What is the general structure of an aldehyde?
R–CHO with carbonyl carbon attached to at least one hydrogen.
What is the general structure of a ketone?
R–CO–R′ with carbonyl carbon attached to two carbon groups.
What is the chemical formula of the carbonyl group?
C=O.
Why is the carbonyl carbon electrophilic?
Because oxygen is more electronegative, making the carbonyl polar.
Why are aldehydes more reactive than ketones?
They have less steric hindrance and fewer electron-donating alkyl groups.
What is the product of oxidising primary alcohols?
Aldehydes
What can aldehydes be further oxidised into?
Carboxylic acids
How are aldehydes prepared by dehydrogenation?
From primary alcohols with copper at 573 K
Which reduction method prepares aldehydes from acid chlorides?
Rosenmund reduction
What sequence prepares aldehydes from nitriles?
Stephen reduction followed by hydrolysis
How are aldehydes prepared from alkenes?
Ozonolysis followed by zinc and water
How are ketones prepared by oxidation or dehydrogenation?
From secondary alcohols
Which reaction prepares ketones using acid chlorides and AlCl₃?
Friedel–Crafts acylation of benzene
What happens first in nucleophilic addition to a carbonyl group?
A nucleophile attacks the electrophilic carbonyl carbon.
What intermediate forms during nucleophilic addition to a carbonyl?
An alkoxide intermediate.
What is the final step in nucleophilic addition after alkoxide formation?
Protonation of the alkoxide to give the addition product.
What alcohol type results from Grignard reaction with methanal after hydrolysis?
A primary alcohol.
What alcohol type forms from Grignard reaction with aldehydes other than methanal?
A secondary alcohol.
What alcohol type forms from Grignard reaction with ketones after hydrolysis?
A tertiary alcohol.
What compound does hydrogen cyanide form with aldehydes or ketones?
Cyanohydrins.
What do sodium bisulfite and aldehydes or ketones form?
Bisulfite addition compounds.
What do alcohols form with aldehydes or ketones under acidic conditions?
Acetals from aldehydes and ketals from ketones.
Which reagents reduce aldehydes to primary alcohols?
Sodium borohydride, lithium aluminium hydride, or hydrogen with nickel.
What does Clemmensen reduction convert aldehydes and ketones into?
Hydrocarbons.
Which reagents are used in Clemmensen reduction?
Zn(Hg) and concentrated HCl.
What reagents are used in Wolff–Kishner reduction?
Hydrazine and KOH with heat.
What does Tollens’ reagent produce with aldehydes?
A silver mirror.
What color precipitate does Fehling’s solution give with aliphatic aldehydes?
Brick-red Cu₂O.
What is the typical Fehling’s test result with aromatic aldehydes?
Generally negative.
What compound does iodoform test produce from methyl ketones?
Yellow CHI₃.
What is required for aldol condensation to occur?
At least one α-hydrogen is required.
What product does aldol condensation initially form?
A β-hydroxy carbonyl compound.
What happens to the β-hydroxy carbonyl compound on heating?
It dehydrates.
When does the Cannizzaro reaction occur?
When aldehydes without α-hydrogen react with concentrated alkali.
What are the products of the Cannizzaro reaction?
One alcohol and one carboxylate.
What is the directing effect of –CHO and –COR groups in electrophilic aromatic substitution?
They are deactivating and meta-directing.
Which named reaction converts acid chlorides to aldehydes?
The Rosenmund reaction.
Which reaction converts nitriles to aldehydes?
The Stephen reaction.
What does Friedel–Crafts acylation convert benzene into?
An aryl ketone.
What is the product of the Cannizzaro reaction on aldehydes without α-hydrogen?
Alcohol plus carboxylate.
Why do aldehydes and ketones have higher boiling points than hydrocarbons?
Because of dipole–dipole forces.
Why do aldehydes and ketones have lower boiling points than alcohols?
They do not self hydrogen-bond.
How does hydrocarbon chain length affect aldehydes' and ketones' water solubility?
Solubility decreases as chain length increases.
What do ammonia derivatives form from aldehydes and ketones?
Oximes, hydrazones, phenylhydrazones, or semicarbazones.
What is lost when ammonia derivatives convert aldehydes or ketones into oximes or hydrazones?
Water.
What is a key feature of crossed aldol condensation?
Two different aldehydes or ketones may react.
How can selectivity be improved in crossed aldol condensation?
When one reactant lacks α-hydrogen.
What does the Etard reaction oxidise in toluene?
The methyl group.
Which reagent is used in the Etard reaction with toluene?
Chromyl chloride (CrO₂Cl₂).
What product results from the Etard reaction of toluene?
Benzaldehyde.
Why does benzaldehyde undergo the Cannizzaro reaction?
Because it has no α-hydrogen.
Test your knowledge with 20 questions on Aldehydes and Ketones.
1. Which structural feature identifies an aldehyde?
2. Which formula represents a ketone?
Review the complete course in the study sheet for Aldehydes and Ketones.
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