Nucleophillic addition to carbonyls

Question 1

What is the LUMO?

Answer 1

Lowest unoccupied molecular orbital

Question 2

What is the HOMO?

Answer 2

Highest occupied molecular orbital

Question 3

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

Answer 3

C=O is polarised

Question 4

Why is there polarity in C=O

Answer 4

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

Question 5

Why is nucleophilic attack able to happen?

Answer 5

The carbon is delta positive

Question 6

What is the oxidation level?

Answer 6

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

Question 7

What is found at the CO2 oxidation level?

Answer 7

Carbon dioxide
Carbonate
Tetrachloromethane

Question 8

What is found at the carboxylic acid level?

Answer 8

Carboxylic acids
Ester 
Acid chloride 
Amide 
Acid Anhydride
Orthoester

Question 9

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

Answer 9

4

Question 10

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

Answer 10

3

Question 11

What is found at the aldehyde oxidation level?

Answer 11

Aldehyde 
Ketone 
Imine 
Hydrate 
Hemiacetal 
Acetal 
Enol

Question 12

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

Answer 12

2

Question 13

What is found at the alcohol oxidation level?

Answer 13

Alcohol 
Ether 
Amine 
Alkyl chloride 
Alkene

Question 14

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

Answer 14

1

Question 15

What is a pi bond equivalent to?

Answer 15

one bond to a heteroatom

Question 16

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

Answer 16

0

Question 17

What must happen if you make a bond to carbon?

Answer 17

You have to break one

Question 18

What are the two steps in the nucleophilic addition mechanism?

Answer 18

1. Nucleophilic attack at the carbonyl carbon

2. Protonation of the oxygen anion forming an OH group

Question 19

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

Answer 19

1. Bond polarity

2. Orbitals

Question 20

How do orbitals cause an electrophilic carbonyl carbon?

Answer 20

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

Question 21

What two orbitals make up C=O?

Answer 21

C-O Pi bonding orbital

C-O Pi star anti bonding orbital

Question 22

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

Answer 22

Smaller on carbon

Larger on oxygen

Question 23

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

Answer 23

Bigger on carbon

Smaller on oxygen

Question 24

What type of reaction is cyanohydrin formation?

Answer 24

Equilibrium

Reversible

Question 25

What is cyanohydrin formed from?

Answer 25

Ketone or aldehyde

Question 26

In cyanohydrin formation, where does the equilibrium lie?

Answer 26

Towards cyanohydrin

Question 27

Why does it turn into cyanohydrin more easily?

Answer 27

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

Question 28

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

Answer 28

Base | Due to high charge density

Question 29

What is used as an alternative source of nucleophilic hydrogen ?

Answer 29

Sodium borohydride

Question 30

What is NaBH4 able to reduce?

Answer 30

Aldehydes and ketones

Question 31

What can NaBH4 not reduce?

Answer 31

Less reactive carbonyl compounds such as esters and amides

Question 32

What s a more powerful hydride donor than NaBH4?

Answer 32

LiAlH4

Question 33

What can't you use LiAlH4 with and why?

Answer 33

Water or alcohols | It is much more reactive and causes a vigorous and violent reaction

Question 34

What type of solvents is LiAlH4 used in? Examples?

Answer 34

Aprotic | Diethylether / THF

Question 35

What type of bonds do organometallic compounds have?

Answer 35

Carbon - metal bond

Question 36

What are organomagnesium compounds called?

Answer 36

Grignard reagents

Question 37

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

Answer 37

Alcohol with the alkyl group found in the reagent

Question 38

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

Answer 38

1. Organometallic reagent eg. MeLi, Et2O | 2. H2O

Question 39

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

Answer 39

a 1,1-diol (hydrate)

Question 40

What does the position of equilibrium depends on?

Answer 40

Nature of the R groups

Question 41

What is the steric argument for the addition of water?

Answer 41

The larger the R groups, the less favourable the equilibrium

Question 42

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

Answer 42

Hemiacetals | Acetals

Question 43

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

Answer 43

Shuttles the proton

Question 44

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

Answer 44

Allowing proton transfer to occur before addition to C=O

Question 45

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

Answer 45

HCl

Question 46

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

Answer 46

It becomes more delta positive and becomes more electrophilic

Question 47

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

Answer 47

NaOH

Question 48

What happens in base catalysis of hemiacetal and hydrate formation?

Answer 48

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

Question 49

Where is the lumo in the C=O?

Answer 49

Pi star

Question 50

Where is the homo in the C=O?

Answer 50

Pi

Question 51

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

Answer 51

1. LiAlH4, THF | 2. H2O

Question 52

What solvents do you use Grignard reagents with?

Answer 52

THF | H2O