C26 - Carbonyl compounds Flashcards
What functional group do aldehydes and ketones contain
Carbonyl
C=O
Where is the carbonyl functional group found in aldehydes
End of the chain
What is the common name for methanal
Formaldehyde
Where is the carbonyl functional group found in ketones
In the middle of the carbon chain
What are rules for naming aldehydes
Suffix -al
C atom always C1
Rules for naming ketones
Suffix -one
Needs to be numbered
Describe oxidation of aldehydes
Aldehyde + [O] —> butanoic acid
Refluxed
Acidified dichromate (VI) ions (Cr2O7 2- / H+)
-Usually as K2Cr2O7 acidified with dilute H2SO4
Displayed formula of oxidation of aldehydes
Displayed formula of oxidation of aldehydes
Don’t undergo oxidation
What colour change occurs when aldehydes are oxidised
Orange to green
How is the C=O double bond formed
Sigma bond between C and O
Pi bond above and below plane
Describe how the C=O bond affects the reactions of carbonyl compounds, in comparison to C=C in alkenes
C=C bond is non polar
C=O bond is polar
Why is C=O bond polar
O more electronegative than C
e- density in double bond lies closer to O atom
Creates slight positive and slight negative charge
What does the polarity of the C=O double bond cause in terms of reactivity
Attracted to nucleophiles
Undergoes nucleophilic substitution
Describe the reduction of an aldehyde
Aldehyde + [H] —> primary alcohol
Warmed with NaBH4/H2O (sodium tetrahydridoborate (III) in aq solution)
Displayed formula for reduction of an aldehyde
Describe reduction of a ketone
Ketone + [H] —> secondary alcohol
Warmed with NaBH4/H2O (Sodium tetrahydridoborate (III) in aq solution)
Displayed formula of reduction of a ketone
What is HCN and its properties
Hydrogen cyanide
-colourless
-poisonous
-liquid
-boils slightly above room temp (cannot be used safely in open lab)
What does the reaction of carbonyl compounds with HCN do to the carbon chain
Increases the length of the carbon chain
Propanal (aldehyde) + HCN
—> hydroxynitrile
(H2SO4/NaCN)
Hydroxynitrile contains OH group and nitrile group
What is the mechanism for nucleophilic addition to carbonyl compounds
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
Displayed formula of mechanism of reaction with NaBH4
Mechanism of reaction with NaCN/H+
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
Displayed formula for mechanism of reaction with NaCN/H+
