Solvolysis of alkyl halides

Studies on the variation in the distribution of stereoisonieric products as a function of the accessible independent variables permit deductions concerning the multiplicity of the reaction paths. A classic example is found in Hughes and Ingold s studies into the mechanism of the solvolysis of alkyl halides in aqueous-alcoholic media, an important variable, being the concentration of base or other nucleophilic reagent (56 ). The obvious variable in hydrogenation studies is the pressure of... 

The typical reactions of carbocation intermediates were discussed in Chapter 7. The solvolysis of alkyl halides is an example of the involvement of carbocations in the SnI mechanism, in other words, where the final outcome is a nucleophilic substitution. The first step is a heterolytic cleavage of the C—X bond. Properties of X which favor heterolytic cleavage, namely electronegativity difference with carbon (the larger, the better) and the degree of overlap of the X orbital with the spn orbital of carbon (the smaller the better), have already been elucidated (Chapter 4). The transition state has partial... 

COMPARISON OF THE HYDROLYSIS OF /-ALKYL FLUOROACETATES WITH THE SOLVOLYSIS OF /-ALKYL HALIDES AT 25°C... 

The steady-state approximation, and solvolysis of alkyl halides and arenesulfonates... 

Solvolysis of alkyl halides in alcohols yields ethers as the products of reaction. 

Figure 89 Neighboring sulfur or nitrogen group assistance of solvolysis of alkyl halides.

C. Bateman, E. D. Hughes, and C. K. Ingold, Mechanism of Substitution at a Saturated Carbon Atom. Part XIX. A Kinetic Demonstration of the Unimolecular Solvolysis of Alkyl Halides, J. Chem. Soc. 960(1940). 

The multiplicity of the reaction products limits deamination as a useful synthetic method for the preparation of olefins but it is of great interest to compare the mode of reaction of the intermediate carbonium ion with those derived from solvolysis of alkyl halides and esters or acid-catalysed dehydration of alcohols. As nitrosation is the rate-determining step, evidence for carbonium-ion intermediates has to come from the nature and stereochemistry of the reaction products rather than from kinetic studies. 

The solvolysis of 3-haIo-3-alkyl-l-butynes (Table 6) is very slow as compared to the solvolysis of /-alkyl halides, but is strongly accelerated by base. Under these conditions the reactions are first-order in both halide and base concentrations, and proceed predominantly with displacement of the halogen (only 3% elimination was found under basic conditions, as compared to 35% in the neutral solvolysis) . 

The first item in Table 8.7 is the toluenesulfonic acid ester (toluenesulfonate, tosylate,-OTs) of 3- Hi-3-methyl-2-butanol, which is permitted to undergo solvolysis in an acetic acid solvent. As might be anticipated (and as shown in Scheme 8.76), the secondary tosylate group leaves and the secondary carbocation suffers a hydride migration (in this case, a deuteride, i.e., rather than H) to generate the more stable tertiary carbocation. The latter is then captured by the nucleophilic solvent. The acetic acid ester of 2-methyl-2-butanol (i.e., 2-acetoxy-2-methylbutane) results. Hydride and alkyl migrations from a less stable carbocation to a more stable carbocation have been used before (Chapter 7) to explain product mixtures resulting from solvolysis of alkyl halides. 

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