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Carbonyl Compounds
AQA A Level Chemistry
Question | Answer |
---|---|
Which homologous series are considered "carbonyls"? | Aldehydes and ketones |
How can aldehydes and ketones be distinguished? | Fehling's solution or Tollen's reagent |
Draw a named carbonyl compound | |
Name a given carbonyl compound | |
How can aldehydes be formed? | Oxidation of a primary alcohol or reduction of a carboxylic acid |
How can ketones be formed? | Oxidation of a secondary alcohol |
Name the reagent and conditions for the reduction of carbonyl compounds | NaBH₄, aqueous |
How is the reductant represented in equations? | [H] |
What is the name of the mechanism for the reduction of carbonyls? | Nucleophilic addition |
Draw a mechanism for the reduction of a given carbonyl | |
Under which conditions are hydroxynitriles formed? | Addition of KCN followed by dilute acid to a carbonyl |
Draw a mechanism for the reaction of KCN with a given carbonyl | |
Explain how nucleophilic additions of carbonyls with KCN can result in a racemic mixture | Carbonyl is planar, KCN can attack from above or below with equal probability, 50:50 chance of forming each enantiomer |
Which hazards are associated with using KCN? | It is highly toxic |
Write an overall equation for the formation of a given hydroxynitrile with HCN | |
Why do aldehydes and ketones have higher boiling points than alkanes with the same number of carbon atoms? | The carbonyl bond means that there are permanent dipole dipole interactions between the molecules which are not present between the alkane molecule |
Why do aldehydes and ketones have lower boiling points than alcohols with the same number of carbon atoms? | There is hydrogen bonding between the alcohol molecules. This is a stronger intermolecular force than the dipole dipole attractions between the carbonyl compounds |
Why are small carbonyl compounds miscible in water? | The formation of hydrogen bonds from the water to the oxygen of the carbonyl compound. |
Why is the carbonyl bond polar? | The difference in electronegativity between carbon and oxygen |
What is the difference in structure between an aldehyde and ketone? | "ALDEHYDES have at least one H attached to the carbonyl group. Ketones have two carbons attached to the carbonyl group. |
Name this molecule CH3CH2COCH2CH3 | "pentan-3-one |
"Draw the structural formulae of this molecule phenylethanone | |
Explain in detail the technique recrystallization. | Dissolve the solute in the minimum volume of hot solvent, cool the solution to allow the crystals to form, remove the crystals by vacuum filtration, dry the resulting crystals in an oven. |
What measurement of a substance is the best measure of its purity | Melting Point |
Give the name of a suitable reducing agent for the reduction of a carbonyl compound to an alcohol. | Lithium Tetrahyridoaluminate, Sodium Tetrahydridoborate |
What is the nucleophile produced by NaBH4 and LiAlH4? | H- |
"Draw the mechanism for the reduction of butanal to butanol | " |
"Why is Propanoyl chloride more easily reduced by Hydride ions than Propanal. | Chlorine are more electronegative than carbon, Atoms attached to the carbonyl carbon that are more electronegative than carbon make it more delta positive More delta positive the carbonyl carbon is the more reactive it is, towards nucleophiles such as H-, |
What are the reagents for the nucleophilic addition of cyanide ions to aldehydes or ketone? | "hydrogen cyanide - HCN in the presence of KCN |
What are the conditions for the nucleophilic addition of cyanide ions to aldehydes or ketone? | "reflux in alkaline solution |
What is the structural formula of the product of the reaction of these two molecules CH3CHO + HCN | "CH3CH(OH)CN |
Draw out the mechanism for the reaction between these two molecules CH3CHO + HCN |