1.3- Butadiene hydrochlorination

Dicbloro-l,3-butadiene [1653-19-6] is a favored comonomer to decrease the regularity and crystallization of chloroprene polymers. It is one of the few monomers that will copolymerize with chloroprene at a satisfactory rate without severe inhibition. It is prepared from by-products or related intermediates. It is also prepared in several steps from chloroprene beginning with hydrochlorination. Subsequent chlorination to 2,3,4-trichloto-1-butene, followed by dehydrochlorination leads to the desired monomer in good yield if polymerization is prevented. 

The empirical shift parameters calculated from the NMR data of the 1,4-polyisoprene derivatives will provide, hereafter, a basis for assigning the carbon resonances observed in the spectrum of hydrochlorinated 1,4-polydimethyl butadiene, which like hydro-chlorinated 1,4-polyisoprene has quaternary carbons substituted by one chlorine atom. 

Hydrochlorinated 1,4-po1ydimethylbutadiene. Figure 8 shows the 22.6 MHz C NMR spectrum of the hydrochlorinated 1,4-polydimethyl butadiene sample. Identification of methyl, methylene, methine, and quaternary carbon resonances was made by off-resonance decoupling experiments. It can be seen that all resonances but the methyl resonance at 15.1 ppm, and the methine resonance at... 

Observed and Predicted Chemical Shifts for Hydrochlorinated 1.4-Pol.ydiniethyl butadiene... 

A single chloro compound, trans-1 -phenyl-3-chloro-1 -butene (7), is formed in hydrochlorination of isomeric 1-phenyl-1,3-butadienes in AcOH135 (Scheme 6.2). The observation is interpreted by the formation of different isomeric allylic carbo-cations (6c and 6t). Rapid rotation of 6c to 6t before captured by the chloride ion ensures selective formation of 7. 

Hydrochlorination of 1,3-Butadiene. A historic process for the synthesis of adi-ponitrile was the transformation of 1,3-butadiene through 1,4-dichlorobutene.187 Addition of HC1 was carried out in the vapor phase (125-230° C) in an excess of 1,3-butadiene. A mixture of isomeric dichlorobutenes (3,4-dichloro-l-butene, cis-and trans-l,4-dichloro-2-butene) was formed. They underwent further transformations to form the dicyanides and then, after hydrogenation, to give adiponitrile. 

Synthetic polyisoprene rubbers were found by Harries during 1910 [19], to be successfully hydrochlorinated. These synthetic polyisoprenes resemble natural rubber, which is also a polymer of isoprene which occurs naturally and therefore hydrogen chloride is rapidly added when the rubber is exposed to it thus forming a protective film of chlorinated rubber or hydrogen chloride. Polybutadiene, and butadiene acrylonitrile rubbers do not add hydrogen chloride from hydrochloric acid. 

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) ... 

Purification of crude vinyl chloride produced by cracking and hydrochlorination, including the lowering to about 5 ppm of the butadiene content by means ofliquid/liquid countercurrent contact with hydrochloric arid, separation by distillation of the light products returned to hydrochlorination, followed by neutralization with dilute caustic soda, scrubbing with water, drying on molecular sieves, and finally the removal of heavy compounds by distillation. 

Chlorobutanes. Chlorobutanes can be obtained by diverse procedures, such as (1) the liquid-phase or thermal chlorination of butane, (2) addition of chlorine or hydrogen chloride to butenes, (3) reaction of hydrochloric acid with butanols and butylene glycols, (4) chlorination of chlorobutenes and chlorobutadienes, and (5) hydrochlorination of tetramethylene oxide (tetrahydrofuran) and butadiene. 

Recently a direct hydrocarboxylation of butadiene succeeded at moderate temperatures (about 120 °C) with a Pd-containing catalyst system [469-471]. Formally the reaction proceeds in the same manner as hydrochlorination by 1.4 addition of the formic add elements, butene-2-carboxy-lic acid-1 is formed. 

In adding hydrogen halides and halogens to the >C=C< double bond of 1,2-PB, the functionalization degree of the polymer is mostly determined by the reactivity of the electrophilic agent. Relatively low degree of polydiene hydrochlorination (10-15%) at interaction of HCl and syndiotactic 1,2-PB [16, 39, 40] is caused by insufficient reactivity of hydrogen chloride in the electrophilic addition reaction by the double bond (Table 3.2). Due to this, more electron-saturated >C=C< bonds in 1,4 units of butadiene polymerization are subjected to modification. 

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