215F07-E2-key - Name_key_ 215 F07-Exam No. 2 Page 2 I. (15...

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Name__ key __________________________ 215 F07-Exam No. 2 Page 2 I . (15 points) For each of the following pairs of compounds, predict which compound is more acidic. Compare the two underlined Hs for each pair and circle the compound that is more acidic for each pair. C H 3 CO H 3 CO H 3 CO H C Cl Cl Cl H a. b. (1) 3 O O H Cl O O H CH 3 CH 2 O (2) a. b. C H O H H H O (3) a. b. (4) (5) a. b. a. b. 3 3 H H H H H 3 CO OCH 3 H 3 CO CH 3 O O O O H H H H 3 3 II. (14 points) (a) Show the structures of the two possible conjugate acids of methyl benzoate and explain, in several words, as to which of the two conjugate acids is more stable and would be expected to form preferentially. Use drawings of pertinent resonance form(s) and several words to explain your answer. Ph O O CH 3 methyl benzoate 6 explanation: conjugate acids Ph O O CH 3 Ph O O CH 3 H H Ph O O CH 3 H Ph O O CH 3 H The positive in this conjugate acid structure is highly stabilized by resonance. (b) The pKa value of the conjugate acid of DBU is considerably higher (~12) than that of a typical imine (estimated to be around 5-7). Explain this difference in pKa values using resonance structures of the conjugate acids of both DBU and an imine. N
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This note was uploaded on 04/01/2008 for the course CHEM 215 taught by Professor Koreeda during the Fall '07 term at University of Michigan.

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215F07-E2-key - Name_key_ 215 F07-Exam No. 2 Page 2 I. (15...

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