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What reagents are needed to halogenate an enol (acidic)
X2 and AcOH
What reagents are needed for the haloform reaction
I2 and NaOH
Give examples of weak bases
K2CO3 Et3N NaOEt
What is the PKaH of K2CO3
12
What is the PKaH of Et3N
10
What is the PKaH of NaOEt
30
What affect does weak bases have on enolate formation
if the PKa of substrate and the PKaH of base are close then the reaction is reversible
Give examples of strong nucleophilic bases
NaNH2 nBuLi tBuLi
What is the PKaH NaNH2
35
What is the PKaH of nBuLi
50
What is the PKaH of tBuLi
55
Describe the problem with strong nucleophilic bases
Strong nucleophilic base will do nucleophilic attack reactions instead of deprotonation reactions so are not typically used in making enolates
Give examples of strong non- nucleophilic bases
NaH LDA LiHMDS
What is the PKaH of NaH
35
What is the PKaH of LDA
35
What is the pKaH of LiHMDS
35
What base do we need to use for the alkylation of enolates
Base strong enough to deprotonation. This means it needs to have a suitable PKaH, the PKaH need to be equal or higher than the proton being removed
What are the crossed Aldol condensation rules
1) One partner must be capable of enolisation - nucleophile 2) the other must not be capable of enolisation and must be more electrophilic than the enolisable partner
What must something a molecule have in order to undergo enolisation
Alpha protons
Describe the kinetic enolates
Kinetic enolates are those which react faster because the end at which the base acts is less hindered
Describe thermodynamic enolates
Thermodynamic enolates are more stable because the double bond is more substituted. Forms slower
How do we make enamines
Enamines are formed by the reaction of secondary amines with aldehydes or ketones Requires catalytic acid and water needs to be removed
Give an example of a catalytic acid which can be used to make enamines
Para-toluene sulphonic acid
What apparatus can be used to remove water when making enamines
Dean-stark apparatus