Organic 20: Enols and Enolates

Question 1

Enols

Answer 1

intermediates in the hydration of alkynes

Question 2

Enolates

Answer 2

conjugate bases of enols; major contributor (of the resonance structures) is the structures with the negative charge on oxygen

Question 3

Lithium diisopropylamide (LDA)

Answer 3

very strong base (comparable to sodium amide); too sterically hindered to undergo competing nucleophilic addition to the carbonyl group

Question 4

Aldol addition

Answer 4

nucleophilic addition of an aldehyde or ketone enolate to the carbonyl group of an aldehyde or a ketone; the most typical case involves 2 molecules of an aldehyde, and is usually catalyzed by bases

Question 5

Aldol condensations

Answer 5

reactions in which 2 molecules of an aldehyde combine to form an alpha, beta-unsaturated aldehyde and a molecule of water

Question 6

Claisen-Schmidt Condensations

Answer 6

mixed aldol condensations in which a ketone reacts with an aromatic aldehyde

Question 7

Directed aldol additions

Answer 7

way to ensure only 1 enolate is present in a reaction by using LDA as the base to remove the alpha proton

Question 8

Malonic ether synthesis

Answer 8

method for preparing carboxylic acids; overall transformation is RX –> alpha-alkylated derivative of acetic acid

Question 9

Asymmetric synthesis

Answer 9

stereoselective introduction of a chirality center in a reactant in which the stereoisometric products are formed in unequal amounts

Question 10

Tautomers

Answer 10

isomers that differ by the placement of an atom or group; keto and enol forms is an example

Question 11

Haloform reaction

Answer 11

formation of CHX3 brought about by cleavage of a methyl ketone on treatment with Br2, CL2, or I2 in aqueous base