Nucleophilic Addition Reactions of Ketones and Aldehydes

Question 1

Acetal Formation: Reactants

Answer 1

Ketone or Aldehyde +

H₃O⁺
——————->
2 eq. ROH

Question 2

ACIDIC Hemiacetal Formation: Reactants

Answer 2

Ketone or Aldehyde +

H₃O⁺
——————->
ROH

Question 3

BASIC Hemiacetal Formation: Reactants

Answer 3

Ketone or Aldehyde +

RO^-
——————->
ROH

(USES AN ALKOXIDE BASE, NOT OH-)

Question 4

Acetal Formation: Process

Answer 4

1) Acid protonates carbonyl oxygen

2) 1st ROH does Nu attack at the carbonyl carbon = neutralizing the OH grp on the carbon

3) (+) ROH grp transfers proton to neutral OH grp on the carbon = H₂O(+) grp

4) Electrons from OR grp push down to kick off water = DB forms to the now OR (+) group

5) 2nd ROH does Nu attack at the carbonyl carbon = neutralizing the OR grp

6) H₂O deprotonates the (+) ROH grp on the carbonyl carbon = H₃O⁺ reformed

7) Acetal has formed!

Question 5

Acetal Reversion to Ketone/Aldehyde: Reactants

Answer 5

Acetal +

H₃O⁺
——————->
H₂O

Question 6

Cyclic Acetal Formation: Reactants

Answer 6

Ketone/Aldehyde:

H₃O⁺
—————————————>
Terminal DIOL = HO-R-OH

Question 7

Protection + Unprotection of Ketone/Aldehyde: Reactants

Answer 7

Ketone/Aldehyde:

H₃O⁺
—————————> Cylic Acetal
DIOL = HO-R-OH

THEN

Cyclic Acetal +

H₃O⁺
——————->
H₂O

Question 8

Difference in reactants between GEMDIOL and ACETAL formation?

Answer 8

Ketone/ aldehyde +

H₃O⁺
——————-> Gemdiol
H₂O

H₃O⁺
——————-> Acetal
2 eq. ROH**

Question 9

What reduction rxns. do ketones/aldehydes undergo?

Answer 9

1) Ketone + Aldehyde reduction via NaBH₄ or LiAlH₄

2) Grignard Rxn. to make alcohols

3) Wolff-Kishner Rxn. to make ALKANE

Question 10

Wolff-Kishner Rxn: Reactants + Product

Answer 10

Ketone / aldehyde +

**H₂NNH_{2
——————->
KOH}

== ALKANE (removes =O; like removing head of a pimple)

Question 11

Wittig Reaction : Reactants

Answer 11

Ketone / aldehyde +

Alkene-PPH₃
—————————–>

Question 12

Wittig Reaction: “Process” (trick to getting product)

Answer 12

1) (-) charge on the carbon of the alkene OPPOSITE the PPH3 grp attacks the carbonyl carbon of ketone/ald.

2) Double bond forms between the carbonyl carbon and the carbon of the alkene (opposite PPH3)

3) Carbonyl oxygen dissociates and PPH3 dissociates!

4) ALKENE formed (Z isomer!!!)

Question 13

When doing wittig synthesis, how do you determine what fragment of an alkene will be the carbonyl reactant and what fragment will be the PPH3 compound?

Answer 13

1) By the degree of the fragment!

–> Side of the Double bond that is LESS substituted will become the PPH3 reactant (1 degree R is favored for PPH3)

2) By EWGs present!

–> Side of double bond without EWGs is preferred for the PPH3 reactant

Question 14

How is the ylide reactant made in the Wittig Rxn?

Answer 14

1) React PRIMARY alkyl halide with PPH3

2) React the alkyl-PPH3 with Bu-L- to form double bond with the PPH3

Question 15

What type of nitrogen compounds do ketones/aldehydes produce upon reacting with amines?