Experiment 6 CHEM 2071 .docx - Experiment 6 Unimolecular...

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Experiment 6: Unimolecular and Bimolecular Nucleophilic Substitution Reactions Erin LaGrone CHEM 2071 007 Drawer 167 Kenny Nguyen 15 November 2018 Purpose The purpose of this experiment is to observe unimolecular substitution reactions through extraction and distillation and to compare the reaction rates of unimolecular and bimolecular substitution reactions.
LaGrone 1 Introduction Compounds containing an electrophilic carbon can react with a compound that can act as a nucleophile by a nucleophilic substitution reaction. There are 2 types of these reactions: unimolecular and bimolecular. A unimolecular nucleophilic substitution reaction, S N 1, consists of 2 steps: the loss of a leaving group and a nucleophilic attack. The first step, loss of a leaving group, is the rate determining step. The rate of this steps relies on the nature of the leaving group. If the leaving group has an easier time leaving the carbon atom, than the reaction will occur more rapidly. These reactions are favored when in a polar protic solvent, and are also typically carried out by a weak base, making them a slower reaction than their counterpart. The mechanism for this reaction is shown in Figure 1. 1 Figure 1. The mechanism of an S N 1 reaction. 1 In bimolecular nucleophilic substitution reactions, S N 2, only 1 step takes place. Since this reaction takes place in 1 step, the 2 steps are concerted. Therefore, the rate determining step of this reaction relies upon both of the actions happening: loss of leaving group and nucleophilic attack. These reactions are favored in a polar aprotic solvent, and use a strong base which makes them occur at a more rapid rate. The mechanism of this reaction is shown in Figure 2.

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