Final - Fall 200604 - 8. (4 pts) Which of the following is...

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4 8. (4 pts) Which of the following is the best mechanistic representation of the reaction of primary alcohols with POCl 3 /pyridine? H O H O P Cl Cl Cl H O PCl 2 O N N H O 2 PCl 2 H O P Cl Cl Cl H O PCl 2 N HO O N H O 2 PCl 2 H O H O P Cl Cl Cl N -H + -H + -H + N H O 2 PCl 2 H O H N H O O P Cl Cl Cl H O PCl 2 O H O 2 PCl 2 H OH O P Cl Cl Cl H POCl 3 N N H O P Cl Cl Cl a) b) c) d) e) H H H H H H H H H H H H H H H H H H H H Comments: This is an example of “arrow-following” mechanistic questions that have precedents in the practice set (see for example TS4: 26, PE4A: 5, PE4B: 7, 8, PE4C: 20, 27 ). One needs to recognize that this is POCl 3 /pyridine elimination of alcohols that takes place by the E2 mechanism that requires 1. conversion of the –OH group into a good leaving group and 1. antiperiplanar transition state (that is why (c) is not a choice). The mechanism is in the book on p. 608. 9. (4 pts) Considering only monochlorides , what would be the yield of the most abundant
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This note was uploaded on 01/12/2010 for the course PSYCH 100 taught by Professor Matchock,robert during the Fall '07 term at Pennsylvania State University, University Park.

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