1.3- Butadiene hydrogen chloride addition

TABLE 3. Product distribution in hydrogen chloride addition to halogeno-substituted 1,3-butadienes, R cII=CK LK CIh... 

Addition of hydrogen chloride to 2 methyl 1 3 butadiene is a kmetically controlled reaction and gives one product in much greater amounts than any isomers What is this product ... 

Chemistry of polychloroprene rubber. Polychloroprene elastomers are produced by free-radical emulsion polymerization of the 2-chloro-1,3-butadiene monomer. The monomer is prepared by either addition of hydrogen chloride to monovinyl acetylene or by the vapour phase chlorination of butadiene at 290-300°C. This latter process was developed in 1960 and produces a mixture of 3,4-dichlorobut-l-ene and 1,4-dichlorobut-2-ene, which has to be dehydrochlorinated with alkali to produce chloroprene. 

Chloro-1,3-butadiene (chloroprene) is the monomer from which the elastomer neoprene is prepared. 2-Chloro-1,3-butadiene is the thermodynamically controlled product formed by addition of hydrogen chloride to vinylacetylene (H2C=CHC=CH). The principal product under conditions of kinetic control is the allenic chloride 4-chloro-1,2-butadiene. Suggest a mechanism to account for the formation of each product. 

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

Formation of both 1,2- and 1,4-addition products occurs not only with halogens, but also with other electrophiles such as the hydrogen halides. The mechanistic course of the reaction of 1,3-butadiene with hydrogen chloride is shown in Equation 13-1. The first step, as with alkenes (Section 10-3A), is formation of a carbocation. However, with 1,3-butadiene, if the proton is added to C1 (but not C2), the resulting cation has a substantial delocalization energy, with the charge distributed over two carbons (review Sections 6-5 and... 

Catalysts from Group VIII metals have given unsatisfactory results. In the polymerization of butadiene with soluble cobalt catalysts tritium is not incorporated when dry active methanol is employed [115], although it is combined when it has not been specially dried [117, 118]. Alkoxyl groups have been found when using dry alcohol [115, 119] but the reaction is apparently slow and not suited to quantitative work [119]. Side reactions result in the incorporation of tritium into the polymer other than by termination of active chains [118], probably from the addition of hydrogen chloride produced by reaction of the alcohol with the aluminium diethyl chloride [108], Complexes of nickel, rhodium and ruthenium will polymerize butadiene in alcohol solution [7, 120], and with these it has not been possible to determine active site concentrations directly. 

Further extension of the reaction pool of Schilf bases 138 was achieved by their reaction with tran -l-methoxy-3-(trimethylsilyloxy)-1,3-butadiene (Danishefsky s diene) to give 2-substituted 5,6-didehydro-piperidin-4-ones 164 [135,136] (Scheme 10.54). The reaction is considered to be a sequence of an initial Mannich reaction between the imine and the silyl enol ether, followed by an intramolecular Michael addition and subsequent elimination of methanol. If the reaction was terminated by dilute ammonium chloride solution, then the Mannich bases 163 could be isolated and further transformed to the dehydropiperidinones 164 by treatment with dilute hydrochloric acid. This result proved that the reaction pathway is not a concerted hetero Diels-Alder type process between the electron-rich diene and the activated imine. The use of hydrogen chloride as a terminating agent resulted in exclusive isolation of the piperidine derivatives 164 formed with... 

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. 

Butadiene shows 1,4-addition reactions with electrophilic reagents other than hydrogen chloride. Two examples are shown here, the addition of hydrogen bromide (in the absence of peroxides) and the addition of bromine ... 

When 2-methyl-1,3-butadiene (isoprene) undergoes a 1,4-addition of hydrogen chloride, the major product that is formed is l-chloro-3-methyl-2-butene. Little or no l-chloro-2-methyl-2-butene is formed. How can you explain this ... 

The addition ofahydrogen halide (hydrogen bromide or hydrogen chloride) to 1-phenyl-1,3-butadiene produces (only) l-phenyl-3-halo-l-butene. (a) Write a mechanism that accounts for the formation of this product, (b) Is this 1,4 addition or 1,2 addition to the butadiene system (c) Is the product of the reaction consistent with the formation of the most stable intermediate carbocation ... 

Although not specified in the table, electrophilic addition to conjugated enynes (as in Scheme 6.70) appears to provide both 1,2- and 1,4-addition simultaneously. Thus, as shown in Scheme 6.71, the addition of hydrogen chloride across the conjugated enyne, but-3-en-l-yne (vinylacetylene, HC C-CH=CH2) produces both 2-chloro-l,3-butadiene (chloroprene [H2C=C(C1)CH=CH2]) and 4-chloro-l,2-butadiene (H20C=CHCH2C1). 

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. 

Ihrman and Impastato in 1961 reported that butadiene-Fe(CO)3 reacted with hydrogen chloride to give a covalent addition product formulated as awri-l-methyl-TT-allylchloroiron tricarbonyl (LXXXVIII) 101). Murdoch... 

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