Carbocations reacting with

Addition begins m the usual way by protonation of the double bond to give m this case a secondary carbocation This carbocation can be captured by chloride to give 2 chloro 3 methylbutane (40%) or it can rearrange by way of a hydride shift to give a tertiary carbocation The tertiary carbocation reacts with chloride ion to give 2 chloro 2 methylbutane (60%)... 

Three significant hydrocarbon ions, [S" ], [9 ] and [10 ], should be mentioned as additional examples of the formation of stable salts of the hydrocarbon ions. The triphenylmethylium ion [8" ], as a prototypical aromatic carbocation, reacts with the chloride ion to give the chloride, a... 

The carbocation reacts with the halide in the next step ... 

The carbocation reacts with the halide ion at equal rates by path (a) or (b) to form the enantiomers as a racemate. 

In the second step, the carbocation reacts with a hydrogen sulfate ion to form an alkyl hydrogen sulfate. 

The carbocation reacts with a molucule of water to form a protonated alcohol. 

The reaction proceeds via a pentacoordinate hydroxycarbonium ion transition state, which cleaves to either fert-butyl alcohol or the tert-butyl cation. Since 1 mol of isobutane requires 2 mol of hydrogen peroxide to complete the reaction, one can conclude that the intermediate alcohol or carbocation reacts with excess hydrogen peroxide, giving fcrt-butyl hydroperoxide. The superacid-induced rearrangement and cleavage of the hydroperoxide results in very rapid formation of the dimethylmethyl-carboxonium ion, which, upon hydrolysis, gives acetone and methyl alcohol. 

This carbocation reacts with a third molecule of 2-methylpropene to give a 12-carbon tertiary carbocation. 

The alcohol is chiral, but the carbocation is not. Thus, irrespective of which enantiomer of 2-phenyl-2-butanol is used, the same carbocation is formed. The carbocation reacts with ethanol to give an optically inactive mixture containing equal quantities of enantiomers (racemic). 

The carbocation reacts with water, which is a nucleophile and is present in large excess ... 

O This secondary carbocation reacts with chloride (17%) A tertiary carbocation... 

Carbocations are common intermediates in organic reactions. Highly substituted alkyl halides can ionize when they are heated in a polar solvent. The strongly electrophilic carbocation reacts with any available nucleophile, often the solvent. 

Complexation of an alkyne to dicobalthexacarbonyl is a well-known way to stabilize carbocationic charges generated in the carbon a to the alkyne. These carbocations react with different nucleophiles. This process, the Nicholas reaction [112], has been used to generate enynes that undergo, in a domino fashion, a PKR. 

The mechanism follows the usual path cyclization of linalyl diphosphate, followed by attack of the n electrons of the second double bond, produce an intermediate carbocation. A carbocation rearrangement occurs, and the resulting carbocation reacts with water to form an alcohol that is oxidized to give a-fenchone. 

The investigations described in this chapter show that nature and concentration of the negative counterion has a great influence on the outcome of carbocationic telomerizations because of the different rates of ion-pair collapse and because of reionization of eventually produced 1 1 adducts from alkyl halides and alkenes. On the other hand, it was found that the rate of attack of a carbocation at an alkene is generally independent of the nature of the complex counterion and that free and paired carbocations react with equal rates. If this conclusion also holds for carbocationic polymerizations, a reinterpretation of many polymerization kinetics becomes necessary. 

A trigonal planar carbocation reacts with nucleophiles from both sides of the plane. 

For S g1 The carbocation reacts with a nucleophile. Nucleophilic attack of CH3OH on the carbocation generates a positively charged intermediate that loses a proton to afford the neutral Snjl product. 

For E1 The carbocation reacts with a base. Two different products of elimination can form because the carbocation has two different p carbons. 

Substitution (S l) occurs when the carbocation reacts with a nucleophile. 

An early example utilizing an allylic ether, shown in Scheme 7.39, was reported by Herscovici et al. [142], and is applicable to various glycals. As shown in Scheme 7.40, the mechanism of these transformations involves formation of the carbocation followed by the evolution of its equilibrium with the illustrated 0-glycoside. As the carbocation reacts with the allylic ether, the reaction is driven to provide the desired product. 

Simple tertiary carbocations react with water/trifluoroethanol (H20/TFE) solvent with an estimated rate constant of 1012s-1, which is somewhat faster than bulk solvent reorganizes.28 Simple primary and simple secondary carbocations are predicted to be even more reactive with nucleophilic solvent than tertiary carbocations. In water solutions, therefore, the rates at which simple primary and secondary carbocations are predicted to react with solvent would exceed the rate of a bond vibration ( 1013 s-1), and consequently they would not be sufficiently stable to exist as an intermediate. An A-2 mechanism would therefore be enforced on the acid-catalyzed hydrolysis of those epoxides that potentially undergo ring opening to form primary or secondary carbocations. 

The estimated rate at which a simple tertiary carbocation reacts with water solvent ( 1012s-1)28 is very close to the rate at which solvent reorganizes (10n-1012s-1).29 It has been suggested that simple tertiary carbocations that are formed as part of ion pairs or ion-molecule pairs react with a solvent molecule that is already present within the solvent shell that is present at the time of formation of the carbocation.30... 

Termination via hydride transfer The carbocations react with isobutane to form the various octane products, along with a t-butyl cation to continue the reaction sequence. 

Steps 2 and 3, however, are new to us. Step 2 involves dissociation of an alky-loxonium ion to a molecule of water and a carbocation, a species that contains a positively charged carbon. In step 3, this carbocation reacts with chloride ion to yield tert-butyl chloride. Both the alkyloxonium ion and the carbocation are intermediates in the reaction. They are not isolated, but are formed in one step and consumed in another during the passage of reactants to products. If we add the equations for steps 1 through 3 together, the equation for the overall process results. A valid reaction mechanism must... 

One extreme in a displacement reaction would be where the leaving group has already departed, and a preformed stable carbocation reacts with the nucleophile. In this event, the cross-coupling reaction might be either direct polar combination of the carbocation with the Grignard reagent or electron transfer to the carbocation followed h radical recombination. 

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