Carbonyls

Question 1

What undergoes nucleophilic addition reactions?

Answer 1

Aldehydes + ketones

Question 2

What undergoes nucleophilic addition elimination reactions?

Answer 2

Carboxylic acid derivatives

Question 3

What does elonate ions + reactions require?

Answer 3

Alpha hydrogen

Question 4

What is the carbon in carbonyl?

Answer 4

Trigonal planar sp2

Question 5

What is the O in carbonyl?

Answer 5

Trigonal planar sp2

Question 6

Describe C-O?

Answer 6

Sigma bond between sp2 orbitals on C + O

Question 7

Where do all sigma bonds lie?

Answer 7

In same plane - 120 degrees part

Question 8

Describe C-O pi bond

Answer 8

Between parallel p orbitals on C + O

Question 9

Compare C=O to C=C

Answer 9

C=O shorter, stronger + more polar than C=C in alkenes

Question 10

What is Lipinski’s Rule of 5 for?

Answer 10

Orally absorbed drugs

Question 11

What are Lipinski’s Rule of 5?

Answer 11

Molecular weight <500
logP <5
H-bond donors <5
H-bond acceptors <10

Question 12

What happens to polar drugs that break Lipinski’s Rule of 5?

Answer 12

Poorly absorbed

Question 13

How may carbonyl group intercact with binding sites?

Answer 13

H-bonding = carbonyl group H-bond acceptor
2 possible interactions (2 L.P on O)
Dipole-dipole interactions

Question 14

Why does reduction aldehyde/ketone give alcohol?

Answer 14

Weakens H-bond interactions

Weakens dipole-dipole moment interactions

Question 15

Is COOH a WA?

Answer 15

YES

Question 16

Why is COOH a WA?

Answer 16

Transfer H+ to H2O to give H3O+ + carboxylate anions RCO2-

Question 17

Why is there a greater acidity in carboxylic acids compared to alcohols?

Answer 17

Resonance stabilisation of carboxylate anion

Carboxylate ion = conjugate base of carboxylic acid

Question 18

When are resonance structure possible?

Answer 18

When more than one valid Lewis structure can be written for a molecule
OR
When two or more adjacent π-orbitals in same place

Question 19

What are resonance structures?

Answer 19

Imaginary representing location of e-

Question 20

What must resonance structures have?

Answer 20

Same no. of e-
Valid Lewis dot structures
Position of all atoms same in all resonance structures

Question 21

Does hybridisation change resonance structures?

Answer 21

NO

Question 22

In alkoxide ion where is the negative charge?

Answer 22

Localised on O

Question 23

In carboxylate ion where is the negative charge?

Answer 23

Delocalised over 2 equivalent O atoms, giving resonance stability

Question 24

How do you purify COOH?

Answer 24

RCOOH
Add dilute NaOH
RCOONa
Add HCl (aq)
Add fresh ether 
RCOOH

Question 25

What does the group bonded to acyl carbon determine?

Answer 25

Class of compound

Question 26

Carbonyl group + OH?

Answer 26

Carboxylic acid

Question 27

Carbonyl group + Cl?

Answer 27

Acid chloride

Question 28

Carbonyl group + OC(O)R?

Answer 28

Acid anhydride

Question 29

Carbonyl group + OR'?

Answer 29

Ester

Question 30

Carbonyl group + NR2?

Answer 30

Amide

Question 31

What is the reactivity for added group?

Answer 31

``` OH Cl OC(O)R DECREASING REACTIVITY OR' NR2 ```

Question 32

How can all added groups be converted back to parent carboxylic acid?

Answer 32

By acid/base hydrolysis

Question 33

What are thioesters + acyl phosphates?

Answer 33

Biological COOH derivatives

Question 34

Why is carbonyl group polar?

Answer 34

O more electronegative than C

Question 35

Why is carbonyl carbon electrophilic?

Answer 35

Susceptible to nucleophilic attack

Question 36

How can the reactivity of aldehydes, ketones, carboxylic acids, esters + amides be enhanced? And why?

Answer 36

By protonation of carbonyl O Carbonyl becomes more electrophilic = carbonyl more susceptible to nucleophilic attack

Question 37

What undergoes nucleophilic addition?

Answer 37

Aldehydes + ketones

Question 38

For weak nucleophiles in nucleophilic addition what is required?

Answer 38

Carbonyl group requires activation = acid catalyst

Question 39

What are aldehydes/ketones converted to in nucleophilic addition?

Answer 39

Alcohols

Question 40

How is nucleophilic addition reversed in basic conditions?

Answer 40

Baes removes H+ Carbonyl formation with loss of leaving group Nucleophile leaving group

Question 41

How is nucleophilic addition reversed in acidic conditions?

Answer 41

Protonation of original nucleophilic species | Loss of leaving group + formation of protonated carbonyl

Question 42

What can nucleophiles be?

Answer 42

Charged OR neutral

Question 43

What are some negative nucleophiles?

Answer 43

``` OH- hydroxide H- hydride R3C- carbanion RO- alkoxide CN- cyanide ```

Question 44

What are some neutral nucleophiles?

Answer 44

H2O water ROH alcohol NH3 ammonia RNH2 amine

Question 45

Can the nucleophile approach above or below C=O plane?

Answer 45

BOTH

Question 46

What does aldehyde have?

Answer 46

Less steric crowding

Question 47

What does ketone have?

Answer 47

More steric crowding

Question 48

What happens in reactions at C=O?

Answer 48

e- pair moves from C=O to electronegative O = tetrahedral alkoxide ion intermediate = new bonds formed = increased steric crowding

Question 49

Why are aldehydes more reactive than ketones?

Answer 49

1 large substituent group bonded to C=O | Ketone = 2

Question 50

Why are alkyl groups e- releasing?

Answer 50

Aldehyde has greater partial positive charge on carbonyl than ketone Aldehyde carbon more electrophilic than ketone carbon

Question 51

Which is more stable primary or secondary carbocation?

Answer 51

Secondary

Question 52

What is more stable aldehyde or ketone?

Answer 52

Ketone | = More stabilisation of delta positive on C

Question 53

How is a cyanohydrin formed?

Answer 53

HCN adds to aldehyde + ketone

Question 54

What is HCN?

Answer 54

Toxic gas

Question 55

Because HCN is toxic what happens?

Answer 55

HCN usually generated in situ | NaCN (excess) + acid

Question 56

What is the equation for HCN?

Answer 56

HCN + H2O ----> CN- + H3O+ | CN- + H3O+ ----> HCN + H2O

Question 57

What is formed when cyanohydrin hydrolysis?

Answer 57

Carboxylic acid

Question 58

What is formed when cyanohydrin reduction?

Answer 58

Amine

Question 59

What aldehyde reduced to?

Answer 59

Primary alcohol

Question 60

What ketone reduced to?

Answer 60

Secondary alcohol

Question 61

What is source of hydride ion in reduction of aldehydes/ketones?

Answer 61

NaBH4 = sodium borohydride OR LiAlH4 = lithium aluminium hydride

Question 62

How many moles of aldehyde/ketone can be reduced by 1 mole of NaBH4?

Answer 62

4