How are stereochemical studies helpful in establishing mechanism of organic reactions Illustrate your answer with the help of examples?
Dependencies between three-dimensional structure of reactants and products formed reflect the structure and relative orientation of the intermediate reacting particles. One of the examples: distinguishing between SN1 and SN2 nucleophilic substitution reactions. When enantiomericaly pure compound, say, (S)-2-bromobutane undergoes nucleophilic substitution, if reaction proceeds via SN1 mechanism through formation of carbocation, the product will be mixture of corresponding R- and S-isomers. In case of SN2 displacement R-isomer will be the only product.