Chapter #7 Flashcards
(22 cards)
Identify the alpha carbon
adjacent to the carbonyl carbon
why is it easy to deprotonate the alpha hydrogen
the oxygen in the carbonyl bond pulls electron density away from these C-H bonds which weakens them
why is an enolate formed via the loss of an alpha hydrogen so stable
resonance stabilization in the structure.
carbanion
a molecule with a negatively charged carbon atom
compare the acidity of the alpha hydrogen in ketone vs. aldehyde
more acidic in aldehyde because the ketone has extra alkyl groups to donate electron density which destabilizes the carbanion.
does nucleophilic attack of aldehydes or ketones have a higher energy intermediate?
ketones, more steric hindrance, requires more energy to accomplish successful reaction.
how does the enol form get its name
en- : double bond between carbons
-ol : alcohol
are there more keto or enol isomers in solution?
more keto
are tautomers resonance structures?
no, because they differ in their connectivity
what are some common strong bases?
KH, OH, LDA
Michael addition
carbanion formed via strong base attacks an alpha,beta-unsaturated carbonyl compound
alpha,beta-unsaturated carbonyl compound
multiple bond between the alpha and beta carbons
compare the thermodynamic and kinetic enolate formation
thermodynamic: more substituted carbon, more stable, slower, favored in reactions with higher temperatures, slow, reversible and weaker, smaller bases.
kinetic: less substituted carbon, less stable, faster, favored in reactions that are rapid, irreversible, at lower temperatures, and with a strong, sterically hindered base.
is the imine or enamine form more prominent in solution
imine
what is special about the aldol condensation reaction?
the carbonyl containing compound is acting as both the nucleophile and the electrophile.
aldol
contains both an aldehyde and alcohol functional group (named after the aldehyde due to priority)
describe steps 1 and 2 of aldol condensation
step 1: formation of the aldol
step 2: dehydration of water molecule
in retro aldol reaction, where does the bond breakage occur?
between the alpha and beta carbons of the carbonyl
what reagents are needed for the retro-aldol reaction?
aqueous base and heat
what describes the product of aldol condensaton
alpha beta unsaturated carbonyl
why is the keto form more stable than the enol form?
the keto form puts more electron density around the electronegative oxygen than the enol form.
how do you stop the aldol condensation reaction at the aldol rather than following through to the alpha beta unsaturated carbonyl?
add acid instead of base
