These reactions may have unexpected stereochemistry due to nearby lone pairs undergoing one of these reactions intramolecularly before a second one of these reactions occurs in a classic case of neighboring group participation. A pentacoordinate (*) transition state simultaneously forms and breaks a bond in a concerted (“con-SIR-ted”) reaction of this type that produces an inversion of (10[1])stereochemistry (10[1])through a backside attack. Depending on solvent and nucleophile, (10[1])these reactions may compete with eliminations. (10[2])SN2 (10[1])(“S-N-2”) and SN1 are nucleophilic mechanisms (10[1])of, for 10 points, what class of reactions in which a functional group is replaced by another functional group? ■END■ (10[1])