CHEM 302: Detailed Study of Chapter 22 - Isomers and Enolate Chemistry

enolate

carbanion that forms with alpha carbon of ketone/aldehyde

nucleophile

enolates act as _____

alpha

H

when forming enolates, the _____ carbon must have at least one ____

enolate

keto

the ____ form of an enolate has the double bond on the O and the lone pair on the C

enol

the _____ form of an enolate has the double bond on the C and the lone pair on the O

keto

the _____ form of the enolate is the reactive species

carbonyl

what is the electrophile that enolates attack

yes

does the addition of enolates to electrophiles require acid workup

no enolyzable H atoms

what is the requirement to be the electrophil carbonyl in enolate reactions

done

practice enolate addition to electrophiles

aldol condensation

if there is an alpha carbon what reaction will occur

aldol condensation

forms conjugated system

why can OH- act as a leaving group in aldol condensation

alpha-beta unsaturated carbonyl

aldol condensation forms what kind of product

aldol

what type of molecule is the reagent

aldol + base --> alpha beta unsaturated carbonyl + water

summary of aldol condensation reaction

keto

right form

enol

left form

enolate

constitutional isomers

the keto and enol forms are ________ in equilibrium

base

acid

keto enol tautomerization can either be ____ or ____ catalyzed

abstract H from alpha C

resonance

deprotonate water to enol

summary of base catalyzed keto enol tautomerization

protonate O

resonance

abstract H from alpha C to enol

summary of acid catalyzed keto enol tautomerization

20

pKa of the alpha C hydrogen of ketones

NaOH

LDA

two bases used to deprotonate ketones to enolates

LDA

base that deprotonates to enolates quantitatively

33

pKa of LDA

lithium diisopropyl amine

what does LDA stand for

LDA

sterically hindered

quality of LDA

NaOH

base that deprotonates a few % at a time as equilibrium is shifted as products react

reagents

helpers

enolates can either be ____ or _____ in SN2 reactions

cyclohexanone

what is a good symmetrical reagent used in many enolate reactions

ketone + base --> enolate + 1 alkyl halide --> ketone + alkyl group on alpha C

summary of enolates in SN2 reactions

enamine

ketone + 2 amine --> enamine

summary of enamine formation

enamine

nitrogen equivalent of keto/enols

H3O+ heat

how to hydrolyze enamine back to amine and ketone

enamine + base --> deprotonated enamine + alkyl bromide --> + H3O+ --> alkylated ketone

summary of enamine as helper in SN2 with alkyl bromide

alkylation

final result of enamine/enolate reactions

enamine + base --> deprotonated enamine + acid chloride --> + H3O+ --> beta keto ketone

summary of enamine as helper in SN2 with acid chloride

alkyl bromide

using _____ with enamine forms alkylated ketone

acid chloride

using ____ with enamine forms beta ketoketone

beta keto ketone

9

pKa of the H on the alpha carbon of a beta keto ketone

H3O+ heat

what reagents are needed to remove the enamine group and reform the ketone