Chloride catalysts bonds

Halobutyl Cures. Halogenated butyls cure faster in sulfur-accelerator systems than butyl bromobutyl is generally faster than chlorobutyl. Zinc oxide-based cure systems result in C—C bonds formed by alkylation through dehydrohalogenation of the halobutyl to form a zinc chloride catalyst (94,95). Cure rate is increased by stearic acid, but there is a competitive reaction of substitution at the halogen site. Because of this, stearic acid can reduce the overall state of cure (number of cross-links). Water is a strong retarder because it forms complexes with the reactive intermediates. Amine cure may be represented as follows ... 

Other coupling reactions were also employed to prepare poly(arylene etherjs. Polymerization of bis(aryloxy) monomers was demonstrated to occur in the presence of an Fe(III) chloride catalyst via a cation radical mechanism (Scholl reaction).134 This reaction also involves carbon-carbon bond formation and has been used to prepare soluble poly(ether sulfone)s, poly(ether ketone)s, and aromatic polyethers. 

It would appear that increasing the amount of stannous chloride catalyst, under our experimental conditions, as well as increasing the amount of oil formed decreases the amount of polar compounds in the oil which decreases the hydrogen bonding and therefore helps to decrease the viscosity of the oil. Spectroscopic evidence indicates that there is little change in the hydrocarbon structures present. 

There is an absence of cis-to-trans isomerization with conversion or time for the C8 (1,5-cyclooctadiene) polymer. This is shown from 52 to 58% conversion after 1 to 16 hours reaction time in Table II and III. The above review (A0, A2, A3, A5) shows that the cis structure in polymers from 1,5-cyclooctadiene using various chloride catalysts fell below 50% cis even to 20% cis units this means that the second cis double bond from the monomer underwent extensive cis-to-trans isomerization following the ring-opening of the first cis bond. Where cis-2-butene isomerizes to trans structure using other catalyst preparations, there is no evidence of this for cis-2-butene using the iodine system. However, polymer molecular... 

In that complex, it may be that water reacts with the coordinated C2H4 to produce a cr-bonded CH2CH2OH group rather than an insertion reaction involving an OH group. The aldehyde is formed as H+ is lost, and the palladium is produced as shown in Eq. (22.31). The palladium chloride catalyst can be recovered (the price of palladium is almost 500/oz as this is written) by the reaction with CuCl2. 

Cycloalkenes such as cyclohexene, 1-methylcyclohexene, cyclopentene, and nor-bornene are hydrosilylated with triethylsilane in the presence of aluminum chloride catalyst in methylene chloride at 0 °C or below to afford the corresponding hydrosilylated (triethylsilyl)cycloalkanes in 65-82% yields [Eq. (23)]. The reaction of 1-methylcyclohexene with triethylsilane at —20 °C occurs regio- and stereoselectively to give c/i-l-triethylsilyl-2-methylcyclohexane via a tra x-hydrosilylation pathway. Cycloalkenes having an alkyl group at the double-bonded carbon are more reactive than non-substituted compounds in Lewis acid-catalyzed hydrosilylations. ... 

Successful catalytic alkylation of isobutane with ethylene has been accomplished in one commercial installation using aluminum chloride catalyst (I). The chief product of the reaction is 2,3-dime thy lbutane, a hydrocarbon having very high aviation octane ratings. Ethylene has also been alkylated with isobutane in a thermal process to give 2,2-dimethylbutane as the chief product component (6). When sulfuric or hydrofluoric acid alkylation with ethylene is attempted, the ethylene forms a strong bond with the acid, and fails to react with isobutane. The net result is the formation of little or no product, accompanied by excessive catalyst deterioration. 

When either an alcohol or an amine function is present in the alkene, the possibility for lactone or lactam formation exists. Cobalt or rhodium catalysts convert 2,2-dimethyl-3-buten-l-ol to 2,3,3-trimethyl- y-butyrolactone, with minor amounts of the 8-lactone being formed (equation 51).2 In this case, isomerization of the double bond is not possible. The reaction of allyl alcohols catalyzed by cobalt or rhodium is carried out under reaction conditions that are severe, so isomerization to propanal occurs rapidly. Running the reaction in acetonitrile provides a 60% yield of lactone, while a rhodium carbonyl catalyst in the presence of an amine gives butane-1,4-diol in 60-70% (equation 52).8 A mild method of converting allyl and homoallyl alcohols to lactones utilizes the palladium chloride/copper chloride catalyst system (Table 6).79,82 83... 

Oxidative coupling of a terminal alkyne is a particularly easily performed carbon-carbon bond forming reaction, which results in a good yield of the symmetrical diacetylene. A widely used procedure involves the oxidation of the alkyne with air or oxygen in aqueous ammonium chloride in the presence of a copper(i) chloride catalyst (Glaser oxidative coupling). 

Complex 3 was found to be inactive in the catalytic asymmetric hydrogenation of 2-(6,-methoxy-2 -naphthyl)acrylic acid. Since 3 accounted for a large portion of the mixed complexes, it was quite clear that the catalytic activity of the mixed species would be substantially increased if the formation of 3 could be avoided. It appeared that preventing the rupture of the phosphorus-naphthyl bond was most critical in an improved synthesis of the mixed Ru-BINAP-chloride catalysts. 

The choice of the anion is also cmcial in systems where the active cationic species is formed from a neutral precursor, as in the case of the nickel allyl chloride catalyst used for asymmetric hydrovinylation (eq. (6) cf. also Section 3.3.3). The previously optimized conditions for this reaction involved the use of highly flammable Al2Et3Cl3 as chloride-abstracting agent and required the use of CH2CI2 at -78 °C. Using NaBARF in compressed CO2, the C-C bond coupling occurs around room temperature with excellent chemo-, stereo-, and enantioselectivity [73]. This example demonstrates nicely that the application of CO2 can have environmental benefits for catalytic processes far beyond the solvent replacement. 

Cyclobutene, cyclopentene, and norbomene also give their polyalken-amers (64). The molecular weights are all high, and the stereochemistries are largely cis. Of these, cw-polypentenamer has also been made with molybdenum, tungsten, and rhenium halide catalysts, and cii-polynor-bomenamer (of lower molecular weight) with a molybdenum chloride catalyst, but polybutenamer made with metal halide catalysts (the metals tried were Ti, Mo, W, V, Cr, and Ru) has never been found to have more than 60% of its double bonds cis (64). 

TT-Allylpalladium chloride (36) reacts with the nucleophiles, generating Pd(0). whereas tr-allylnickel chloride (37) and allylmagnesium bromide (38) reacts with electrophiles (carbonyl), generating Ni(II) and Mg(II). Therefore, it is understandable that the Grignard reaction cannot be carried out with a catalytic amount of Mg, whereas the catalytic reaction is possible with the regeneration of an active Pd(0) catalyst, Pd is a noble metal and Pd(0) is more stable than Pd(II). The carbon-metal bonds of some transition metals such as Ni and Co react with nucleophiles and their reactions can be carried out catalytic ally, but not always. In this respect, Pd is very unique. 

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