Chapter 19- Aldehydes and Ketones Flashcards
What is the suffix for ketones?
-one
What is the suffix for aldehydes?
-al
What is the IR signal for a ketone?
~1715 cm -1
What is the IR signal for an Aldehyde?
A weak 2700-2800 C-H stretch
How do you turn a Primary ROH into an aldehyde?
PCC, CH2Cl2
or
DMP, CH2Cl2
or
1) DMSO (COCl2)
2) Et2
How do you create an aldehyde from an RH=RH (alkene)?
Ozonolysis-
1) O3
2) DMS
How do you create a ketone from an alkene?
Ozonolysis-
1) O3
2) DMS
How do you create an aldehyde from an alkyne?
Hydroboration oxidation-
1) R2B-H
2)H202, NaOH
How do you create a ketone from an alkyne?
Acid Hydration-
H2SO4, H2O
HgSO4
Name this molecule
Formaldehyde
Name this molecule
Acetaldehyde
Name this molecule
Benzaldehyde
How do you make a ketone from a secondary alcohol?
Oxidation reaction with
Na2Cr2O7
H2SO4, H2O
How do you synthesize a ketone attached to a benzene ring from a benzene ring?
Friedel-Crafts acylation
How do you synthesize an aldehyde attached to a benzene ring from a benzene ring?
Gattermann-Koch formylation
CO, HCl
AlCl3/CuCl
Describe the carbon of the carbonyl within the aldehyde/ketone
-Electrophilic
-Has a delta plus from Induction
-Attacked by nucleophiles
match the strength of the nucleophiles to the type to conditions and if it is reversible or not
Weak Nucleophile, Acid Conditions, Reversible
Strong nucleophile, base conditions, irreversible.
What is more reactive? Aldehydes or Ketones?
why?
Aldehydes are more reactive:
1. Less sterically hindered
2. Only has one electron donating alkyl group, a delta plus on the carbonyl carbon
How do you turn a ketone into a Secondary Alcohol? (Hydride strong nucleophile reagent)
1)LAH
2)H2O
or
NaBH4, MeOH
form enantiomers
What is another way to make an alcohol from a ketone/aldehyde with a strong carbon nucleophile?
Grignard reagent
How do you make a cyanohydrin from an aldehyde/ketone?
KCN, HCN
In the presence of water, what is a ketone/aldehyde in equilibrium with?
Its hydrate
How do you synthesize an acetal?
An aldehyde/ketone, 2 moles of ROH, acid catalyzed.
What is an Acetal?
Tetrahedral carbon with two OR groups on it
What are two acid catalysts used for acetal formation?
TsOH or Sulfuric Acid
Are acetals favored at equilibrium for most aldehydes?
Yes
Are acetals favored at equilibrium for most ketones?
No
In acetal formation, under acidic conditions, what charge should the reaction species have?
A neutral or +1 formal charge
In acetal formation, what is synthesized when a Diol is used
A cyclic acetal
How can you control the reversibility of acetal formation
Add/Take away water
remove water: favor acetal
Add water: favor ketone/aldehyde
What do you synthesize when an acetal undergoes hydrolysis?
An aldehyde/ketone
Will an acetal react under base conditions?
No
No reaction occurs
What is a hemiacetal?
The intermediate formed in the conversion of a ketone/aldehyde to an acetal. These are hard to isolate, but cyclic hemiacetals can be isolated
When is a cyclic hemiacetal possible?
When a compound contains both a carbonyl and a hydroxy group
What is created when an aldehyde/ketone is reacted with two moles of thiol
(RSH)?
A thioacetal
Works the same way as alcohols, even the cyclic ones
How can a thioacetal be converted to an alkane?
Raney nickel (RaNi)
What is synthesized when an aldehyde/ketone reacts with a primary amine under acidic conditions?
an Imine
C=N
What does the pH have to be for the formation of an imine?
~4-5
Too low: all amines are pronated
Too high: not enough acid to catalyze reaction
What is the product?
Cyclohexanone imine + water
What is the product?
What is the product?
What is synthesized when an aldehyde/ketone reacts with a secondary amine under acidic conditions?
An enamine
What happens when an imine/enamine is reacted with water?
It undergoes hydrolysis and reverts back into an aldehyde/ketone
Describe the steps of the Wolff-Kishner Reduction
It converts a ketone to an alkane
Form hydrazone, then heat with strong base like KOH or potassium tert-butoxide.
- Use a high-boiling solvent: ethylene glycol, diethylene glycol, or DMSO.
- A molecule of nitrogen is lost in the last steps of the reaction
What do you get when you react an aldehyde/ketone with a phosphorus ylide (RCPPh3)?
An alkene (Wittig reaction)
How does one synthesize a Wittig reagent?
Start with an alkyl halide
1.PPh3
2. BuLi (CH3CH2CH2CH2 Li)
What type of alkene is favored when the Wittig reagent is derived from a simple alkyl halide?
Z alkene (same side)
What type of alkene is favored when the Wittig reagent contains an electron withdrawing group or a sterically bulky group?
E alkene (different sides)
