Chapter 19

Question 1

Describe the Aldol Condensation Reaction. What reagents are involved

Answer 1

A condensation reaction in organic chemistry in which an enol or an enolate ion reacts with a carbonyl compound to form a beta-hydroxyaldehyde or beta-hydroxyketone. Followed by dehydration to give a conjugated enone.

Generally he least hindered carbonyl will change to an enol/enolate.

Na2CO3 (aq) or NaOH or LDA. Strong base (LDA) steals least substituted alpha carbon

Question 2

Describe Claisen condensation reactions. What reagents are involved?

Answer 2

The addition of two esters or an ester and a acid halide. One Ester’s OR/X removes and that carbon is attached via a bond to the other Ester’s alpha carbon. The presence of an alpha hydrogen therefore determines which substrate binds to which.

NaOMe/Et or LDA (strong base) and H3O to protonate

Question 3

Aldehyde + Base

Answer 3

Aldol

Question 4

Aldol + NaBH4

Answer 4

1,3 diol (the =O changes to an -OH)

Question 5

Aldol + H+

Answer 5

a,b-unsaturated aldehyde

Removal of a water via the protonation of the -OH. Creates a double bond.

Question 6

Addition of H2/Ni and high pressure

Answer 6

Removes double bonds. Changes =O to -OH.

Question 7

Addition of H2, Pd-C

Answer 7

Removes double bonds

Question 8

Addition of LiAlH4

Answer 8

Changes =O to -OH

Question 9

Addition of a nucleophile to an a,b-Unsaturated Aldehyde or Ketone (Conjugated double bonds with one of the double bonds being part of an carbonyl).

Answer 9

Simple addition (the carbon of the carbonyl group, breaking the double bond): The addition of an H2O protonates the O-.

Conjugate addition (the outer carbon of the other double bond, breaking both double bonds and creating one in between): The addition of an H20 shifts the double bond and recreates the Carbonyl

Question 10

Addition of RMgBr to an a,b-Unsaturated Aldehyde or Ketone (Conjugated double bonds with one of the double bonds being part of an carbonyl).

Answer 10

Same rules as nucleophile. Simple addition is major product.

Question 11

Location of the addition of base to an a,b-Unsaturated Aldehyde or Ketone (Conjugated double bonds with one of the double bonds being part of an carbonyl).

Answer 11

Weak bases tend to give conjugate strong bases tend to do simple.

HCN and Amines are weak

Question 12

Describe Michael Addition.

Answer 12

The use of NaOMe (cat) MeOH or other reagent + another double bonded reagent to bond two compounds together. The double bond from one compound “expands” to connect to the other compound