Stereochemistry unimolecular nucleophilic substitution

Illustrate the stereochemistry associated with unimolecular nucleophilic substitution by con structmg molecular models of cis 4 tert butylcyclohexyl bromide its derived carbocation and the alcohols formed from it by hydrolysis under S l conditions... 

The most synthetically useful nucleophilic substitution reaction is the bimolecular Sn2 reaction, shown in the section 2.7.A. A unimolecular substitution (ionization followed by substitution) is less useful in synthesis in a general sense, but is often the best specific reaction to effect a particular functional group exchange. In Chapter 12 we will see many examples where cationic reactions are very useful. Unimolecular substitution also occurs as a side reaction in aqueous media and can influence both the yield, stereochemistry, and regiochemistry of the final product. 

There is good evidence for the existence of the 4-oxo intermediate and this means that the reversal of configuration does not arise from a bimolecular nucleophilic substitution (or Sn2 reaction), but from a unimolecular (Snl) reaction forming a carbonium ion. Hence the stereochemistry must reflect... 

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