Addition reactions hydrochlorination

The hydrochlorination of natural rubber is a straightforward addition reaction which proceeds according to Markownikoff s rule ... 

Chlorine and sodium hydroxide are the main products of the industrial chlor-alkali electrolysis that is described as a process example in Section 6.19. Hydrochloric acid is produced by reaction from the elements H2 and CI2 or by the reaction of chloride salts such as, for example, NaCl or CaCl2, with sulfuric acid. Other important sources of HCl are industrial chlorination processes using CI2 as chlorination agent (e.g., chlorination of benzene to form chlorobenzene and HCl or the chlorination of methane to give chloromethane and HCl) or industrial dehydrochlorination processes (e.g., production of vinyl chloride and HCl from 1,2-dichloroethane). The main uses of hydrochloric acid are addition reactions to unsaturated compounds (by hydrochlorination or oxychlorination), formation of chlorine in the Deacon process, production of chloride salts from amines and other organic bases, dissolution of metals, regeneration of ion exchange resins, and the neutralization of alkaline products. 

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. 

Halogenation and dehalogenation are catalyzed by substances that exist in more than one valence state and are able to donate and accept halogens freely. Silver and copper hahdes are used for gas-phase reactions, and ferric chloride commonly for hquid phase. Hydrochlorination (the absoration of HCl) is promoted by BiCb or SbCl3 and hydrofluorination by sodium fluoride or chromia catalysts that form fluorides under reaction conditions. Mercuric chloride promotes addition of HCl to acetylene to make vinyl chloride. Oxychlori-nation in the Stauffer process for vinyl chloride from ethylene is catalyzed by CuCL with some KCl to retard its vaporization. 

Another convenient procedure for hydrochlorination involves adding trimethylsilyl chloride to a mixture of an alkene and water. Good yields of HC1 addition products (Markovnikov orientation) are formed.3 4 These conditions presumably involve generation of HC1 by hydrolysis of the silyl chloride, but it is uncertain if the silicon plays any further role in the reaction. 

A highly economical production of ethyl chloride combines radical ethane chlorination and ethylene hydrochlorination.185 186 Called the Shell integrated process, it uses the hydrogen chloride produced in the first reaction to carry out the second addition step ... 

The reaction has been carried out using HCI either neat or in acetic acid,84 or in the presence of HgCh,83 BiCla86 or Me4NCl.M In acetic acid, mixtures of syn and anti adducts are produced,84 but reactions catalyzed by HgCl2 proceed by stereospecific anti addition.83-87 The reaction of r-butylacetylene affords the expected vinylic chloride, plus a mixture of isomeric dichloride adducts.84-88 The hydrochlorination of phenylacetyiene produces mixtures of syn and anti adducts in which the ratio is significantly affected by the solvent and catalyst used.84-89-90... 

Hyperconjugation appears to be the dominant factor governing the diastereoselectivity of the hydrochlorination of 5-substituted 2-methyleneadamantanes 3 (Table 2)36. However, the product distribution for epoxidation suggests that the stereochemical course of electrophilic additions not mediated by carbocations is most likely regulated by direct field effects36. Note that, unlike in the previous reactions, the facial selectivity in this case reflects the preference for the nucleophilic attack on the corresponding carbocation. 

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. 

Modification by attachment of new chemical groups for example chlorine, epoxy, etc. Attachment of these groups will result addition or substitution reactions at the olefinic double bonds and format chlorinated NR, hydrochlorinated NR and epoxidized NR (ENR). Chlorination and hydrochlorination of NR can be carried out in dry, solution or latex form. Due to its resistance against alkalis and acids, and its wear... 

Table III shows the results of hydro-bromination and hydrochlorination of the ethyl trans-cinnamate inclusion complexes. No hydrochlorination was observed at various temperatures after long exposure of hydrogen chloride gas similar to the reaction of trans-cinnamic acid [14]. Addition of hydrogen bromide to the ester gave an optically active and regioselective product, ethyl R-(+)-3-bromo-3-phenyl-propanoate in 46 % e.e. from the a-cyclodextrin, or ethyl S-(-)-3-bromo-3-phenylpropanoate in 31 % e.e. from the 3-cyclodextrin inclusion complex.

Reactions of Both Functional Groups. Hydrolysis of acrylonitrile catalyzed by hydrochloric acid yields 3-chloropropionic acid. Alcoholysis and chlorination occur simultaneously in the presence of sulfuric acid. Similarly, alcoholysis and hydrochlorination also occur. Addition of both ammonia and hydrogen produces both trimethylenediamine and propylamine. Treatment of acrylonitrile... 

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. 

The purified monovinyl acetylene is then hydrochlorinated in a concentrated solution of hydrochloric acid and cuprous chloride. The reaction first involves 1,4- addition of hydrochloric acid to give a chlorallene which promptly rearranges to give the desired monomer together with a by-product, l,3-dichloro-2-butene, (Carothers et al., 1932 1933). The dried polychloroprene is then separated from this and other by-products by vacuum distillation in the presence of inhibitors ... 

As has been shown, a fall in the depth of hydrochlorination per cycle (Fi) leads to a decrease in the size of the reaction volume required for total conversion of the raw material, and hence to an increase in the output of the reactor. However, in addition, a fall in Fi leads to an increase in the size of the recycling coefficient of the raw material, which under certain conditions may cause the costs of carrying out the recycling operation to rise to an uneconomic level. Thus, in recycling systems the choice of the size of the quantity Fi should be based on a study of the technical and economic parameters of the process. However, whatever the conditions, the economics and degree of refinement of the technology will depend to a large extent on the chemical reaction rate and the output that are attainable with the system employed. 

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