Carbonyl compounds Flashcards
What are the 2 types of carbonyls?
Ketones and aldehydes.
What is the carbonyl functional group?
C=O.
Where is the carbonyl functional group found in aldehydes?
At the end of a carbon chain, attached to one or two hydrogen atoms.
What is the structural formula and the suffix for aldehydes?
CHO, -al.
Where is the carbonyl functional group found in ketones?
Joined to two carbon atoms in the carbon chain.
What is the structural formula and the suffix for ketones?
CO, -one.
What is the equation for the oxidation of aldehydes?
Aldehyde + [O] = Carboxylic acid.
What are the conditions required in the oxidation of aldehydes?
Must be refluxed with acidified dichromate ions, CrO72-/H+ and dilute H2SO4.
Why don’t ketones undergo oxidation reactions?
Because they have a lack of reactivity and so resistant to oxidation.
Where does the reactivity of aldehydes and ketones come from?
The nature of the C=O double bond which is made up of a sigma and Pi bond.
What is the difference between a C=O bond and a C=C bond?
The C=C bond in alkenes is non-polar and the C=O bond in carbonyl compounds is polar.
Why is the C=O bond polar?
Because oxygen is more electronegative than carbon so the electron density in the double bond lies closer to the oxygen atom than to the carbon atom so the carbon end is slightly positive and the oxygen end is slightly negative.
What does this polarity of the C=O bond allow aldehydes and ketones to do?
React with some nucleophiles.
What is a nucleophile?
An electron pair donor as it is attracted and attacks the slightly positive carbon atom, it results in addition across the C=O double bond - NUCLEOPHILIC ADDITION.
What is another difference between carbonyl compounds and alkenes in terms of reactions?
Carbonyl compounds react with nucleophiles by nucleophilic addition but alkenes react with electrophiles by electrophilic addition.
What 2 things do carbonyl compounds react with?
NaBH4 and HCN.
What happens when NaBH4 is reacted with carbonyl compounds?
It is used as a reducing agent to reduce aldehydes and ketones to alcohols.
What is the equation for reacting ALDEHYDES with NaBH4?
Aldehyde + 2[H] = Primary alcohol
What is the equation for reacting KETONES with NaBH4?
Ketone + 2[H] = Secondary alcohol
What are the conditions when reacting carbonyl compounds with NaBH4?
Warmed with NaBH4 and water (goes on the arrow).
What is [H]?
A reducing agent.
How do carbonyl compounds react with HCN?
Hydrogen cyanide adds across the C=O bond of aldehydes and ketones.
What is used to mimic HCN and why can’t HCN be used in a laboratory?
Sodium cyanide and sulfuric acid (still potentially very hazardous) as HCN is a very poisonous liquid and boils slightly above room temperature.
Why is the reaction of carbonyl compounds with HCN useful/its main purpose?
It provides a mean of increasing the length of the carbon chain.
