatography. 

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