Dolbier HW Solutions 490

Dolbier HW Solutions 490 - 2 OCH 2 CH 3 H 3 C CH 3 CCOCH 2...

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21.15 To undergo a Claisen condensation, an ester must have at least two protons on the a carbon: The equilibrium constant for condensation is unfavorable unless the b -keto ester can be deproton- ated to form a stable anion. ( a ) Among the esters given, ethyl pentanoate and ethyl 3-methylbutanoate undergo the Claisen condensation ( b ) The Claisen condensation product of ethyl 2-methylbutanoate cannot be deprotonated; the equilibrium constant for its formation is less than 1. ( c ) Ethyl 2,2-dimethylpropanoate has no protons on its a carbon; it cannot form the ester enolate required in the f rst step of the Claisen condensation. 21.16 ( a ) The Claisen condensation of ethyl phenylacetate is given by the equation 1. NaOCH 2 CH 3 2. H 1 C 6 H 5 CH 2 COCH 2 CH 3 O Ethyl phenylacetate C 6 H 5 CH 2 CCHCOCH 2 CH 3 O O C 6 H 5 Ethyl 3-oxo-2,4-diphenylbutanoate
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Unformatted text preview: 2 OCH 2 CH 3 H 3 C CH 3 CCOCH 2 CH 3 O CH 3 C 1 no reaction Ethyl 2,2-dimethylpropanoate Ethyl 2-methylbutanoate CH 3 CH 2 CHCOCH 2 CH 3 O CH 3 No protons on a-carbon atom; cannot form stabilized enolate by deprotonation CH 3 CH 2 CHCCCOOCH 2 CH 3 O CH 3 CH 2 CH 3 CH 3 NaOCH 2 CH 3 K , 1 1. NaOCH 2 CH 3 2. H 1 (CH 3 ) 2 CHCH 2 COCH 2 CH 3 O Ethyl 3-methylbutanoate (CH 3 ) 2 CHCH 2 CCHCOCH 2 CH 3 O O CH(CH 3 ) 2 Ethyl 2-isopropyl-5-methyl-3-oxohexanoate 1. NaOCH 2 CH 3 2. H 1 CH 3 CH 2 CH 2 CH 2 CCHCOCH 2 CH 3 O CH 2 CH 2 CH 3 O Ethyl 3-oxo-2-propylheptanoate CH 3 CH 2 CH 2 CH 2 COCH 2 CH 3 O Ethyl pentanoate NaOCH 2 CH 3 1 2RCH 2 COCH 2 CH 3 O 2CH 3 CH 2 OH Na 1 1 RCH 2 CCCOCH 2 CH 3 R O O 2 a 584 ESTER ENOLATES...
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