C26 - Carbonyl compounds

Question 1

What functional group do aldehydes and ketones contain

Answer 1

Carbonyl
C=O

Question 2

Where is the carbonyl functional group found in aldehydes

Answer 2

End of the chain

Question 3

What is the common name for methanal

Answer 3

Formaldehyde

Question 4

Where is the carbonyl functional group found in ketones

Answer 4

In the middle of the carbon chain

Question 5

What are rules for naming aldehydes

Answer 5

Suffix -al
C atom always C1

Question 6

Rules for naming ketones

Answer 6

Suffix -one
Needs to be numbered

Question 7

Describe oxidation of aldehydes

Answer 7

Aldehyde + [O] —> butanoic acid
Refluxed
Acidified dichromate (VI) ions (Cr2O7 2- / H+)
-Usually as K2Cr2O7 acidified with dilute H2SO4

Question 8

Displayed formula of oxidation of aldehydes

Answer 8

Question 9

Displayed formula of oxidation of aldehydes

Answer 9

Don’t undergo oxidation

Question 10

What colour change occurs when aldehydes are oxidised

Answer 10

Orange to green

Question 11

How is the C=O double bond formed

Answer 11

Sigma bond between C and O
Pi bond above and below plane

Question 12

Describe how the C=O bond affects the reactions of carbonyl compounds, in comparison to C=C in alkenes

Answer 12

C=C bond is non polar
C=O bond is polar

Question 13

Why is C=O bond polar

Answer 13

O more electronegative than C
e- density in double bond lies closer to O atom
Creates slight positive and slight negative charge

Question 14

What does the polarity of the C=O double bond cause in terms of reactivity

Answer 14

Attracted to nucleophiles
Undergoes nucleophilic substitution

Question 15

Describe the reduction of an aldehyde

Answer 15

Aldehyde + [H] —> primary alcohol
Warmed with NaBH4/H2O (sodium tetrahydridoborate (III) in aq solution)

Question 16

Displayed formula for reduction of an aldehyde

Answer 16

Question 17

Describe reduction of a ketone

Answer 17

Ketone + [H] —> secondary alcohol
Warmed with NaBH4/H2O (Sodium tetrahydridoborate (III) in aq solution)

Question 18

Displayed formula of reduction of a ketone

Answer 18

Question 19

What is HCN and its properties

Answer 19

Hydrogen cyanide
-colourless
-poisonous
-liquid
-boils slightly above room temp (cannot be used safely in open lab)

Question 20

What does the reaction of carbonyl compounds with HCN do to the carbon chain

Answer 20

Increases the length of the carbon chain

Question 21

Propanal (aldehyde) + HCN

Answer 21

—> hydroxynitrile
(H2SO4/NaCN)
Hydroxynitrile contains OH group and nitrile group

Question 22

What is the mechanism for nucleophilic addition to carbonyl compounds

Answer 22

1) lone pair of e- from hydride ion (H-) attracted and donated to delta+ C atom in C=O bond
2) Dative covalent bond formed between hydride ion and carbon atom
3) Pi bond in C=O double bond breaks by heterolytic fission forming negatively charged intermediate
4) O atoms of intermediate donates lone pair of electrons to H atom in water molecule, intermediate been protonated to form alcohol

Question 23

Displayed formula of mechanism of reaction with NaBH4

Answer 23

Question 24

Mechanism of reaction with NaCN/H+

Answer 24

1) Lone pair pair of electrons from cyanide ion (CN-) attracted and donated to delta+ C atom in C=O bond, forming dative covalent bond
2) Pi bond in C=O breaks by heterolytic fission forming negatively charged intermediate
3) Intermediate is protonated by donating lone pair of electrons- to a hydrogen ion forming product
4) Product is hydroxynitrile

Question 25

Displayed formula for mechanism of reaction with NaCN/H+

Answer 25