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SN2 reactions

The following are animations of gas-phase trajectories for reactants with different amounts and types of energies. The reactant energy includes a relative translational energy, Erel, between Cl- + CH3Br, and a temperature, Tvr, for the CH3Br vibrational and rotational energies.

Select Trajectories of the Cl- + CH3Br → ClCH3 + Br- SN2 Reaction

Cl-+ CH3Br → ClCH3 + Br - 

Nucleophilic substitution by a direct mechanism; Erel = 50 kcal/mol and Tvr = 300K

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Cl- + CH3Br → Cl----CH3Br → ClCH3Br + Br-

Nucleophilic substitution by an indirect mechanism, involving the Cl----CH3 complex; Erel = 1.0 kcal/mol and Tvr = 300K

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Cl- + CH3Br → Cl----CH3Br → ClCH3---Br-→ ClCH3+Br-

Nucleophilic substitution by an indirect Reaction mechanism, involving both Cl----CH3Br and ClCH3---Br- complex; Erel = 1.0 kcal/mol and Tvr = 300K

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Cl- + CH3Br → Cl- + CH3Br

A non-reactive collision; Erel = 1.0 kcal/mol and Tvr = 300K

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Cl-+CH3Br → Cl----CH3Br → Cl-+CH3Br

A non-reactive collision forming the Cl----CH3Br complex, which dissociates back to reactants; Erel = 1.0 kcal/mol and Tvr = 300K.

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Cl-+CH3Br → Cl----CH3Br → ClCH3---Br-→ Cl----CH3Br → Cl-+CH3Br

Nucleophilic substitution by an indirect mechanism involving both the Cl----CH3Br and ClCH3---Br - complex and recrossing the transition state separating these complexes; Erel = 1.0 kcal/mol and Tvr = 300K.

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