Ethyl chloride, polymerization

It has been observedt that poly(1,1-dimethyl propane) is the product when 3-methylbutene-l is polymerized with AICI3 in ethyl chloride at -130°C. Write structural formulas for the expected repeat units and those observed and propose an explanation. 

Chlorinated by-products of ethylene oxychlorination typically include 1,1,2-trichloroethane chloral [75-87-6] (trichloroacetaldehyde) trichloroethylene [7901-6]-, 1,1-dichloroethane cis- and /n j -l,2-dichloroethylenes [156-59-2 and 156-60-5]-, 1,1-dichloroethylene [75-35-4] (vinyhdene chloride) 2-chloroethanol [107-07-3]-, ethyl chloride vinyl chloride mono-, di-, tri-, and tetrachloromethanes (methyl chloride [74-87-3], methylene chloride [75-09-2], chloroform, and carbon tetrachloride [56-23-5])-, and higher boiling compounds. The production of these compounds should be minimized to lower raw material costs, lessen the task of EDC purification, prevent fouling in the pyrolysis reactor, and minimize by-product handling and disposal. Of particular concern is chloral, because it polymerizes in the presence of strong acids. Chloral must be removed to prevent the formation of soflds which can foul and clog operating lines and controls (78). 

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. 

Other minor uses of ethyl chloride iaclude blowiag agents for thermoplastic foam (51) and styrene polymer foam (52), the manufacture of polymeric ketones used as lube oil detergents (53), the manufacture of acetaldehyde (qv) (54), as an aerosol propellent (55), as a refrigerant (R-160), ia the preparation of acid dyes (56), and as a local or general anesthetic (57,58). 

The first sulfur curable copolymer was prepared ia ethyl chloride usiag AlCl coinitiator and 1,3-butadiene as comonomer however, it was soon found that isoprene was a better diene comonomer and methyl chloride was a better polymerization diluent. With the advent of World War II, there was a critical need to produce synthetic elastomers in North America because the supply of natural mbber was drastically curtailed. This resulted in an enormous scientific and engineering effort that resulted in commercial production of butyl mbber in 1943. 

In order to obtain compounds with Ti-O-P and Zr-O-P units, the hexaethoxy-derivative, NsPaCOEOg, was treated with titanium and zirconium tetrachlorides. In each case, hygroscopic solids of the type NaPaCOEOiOaMCU (M = Ti or Zr) and ethyl chloride were obtained. The degree of polymerization of these solids was 1.6—1.8, and on the basis of their i.r. and n.m.r. spectra, two alternative structures, (46) and (47), were proposed. In an alternative route to the same type of compound, N3P3CI6 was treated with tetra-n-butoxytitanium in o-xylene. Butyl chloride was liberated and a solid was obtained which has been assigned the structure (48). Its thermal decomposition was studied by differential thermal analysis. 

For isobutene polymerized in ethyl chloride by SnCl4 and H20 a transfer mechanism involving the catalytic complex has been suggested on kinetic grounds [4] ... 

Water has also been shown to be essential for the liquid phase polymerization of isobutylene with stannic chloride as catalyst (Norrish and Russell, 87). The rates of reaction were measured by a dilatometric method using ethyl chloride as common solvent at —78.5°. With a mixture consisting of 1.15% stannic chloride, 20 % isobutylene, and 78.8% ethyl chloride, the rate of polymerization was directly proportional to the amount of added water (up to 0.43% of which was added). A rapid increase in the rate of polymerization occurred as the stannic chloride concentration was increased from 0.1 to 1.25% with higher concentrations the rate increased only gradually. It was concluded that a soluble hydrate is formed and functions as the active catalyst. The minimum concentration of stannic chloride below which no polymerization occurred was somewhat less than half the percentage of added water. When the concentration of the metal chloride was less than about one-fifth that of the added water, a light solid precipitated formation of this insoluble hydrate which had no catalytic activity probably explains the minimum catalyst concentration. The addition of 0.3% each of ethyl alcohol, butyl alcohol, diethyl ether, or acetone in the presence of 0.18% water reduced the rate to less than one-fifth of its normal value. On the other hand, no polymerization occurred on the addition of 0.3 % of these substances in the absence of added water. The water-promoted reaction was halved when 1- and 2-butene were present in concentrations of 2 and 6%, respectively. 

Similarly with the raising of the b.p. in violet or reddish-violet soln. of iodine in benzophenone, carbon disulphide, ethyl chloride, chloroform, carbon tetrachloride, ethylene chloride or benzene or in brown soln. of ethyl alcohol, methyl alcohol, thymol, ethyl ether, methylal, or acetone. The values for the last three solvents were rather low, presumably because of the chemical action of solute on solvent. High values with benzene are attributed to the formation of a solid soln. of solvent and solid. Confirmatory results were found by J. Hertz with naphthalene, and by E. Beckmann and P. Wantig with pyridine. The results by I. von Ostromisslensky (o-nitrotoluene), by G. Kriiss and E. Thiele (glacial acetic acid), and by H. Gautier and G. Charpy indicate polymerization, but they are not considered to be reliable. 

According to Ketley (7), who studied the infrared spectra of poly(4-methyl-1-pentene) samples prepared with A1C13, AlBr3, and EtAia2 in n-pentane and ethyl chloride diluent in the range — 78 to —130°, isomerization polymerization increases with decreasing temperature and increasing dielectric constant. 

The effect of monomer concentration on the rate of polymerization of 4-methyl-1-pentene was investigated using ethylaluminum dichloride coinitiator in ethyl chloride solvent at — 30°, — 50°, — 70°, and — 80° C. Results are compiled in Table 5 and shown in Fig. 18. 

The results of the study of the effect of synthesis conditions on the composition of poly(4-methyl-l-pentene) have shown that even under conditions most favorable for the successful competition of isomerization with propagation, i.e., —120° C, using EtAlCl2, in ethyl chloride, the polymer contains only 50% of the desired 1,4-structure. It appears that in the series (n— l)-methyl-l-alkenes as n increases the likelihood of obtaining completely isomerized products via cationic isomerization polymerization is decreased. This is supported qualitatively by results obtained in the cationic polymerization of 4-methyl-l-hexene, an (n—2)-methyl-1-alkene (17). 

The rate of polymerization in ethyl chloride solvent using EtAlCl2 coinitiator has been found to be first order in monomer concentration with an activation energy of 9.5 0.5 kcal/mole. 

Propylene has been polymerized with highly cationic catalysts such as aluminum chloride plus ethyl chloride (61). However, this polypropylene was amorphous and considerably different from the Ziegler-Natta polypropylene. It had large amounts of chain branching which resulted from the highly cationic nature of this catalysts. Olah, Quinn and Kuhn (62) have studied the cationic polymerization of propylene utilizing complexes of BF3 with various alkyl fluorides. Apparently these cationic catalysts produced only amorphous polymers. 

As mentioned, the spectrum and amount of impurities formed during oxychlorination is much larger compared with direct chlorination. Some key impurities are listed below 1,1,2-trichloroethane (TCE), chloral (CCl3-CHO), trichloroethylene (TRI), 1,1- and 1,2-dichloroethylenes, ethyl chloride, chloro-methanes (methyl-chloride, methylen-chloride, chloroform), as well as polychlorinated high-boiling components. In particular, chloral needs to be removed immediately after reaction by washing because of its tendency to polymerization. 

The concept of intra-intermolecular or cydopolymerization was first described in 1957 for free radical systems (102) and shortly thereafter extended to cationic initiators. Jones (103) polymerized alloocimene with boron trifluoride etherate in ethyl chloride at 0° C. The product was a low melting (85—87° C.) soluble (benzene, carbon tetrachloride, etc.) material. The iodine number of the polymer indicated one residual double bond per monomer unit. The following polymerization mechanism was proposed ... 

Carbon-14-labelled triethyloxonium hexachloroantimonate, [( 3115)2002115] (SbClg)", 18 (specific activity 1.15 x 10 Bq g ), has been obtained by treating the C-labelled ( 2115)20 Sb l5 complex with ethyl chloride. The salt was used to clarify the mechanism of initiation of polymerization of 2,3,4-tri-O-methyl-L-glucosane (19) , since it has been noted" " " that the incorporation of the radioactive label into the polymer increases with the increase in the degree of conversion of the monomer (at 10. 5% of the equilibrium yield of the polymer, 2.5% of the initial radioactivity of 18 has been... 

Rose also derived heats of polymerization. The values he obtained were 20.0 kcalmole for polymerization in methyl chloride solution at —20°C and 19.3 kcalmole" for polymerization in a mixture of ethyl chloride and methyl chloride at —9°C. It is at once a bit unfortunate that this elegant piece of work was carried out as early as 1956 before catalysts leading to less complicated kinetics were discovered, and a tribute to Rose s careful work that he was able to sort out the many complications involved. No other detailed kinetic study of the polymerization of oxetane was made until many years later. In 1971 Saegusa et al. [52], reported a kinetic study of the polymerization of oxacyclobutane initiated by a BF3—THF complex. 

Rose [50] also investigated the polymerization of 2-methyl oxacyclo-butane and of 3,3-dimethyloxacyclobutane enough to learn that they followed a course analogous to that of the parent compound. He also found a heat of polymerization at —9°C of 16.1 kcalmole for 3,3-dimethyloxacyclobutane polymerized in a mixture of ethyl chloride and methyl chloride. Again Saegusa et al. [54] have extended the work to clarify the effect on the propagation rate of a methyl substituent at the 3 position of oxetane. They also examined the solvent effects of CH2CI2 and methylcyclohexane for these two substituted monomers. 

To avoid complications, AICI3 catalyst solution was prepared under mild conditions. The salt was dissolved in ethyl chloride overnight at —78° C. A faintly yellow solution was obtained. Preliminary experiments showed that such a solution readily polymerizes isobutene. It was also observed that these solutions can be supercooled to about —150° C. without precipitation or freezing-out of AICI3. At lower temperatures, however, the solution solidifies. 

Ethyl chloride, methylene chloride, difluorodichloromethane, tetrafluoromethane, etc. are generally used as solvents for cationic polymerization. For the quantitative characterization of electrophilic (electron acceptor) and nucleophilic (electron donor) solvents, acceptor (AN) and donor (DN) numbers, respectively, are proposed. 

The process is suppressed by typical inhibitors of cationic (substances containing atoms with an unshared electron pair pyridine, amines, DMF, ketones, alcohols, nitriles) or anionic (ethyl chloride and acetonitrile) polymerization. Water, methanol, and ammonia are universal ionic inhibitors which affect radical processes only slightly. 

Ethyl chloride shows the same kind of linear response to static exposure but at a much lower level. Under static conditions vinyl chloride is adsorbed more readily on the metal than is ethyl chloride. The two-stage interaction seen with vinyl chloride under sliding conditions may indicate its polymerization on the surface when the exposure factor is high enough. 

Eastham found that when EO polymerization was initiated in ethyl chloride with BF3 in the presence of water, a relatively fast polymerization proceeded until a molecular weight of about 700 was reached 17). At this point the polymer yield remained constant and only the formation of 1,4-dioxane was observed. Thus, at [EO] = 2.0mol 1 1 and [BF3] = 2- 10 2 mol l-1 (in C2H5 Cl at room temperature) approximately 80% 1,4-dioxane was formed at [H20] = 2 10 2 mol -1 1, whereas at H20 = 7.4 10-2 mol 1 1 the yield of 1,4-dioxane was reduced to approximately 40%. 

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