Chem. 262 Notes 3

Chem. 262 Notes 3 - protonate the anion of o-cresol. Also...

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Experiment 3: Nucleophilic substitution reactions proceed by straightforward mechanisms that involve the replacement of a leaving group with a nucleophile. Recall from Chemistry 261 that both the SBNB1 and SBNB2 reactions require the use of a nucleophile, an organic substrate with a good leaving group, and a suitable solvent that is able to dissolve the reactants. 1. Identify the nucleophile, electrophile, and leaving group in the reaction. The nucleophile was the anion of o-cresol; the electrophile was the sodium chloroacetate cation that displaced the chloride ion, the leaving group. 2. Why is the sodium salt of the chloroacetic acid used in the reaction, instead of the chloroacetic acid itself? There are two reasons. Give both to receive full credit. The sodium salt of chloroacetic acid is used in this reaction instead of chloroacetic acid because if the salt is not used, the reaction would not go to completion because chloroacetic acid would
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Unformatted text preview: protonate the anion of o-cresol. Also the carboxylic acid would be strong enough to immediately re-protonate o-cresol, destroying the Oxygen anion and nucleophile, ruining any chance of nucleophilic substitution. 3. What is the purpose of adding sulfuric acid to the reaction mixture? The purpose of adding sulfuric acid to the reaction mixture was to re-protonate the anionic salt of the carboxylic acid. 4. NMR is a powerful technique used by synthetic chemists for molecular structure elucidation. In this experiment, how can proton NMR provide evidence that the substitution reaction occurred? Hint: what key proton peak should be present in the product but not the starting material? NMR could be used to identify the proton peak at 1700 ppm illustrating the carbonyl group, allowing one to identify which molecule is predominant in the solution....
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This note was uploaded on 05/20/2011 for the course CHEM 262 taught by Professor Forbes during the Spring '08 term at UNC.

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