Test 2 Reactions

Question 1

keto-enol tautomerization

Answer 1

rapidly interconverting structural isomers that establish an equilibrium under acidic or basic conditions. Typically the keto form is favored unless the enol form can hydrogen bond.

Question 2

Acid-catalyzed halogenation of ketones

Answer 2

Question 3

Haloform Reaction

Answer 3

Alpha halogenation under basic conditions

Haloform is formed when you have a methyl ketone and react it with Br2 - you will get multiple halogenations and the haloform will be formed as a result of -CBr3 being kicked out as the leaving group and then protonated.

Question 4

Alpha Halogenation under Basic conditions

Answer 4

Can use NaOH or LDA to make the enolate. If using excess Br2, you can get multiple halogenations at the alpha carbon. If you want only 1 halogenation, use 1 molar equivalent of Br2 (or whatever halogen).

Question 5

NaOH vs. LDA

Answer 5

NaOH will deprotonate the more sterically hindered alpha carbon, resulting in the thermodynamic (more stable) enolate. LDA will deprotonate the less sterically hindered alpha carbon (b/c LDA is big and bulky) and results in the kinetic enolate.

Question 6

Alkylation of enolates

Answer 6

Use LDA or NaOH to form enolate and then alkylate using an alkyl halide.

Question 7

Aldol Addition

Answer 7

Ketone or aldehyde treated with NaOH and H2O results in a Beta-hydroxyaldehyde (or B-hydroxyketone)

Question 8

Retro Aldol

Answer 8

B-hydroxyaldehyde –> aldehyde

B-hydroxyketone –> ketone

Treat with NaOH and H2O

Question 9

Aldol Condensation

Answer 9

Aldol Addition + dehydration

Starting material: aldehyde or ketone

Treat with: NaOH, H2O, heat

Product: alpha, beta-unsaturated carbonyl

Question 10

Claisen Condensation

Answer 10

Ester treated with 1. NaOR (R group needs to be the same as the R group that’s attached to the ester oxygen in the starting compound).

2. H+ workup

Product: B-keto ester (1,3 dicarbonyl)

Note: you need 2 alpha hydrogens for this reaction to go to completion

Question 11

Dieckmann

Answer 11

Intramolecular Claisen Condensation

Question 12

Malonic Ester synthesis

Answer 12

1. Deprotonate diethyl malonate with -OEt
2. Add alkyl halide -> doubly stabilized enolate attacks, kicks out halogen leaving group, and takes the R group
3. H+ –> hydrolyzes both esters
4. Heat –> decarboxylation

Product: modified carboxylic acid (carboxylic acid with an R group)

Question 13

Acetoacetic Ester synthesis

Answer 13

Similar to malonic acid synthesis, except the product is a modified methyl ketone instead of carboxylic acid. (A modified acetone.)

1. Ethyl acetoacetate is treated with -OEt to form doubly stabilized enolate
2. Alkylate with alkyl halide
3. Hydrolize ester moiety
4. Heat –> decarboxylation

Question 14

Michael Additions

Answer 14

Characterized by addition at the Beta position of an alpha, Beta-unsaturated aldehyde/ketone (instead of at the carbonyl)

Question 15

Michael donors

Answer 15

A doubly stabilized enolate will react primarily at the Beta position (instead of attacking the carbonyl).

Question 16

Robinson Annulation

Answer 16

Michael Addition + Aldol condensation –> builds a new ring onto an existing ring

Question 17

Stork Enamine

Answer 17

Ketone –> 1,5 dicarbonyl

1. Ketone treated with secondary amine and acid –> enamine
2. Michael addition
3. Hydrolysis turns amine group back into carbonyl