Methyl acetylene polymerization

Mesitylene from Allylene.— In a similar way methyl acetylene or allylene polymerizes and yields mesitylene which is tri-methyl benzene. 

Explain the following observations (a) Ru(CO) Ij and Pt(CO)jIj act as promoters in Ir-catalyzed carbonylation but not in Rh-catalyzed carbonylation of methanol (b) in the concentration of LP ([LP]) versus initial rate plots of methyl acetate carbonylation, at low [Li ] the initial rate increases and then at higher [LP] it levels off (c) acetaldehyde and propionic acid are side products of Rh- and Ir-catalyzed carbonylations (d) instead of methyl acetate, dimethylether can also be carbonylated to give acetic anhydride (e) in the Pd-catalyzed carbonylation of methyl acetylene, the amount of CHjCH=CH(C02Me) formed is very httle (f) Co-catalyzed carbonylation of benzyl chloride to phenyl acetic acid requires a phase-transfer catalyst (g) a neutral catalytic intermediate may be involved in Rh-catalyzed WGS reaction (h) complexes of the general formula A X where A is a Lewis acid are effective catalysts for polymerizing epoxides with CO (i) reaction... 

By-products from EDC pyrolysis typically include acetjiene, ethylene, methyl chloride, ethyl chloride, 1,3-butadiene, vinylacetylene, benzene, chloroprene, vinyUdene chloride, 1,1-dichloroethane, chloroform, carbon tetrachloride, 1,1,1-trichloroethane [71-55-6] and other chlorinated hydrocarbons (78). Most of these impurities remain with the unconverted EDC, and are subsequendy removed in EDC purification as light and heavy ends. The lightest compounds, ethylene and acetylene, are taken off with the HCl and end up in the oxychlorination reactor feed. The acetylene can be selectively hydrogenated to ethylene. The compounds that have boiling points near that of vinyl chloride, ie, methyl chloride and 1,3-butadiene, will codistiU with the vinyl chloride product. Chlorine or carbon tetrachloride addition to the pyrolysis reactor feed has been used to suppress methyl chloride formation, whereas 1,3-butadiene, which interferes with PVC polymerization, can be removed by treatment with chlorine or HCl, or by selective hydrogenation. 

Methyl ethyl ketone may also he produced hy the catalyzed dehydrogenation of sec-hutanol over zinc oxide or brass at about 500°C. The yield from this process is approximately 95%. MEK is used mainly as a solvent in vinyl and acrylic coatings, in nitrocellulose lacquers, and in adhesives. It is a selective solvent in dewaxing lubricating oils where it dissolves the oil and leaves out the wax. MEK is also used to synthesize various compounds such as methyl ethyl ketone peroxide, a polymerization catalyst used to form acrylic and polyester polymers and methyl pentynol by reacting with acetylene ... 

Methylene cyclopropene (5), the simplest triafulvene, is predicted to be of very low stability. From different MO calculations5 it has been estimated to possess only minor resonance stabilization ranging to 1 j3. Its high index of free valency4 at the exocyclic carbon atom causes an extreme tendency to polymerize, a process favored additionally by release of strain. Thus it is not surprising that only one attempt to prepare this elusive C4H4-hydrocarbon can be found in the literature. Photolysis and flash vacuum pyrolysis of cis-l-methylene-cyclopropene-2,3-dicarboxylic anhydride (58), however, did not yield methylene cyclopropene, but only vinyl acetylene as its (formal) product of isomerization in addition to small amounts of acetylene and methyl acetylene65 ... 

Some chemicals are susceptible to peroxide formation in the presence of air [10, 56]. Table 2.15 shows a list of structures that can form peroxides. The peroxide formation is normally a slow process. However, highly unstable peroxide products can be formed which can cause an explosion. Some of the chemicals whose structures are shown form explosive peroxides even without a significant concentration (e.g., isopropyl ether, divinyl acetylene, vinylidene chloride, potassium metal, sodium amide). Other substances form a hazardous peroxide on concentration, such as diethyl ether, tetrahydrofuran, and vinyl ethers, or on initiation of a polymerization (e.g., methyl acrylate and styrene) [66]. 

Poly (acetylenes) [16], There are several catalysts available for polymerization of substituted acetylenes. Whereas Ziegler-Natta catalysts are quite effective for polymerization of acetylene itself and simple alkylacetylenes, they are not active towards other substituted acetylenes, e.g. phenylacetylenes. Olefin-metathesis catalysts (Masuda, 1985 Masuda and Higashimura, 1984, 1986) and Rh(i) catalysts (Furlani et al., 1986 Tabata, 1987) are often employed. In our experience, however, many persistent radicals and typical nitrogen-containing functional groups serve as good poisons for these catalysts. Therefore, radical centres have to be introduced after construction of the polymer skeletons. Fortunately, the polymers obtained with these catalysts are often soluble in one or other organic solvent. For example, methyl p-ethynylbenzoate can be polymerized to a brick-coloured amorph- See the Appendix on p. 245 of suffixes to structural formula numbers. 

Aramendia et al. (22) investigated three separate organic test reactions such as, 1-phenyl ethanol, 2-propanol, and 2-methyl-3-butyn-2-ol (MBOH) on acid-base oxide catalysts. They reached the same conclusions about the acid-base characteristics of the samples with each of the three reactions. However, they concluded that notwithstanding the greater complexity in the reactivity of MBOH, the fact that the different products could be unequivocally related to a given type of active site makes MBOH a preferred test reactant. Unfortunately, an important drawback of the decomposition of this alcohol is that these reactions suffer from a strong deactivation caused by the formation of heavy products by aldolization of the ketone (22) and polymerization of acetylene (95). The occurrence of this reaction can certainly complicate the comparison of basic catalysts that have different intrinsic rates of the test reaction and the reaction causing catalyst decay. 

Surprisingly, tin vapor fails to react on condensation with alkyl chlorides or bromides. It will react with some alkyl iodides thus, with methyl iodide, a high yield of polymeric MeSnl is obtained together with very small yields of volatile methyliodostannanes. Allyl chloride gives Sn(C3Hs)3Cl in moderate yield. The reaction with HC1 and acetylene is more complex, the intermediate may be H—Sn—Cl ... 

Diels-Alder reactions of bis(trimethylsilyl)acetylene.1 A catalyst obtained from TiCl4 and (C2H5)2A1C1 (1 20) effects Diels-Alder reactions of this acetylene with butadiene and methyl-substituted derivatives to form l,2-bis(trimethylsilyl)-cyclohexa- 1,4-dienes in 70-78% yield (equation I). The yield is low (15%) only when R, R4 = CH3,R2,R3 = H because of polymerization of the diene. The products undergo thermal dehydrogenation at 240° to form l,2-bis(trimethylsilyl)ben-zenes in almost quantitative yield. This cycloaddition has been effected in low yield with an iron-based catalyst. 

The acetylene substitution reaction proceeds much more rapidly than the related olefin reaction. The acetylene products and starting materials also undergo side reactions such as polymerization concurrently with the substitution. The best yields are obtained when the reactants are diluted with a large excess of amine, or carried out at lower temperatures in methanol with sodium methoxide as the base. Vinylacetylene derivatives can also be prepared by this reaction starting with vinylic halides. For example, ( )-methyl 3-bromo-2-methylpropenoate and r-butylacetylene react in 2 hours at 100° to form the expected vinylacetylene derivative in 59% yield ... 

Over the last few years it has become clear that rhodium(II) acetate is more effective than the copper catalysts in generating cyclopropenes.12 126 As shown in Scheme 28,12S a range of functionality, including terminal alkynes, can be tolerated in the reaction with methyl diazoacetate. Reactions with phenyl-acetylene and ethoxyacetylene were unsuccessful, however, because the alkyne polymerized under the reaction conditions. 

The vinyl ether of the oxime 55, 2-methyl-l-vinyloxy-3-butanone oxime (58) with excess acetylene also gives the pyrrole 57, however, none of the pyrrole 56 is formed in this case (Scheme 29). Upon distillation, pyrrole 57 polymerizes readily, which is one reason for its low yield. 

N-Methyl- and N-phenyl-2-vinylpyrroles 20a,b react with DMAD at reflux temperature in chloroform to give, in moderate yields, the dihydroindoles 22 via a 1,3-H shift from the Diels-Alder intermediate 21 (55-75%) (80JOC4515). These adducts were readily converted into the corresponding indoles 23 with Dichlorodicyanoquinone (DDQ). 2-Vinyl-pyrrole failed to give [4 + 2]-cycloadducts with acetylenic esters (80JOC4515). Spectroscopic analysis of the product mixtures indicated the presence of polymeric compounds resulting from Michael addition reactions. 

Our kinetic work (10) showed that the small molecule radical produced by chain transfer with monomer had to be a stable radical. This was confirmed in the present paper by analysis of the isotope effect on the bulk polymerization rates. The isotope effect on molecular weights and rates unequivocally showed that almost 100% of the chain transfer involved the vinyl hydrogen. There is some evidence in the literature to support the idea of a stable vinyl radical. Phenyl acetylene acts as a retarder when copolymerized with styrene or methyl methacrylate (25). Thus the phenyl vinyl radical is very stable compared to the growing styryl or methacrylyl radical. 

Table 10.1 presents typical specifications for a polymerization-grade product, as well as some physical properties. Prohibited impurities refer to inhibitors (croton-aldehyde, vinyl acetylene), chain-transfer agents (acetic acid, acetaldehyde, acetone) and polymerizable species (vinyl crotonate), while methyl and ethyl acetate impurities are tolerated. 

While caoutchouc was first obtained by polymerizing isoprene it has been found that other hydrocarbons containing the buta i-ydi-ene group will likewise yield caoutchouc. Such hydrocarbons have been obtained from several sources, e.g., turpentiney petroleuniy coaly acetylene. Also compounds related to succinic acid, e.g., pyrotartaric acid (methyl succinic acid) are possible of transformation into isoprene. Levulinic acid, which is aceto propionic acid, CHa—CO—CH2—CH2—COOH, yields a cyclic sulphur compound, methyl-thiophen (p. 853), which, like methyl pyrrolidine, yields isoprene. Ethyl alcohol by conversion into acetone and then by aldol condensation with ethane yields 2-methyl buta 2-ene, CHa—C = CH—CHa which may be transformed... 

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