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Dolbier HW Solutions 389 - 4 H 2 O(CH 3 3 CCCH 3 O...

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( d ) Conversion of 3-pentanone to 3-hexanone requires addition of a methyl group to the -carbon atom. The best way to add an alkyl group to the carbon of a ketone is via conjugate addition of a dialkylcuprate reagent to an , -unsaturated ketone. ( e ) The compound to be prepared is the mixed aldol condensation product of 3-pentanone and benzaldehyde. The desired reaction sequence is 18.25 ( a ) The fi rst step is an halogenation of a ketone. This is customarily accomplished under condi- tions of acid catalysis. In the second step the carbonyl group of the -bromo ketone is reduced to a secondary alcohol. As actually carried out, sodium borohydride in water was used to achieve this transformation. (CH 3 ) 3 CCCH 2 Br O 1-Bromo-3,3-dimethyl-2-butanone (CH 3 ) 3 CCHCH 2 Br OH 1-Bromo-3,3-dimethyl-2-butanol (54%)
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Unformatted text preview: 4 H 2 O (CH 3 ) 3 CCCH 3 O 3,3-Dimethyl-2-butanone (CH 3 ) 3 CCCH 2 Br O 1-Bromo-3,3-dimethyl-2-butanone (58%) Br 2 H 1 CH 3 CCCH 2 CH 3 O C 6 H 5 CH 2-Methyl-1-phenyl-1-penten-3-one CH 3 CHCCH 2 CH 3 O C 6 H 5 CHOH Aldol addition product (not isolated; dehydration occurs under conditions of its formation) CH 3 CH 2 CCH 2 CH 3 O 3-Pentanone CH 3 CHCCH 2 CH 3 O Enolate of 3-pentanone HO 2 2 H 2 O C 6 H 5 CH 2 O C 6 H 5 CH O 1 CH 3 CHCCH 2 CH 3 CH 3 CCCH 2 CH 3 O C 6 H 5 CH 2-Methyl-1-phenyl-1-penten-3-one O 2 1-Penten-3-one [prepared as described in part ( b )] H 2 C CHCCH 2 CH 3 O 3-Hexanone O CH 3 CH 2 CH 2 CCH 2 CH 3 1. LiCu(CH 3 ) 2 2. H 2 O CH 3 CH 2 CH 2 CCH 2 CH 3 O O H 2 C CH 3 1 CHCCH 2 CH 3 2 b ENOLS AND ENOLATES 483...
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