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Medicinal Chemistry > Carbonyls > Flashcards

Carbonyls Flashcards

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1
Q

What undergoes nucleophilic addition reactions?

A

Aldehydes + ketones

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2
Q

What undergoes nucleophilic addition elimination reactions?

A

Carboxylic acid derivatives

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3
Q

What does elonate ions + reactions require?

A

Alpha hydrogen

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4
Q

What is the carbon in carbonyl?

A

Trigonal planar sp2

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5
Q

What is the O in carbonyl?

A

Trigonal planar sp2

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6
Q

Describe C-O?

A

Sigma bond between sp2 orbitals on C + O

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7
Q

Where do all sigma bonds lie?

A

In same plane - 120 degrees part

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8
Q

Describe C-O pi bond

A

Between parallel p orbitals on C + O

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9
Q

Compare C=O to C=C

A

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

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10
Q

What is Lipinski’s Rule of 5 for?

A

Orally absorbed drugs

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11
Q

What are Lipinski’s Rule of 5?

A

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

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12
Q

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

A

Poorly absorbed

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13
Q

How may carbonyl group intercact with binding sites?

A

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

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14
Q

Why does reduction aldehyde/ketone give alcohol?

A

Weakens H-bond interactions

Weakens dipole-dipole moment interactions

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15
Q

Is COOH a WA?

A

YES

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16
Q

Why is COOH a WA?

A

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

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17
Q

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

A

Resonance stabilisation of carboxylate anion

Carboxylate ion = conjugate base of carboxylic acid

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18
Q

When are resonance structure possible?

A

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

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19
Q

What are resonance structures?

A

Imaginary representing location of e-

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20
Q

What must resonance structures have?

A

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

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21
Q

Does hybridisation change resonance structures?

A

NO

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22
Q

In alkoxide ion where is the negative charge?

A

Localised on O

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23
Q

In carboxylate ion where is the negative charge?

A

Delocalised over 2 equivalent O atoms, giving resonance stability

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24
Q

How do you purify COOH?

A 
RCOOH
Add dilute NaOH
RCOONa
Add HCl (aq)
Add fresh ether 
RCOOH
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25
Q

What does the group bonded to acyl carbon determine?

A

Class of compound

26
Q

Carbonyl group + OH?

A

Carboxylic acid

27
Q

Carbonyl group + Cl?

A

Acid chloride

28
Q

Carbonyl group + OC(O)R?

A

Acid anhydride

29
Q

Carbonyl group + OR’?

A

Ester

30
Q

Carbonyl group + NR2?

A

Amide

31
Q

What is the reactivity for added group?

A 
OH
Cl
OC(O)R    DECREASING REACTIVITY 
OR'
NR2
32
Q

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

A

By acid/base hydrolysis

33
Q

What are thioesters + acyl phosphates?

A

Biological COOH derivatives

34
Q

Why is carbonyl group polar?

A

O more electronegative than C

35
Q

Why is carbonyl carbon electrophilic?

A

Susceptible to nucleophilic attack

36
Q

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

A

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

37
Q

What undergoes nucleophilic addition?

A

Aldehydes + ketones

38
Q

For weak nucleophiles in nucleophilic addition what is required?

A

Carbonyl group requires activation = acid catalyst

39
Q

What are aldehydes/ketones converted to in nucleophilic addition?

A

Alcohols

40
Q

How is nucleophilic addition reversed in basic conditions?

A

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

41
Q

How is nucleophilic addition reversed in acidic conditions?

A

Protonation of original nucleophilic species

Loss of leaving group + formation of protonated carbonyl

42
Q

What can nucleophiles be?

A

Charged OR neutral

43
Q

What are some negative nucleophiles?

A 
OH- hydroxide
H- hydride
R3C- carbanion 
RO- alkoxide 
CN- cyanide
44
Q

What are some neutral nucleophiles?

A

H2O water
ROH alcohol
NH3 ammonia
RNH2 amine

45
Q

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

A

BOTH

46
Q

What does aldehyde have?

A

Less steric crowding

47
Q

What does ketone have?

A

More steric crowding

48
Q

What happens in reactions at C=O?

A

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

49
Q

Why are aldehydes more reactive than ketones?

A

1 large substituent group bonded to C=O

Ketone = 2

50
Q

Why are alkyl groups e- releasing?

A

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

51
Q

Which is more stable primary or secondary carbocation?

A

Secondary

52
Q

What is more stable aldehyde or ketone?

A

Ketone

= More stabilisation of delta positive on C

53
Q

How is a cyanohydrin formed?

A

HCN adds to aldehyde + ketone

54
Q

What is HCN?

A

Toxic gas

55
Q

Because HCN is toxic what happens?

A

HCN usually generated in situ

NaCN (excess) + acid

56
Q

What is the equation for HCN?

A

HCN + H2O —-> CN- + H3O+

CN- + H3O+ —-> HCN + H2O

57
Q

What is formed when cyanohydrin hydrolysis?

A

Carboxylic acid

58
Q

What is formed when cyanohydrin reduction?

A

Amine

59
Q

What aldehyde reduced to?

A

Primary alcohol

60
Q

What ketone reduced to?

A

Secondary alcohol

61
Q

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

A

NaBH4 = sodium borohydride
OR
LiAlH4 = lithium aluminium hydride

62
Q

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

A

4

Medicinal Chemistry (19 decks)

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