Assignment 20_21-2

Assignment 20_21-2 - unless the substrate is an acyl...

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Assignment 20/21 - 2 1. Write the mechanism of each of the following reactions. In each reaction, indicate the slow step. Use curved arrows. You are encouraged do think about two things before you start to write out each mechanism: Ask yourself: First, are the conditions base/neutral or acidic. ...then ask: (1) Based on the leaving group in the acyl-C substrate, which step is rate-determining ? (ejection of leaving group is always rate-determining unless the substrate is an acyl chloride in which case the attack of the nucleophile is the rate-determining step) (2) Does the leaving group get protonated before it is ejected? General answer: Under acid conditions, the leaving group will always get protonated before leaving group departure
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Unformatted text preview: unless the substrate is an acyl chloride (Cl- leaving group is too weakly basic to get protonated) ..... Under base/neutral conditions, the leaving will always leave without prior protonation unless the substrate is an amide (the amine leaving group of an amide will get protonated before it departs). CH 3 C O Cl + O-CH 3 .. .. : C O O-CH 3 .. .. + Cl-CH 3 C O O-CH 3 .. .. + H 2 O H + heat CH 3 C O O-CH 3 .. .. + OH-heat .. : H 2 O .. : CH 3 C O NH 2 CH 3 C O OH + HOCH 3 CH 3 C O OH + HOCH 3 Note: will be present as CH 3 C O O because of basic conditions + OH-heat H 2 O .. : CH 3 C O OH + NH 3 A. B. C. D....
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This note was uploaded on 04/07/2009 for the course CHE 312 taught by Professor Drake during the Spring '08 term at American International.

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Assignment 20_21-2 - unless the substrate is an acyl...

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