Chem302extraproblems11

Chem302extraproblems11 - 4. Draw a mechanism for the...

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Chem 302 – Winter 2011 – Problem Set 1 1. The phenols named below have approximately p K a values of 4, 7, 9, 10 and 11. Suggest with explanations which p K a value belongs to which: phenol, 2,4-dinitrophenol, 4-nitrophenol, 2,4,5-trimethylphenol, phenol, 2-chlorophenol. 2. Bromination of phenol affords 2,4,6-tribromophenol. Actually, it is possible to brominate 2,4,6-tribromophenol if we use bromine in acetic acid, but the product is the structure shown below. Give a mechanism for the formation of the product. This product can be used for bromination as in the monobromination of this amine. Suggest a mechanism and explain the selectivity.
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3. The local anesthetic proparacaine is made by this sequence of reactions. Deduce a structure for each product. Draw a mechanism for each step and explain why it gives that particular product. Hint: look at the structure of the products and identify components that correspond to the structures of the reagents used. You may need to review reactions learned in your previous introductory org chemistry courses.
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Unformatted text preview: 4. Draw a mechanism for the following reactions. 5. (a) Enamines are excellent precursors to monoalkylated ketones. Provide a mechanism for the following reactions: (b) An advantage of enamines is that they provide monoalkylated ketones in fairly good yields. In fact, direct monoalkylation of cyclohexanone (i.e. adding methyl iodide directly to the enolate of cyclohexanone) does not work very well. Why is that? (c) It has been suggested that the real advantage to the use of enamines is that they contain a nucleophilic carbon. Identify this carbon in the enamine shown above. What is the ultimate source of electrons that it uses in acting as a nucleophile? (d) What product (X) would result in (a) above if benzoyl chloride was used instead of methyl chloride? Now, suppose that X is further treated with (i) sodium ethoxide and (ii) methyl iodide. What product (Z) would result?...
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Chem302extraproblems11 - 4. Draw a mechanism for the...

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