Substitution,Nucleophilic, Bimolecular-S2 一人]人 transition state Rate k[Nuc:][R-X] Second Order Rate Kinetics Substitution, Nucleophilic, Bimolecular – SN2 C X  +  − Nuc : Nuc C X Nuc C + X transition state  −  − Rate = k[Nuc: ][R-X] Second Order Rate Kinetics