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CHY1101 - Organic chemistry > Nucleophillic addition to carbonyls > Flashcards

Nucleophillic addition to carbonyls Flashcards

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1
Q

What is the LUMO?

A

Lowest unoccupied molecular orbital

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2
Q

What is the HOMO?

A

Highest occupied molecular orbital

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3
Q

What is the key difference between c=o and c=c?

A

C=O is polarised

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4
Q

Why is there polarity in C=O

A

The oxygen is more electronegative than carbon which means it has a delta negative charge, leaving carbon with a delta positive

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5
Q

Why is nucleophilic attack able to happen?

A

The carbon is delta positive

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6
Q

What is the oxidation level?

A

The number of bonds from carbon to atoms other than C or H

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7
Q

What is found at the CO2 oxidation level?

A

Carbon dioxide
Carbonate
Tetrachloromethane

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8
Q

What is found at the carboxylic acid level?

A 
Carboxylic acids
Ester 
Acid chloride 
Amide 
Acid Anhydride
Orthoester
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9
Q

How many bonds to heteroatom does the CO2 oxidation level have?

A

4

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10
Q

How many bonds to heteroatom does the carboxylic acid level have?

A

3

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11
Q

What is found at the aldehyde oxidation level?

A 
Aldehyde 
Ketone 
Imine 
Hydrate 
Hemiacetal 
Acetal 
Enol
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12
Q

How many bonds to heteroatom does the aldehyde oxidation level have?

A

2

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13
Q

What is found at the alcohol oxidation level?

A 
Alcohol 
Ether 
Amine 
Alkyl chloride 
Alkene
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14
Q

How many bonds to heteroatoms does the alcohol oxidation level have?

A

1

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15
Q

What is a pi bond equivalent to?

A

one bond to a heteroatom

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16
Q

How many bonds to heteroatom does the alkane oxidation level have?

A

0

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17
Q

What must happen if you make a bond to carbon?

A

You have to break one

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18
Q

What are the two steps in the nucleophilic addition mechanism?

A
  1. Nucleophilic attack at the carbonyl carbon

2. Protonation of the oxygen anion forming an OH group

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19
Q

What are the two reasons for the carbonyl carbon being electrophillic ?

A
  1. Bond polarity

2. Orbitals

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20
Q

How do orbitals cause an electrophilic carbonyl carbon?

A

Electrons are transferred from the homo of the nucleophile into the lumo of the carbonyl compound

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21
Q

What two orbitals make up C=O?

A

C-O Pi bonding orbital

C-O Pi star anti bonding orbital

22
Q

What are the characteristics of the C-O pi bonding orbital?

A

Smaller on carbon

Larger on oxygen

23
Q

What are the characteristics of the C-O pi star anti bonding orbital?

A

Bigger on carbon

Smaller on oxygen

24
Q

What type of reaction is cyanohydrin formation?

A

Equilibrium

Reversible

25
Q

What is cyanohydrin formed from?

A

Ketone or aldehyde

26
Q

In cyanohydrin formation, where does the equilibrium lie?

A

Towards cyanohydrin

27
Q

Why does it turn into cyanohydrin more easily?

A

Steric effect
Larger R groups
Reduction in angle when converting sp2 to 2p3

28
Q

What does the hydride ion (H-) act as?

A

Base

Due to high charge density

29
Q

What is used as an alternative source of nucleophilic hydrogen ?

A

Sodium borohydride

30
Q

What is NaBH4 able to reduce?

A

Aldehydes and ketones

31
Q

What can NaBH4 not reduce?

A

Less reactive carbonyl compounds such as esters and amides

32
Q

What s a more powerful hydride donor than NaBH4?

A

LiAlH4

33
Q

What can’t you use LiAlH4 with and why?

A

Water or alcohols

It is much more reactive and causes a vigorous and violent reaction

34
Q

What type of solvents is LiAlH4 used in? Examples?

A

Aprotic

Diethylether / THF

35
Q

What type of bonds do organometallic compounds have?

A

Carbon - metal bond

36
Q

What are organomagnesium compounds called?

A

Grignard reagents

37
Q

What is formed when the organometallic reagents have reacted with the C=O?

A

Alcohol with the alkyl group found in the reagent

38
Q

What are the two steps of reagents used for organometallic reactions?

A
  1. Organometallic reagent eg. MeLi, Et2O

2. H2O

39
Q

When you add water to C=O of aldehydes and ketones, what is formed?

A

a 1,1-diol (hydrate)

40
Q

What does the position of equilibrium depends on?

A

Nature of the R groups

41
Q

What is the steric argument for the addition of water?

A

The larger the R groups, the less favourable the equilibrium

42
Q

What is formed when alcohols are added to aldehydes and ketones?

A

Hemiacetals

Acetals

43
Q

What is the role of the ethanol in the addition of water to aldehydes and ketones?

A

Shuttles the proton

44
Q

How do strong acids and bases increase the rate of formation of hydrates and hemiacetals?

A

Allowing proton transfer to occur before addition to C=O

45
Q

In acid catalysis of hydrate and hemiacetal formation, what catalyst can be used?

A

HCl

46
Q

In acid, why is it good to protonate to carbon first before attack of C=O?

A

It becomes more delta positive and becomes more electrophilic

47
Q

In base catalysis of hydrate and hemiacetal formation, what catalysis can be used/

A

NaOH

48
Q

What happens in base catalysis of hemiacetal and hydrate formation?

A

The nucleophile is deprotonated first and this makes the alcohol more nucleophilic

49
Q

Where is the lumo in the C=O?

A

Pi star

50
Q

Where is the homo in the C=O?

A

Pi

51
Q

What reagents/solvents are used to form an alcohol from a ketone/aldehyde?

A
  1. LiAlH4, THF

2. H2O

52
Q

What solvents do you use Grignard reagents with?

A

THF

H2O

CHY1101 - Organic chemistry (22 decks)

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