Ch. 7: Aldehydes and Ketones II Flashcards
where is an alpha carbon located in a molecule
adjacent to the carbonyl carbon
where are alpha hydrogens located in a molecule
attached to the alpha carbon
what is a carbanion
a molecule with a negatively charged carbon atom
enol
tautomer that has one form featuring a C=C bond and one form featuring and -OH bond
which enol tautomer is favored
the ketone
where does the double bond form on a kinetic enolate
between the carbonyl and the less substituted carbon
kinetic = fast but less stable…less substituted carbon = less steric hinderance = faster product
where does the double bond form on a thermodynamic enolate
between the carbonyl and the more substituted carbon
thermo = slow but more stable…more substituted carbon = more steric hinderance = slower product
when are kinetic enolates favored
- fast rxns
- irreversible rxns
- low temps
- strong, sterically hindered base
when are thermodynamic enolates favored
- slow rxns
- reversible rxns
- high tems
- weak, small bases
what occurs during a Michael addition rxn
a dicarbonyl is enolized
then acts as a nucleophile to attack an alpha, beta - unsaturated carbonyl compound
what occurs during step 1 aldol condensation rxn
aldehyde or ketone is enolized and reacts with itself
enolate form acts as a nucleophile, ketone from acts as an electrophile to form a carbon-carbon bond
what functional groups does an aldol contain
an aldehyde and an alcohol
what occurs during step 2 of an alcohol condensation rxn
strong base and high temps remove a water molecule (HO- and H-) forming an alpha, beta - unsaturated carbonyl compound
what occurs during a retro-aldol rxn
bonds between alpha and beta carbon of a carbonyl are broken
driven with heat and aqueous base
