Chapter 7- Aldehydes and Ketones Flashcards
what does a basic solution do to a-hydrogens
a-hydrogens (very acidic, but less in ketones) will easily deprotonate in a basic solution
what stabilizes/ destabilizes organic anions
electron-withdrawing groups like oxygen stabilize organic ions.
electron-donating groups like alkyl groups destabilize organic ions.
list of strong bases
lithium diisopropyl amide (LDA) potassium hydride (KH)
Michael addition
carbanion attacks an a,B-unsaturated carbonyl compound- a molecule with a multiple bond between the a- and B-carbons next to a carbonyl.
kinetic and thermodynamic enolates
kinetically controlled product is formed more rapidly but is less stable. (double bond to less substituted carbon)
thermodynamically controlled product is formed more slowly, but is more stable and features the double bond being formed with the more substituted a-carbon.
when are kinetic products favored (kinetic enolate)
reactions that are:
- rapid
- irreversible
- lower temperatures
- strong, sterically hindered bases
when are thermodynamic products favored (thermodynamic enolate)
reactions that are:
- slow
- reversible
- higher temperatures
- weak, smaller bases
aldol condensation
an aldehyde or ketone acts both as an electrophile (keto form) and a nucleophile (enol or enolate form), and the end result is the formation of a carbon-carbon bond.
- enolate is more nucleophilic than enol b/c its negatively charged.
- aldol (molecule with both an aldehyde and an alcohol group)
what happens in a condensation reaction
two molecules are joined with the loss of a small molecule
retro-aldol reaction
reverse of an aldol condensation. aqueous base is added and heat is applied.
a bond is broken between the a- and B-carbons of a carbonyl, forming two aldehydes, two ketones, or one aldehyde and one ketone.
what happens when you treat an aldehyde or ketone with a strong base?
more nucleophilic and generates a carbanion.
