Ch19 - 440 S olutions Chapter 19: Enolate Anions and...

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440 Solutions Chapter 19: Enolate Anions and Eniunin.es CHAPTER 19 Solutions to the Problems Problem 19 1 Draw the product of the base-catalyzed aldol reaction of each compound. (a) Phenylacetaldehyde (b) Cyclopentanone Two new chiral centers are created in each reaction, So racemic mixtures of stereoisomers will be produced. Problem 192 Draw the product of dehydration of each aldol product in Problem 19.1. ° ° OH I * II II C6HsCH2~HTHCH C6H s C.H 2 CH=?CH + H 2 0 C 6 H s C 6 H s Problem 19.3 Draw the product of the base-catalyzed crossed aldol reaction between benzaldehyde and 3-pentanone and the product formed by its dehydration. ° < )--~H + 0- 0. dehydration' II ~ II' ----_. 'I ~ CH=CCCH 2 CH 3 . I - CH 3 Problem 194 Show the product of Claisen condensation of ethyl 3-methylbutanoate in the presence of sodium ethoxide followed by acidification with aqueous HCI. .. to Chapter 19: Enolate Anions and Ena~ines Solutions 441 Problem 19.5 Complete the equation for this crossed Claisen condensation. 1-. B6Na+ OB I + 2. H 2 0, HCI (excess) One new chiral center is created in the reactipn, soa racemic mixture will be produced. . Problem 19.6 Show how to convert benzoic acid to 3-methyl-I-phenyl-l-butanone (isobutyl phenyl ketone) by the following synthetic strategies, each of which uses a different type of reaction to form the new carbon-carbon bond to the carbonyl group of benzoic acid. ~COOH V ? Benzoic acid 3-Methyl-l-phenyl-l-butanone (a) A lithiumdiorganocopper (Gilman) reagent Treatment of benzoic acid with thionyl chloride gives benzoyl chloride. Treatment of benzoyl chloride with lithium diisobutylcopper followed by hydrolysis in aqueous acid gives the desired product. ' II cr ° CCI ~COOH . V I 1) [(CH3hCHCH2bCuLi •. .SOCI 2 ~ 2) H 2 0, HCI (b) A Claisell'condensation A crossed Claisen condensation of ethyl benzoate and ethyl 3-methylbutanoate gives a ~-ketoester. Saponification of the ester followed by acidification gives the ~-ketoacid. Heating causes decarboxylation and gives the desired product. . to 2) H 2 0, HCI (Claisen condensation) heat - Problem 19.7 Following are structural formulas for two enamines. Draw structural formulas for the secondary amine and carbon,)'1 compound fiom which each is derived. (al·vr:Q ~O+H20 I H
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,Solutions Chapter 19: EnolateAnions and Enamines 442 H 3 C" /CH 3 - 6 N H 3 C, /Ctl 3 H+ (b) + N + H 2 O I H PFOblem 19,8 Write a mechanism for the hydrolysis of the following iminium chloride in aqueous Hel: cj 0:. .. + Hat H,O---'--- (racemic) The positively charged iminium ion is attacked by water acting as a nucleophile. A proton is transferred to the nitrogen, followed by departure of the amine and formation of the carbon-oxygen double bond. The reaction is completed with a proton transfer step to produce the product ketone and protonated morpholine. Under the acidic conditions in this reaction, an enamine is not formed, so hydrolysis predominates. Step 1:
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Ch19 - 440 S olutions Chapter 19: Enolate Anions and...

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