Hall

Question 1

What reagents are needed to halogenate an enol (acidic)

Answer 1

X2 and AcOH

Question 2

What reagents are needed for the haloform reaction

Answer 2

I2 and NaOH

Question 3

Give examples of weak bases

Answer 3

K2CO3
Et3N
NaOEt

Question 4

What is the PKaH of K2CO3

Answer 4

12

Question 5

What is the PKaH of Et3N

Answer 5

10

Question 6

What is the PKaH of NaOEt

Answer 6

30

Question 7

What affect does weak bases have on enolate formation

Answer 7

if the PKa of substrate and the PKaH of base are close then the reaction is reversible

Question 8

Give examples of strong nucleophilic bases

Answer 8

NaNH2
nBuLi
tBuLi

Question 9

What is the PKaH NaNH2

Answer 9

35

Question 10

What is the PKaH of nBuLi

Answer 10

50

Question 11

What is the PKaH of tBuLi

Answer 11

55

Question 12

Describe the problem with strong nucleophilic bases

Answer 12

Strong nucleophilic base will do nucleophilic attack reactions instead of deprotonation reactions so are not typically used in making enolates

Question 13

Give examples of strong non- nucleophilic bases

Answer 13

NaH
LDA
LiHMDS

Question 14

What is the PKaH of NaH

Answer 14

35

Question 15

What is the PKaH of LDA

Answer 15

35

Question 16

What is the pKaH of LiHMDS

Answer 16

35

Question 17

What base do we need to use for the alkylation of enolates

Answer 17

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

Question 18

What are the crossed Aldol condensation rules

Answer 18

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

Question 19

What must something a molecule have in order to undergo enolisation

Answer 19

Alpha protons

Question 20

Describe the kinetic enolates

Answer 20

Kinetic enolates are those which react faster because the end at which the base acts is less hindered

Question 21

Describe thermodynamic enolates

Answer 21

Thermodynamic enolates are more stable because the double bond is more substituted. Forms slower

Question 22

How do we make enamines

Answer 22

Enamines are formed by the reaction of secondary amines with aldehydes or ketones
Requires catalytic acid and water needs to be removed

Question 23

Give an example of a catalytic acid which can be used to make enamines

Answer 23

Para-toluene sulphonic acid

Question 24

What apparatus can be used to remove water when making enamines

Answer 24

Dean-stark apparatus

Question 25

What doe enamines get hydrolyses to

Answer 25

Ketones

Question 26

What reagents do we used to hydrolyse enamines

Answer 26

H2O and an acid catalyst HCl

Question 27

What are the advantages to using enamines over enolates

Answer 27

Enamines are less nucleophile than enolates

Question 28

Why do we use enamines instead of enolates

Answer 28

enamines are not very nucleophilic so they prevent self condensation reactions

Question 29

What reagents do we need to make silicon enolate

Answer 29

TMSCl Et3N

Question 30

What is the dieckmann reaction

Answer 30

an intramolecular claisen condensation that cyclises a diester

Question 31

What is a claisen condensation

Answer 31

a reaction where two esters act in the presence of a strong base to produce a beta-keto ester

Question 32

What is the mannich reaction

Answer 32

3 component condensation reaction involving formaldehyde, and enolizable ketone and a secondary amine

Question 33

When is 1,2 addition favoured

Answer 33

kinetic conditions (low T) Reactive carbonyls (aldehydes and ketones) Hindered beta carbon Hard nucleophiles

Question 34

When is 1,4 addition favoured

Answer 34

thermodynamically conditions (high T) Unreactive carbonyls (esters and amides) Unhindered beta carbon Soft nucleophile

Question 35

In retrosynthesis what does disconnection mean

Answer 35

backwards synthetic step that involves breaking an imaginary bond

Question 36

What is a synthon

Answer 36

the theroretical chemicals

Question 37

What do we mean by synthetic equivalent

Answer 37

real chemicals/ act like synthons

Question 38

What do we mean by umpolung synthons

Answer 38

wrong polarity synthons

Question 39

What do we mean by latent synthons

Answer 39

correct polarity synthons

Question 40

What does any disconnection lead to

Answer 40

any disconnection leads to two sets of synthons