Aldehydes and Ketones II: Enolates

carbon adjacent to carbonyl carbon

hydrogen attached to α-carbon; relatively acidic and can be removed by a strong base

effect of oxygen of carbonyl that weakens the C-H bonds on α-carbons

deprotonation of an α-carbon, forming a carbanion:

less reactive toward nucleophiles because of α-carbon destabilization and steric hindrance

presence crowds transition step and increases its energy; also donates electron density to carbanion, making it less stable

traditional form aldehydes and ketones exist in (C=O)

less common form aldehydes and ketones exist in; ene + ol = double bond + hydroxyl group

isomers that can be interconnected by moving a hydrogen and a double bond; keto and enol forms are ____ of one another

deprotonated form of enol; they are good nucleophiles

enolization (tautomerization):

reaction where an enolate attacks an α, β-unsaturated carbonyl, creating a bond

step of Michael addition- base deprotonates α-carbon (making it a good nucleophile):

step of Michael addition- carbanion attacks the double bond (resulting in Michael addition):

enolate favored by fast, irreversible reactions at lower temperatures with strong, sterically hindered bases

enolate favored by slower, reversible reactions at higher temperatures with weaker, smaller bases

kinetic and thermodynamic enolate:

tautomers of imines; imines are thermodynamically favored, so are the more common tautomer

enamination (tautomerization):

reaction where the aldehyde or ketone acts as both nucleophile and electrophile, resulting in formation of a C-C bond in a new ____ molecule

aldol condensation: contains both aldehyde and alcohol functional groups

aldol condensation: the enolate formed from deprotonation of the α-carbon acts as the ____

aldol condensation: the aldehyde or ketone in form of the keto tautomer acts as the ____

aldol condensation: first step; two molecules come together forming the aldol