Relative hydrolysis rates of 2-alkyl-2-adamantyl p-nitrobenzoates

One feature of the reactions of these strained substrates is their reluctance to form strained products. The cationic intermediates usually escape to elimination products in preference to substitution products. Rearrangement reactions are common. 2-Methyl-2-adamantyl p-nitrobenzoate gives 82% methyleneadamantane by elimination and 18% 2-methyl-2-adamantanol by substitution on hydrolysis in 80% acetone. Elimination accounts for 95% of the product from 2-neopentyl-2-adamantyl p-nitrobenzoate. The major product (83%) from 2-tert-butyl-2-adamantyl p-nitrobenzoate is the rearranged alkene 6  

Although steric effects and substituent effects leading to carbonium ion stabilization are of greatest importance in governing the mechanism and relative rate of nucleophilic substitution processes, there are other substituent effects that are recognized and of importance. We have mentioned earlier in this chapter that arylmethyl and allylic cations are stabilized by electron delocalization. It is therefore easy to understand why substitution reactions of the ionization type proceed more rapidly in such systems than in simple alkyl systems. It has also been observed that nucleophilic substitutions of the direct displacement type also take place more readily, but the reason for this is not apparent. Allyl chloride is 33 times more reactive than ethyl chloride toward iodide ion in acetone, and benzyl chloride is 93 

Streitwieser, Jr., Solvolytic Displacement Reactions, McGraw-Hill Book Co., New York, 1962, p. 13. 

Studies of the stereochemical course of nucleophilic substitution reactions have proven to be a powerul tool for consideration of mechanisms. As is always true, a proposed mechanism can never be established with complete certainty. The available data can be used only to suggest reasonable possibilities or to exclude mechanisms that are inconsistent with experimental facts. 

The method by which the stereochemical course of a nucleophilic substitution reaction is determined can be illustrated for the case of 2-octyl tosylate  

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Table 5.10. Relative Hydrolysis Rates of 2-Alkyl-2-adamantyl p-Nitrobenzoates" ... 

Relative hydrolysis rates of 2-alkyl-2-adamantyl p-nitrobenzoates... 

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