Ethylene with halogens

M. Brenda, A. Greiner, and W. Heitz, Model reactions for the synthesis of poly(l,4-phenylenevinyl-ene). The palladium catalyzed arylation of ethylene with halogenated arenes or benzoyl chlorides, Mak-romol. Chem. 79/ 1083 (1990). 

Many of the features of the generally accepted mechanism for the addition of halogens to alkenes can be introduced by referring to the reaction of ethylene with bromine... 

Polymerization. The first successful polymerizations of VDE in aqueous medium using peroxide initiators at 20—150°C and pressures above 30 MPa were described in a patent issued in 1948 (73). About a year later, the first copolymerizations of VDE with ethylene and halogenated ethylenes were also patented (74). After a hiatus of over 12 years a commercially feasible process was developed and PVDE was ready for market introduction (2). 

Acyl halides may also be added to ethylene ia the presence of aluminum chloride to form halogenated ketones. At low temperatures, ethylene reacts with halogens to yield dihaloethanes. At high temperatures, trichloroethylene and perchloroethylene are formed. The most profitable route for chloroethylene is via ethylene dichloride (see Chlorocarbonsandchlorohydrocarbons). 

Ammonia can also react violently with a large selection of chemicals including ethylene oxide, halogens, heavy metals, and oxidants such as chromium trioxide, dichlorine oxide, dinitrogen tetroxide, hydrogen peroxide, nitric acid, liquid oxygen, and potassium chlorate. 

How is the course of halogen substitution in the benzene nucleus to be explained It is not at all probable that direct replacement of hydrogen occurs, such as we must assume in the formation of benzyl chloride and in the reaction between methane and chlorine, since the hydrogen attached to the doubly bound carbon atom of olefines exhibits no special reactivity. However, various facts which will be considered later (p. 164) indicate that benzene reacts with halogen in fundamentally the same way as does ethylene. The behaviour of ethylene towards bromine is the subject of the next preparation. 

Howard, C.J. Rate constants for the gas-phase reactions of OH radicals with ethylene and halogenated ethylene compounds, J. Chem. Phys., 65(ll) 4771-4777, 1976. 

With very few exceptions, quantitative epoxide assay techniques currently in use are derived from the reeotion of ethylene oxides with halogen adds, notably hydrochloric acid and hydrobromio add, in a variety of solvents. Acid uptake may be determined by any of several reliable procedures. These include titration with standard base8 nr back-titration with standard acid.744 The end-point may be detected visually in the presence of suitable acid-base indicators, or by the more precise technique of potontionaetry.447.4 -470 A useful alternative, applicable in the presence of easily hydrolysed substances or of amines that buffer the end-point, is the technique of argentiometry. In this procedure excess of halide ion is titrated with silver nitrate in tV presence of ferric thiocyanate indicator,470 1884 or potentiometri-cally.188 ... 

Other monoalkylated ethylene oxides reported to undergo ready cleavage on treatment with halogen adds (Eq. 701) include 1,2-epoxy-butane,1 1,2-epoxyhexane,1 00 and 1,2-epoxyheptane. 41 Although the last two have been said to yield only secondary alcohols, corresponding to exclusive attack of halide on the terminal epoxide carbon atom, it ie probable that isomeric alcohols are also formed in small undetected quantities... 

Chlorination of ethylene with CI2 in C2FI4CI2 solution has been studied with and without FeCl3 catalysis at 293-308 K. Simultaneous addition and substitution was detected97. The yields of the styrene low-temperature halogenation products with DMF.CI2 or DMF.Br2 have been found to exceed the yields using free halogen in DMF solution98. 

Fermentation-derived organic acids and their esters are potentially important chemical feedstocks for polymers and specialty polymers, but most significantly as alternative solvents for industrial and consumer applications. For example, lactate esters are derived from renewable carbohydrate raw materials such as cornstarch. They exhibit much lower toxicity compared with halogenated hydrocarbons and ethylene glycol ethers and are environmentally benign. Some studies suggested that lactate ester solvents have the potential of replacing petroleum-based solvents... 

Perhalomethanes function as halogenating agents also by addition to olefins. This reaction has been discovered by Joyce, Hanford and Harmon who have reported the telomer-ization of ethylene with CC14 or with chloroform in presence of free radical initiators (equation 83)638 639. 

Diatomic halogen molecules such as bromine are not the only chemicals that can add across double bonds. In fact, any protic acid, under the proper conditions, can undergo such reactions. Specifically, as shown in Scheme 7.5, reaction of ethylene with an acid, HX, where X is OH, CN, or any halide produces a substituted ethane. 

Other monoalkylated ethylene oxides reported to undergo ready cleavage on treatment with halogen adds < q. 701) indude 1,2-epoxy-... 

Barbash J. E. (1993) Abiotic reactions of halogenated ethanes and ethylenes with sulfide, nitrate and pH-buffer anions in aqueous solution. PhD Dissertation, Department of Environmental Science and Engineering, Stanford University, Stanford, CA, 417p. 

Synthesis from Propane.—The constitution of glycerol has been established by a series of reactions, as follows When secondary, or iso-propyl alcohol, propan-ol-2, is dehydrated an unsaturated compound is formed, viz., propene, the three carbon member of the ethylene series of hydrocarbons. When propene is treated with halogens, e.g.y chlorine, two atoms of the halogen add on directly and a saturated di-chlor compound results (see p. 158). 

The long-chain grown (v > 10 ) in the mixed 1 1 crystals of ethylene with chlorine and bromine was studied elsewhere [122, 123]. The peculiarity of these crystals is the alternating quasi-one-dimensional packing of ethylene and halogen molecules determined by donor-acceptor interaction. The axis of halogen molecules is orthogonal to the parallel planes of ethylene molecules [129, 130]. At temperatures above 90 K a spontaneous molecular... 

Even as a toluene emulsion, these complexes show catalytic activity towards ethylene and propylene which is several orders higher than that of TT-allylnickel halides. Paralleling the increase in catalytic activity, the selectivity of this catalyst is also increased—i.e., the products are mainly ethylene or propylene dimers. The most active catalytic systems for dimerizing ethylene and propylene are obtained by replacing toluene with halogenated hydrocarbons such as chlorobenzene since in these more polar solvents, the complexes XIII are soluble. 

In principle other halogens apart from iodide may also be used as a promoter. For bromide, Monsanto reports the synthesis of propionic acid from ethylene with selectivities of more than 99 % when a large excess of bromide in the form of hy-drobromic acid is added to a rhodium catalyst [21]. The carbonylation is catalytic both with respect to the rhodium and the bromide components. Nonhalogen promoters in combination with rhodium as catalyst are phenols, thiophenols, thiocar-boxylic acids, and sulfonic acids [22]. 

On the other hand, the selective reduction of an a,P-ethylenic-a-chloroester 2.2 to an a-chloroallylalcohol 2.3 [DWl] comes from the inability of DIB AH to react with halogenated derivatives in cold toluene [YGl] (Figure 2.2). 

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