Primary alcohols can be oxidised to aldehydes.
Which statement shows the correct reagents and observations for this reaction?
| Reagent | Observation |
A | Acidified silver nitrate solution | White precipitate forms |
B | Fehling’s solution | Brick-red precipitate forms |
C | Tollens’ reagent | Silver mirror forms |
D | Acidified potassium dichromate | Colour change from orange to green |
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Aldehydes can undergo oxidation reactions to form carboxylic acids.
Which equation shows the correct oxidation of an aldehyde to its corresponding carboxylic acid?
CH3CH2OH + [O] → CH3COOH + H2
CH3CHO + [O] → CH3CHCOOH
CH3CH2CHO + [O] → CH3CH2COOH
CH3COCH3 + [O] → CH3CH2COOH
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Ketones can be reduced to secondary alcohols.
Which reagents and conditions are required to reduce a ketone to a secondary alcohol?
Reflux with acidified potassium dichromate solution
Heat with aqueous sodium tetrahydridoborate
Hydrogen gas at 60 oC with a nickel catalyst
Reflux with concentrated hydrochloric acid and a tin catalyst
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Aldehydes and ketones can both react with HCN to form hydroxy nitrile compounds.
Which is the correct mechanism for this reaction?
Electrophilic addition
Electrophilic substitution
Nucleophilic addition
Nucleophilic substitution
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How many structural isomers with the molecular formula C4H8O react with Fehling’s solution?
1
2
3
4
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The colour of warm acidified sodium dichromate(VI) changes from orange to green when added to compound Y. 1 mol of Y reacts with 2 mol of hydrogen cyanide in the presence of potassium cyanide.
What could Y be?
H2C=CHCH2CHO
CH3CH2CH2CHO
HC(O)CH2CH2CHO
CH3COCH2COCH3
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What is formed when butanone is heated under reflux with a solution of NaBH4?
butane
butan-1-ol
butan-2-ol
butanal
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Which of the following statements about aldehydes and ketones is not true?
Shorter chain aldehydes and ketones mix completely with water
They show strong absorption in infra-red at about 1700 cm-1
Typical reactions are nucleophilic additions
They are good reducing agents
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The mechanism for the reaction between propanone and hydride ions is shown below
The correct row shown is
| Role of hydride ions | Role of propanone |
A | electrophile | nucleophile |
B | nucleophile | electrophile |
C | oxidising agent | reducing agent |
D | Brønsted-Lowry acid | Brønsted-Lowry base |
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Which carbonyl compound(s) produce(s) a carboxylic acid when they are treated with acidified K2Cr2O7 or Tollens’ reagent?
CH3CH2CH2CHO and CH3CH2COCH3
CH3CH2CH2CHO and CH3CH2CH(OH)CH3
CH3COCH3
CH3CH2CH2CHO and CH3CH2CHO
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Lithium tetrahydridoaluminate(III), LiAlH4, in an organic solvent behaves in a similar way to sodium tetrahydridoborate, NaBH4, in an aqueous solution. If LiAlH4 reacts with a carbonyl compound, which of the following could not be formed?
3,4-dimethylhexan-2-ol
3,3-dimethylhexan-1-ol
2,3-dimethylhexan-2-ol
2,2-dimethylhexan-3-ol
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A carbonyl compound reacted with potassium cyanide followed by dilute acid. The product had no effect on plane polarised light.
Which of the following could not have been the carbonyl compound?
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Citronellal is an aldehyde that is used as an insect repellent with a characteristic lemon scent. Heptan-2-one is a ketone that gives blue cheese its distinctive aroma.
When the following tests are carried out on these compounds, which row best describes what would be noticed about these smells?
| Test | Citronellal | Heptan-2-one |
A | Acidified potassium dichromate(VI) solution and heat under reflux | Smell disappears | Smell disappears |
B | Aqueous sodium tetrahydridoborate(III) and heat under reflux | Smell disappears | Smell remains |
C | Potassium cyanide then dilute acid | Smell remains | Smell disappears |
D | Tollens’ reagent and gently warmed | Smell disappears | Smell remains |
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A carbonyl compound gave a negative test result with Tollens’ reagent.
Which of the following statements is correct about the carbonyl compound?
It would produce a brick-red precipitate when reacted with Fehling’s solution
It would be reduced by aqueous sodium tetrahydridoborate(III) to a secondary alcohol
When reacted with potassium cyanide followed by dilute acid, the carbonyl would undergo a nucleophilic substitution reaction
It would undergo an oxidation reaction with acidified potassium dichromate(VI) to form a carboxylic acid and the solution would turn green
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Carbonyl compounds are reduced when reacted with potassium cyanide followed by dilute acid.
Which pair of statements about the reaction mechanism and product is not correct?
| Statement 1 | Statement 2 |
A | The C=O double bond is polar with the oxygen end slightly negative | The overall charge on a cyanide ion is due to the negatively charged carbon atom |
B | The cyanide ion acts as a nucleophile | The C=O double bond breaks by homolytic fission and the oxygen atom gains an electron |
C | A hydroxynitrile is formed | This method of organic synthesis may increase the length of the carbon chain |
D | The hydrogen ion that reacts with the intermediate comes from the dilute acid | The intermediate donates a pair of electrons to a H+ ion |
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