Chloride anion elimination

The first step in the polymerization is the electron transfer from sodium to dichlorosilane and the formation of the corresponding radical anion. The latter upon elimination of the chloride anion is transformed to the silyl radical. To fit the chain growth mechanism, the reactivities of the macromolecular radicals must be higher than the reactivities of the monomeric radicals. The latter after electron transfer and elimination of chloride anion could be transformed to the reactive silylenes. Thus, in principle, two or more mechanisms of chain growth are possible ... 

The formation of these compounds has been rationalized according to Scheme 6. The reaction of Os (E )-CH=C 11 Ph C1 (C())( P Pr3)2 with n-BuLi involves replacement of the chloride anion by a butyl group to afford the intermediate Os (/i> CH=CHPh ( -Bu)(CO)(P Pr3)2, which by subsequent hydrogen (3 elimination gives OsH ( >CI I=CHPh (CO)( P Pr3)2. The intramolecular reductive elimination of styrene from this compound followed by the C—H activation of the o-aryl proton leads to the hydride-aryl species via the styrene-osmium(O) intermediate Os r 2-CH2=CHPh (CO)(P Pr3)2. In spite of the fact that the hydride-aryl complex is the only species detected in solution, the formation of OsH ( )-CH=CHPh L(CO)(P Pr3)2 and 0s ( )-CH=CHPh (K2-02CH)(C0)(P,Pr3)2 suggests that in solution the hydride-aryl complex is in equilibrium with undetectable concentrations of OsH ( )-CH=CHPh (CO)(P,Pr3)2. This implies that the olehn-osmium(O) intermediate is easily accessible and can give rise to activation reactions at both the olefinic and the ortho phenyl C—H bonds of the... 

Carbon tetrachloride is a solvent that is chemically inert, highly resistant to oxidation, but biologically toxic. Despite its chemical stability, P450 is able to convert carbon tetrachloride to several reactive species. Reduced P450 transfers an electron to chloride leading to the elimination of a chloride anion and the generation of the reactive trichloromethyl radical (10). Trichloromethyl radical can undergo a second one-electron reduction to... 

Almost all stable carbenes behave as 2-electron-CT-donating ligands with a few exceptions. In particular, in almost all cases corresponding Rh(I) complexes were targeted due to the easy synthetic method. An exception is the cyclopropenylidene carbene, with an extremely acute carbene angle. In this case, a second equivalent of carbene squeezes into the rhodium center, eliminating a chloride anion, giving the cationic dicarbenic rhodium(l) complex [51] (Scheme 5). 

An annulation protocol has been elaborated that uses lithiated 3,3-dichloropropene 124 generated in situ by deprotonation as a key intermediate. When added to a cycloalkanone, the homoallylic alcohol 125 forms upon aqueous workup. Its subsequent treatment with trifluoroacetic acid brings about elimination of water and dissociation of a chloride anion. 

Formation of a chromate ester is followed by the opening of cyclopropane, driven by attack of chloride and elimination of chromate anion. 

As a consequence of electroneutrality in the two fluid phases, the mass content of chloride anions is no longer an independent variable and it can be eliminated in favor of the mass content of the cations sodium. A direct consequence is that the electrical field does not enter the elastic constitutive equations, that can be phrased in terms of chemical, rather than electro-chemical, potentials. 

Oxidation of internal perfluoroolefins by alkaline solutions of hydrogen peroxide and alkaline and alkaline-earth hypohalides leads to the formation of olefin oxides, the yield of the target product being 40-50%. The reaction with sodium hypochlorite in an alkali in the presence of acetonitrile is an example of epoxidation performed by the nucleophilic attack of the OC1-anion of the multiple bond with further elimination of the chloride anion by the intermediate carbanion (79IZY2509, 79IZV2812, 79RP666176,... 

This is an example of the second step of an E2 (bimolecular elimination) reaction mechanism. Note the displacement of the chloride anion is the result of an anion present on an adjacent carbon atom. Arrow pushing is illustrated below ... 

Next, the carboxylate anion participates in an addition-elimination reaction with isobutyl chloroformate. Elimination of a chloride anion results in formation of intermediate A. These reactions are generally facilitated by the introduction of an amine base such as triethylamine (not shown in this problem). The mechanism is illustrated below using arrow pushing, and the illustrated product belongs to a class of compounds known as mixed carbonic anhydrides. 

In this book, there have been many references to oxidation and reduction reactions. While these reactions are not within the scope of the discussions of this book, their mechanisms do involve the processes presented herein. In the case of the Swem oxidation, the first step is an addition-elimination reaction between dimethyl sulfoxide and oxallyl chloride. This process, illustrated below using arrow pushing, involves addition of the sulfoxide oxygen to a carbonyl with subsequent elimination of a chloride anion. 

Although fluoride anion is a worse leaving group than chloride anion, the product farmed by ejection of fluoride, Z, predominates, probably because its elimination creates a double bond conjugated with the aromatic ring. 

In step 1, carbon dioxide is lost from the trichloroacetate anion. In step 2, elimination of chloride anion produces dichlorocarbene. Step 2 is the same for both the above reaction and the base-induced elimination of HC1 from chloroform, and both reactions proceed through the trichloromethanide anion intermediate. 

The generally accepted mechanism of the Ramberg-Backlund reaction (Scheme 39) involves the deprotonation of the a-chlorosulfone by the base to give the sulfonyl carbanion (92). The latter undergoes an intramolecular nucleophilic attack on the a-carbon atom with elimination of the chloride anion and formation of the episulfone (93), which is unstable and extrudes sulfur dioxide to yield the alkene (Scheme 39).6 The Ramberg-Backlund reaction, unlike the Julia reaction, yields mainly the (Z)-alkene from acyclic starting materials. 

The NH2 anion is a very strong base and removes a proton from the aromatic ring. This anion then eliminates a chloride anion, to leave an aromatic species that also contains a triple bond. This is called an aryne intermediate. This may be attacked by another NH2 anion (or possibly, by NH3) in... 

The best way to introduce the formyl group in the proper position is through a Reimer-Tiemann reaction. This involves treating a phenol with chloroform in the presence of base. Under these conditions, chloroform sequentially loses a proton and a chloride anion in an a-elimination (elimination with both leaving groups on same carbon) to form a dichlorocarbene. 

CHs-Halide bond formation is a side reaction in the Shilov methane oxidation process (Scheme 24) [64]. Mechanistic analysis of several catalytic steps by Bercaw and coworkers showed that the formation of the carbon-chlorine bond takes place in parallel to the formation of methanol, often being the major reaction pathway [65]. The reaction most likely involves a nucleophilic attack of the chloride-anion at the coordinated methyl group of the Pt(IV) intermediate [66]. Thus, the overall mechanism is closely related to the organic SN2-type reaction. Further support for such a mechanism operating in Pt(lV) systems came from the Goldberg group which reported the competitive CH3-I and CH3-CH3 reductive elimination reactions in platinum phosphine complexes (Scheme 25) [67, 68]. 

As both nucleophiles, Z and Y , can participate in a reductive elimination reaction, a mixture of reaction products, R-Z and R-Y, forms. Such behavior is observed in the Shilov reaction (Fig. 2). Formation of a mixture of methanol and methyl chloride is considered in Shilov chemistry as a result of occurrence of two concurrent S 2 processes with water and chloride anion as competing nucleophiles [18, 19]. The rate of the formation of chloromethane in aqueous solutions of [MePt Clsl in this reaction was shown to be first order in chloride ion concentration. 

Aryl diazonium salts are considered more reactive toward oxidative addition than aryl iodides. Furthermore, the presence of the anion eliminates the need for an additional base [62]. The reactions of various aryl diazonium fluoroborate salts with styrene mediated by Pd(OAc)2/bis-(2,6-diisopropylimidazolium chloride) proceeds in almost all solvents at room temperature. In the opti-... 

Water-soluble ionic liquids, typically acetate, trifluoroacetate and tetrafluoro-borate salts, can be obtained by the addition of the corresponding silver salt and elimination of the precipitate. This method leads to highly pure ionic liquids containing a very low amount of the chloride anion. However, starting silver salts are expensive, and an equivalent of waste material (AgCl) is generated. 

The associative pathway of ligand exchange starts from the addition of a nucleophile to the positively charged iodine atom of a X -iodane with the initial formation of a trans hypervalent 12-1-4 square-planar species. This intermediate species isomerizes to the cis 12-1-4 square-planar intermediate and eliminates the ligand L to afford the final product (Scheme 1.4). Such a mechanism has been validated by the isolation and X-ray structural identification of several stable 12-1-4 species. For example, the interaction of ICI3 with chloride anion affords tetrachloroiodate anion, ICl4, which has a distorted square-planar structure as established by X-ray analysis of the trichlorosulfonium salt, CI3S+ ICU [209]. 

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