Ethyl chloride dehydrochlorination

Ethyl chloride can be dehydrochlorinated to ethylene using alcohoHc potash. Condensation of alcohol with ethyl chloride in this reaction also produces some diethyl ether. Heating to 625°C and subsequent contact with calcium oxide and water at 400—450°C gives ethyl alcohol as the chief product of decomposition. Ethyl chloride yields butane, ethylene, water, and a soHd of unknown composition when heated with metallic magnesium for about six hours in a sealed tube. Ethyl chloride forms regular crystals of a hydrate with water at 0°C (5). Dry ethyl chloride can be used in contact with most common metals in the absence of air up to 200°C. Its oxidation and hydrolysis are slow at ordinary temperatures. Ethyl chloride yields ethyl alcohol, acetaldehyde, and some ethylene in the presence of steam with various catalysts, eg, titanium dioxide and barium chloride. 

Fig. 24. Schematic effect of dihedral angle the magnitude of the coupling constant for vicinal protons, Ji,2i or the half-wave potentials for the reduction of cyclic vicinal dibromides (polarographio debromination), A = — JBj/2 (volts vs. S.C.E.) or A = 2D2, the sum of the squares of the displacement of the atoms in dehydrochlorination of ethyl chloride by PLM.

Hiberty40 used the single determinant ab initio molecular orbital theory to study the unimolecular HC1 elimination from ethyl chloride. The calculations of three potential energy surfaces corresponding to -elimination, planar //-elimination, and nonplanar anti-elimination were performed and the dehydrochlorination process was predicted to be syn, and to proceed via a planar four-membered transition state. According to these estima-... 

An additional example of neighboring group participation in the gas-phase pyrolysis of 2-substituted ethyl chlorides was the elimination kinetics of 2-dimethylaminoethyl chloride67. The magnitude of the effect of Me2N on the dehydrochlorination rate (Table 14) led to a similar consideration to that for CH3SCH2CH2C1 by assuming the transition state for the elimination as an intimate ion-pair as represented above. 

In connection with the methoxy participation, the gas-phase pyrolytic elimination of 4-chloro-1 -butanol was investigated177. The products are tetrahydrofuran, propene, formaldehyde and HCl. It is implied that the OH group provides anchimeric assistance from the fact that, besides formation of the normal unstable dehydrochlorinated intermediate 3-buten-l-ol, a ring-closed product, tetrahydrofuran, was also obtained. The higher rate of chlorobutanol pyrolysis with respect to chlorethanol and ethyl chloride (Table 27) confirmed the participation of the OH group through a five-membered ring in the transition state. 

Vinylthiophene has been prepared by the dehydration of a-(2-thienyl)ethanol,3-6 by the condensation of vinyl chloride with 2-thienylmagnesium bromide in the presence of cobaltous chloride,6 and by the dehydrochlorination of cc-(2-thienyl) ethyl chloride.7... 

The low temperature polymerisation of isobutene by SnCl4 in ethyl chloride is one of the classical studies of the golden era of cationic polymerisation. Norrish and Russell " found that with no added water an extremely slow reaction period was followed by a sudden acceleration. A similar phenomentm was later reported by Polton and Sigwalt for the polymerisation of indene in a dry system. It seems reasonable to suppose that the slow initial process reflects direct initiation in both systems, and that the sudden accelemtion arises from the internal production of a cocatalyst, probably hydrogen chloride formed from the dehydrochlorination of active species. 

The dependences shown in Fig. 3 reveal that employing a catalyst with a larger specific surface area with rising temperature would, probably, lead to the deep oxidation of vinyl chloride and, to a lesser extent, of ethylene, resulting in a decrease in the total yield of ethylene and vinyl chloride. A certain increase in the overall yield of COx products, which was observed for catalyst 2, is accompanied with an increase in the total yield of ethylene and vinyl chloride. This suggests that saturated chlorinated hydrocarbons — ethyl chloride and 1,2-dichloroethane — are oxidized predominantly and that the rate of oxidation is lower rate compared to that of the dehydrochlorination of these compounds. 

We can suppose on the strength of the data listed in Table 2 that at the short times-on-stream, the major contribution to the formation of deep oxidation products is made by saturated chlorinated hydrocarbons 1,2 dichloroethane and ethyl chloride. On increasing time-on-stream to more than 6 s, we observed a sharp increase in the yield of deep oxidation products together with the decrease in the yield of vinyl chloride. It is likely that at the longer times-on-stream, the rate of deep oxidation of vinyl chloride would increase and become higher than the rate of dichloroethane dehydrochlorination. Taking into account this fact, we believe that the optimum time-on-stream assuring the best total yield of ethylene and vinyl chloride would be 3—5 s. 

As in steam cracking, a large number of by-products is produced. Some of them result from the consecutive reactions of the chlorination of vinyl chloride and of its derivatives obtained by dehydrochlorination (tri-, tetra-, pentachloroethane, perchloro-ethane, di-, trichloroethylene. perchloroethyleneX and the others from the hydrochlorination of vinyl chloride il.l-dichloroethane), while others result from decomposition reactions (acetylene, cokei or conversion of impurities initially present (hydrocarbons such as ethylene, butadiene and benzene, chlorinated derivatives such as chloroprene, methyl and ethyl Chlorides, chloroform, carbon tetrachloride, eta, and hydrogen) ... 

No direct data for the decomposition of alkyl halides by clean, active metal surfaces seem to be available. Campbell and Kemball [11], in their study of the hydrogenolysis of ethyl chloride, cite evidence for the dehydrochlorination reaction... 

Active Figure 17.20 Dehydrochlorination of menthyl and neomenthyl chlorides, (a) Neomenthyl chloride loses HCI directly from its more stable conformation, but (b) menthyl chloride must first ring-flip before HCI loss can occur. The abbreviation "Et represents an ethyl group. Sign in at www.thomsonedu.com to see a simulation based on this figure and to take a short quiz. 

The Schotten-Bauman condensation produces polyanhydrides with moderate molecular weights by a dehydrochlorination reaction between a diacid chloride and a dicarboxylic acid. The polymerization takes place by reacting the monomers for 1 hr at room temperature, and it can be conducted via solution or interfacial methods. Solvents that are used in solution polymerization include dichloromethane, chloroform, benzene, and ethyl ether. The degree of polymerization obtained with this method is approximately 20-30. Lower molecular weight products are obtained for less reactive monomers such as isophthaloyl chloride. 

The reagent is generated in situ by dehydrochlorination of ethoxyacetyl chloride with triethylamine at —78°. It appears to be fairly stable at this temperature but slowly polymerizes at room temperature. It is also formed to some extent by photochemical Wolff rearrangement of ethyl diazoacetate. 

A technical procedure for the synthesis of (3S,3 S)-83 and (3R,3 R)-83 starting from 6-oxoisophorone (56) has recently been developed. For the synthesis of the (3S,3 S)-isomer [(3S,3 S)-83], 6-oxoisophorone (56) was transformed to the (3R)-hydroxyketone (3R)-58 which was reacted with sulphuryl chloride to produce the diastereoisomeric chloroketones (3S,5R)-84 and (3S,5S)-84. Subsequent dehydrochlorination with 5-ethyl-2-methylpyridine gave the chiral building block 85 in 92% yield referred to (3R)-58 [55,56] Scheme 20). 

Some of the chelate compounds can act as dienophilic reagents, decomposing polyene structures formed as a result of dehydrochlorination of the polymer [24]. Compounds of calcium with 1,3-dicarbonyl derivatives, capable of keto-enol tautomerism, for example, with the ethyl ester of acetoacetic acid [199], have been proposed for the stabilization of polyvinyl chloride ... 

Poly(p-phenylene vinylene)s have been synthesized by various methods, such as the reaction of p-xylene-bis(triphenylphosphonium chloride) with terephthalaldehyde in the presence of lithium ethylate (Wittig reaction) [64], the reaction of p-xylene tetrabromide with alkyllithium in tetrahydrofuran [65], and the polymerization of a precursor polymer [66]. Poly(p-xylyli-dene)s have been synthesized by dehydrochlorination of p-xylene dichloride with sodium hydride in dimethylformamide [67]. 

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