SN2 reactions that involve breaking a bond to a chirality center can be used to relate configurations of molecules because the stereochemistry of the reaction is known.
(a) Illustrate how this is true by assigning R, S configurations to the 2-chlorobutane enantiomers based on the following data. [The configuration of (-)-2-butanol is given in Section 5.8C.]

(b) When optically pure (+)-2-chlorobutane is allowed to react with potassium iodide in acetone in an SN2 reaction, the 2-iodobutane that is produced has a minus rotation.
What is the configuration of (-)-2-iodobutane? Of (+)-2-iodobutane?

(+)-2-Chlorobutane -2-Butanol Sy2 [] = +36.00 Enantiomerically pure [a]25 -13.52 Enantiomerically pure