Exam 3 FS07-Blank - 1. (25 pts) Acidity and the reactions...

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2 1. (25 pts) Acidity and the reactions of alcohols and amines. a. (8 pts) We have learned that leaving group ability tracks with the pKa of the conjugate acid. On these grounds, the following two similar reactions are both solidly favorable. But only the first works; the second fails completely. Why? Briefly explain in words and equations (Hint: what else can these partners do?). pKa values: H 3 O + –1.7 CH 3 OH 2 + –2.2 (CH 3 ) 2 OH + –3.8 CH 3 NH 3 + +10.6 CH 3 NH 2 + CH 3 O(CH 3 ) 2 + (CH 3 ) 2 NH 2 + + (CH 3 ) 2 O Works great! CH 3 NH 2 + CH 3 OH 2 + (CH 3 ) 2 NH 2 + + H 2 O Fails to go this way! b. (7 pts) Explain the following pKa sequence (think about hybridization): pKa values: H 3 CCH 2 NH 3 + ~11 CH 3 CH=NH 2 + ~5 CH 3 C NH + <-5 c. (10 pts) In quiz 4 we saw that a double bond in the molecule can accelerate the ionization that starts S N 1 or E1 reactions. Thus 3-chloro-1-butene is ca. 10 3 times faster at ionizing than 2-chloropropane, which is explained in terms of resonance. But consider 2-chloro-1-
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This note was uploaded on 02/17/2012 for the course MTH 133 taught by Professor Staff during the Fall '08 term at Michigan State University.

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Exam 3 FS07-Blank - 1. (25 pts) Acidity and the reactions...

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