Choose the appropriate reagent(s), Z, for the following interconversion:
Correct Answer: C.SOCL2, then NaCN
In this reaction, there is a substitution with net retention of configuration at the chiral (stereogenic) center. An SN2 process leads to a single inversion of configuration, whereas, two consecutive SN2 processes will result in the required net retention (double inversion).
In process A, a sulfonateester leaving group is initially formed (with no change in configuration) and then cyanide displaces the leaving group with inversion; i.e., the enantiomer of the required product is formed. In process C, the alcohol is converted by addition of thionyl chloride (SOCl2) to the alkyl chloride with inversion of conversion. Displacement of the chloride by the cyanide anion (with another inversion of configuration) leads to the required product.
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