7.1 SN2 Reaction | Organic Chemistry

Chad provides a comprehensive lesson on the SN2 reaction, a bimolecular substitution reaction. He begins with a description of the anatomy of a nucleophilic substitution reaction specifically identifying the role of the nucleophile and the leaving group. He then provides an example of an SN2 reaction covering both the SN2 mechanism (back-side attack) and the 2nd order rate law describing how the sn2 reaction rate is proportional to both the concentration of the nucleophile and the concentration of the substrate. He then explains how back-side attack results in inversion of configuration (aka Walden inversion) and shows the transition state associated with the SN2 reaction.

Chad then moves on to explaining substrate effects, how less substituted substrates are more reactive and includes a brief discussion of beta branching. He then describes nucleophile effects, how a strong nucleophile is required for SN2 reactions, and how to identify strong nucleophiles. He also covers trends in nucleophile strength in both polar aprotic and polar protic solvents. He then describes the preference for polar aprotic solvents for most SN2 reactions and lists several examples of both polar aprotic and polar protic solvents. Chad concludes the lesson with a discussion of what makes a good leaving group and identifies several good leaving groups including many halogens and sulfonate esters (OTs).

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00:00 Lesson Introduction
00:59 Introduction to Nucleophilic Substitution Reactions
02:08 SN2 Reaction Mechanism and Rate Law
08:16 Walden Inversion and Back-Side Attack
09:44 The Transition State in SN2 Reactions
12:31 Substrate Effects on SN2 Reactions
16:12 Beta Branching in SN2 Reactions
17:57 Strong Nucleophiles in SN2 Reactions
19:21 Trends in Nucleophile Strength in Polar Aprotic and Polar Protic Solvents
24:19 Polar Aprotic vs Polar Protic Solvents in SN2 Reactions
25:27 Good Leaving Groups in SN2 Reactions

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